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L
ong-span bridges have always held a fascination for structural engineers – and indeed, for the general public – with the longest bridges of each type generally categorised by their worldwide rating. When a new record is set, as seems to happen on a regular basis, the latest title-holder is accorded great publicity and guaranteed an audience around the world. But as our supplement makes clear, the biggest challenges in long-span bridge engineering are not necessarily the record-breaking structures. These may be challenging when they are under construction – particularly if they are being built in regions which experience extreme weather conditions – but often they employ tried and tested design approaches and construction technologies, with the longer spans generally driven by topography or other project-specific project-s pecific criteria. The skills of engineers and architects working on any long-span bridges can often be tested more thoroughly when it comes to designing them for highly-seismic locations, using unusual combinations such as those with multiple cable-supported spans in series, or being tasked with creating aesthetically-pleasing structures at this kind of scale. In this special supplement we kick off with an overview of long-span bridges in China, where many of the world’s longest spans can currently be found; canvass opinion on the hot-topics in long-span bridges around the world, and report on some of the ongoing, planned and recentlycompleted long-span crossings. It is by no means exhaustive, that would be impossible in a publication of this size, but I hope it will give readers a flavour of some of the challenges the industry is facing today
Circulation manager Maggie Spillane Designer Lisa Arcangeli Production Gareth Toogood Managing director Graham Bond Contributors
Helena Russell
Lisa Russell, Man-Chung Tang
Editor Cover image: Rendering of Hålogaland Bridge which is under construction in Norway (Dissing & Weitling) Bridge design & engineering is published quarterly and is available on
subscription at the rate of UK£105/€162/US$218 per year, which includes four issues of Bd&e and and eight issues of Bridge update newsletter. newsletter. Subscription payment can only be accepted in the currency of the country in which a company is registered. registered. If not registered in the UK, the EU or the US, payment should be made in US dollars.
Contents
Bridge design & engineering (ISSN No: 1359-7493, USPS No: 003-140) is
published quarterly by Hemming Group and distributed in the USA by by SPP, 17B S Middlesex Ave, Monroe NJ 08831. Periodicals postage paid at New Brunswick, NJ. POSTMASTER: send address changes to Bridge design & engineering , 17B S Middlesex Ave, Monroe NJ 08831. Every effort is made to ensure that the content of this publication is accurate but the publisher accepts no responsibility for effects arising there from. We do not accept responsibility for loss or damage to unsolicited contributions. Opinions expressed expressed by the contributors and advertisers are not necessarily those of the publisher publisher.. This publication is protected by copyright and no part may be reproduced in whole or in part without the written permission of the publisher. Printed by Latimer Trend ISSN 1359-74 1359-7493 93 Published by Hemming Information Services (a division of Hemming Group Limited) ©Hemming Group Ltd 2016
LONG-SPAN BRIDGES SUPPLEMENT 2016
04
THE LONG GAME: Half of the world’s top twenty longest-span suspension bridges are in China, as are six out of nine of the longest spans of other types of bridges. Man-Chung Tang reports on recent progress in the current international hot-spot for long-span bridges
14
EXTREME LENGTHS: Some of our longest-span bridges have been around for several decades now, and to a large extent the technologies and engineering know-how of these structures are tried and tested. Lisa Russell explores the influences on long-span bridge design today, and the challenges of our ageing structures.
34
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LONG-SPAN BRIDGES
The long game
Half of the world’s top twenty longest-span suspension bridges are in China, as are six out of nine of the longest spans of other types of bridges. Man-Chung Tang reports on recent progress in a hot-spot for long-span bridges
04
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LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES
under construction, ten of them are in China. There is no doubt this bridge boom is an exciting time for bridge lovers. In terms of bridge technology, China is a latecomer, but it has been a rapid learner. The country’s first real long-span bridge, the 423m-span cable-stayed Nanpu Bridge in Shanghai, was opened to traffic in 1992, while most of the longest spans in Europe and North America were completed many years previously. Real long-span suspension bridges flourished in the 1930s in the USA while segmental girder bridges and cablestayed bridges began in the early 1950s in Germany. So bridge building is neither a modern technology nor considered a high-tech venture. Building a conventional long-span bridge today – even the world’s longest span – is only contingent on cost, as the technology for building bridges is already mature. In many ways it is the speciality bridge that hold more interest, though they may not be the longest spans
O
ver the last 30 years, China
four categories of bridges in the world –
has built a huge network of
girder bridges, cable-stayed bridges, arch
in the world, or even in China.
highways of about 4,000,000km
bridges and suspension bridges – the
Girder bridges
of regular highways and more
definition of long span depends on the
Of all bridge types, the girder bridge is the most common. But the Shibanpo Bridge in
than 75,000km of expressways. A comparison of China’s expressway system
type of structure. A 300m span might be very long in a girder bridge, but it would
to the US Interstate bears discussion. The
be considered very short if it were a
structure, currently holds the world record
US began to build the Interstate system in
suspension bridge.
for span length. It is located next to an
1956 while China did not start until 1987.
The table below lists the three longest
Chongqing, which is a 330m-span hybrid
existing girder bridge which was completed
Being the strongest economy in the world
spans in the world in the four categories
in 1981 and because of the proximity of
at that time, the US interstate system took
of bridges; of these 12, seven of them are
the two bridges, it was natural to design
off very quickly. By contrast, China was a
in China, and of the 20 longest suspension
the new structure as a girder bridge for
very poor country in 1987 and the country’s
bridges, which are also the 20 longest
aesthetic reasons.
network of expressways was slower to
spans of all bridges either completed or
The span arrangement of the old
develop. But eventually, it overtook the US and now has the greatest length of
Bridge type
Name
Span (m)
Country
Year completed
Suspension
Akashi-Kaikyo
1991
Japan
1998
needed; its cities are also developing and
Xihoumen
1650
China
2009
need increased river-crossing capacity. It
Great Belt East
1624
Denmark
1998
Russky
1104
Russia
2012
Sutong
1088
China
2008
Stonecutters
1018
China
2009
Chaotianmen
552
China
2009
Lupu
550
China
2003
Bosideng
530
China
2012
Shibanpo
330
China
2006
Stolmasundet
301
Norway
1998
Costa e Silva
300
Brazil
19 74
expressways of any country in the world. The expansion of China’s highway system is not the only reason so many bridges are
is somewhat sobering to consider that in
Cable-stayed
1985, there were only three bridges over the entire 6,300km length of the Yangtze River – one in Chongqing, one in Nanjing and one in Wuhan.
Arch
Today, there are more than a hundred. In addition to those major bridges, a large number of crossings have also been built over other rivers and valleys, and many of these are long span bridges. How is long-span defined? Among the
LONG-SPAN BRIDGES SUPPLEMENT 2016
Girder
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LONG-SPAN BRIDGES
hand would have required very thick plates and would have been too difficult and too expensive to fabricate, especially the girder portion over the piers. To avoid these problems, TY Lin International designed a prestressed concrete girder bridge with a 130m-long steel box at the mid span. The concrete portion of the bridge was built segmentally using form travellers – a large number of concrete segmental bridges had already been built in China, so this was rather routine. The steel box girder was fabricated in Wuhan, which is about 1,000km downstream of the bridge site. To facilitate its transportation, the steel box was designed to act as a barge as well. After closing the two ends it was launched like a ship onto the Yangtze River and towed to bridge has two main spans of 156m and
all-concrete box girder bridge is the 301m
the site where it was lifted and connected
174m, and the original intention was to align
span Stolmasunde Bridge in Norway, which
to the two cantilevers. The lifting operation
the piers of the new bridge with those of
was completed in 1998, while the longest
was completed within the permitted 12-hour
the old bridge. However the Waterways
all-steel girder bridge is the 300m span
window and the bridge was opened to
Authority was concerned that the 174m-long
Costa e Silva Bridge in Brazil, completed in
traffic in 2006.
main span of the old bridge was already
1974.
very tight for modern river traffic and
06
For the Shibanpo Bridge, with its
Arch spans
the presence of the new piers would have
330m-long main span, a concrete structure
The world’s three longest span arch
created a tunnel effect for ship navigation. Thus, the authority insisted that the pier
would have been too heavy and the longterm deflection would have been difficult
bridges are all in China; the 552m span
between the two spans be deleted, creating
to control, especially at the middle portion
Yangtze River in Chongqing; the 550m span
a 330m-long main span. To date, the longest
of the bridge. A steel bridge on the other
Lupu Bridge crossing the Huangpu River
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Chaotianmen Bridge which crosses the
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LEGENDARY CONSTRUCTION
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in Shanghai and the 530m-span Bosideng
Bridge over the Yangtze River in Luzhou. The Chaotianmen Bridge is a truss arch,
to the Bosideng Bridge for the first time. Currently, the world’s longest concrete
this second bridge which had a span of
arch span is the Wanxian Bridge in
602m and was the world’s longest cable-
the arch ribs of the Lupu Bridge have box
Chongqing – a 420m span bridge which
stayed bridge when it opened to traffic in
shape cross-sections and the arch ribs of the Bosideng Bridge are concrete-filled
crosses the Yangtze River in Wanxian and was opened to traffic in 1997. The arch rib
September 1993. This bridge opened 16
steel tubes. The design and construction
is shaped like a catenary and is 16m wide
of first two bridges was fairly conventional
and 7m deep with a rectangular triple-cell
Bridge, even though it began construction later.
with the Chaotianmen Bridge constructed
box concrete section. An arch truss made
as a pair of cantilevers and the arch ribs of
of steel tubes was first erected with the
were all designed and built by the Chinese
the Lupu Bridge built using highlines and
help of temporary cable stays. This steel
themselves with only DRC Consultants,
temporary cable stays.
arch was designed to be embedded in the
which merged with TY Lin International in
China has built more than 400 arch
months before the 856m span Normandy
It is interesting to note that these bridges
concrete section and was used as a form
1995, as a special consultant to the owner,
bridges using concrete filled steel tubes, as
support for the concrete arch, which was
the designer and the contractor.
this type of construction is very economical
cast segmentally from both abutments
in China and many steel fabricators have
toward the span centre. The concrete deck
longest cable-stayed bridge, the Sutong
acquired the equipment needed to produce
is 23m wide and 140m above the normal
Bridge in Jiangsu Province, not far from
the spirally-welded steel tubes used for
water level of the Yangtze River, and it
Shanghai. It crosses the Yangtze River near
this type of arch bridge. Erection is mainly
consists of precast T-beams resting on
Suzhou. The main bridge has a main span of
done using highlines and most of these arch
vertical spandrel columns.
1,088m with side spans of 300m and 100m
spans are relatively moderate in length.
China currently has the world’s second
and a roadway width of 30.5m. It was the
Cable-stayed bridges
world’s longest cable-stayed bridge when it
Sichun, which opened to traffic last year,
The first major cable-stayed bridge to be
opened to traffic in 1997.
has a span of 530m, with the steel portion of the arch measuring 518m. The arches
built in China was the Nanpu Bridge over the Huangpu River in Shanghai, which
Suspension bridges
typically consist of a group of steel tubes
opened to traffic in December 1991. Its
As previously noted, half of the 20 longest
braced against each other by smaller
main span of 423m was the longest in
span suspension bridges in the world
steel tubes. The main tubes are filled
China at the time of its completion. The
today are in China. Considering that China
with concrete after the arch has been
same team of engineers and contractors
only built its first long-span suspension
constructed. To ensure that the tubes were
went on to design and build another cable-
bridge, the 888m span Humen Bridge in
completely filled with concrete, the vacuum
stayed bridge, the Yangpu Bridge, also over
Guangdong Province 17 years ago, the pace
pumping method was successfully applied
the Huangpu River in Shanghai. It took
of construction has been remarkable.
But the Bosideng Bridge in Luzhou,
8
them just 29 months to design and build
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LONG-SPAN BRIDGES SUPPLEMENT 2016
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LONG-SPAN BRIDGES
of the plans to continue building many more long-span bridges, the industry was willing to invest in new equipment and learn new technologies. At the current time, China probably has the most modern steel fabrication facilities in the world; the steel components of the new San Francisco Oakland Bay Bridge in California, USA, including the girder, the tower and the cables were all fabricated in China. Worth mentioning are a few smaller suspension bridges in mountainous areas: the 1,176m span Aijai Bridge in Hunan, completed in 2012; the 1,088m span Balinghe Bridge in Guizhou, completed in 2009, and the 1,196m span Longjiang Bridge in Yunnan, which will open to traffic in 2016. In these cases, because transportation through mountainous terrain can be difficult, a long-span bridge across the entire valley is sometimes the best solution. As well as the challenge of supply of materials, the construction of a suspension bridge over such a mountainous area poses two major difficulties; erection of the lead strand for the catwalk and erection of the main girder. Unlike construction of a bridge over water where the lead strand can be carried by a barge from one tower to the other, the same solution is not possible in the mountains where it would be caught by trees and rocks along the way. For the Longjiang Bridge, the lead cable was carried from one end of the bridge to the other end by a drone; in Xihoumen Bridge by an airship, and in Siduhe Bridge by a rocket which was provided by the military. The girders of most suspension bridges are erected by raising the segments from a barge, but again this is not possible if the terrain underneath the bridge is not accessible. So, a new method was developed for the Aijai Bridge. Firstly, a temporary ‘rail system’ was attached to the suspenders at the girder level once the main cables and all suspenders were in place. The segments were then pulled along this rail system one by one from the work platform at the tower Since that time, China has built many
deck and have been produced exclusively
to their final position, until the entire girder
long-span suspension bridges. The world’s
in China by Chinese fabricators. Likewise,
was completed.
second longest suspension bridge, the
the wires for the main cables are also
1,650m span Xihoumen Bridge in Zhoushan
manufactured in China and both air
anchored suspension bridges, although
was opened to traffic in December 2009.
spinning and prefabricated strands have
most of them have spans at the shorter
been used for the installation of the main
end of the spectrum. They are suitable for
cables in those suspension bridges. Because
sites with poor soil conditions which are
Almost all long-span suspension bridges have a steel box girder with an orthotropic
10
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China has built a large number of self-
LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES
not good for building anchors. However, the Pingsheng Bridge in Foshan, which was completed in 2006, has a main span of 350m, and was the longest self-anchored span in the world until 2013, when the new east span of the San Francisco Oakland Bay Bridge with its 385m-long main span was opened to traffic. A year later, this was overtaken by another Chinese bridge, the 420m span Huanghe Bridge in Zhengzhou, Henan. Nevertheless, the Pingsheng Bridge and San Francisco Oakland Bay Bridge spans have only single towers, while the Huanghe Bridge has two. This record is set to be broken again in the near future, as a record-breaking selfanchored suspension bridge designed by TY Lin International and Smedi is currently under construction – the Ergongyan Bridge in Chongqing. This bridge is being built next to an existing suspension bridge with a 600m span, and for aesthetic reasons, the new suspension bridge will also have a 600m span. The ideal solution would have been to build the new structure as a traditional suspension bridge. However, the soil conditions at the site were not reliable enough to be able to securely anchor the main cables, hence the client decided to build a self-anchored suspension bridge even though the main span will be rather long. The towers are now under construction and the girder will be erected using temporary stay cables. Once the girder is in place, the main cables will be installed and the load of the girder will be transferred to the suspenders, after which the stay cables will be removed.
Partially cable-supported girder bridges A further development on the extradosed bridge concept has recently been developed in China for medium-span bridges; the partially cable-supported girder bridge. The process involves first designing the structure as a girder bridge, which does not have sufficient capacity to carry all of the loads; this is supplemented by the forces from the cables. Cables can be provided as
that it is a girder bridge with post-tensioning
supported girder bridge does not have these
a suspension system, a stay-cable system
tendons raised above the deck to gain more
restrictions and the cables are designed as
or from an arch rib. The system ensures
eccentricity. The ‘cables’ are designed as
stay cables.
that the capacity of the girder and the cable
prestressing tendons with higher allowable
system are both fully exploited. It may look
stresses, and they must have a relatively
bridge and a partially cable-supported girder
similar to an extradosed bridge, but the
flat inclination and the bridge towers
bridge is the function of the girder and
basic premise of an extradosed bridge is
must be relatively short. A partially cable-
the cable system. In a traditional cable-
LONG-SPAN BRIDGES SUPPLEMENT 2016
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The difference between a cable-stayed
11
LONG-SPAN BRIDGES
China, which was completed in 2008 and has two spans of 100m. The longest partially cable-supported girder bridge is the Dongshuimen Bridge in the city of Chongqing which was opened to traffic in 2014. It has a 445m-long main span and the girder is 13m deep to accommodate transit trains on the lower deck. It is located at the tip of the peninsular where the Jialing River meets the Yangtze River. The client wanted a bridge that was prominent and beautiful to serve as a landmark, but the design had to minimise any obstruction of the view of the city. The design of this partially cable-supported girder bridge, takes full advantage of the carrying capacity of such a deep girder with its span to girder depth stayed bridge, the cables are designed to
the girder itself can carry a large proportion
ratio of 34, so fewer cables were required,
carry all the loads from the girder and the
of the loads so the cable system is only to
which makes the bridge even more
capacity of the girder is only there to resist
carry the load that the girder is not able
local bending moments and axial forces.
to carry. Thus the required capacity of the
transparent. It has a sister bridge on the other side of the peninsular, the Qianximen
Therefore the girder of a cable-stayed
cables and the towers is much less than
Bridge, which was also designed as a
bridge can be made very flexible, often with
that in a traditional cable-stayed bridge.
partially cable-supported girder bridge.
a span to girder depth ratio of more than
In the case of the Sanho Bridge, for
Over the last 30 years, China has built
150 or even 300, as in case of the ALRT
example, the cables carry only 50% of the
many new bridges and with its population of
Skytrain Bridge in Vancouver, Canada. As
total load. This means a saving of 50%
1.4 billion and its boom in construction, this
a rule of thumb, the span to girder depth
of the cables and tower compared to a
trend looks set to continue.
ratio for a girder bridge is around 20. For many medium span bridges, the span to
conventional cable-stayed bridge.
depth ratio is often in the range of 25 to 45;
bridge was the Sanho Bridge in Shengyang,
The first partially cable-supported girder
Man-Chung Tang is chairman of the board of TY Lin International
LONG MULTIPLICATION
I
n recent years, many multi-span cablesupported bridges have been designed and built in China, including the Taizhou Bridge, the world’s largest multi-span suspension bridge (see page 15) and the Jiashao Bridge (right) , which is the largest multi-span cablestayed bridge. Jiashao Bridge crosses Hangzhou Bay in Zhejiang Province and is a six-tower cablestayed bridge which has five main spans each 428m long, and side spans of 200m. It is the largest multi-span cable-stayed bridge in the world and has a deck width of 55.6m. Compared to a traditional cable-stayed bridge, the multi-tower version has a lower vertical stiffness under live load, and hence this needs to be improved by increasing the size of the tower, increasing the stiffness of the deck or adding auxiliary cables; none of these options was practicable for the Jiashao Bridge so alternatives had to be developed. An x-shaped bracket was designed to support the deck in plan at the towers and a rigid hinge in the middle of the bridge releases
12
China Foto Press/Getty Images
the temperature-induced load and longitudinal displacement, hence reducing its impact on the towers, while constraining rotation, deformation and shearing displacement of the bridge deck. One of the other major challenges for the Jiashao Bridge was design of a maintenance
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gantry for the twin box-girder deck; a traditional system could not be used due to the obstruction caused by the brackets at the towers, and the rigid hinge at the centre of the main span. By design of a special gantry, the number of units required was reduced from 20 to just four.
LONG-SPAN BRIDGES SUPPLEMENT 2016
YOUR CHALLENGES, OUR SOLUTIONS. Cable stayed bridge, Marchetti viaduct, Ivrea (Italy)
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LONG-SPAN BRIDGES
Spanning the future Some of our longest-span bridges have been around for several decades now, and to a large extent the technologies and engineering know-how of these structures are tried and tested. Lisa Russell explores the influences on long-span bridge design today, and the challenges of our ageing structures our decades on from the advent of
F
Bridge is a good example where engineers
the long-span bridge market and at spans
the aerodynamic box girder bridge
took advantage of the retrofitting to improve
between 150m and 1,000m, cable-stayed
deck on the Severn Bridge in the
the aerodynamic performance and breathe
bridges now appear to be the preferred
UK, the impact of wind loading is still
new life into an ageing structure.”
option for most clients and engineers,” said Colford in his paper. Even in the USA,
one of the most critical factors in the
design of long-span bridges. But more recent
often the subject of discussion within the
where the development and use of cable-
influences such as new procurement routes,
engineering community, as Aecom vice
stayed bridges has lagged behind Europe,
and the introduction of high-strength materials
president Barry Colford pointed out in his
the cable-stayed form seems to be gaining
also have an impact on the process.
keynote at last year’s European Bridge
in popularity. “Whether the industry wants
Conference in Edinburgh, Scotland.
to continue to push the envelope out and
“Wind effects continue to be the governing factor in the structural design of long-span
In terms of numbers there are around 220
build cable-stayed bridges of 1,200m span
bridges, and more advanced testing rigs
cable-supported bridges throughout the
or more remains to be seen. Both forms of
and advanced computational methods are
world with spans greater than 300m; the
cable-supported bridge have advantages and
being used nowadays to better mitigate the
majority are either suspension bridges or
disadvantages,” he says. Recent problems
aerodynamic instabilities,” agrees Ender
cable-stayed bridges and there is almost an
with corrosion of main cables may have
Ozkan, a technical expert at Rowan Williams
equal split in numbers of each of these two
dented confidence in suspension bridges,
Davies & Irwin. “Another area of interest for
main types.
but Colford believes that the success of
aerodynamic performance is the retrofit of existing long-span bridges. Bronx Whitestone
14
But the definition of a long span is
“As might be expected, it is economics at the construction stage that is driving
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dehumidification retrofit projects could reverse this.
LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES
New forms
China’s Taizhou Bridge, which opened in 2012, was first three-tower, two-main span continuous suspension bridge system. The structural behaviour of this type of system is different from that of a conventional two-tower suspension bridge system, says Robin Sham; cable slip at the saddles must be prevented under all loading conditions, which leads to conflicting demands at the central tower. A flexible tower would help prevent cable slip but would be ineffective in the control of girder deflection; while a stiff central tower would
make it hard to prevent cable slip, although it would improves deflection control of the girder. The main reason for adopting the three-tower form is that it enables very large distances to be crossed, with only the minimal number of bridge supports, Sham says. One of the challenges at Taizhou was that the superstructure construction for a three-tower suspension bridge system is much more complicated than that for a two-tower system, particularly in the main cable erection, main girder erection and bridge geometry control. Another different form of cable-supported
CHACAO CHANNEL BRIDGE, CHILE
C
hacao Channel Bridge is a flagship project for Latin America - though one that is still some way from coming to fruition. It will be the region’s the first multisuspension bridge with spans longer than 1,000m; the three-tower crossing will have main spans of 1,155m and 1,055m. At present, the client – Chile’s Ministry of Public Works – is in the process of reviewing the final design. Construction is due to start soon and the target is for the bridge to come into operation in 2020.
LONG-SPAN BRIDGES SUPPLEMENT 2016
The project has had a long gestation and has been talked about for decades as part of the plan for a road to link the wh ole of the American contintent, from Alaska to south of Chile. A scheme to build the bridge under a publicprivate partnership was cancelled in 2006, mainly for financial reasons. The project was then re-evaluated during 2011-2012 from both economic and technical standpoints. The decision was taken to use traditional funding to build the bridge for a maximum cost of US$740
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bridge is currently reaching completion in Turkey. The final deck segment was raised into place in early March of a hybrid cablestayed suspension bridge that is being built north of Istanbul over the Bosphorus Straits; a concept developed by Michel Virlogeux and T Engineering. The Third Bosphorus Bridge – officially called the Yavuz Sultan Selim Bridge – is being built by a joint venture of Astaldi and IC Ictas and has 1,408m main span – far longer than the world record for a traditional cablestayed bridge, the 1,104m-span Russky Bridge. The new bridge’s A-shaped towers stand a
million, including associated work such as access roads. The government signed a contract with a joint venture of OAS, Hyundai, Systra and Aas-Jakobsen in February 2014. Chile is one of the countries most affected by earthquakes, making the project particularly challenging. Not only is the bridge in a highly seismic region, but also there are strong winds, high tides and fast currents to address – all significant issues for construction. Both cablestayed and suspension bridge options were studied before concluding that a suspension bridge would offer many advantages, including in terms of seismic behaviour.
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LONG-SPAN BRIDGES
LOOKING AFTER OLDER BRIDGES
M
any of today’s challenging issues for bridge engineers come from looking after old structures. In the years to come, Cowi’s Tina Vejrum expects to see more projects to replace decks on existing suspension bridges, following Canada’s original lead with the Lions’ Gate Bridge and now the ongoing Macdonald Bridge project. “I think there is a new market there with interesting challenges,” she says. A number of such bridges are reaching the end of their service life, she says. “Fortunately on a suspension bridge we can replace the deck – it’s a lot easier than for a cable-stayed bridge.” Limiting closure times is a key issue, as too is maintaining the aerodynamic stability in the interim phase where the bridge is not fully connected and has two different cross sections. Another issue is deterioration of the main cables of suspension bridges. Following successful use elsewhere, dehumidification is being discussed for a number of US bridges including the George Washington, Anthony Wayne and Benjamin Franklin. And in February, the Delaware River & Bay Authority awarded American Bridge a US$33.6 million contract to install a dehumidification system for the main suspension cables on both structures of the Delaware Memorial Bridge. Dehumidification on main cables has passed the ‘tipping point’ in the USA, believes Aecom’s Barry Colford. “What has convinced owners (and me) are the results from acoustic monitoring of the UK bridges following application of dehumidification. These are of course confidential and sensitive but owners are likely to be aware of them through the International Cable Supported Bridge Operators’ Association,” he says. It not only the results from acoustic monitoring that have increased confidence in the effectiveness of dehumidification. The results of internal inspections post dehumidification have been very encouraging, Colford adds. Hydrogen embrittlement needs moisture to generate hydrogen ions and of course corrosion needs moisture and oxygen. “If we can stop moisture from getting into cables then we can potentially stop both of these things happening,” he says. The whole ethos is to make sure that the service life of the cables matches the service life of the bridge. “I do think that dehumidification is the only way that we can be given
16
some assurance that this will happen. We now know that painting in itself doesn’t stop moisture getting into cables. We also know that oiling doesn’t appear to work either.” Aecom has been working on the dehumidification of the two Chesapeake Bay Bridges and the scheme is now up and running. “The cables have dried out really well,” says Colford. Novel solutions involving complex surgery can also be required when long-span crossings age, but some of the issues may not become apparent until work begins. A recent project at the Humber Bridge has highlighted the need for the client, designer and contractor to work closely together to address any unexpected challenges on site. It has also demonstrated some of the potential difficulties of using the new higher-strength steels. The Humber Bridge opened in 1981 and its 1,410m-long suspended main span held the world record until 1997. The ends of the deck boxes at the towers and anchorages were supported by pairs of steel A-frames to allow free longitudinal movement of the deck boxes under traffic and other effects, and providing horizontal restraint under wind loading. Routine inspections had raised concerns over a lack of articulation and wear, so a scheme was designed by Arup for the Humber Bridge Board, to replace the 3.8m-high A-frames with vertical pendels and wind-shoes (Bd&e issue no 73) . Owners of similar long-span bridges are likely to have to contend with similar issues in the coming years, says Spencer Group deputy managing director Richard Burgess. His firm won the contract and completed the work in 2015, without needing to close the bridge. High-strength steel, grade S690 had been specified to reduce the element sizes in the limited space available. “But we found that we couldn’t meet the weld strength requirements with that steel,” says Burgess. “When we dropped down a grade we got a far more compliant material – it was more weldable and still met the strength requirements for the bridge,” he says. As a result, engineers believe caution is needed over the use of such steel in bridges, where demanding fracture toughness requirements may be coupled with the heightened risk of hydrogen embrittlement.
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LONG-SPAN BRIDGES
record-breaking aking 322m-tall and its 59m width record-bre will accommodate an eight-lane motorway and two railway lines (Bd&e issue no 80) It is an innovative structure, structure, not only because of its hybrid design but also because the cables are the biggest ever installed on a bridge, explains Erik Mellier Mellier,, technical director of Freyssinet, Freyssinet, which designed and installed the cables. Another notable feature is the use of 1,960MPa 1,960MP a strand. “It is the first time that we are using such a high-strength strand,” strand,” he says. “We have celebrated the biggest stay cable ever installed in terms of length and size,” says Mellier. The longest of the cables are 597m Mellier. long, and have 151 strands. Compact cables are being used, to reduce the drag. The company has taken advantage of its earlier work at Russky Island. “It was a good thing to have done before, because we could take all the experience we had accumulated there and adapt it to this project,” says Mellier. Mellier. The initial challenges were in the design
LONG-SPAN BRIDGES SUPPLEMENT 2016
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LONG-SPAN BRIDGES
price matters - and all too often they are right, he says. “But in fact we can usually save them money,” he adds. For instance, this might come from input such as reducing the concrete quantities for the bridge. “Our main problem as architects is that architecture is still considered an add-on to bridge design,” says Jensen. Yet in working with engineers, no-one can see where the architect’s work stops and the engineer’s begins; it doesn’t matter who came up with which idea – “we always work as a team”, he adds. Balancing different demands in procurement causes much debate, including the extent to which you prescribe details, while leaving sufficient opportunity for achieving value. Client-based designs with construction-only contracts do still happen, particularly in some regions such as the Middle East. These days, markets such as the USA or Europe tend to go down the design and build route, or public-private partnerships, says Stuart Withycombe, Withyco mbe, who is CH2M’s director of major of the system, which had to be upgraded
bridges, particularly as they have an enormous
compared to the standard. “We carried out a
impact on the visual environm environment, ent, much more
crossings. “How far you take the definition drawings determines how much room you
quite significant testing campaign, with fatigue
than buildings.
leave for choice in terms of design,” he adds.
tests both in Germany and Chicago,” says
It is also surprising because clients seem fully aware of the power of bridges as symbols; in any project brief these days there is a clause
justifi jus tificat cation ion fo forr prov provisi ision on of a high high le level vel of
stage about deformations and fatigue of the
saying that the bridge must be a landmark, a
definition. But in other areas, maybe less so.”
cables. A special test was carried out, looking
signature structure or an ‘icon’. “Therefore it’s
at the behaviour of the cable under high
very disappointing that at the end of the day
procurement method naturally naturally has a
deflections.
they just take the cheapest one,” he says.
considerable effect on who pockets any
The client isn’t even necessarily saving much
your output looks like then I think there is
As well as appearance, the choice of
savings that arise from value engineering. In
Looks matter
- if any - money. “As far as we’re concerned,
design-bid-build, savings arising from changes
Every long-span bridge is the result of
there is no real relationship between cost and
that are accepted by the client may be shared
countless decisions - but some of those
let’s call it ‘beauty’,” he says. “There is no reason
50:50 between client and contractor. contractor. But in
decisions naturally have a far more profound
why a cheap bridge can’t be a beautiful bridge.”
design-build, the contractor will simply seek to
There are many great bridges being built
put in the lowest price possible; all the savings
impact than others. The choice of procuremen procurementt method is one of the most fundamental,
around the world - but also quite a few
from the innovations therefore therefore go to the
affecting everything from the type of bridge
mediocre and some outright ugly ones, he
owner. “At the same time, the concern is that
to how much influence the contractor and the
feels. The reason for this is not lack of talented
the owner may not get exactly what it wanted,”
eventual maintenance maintenance team will have on what
bridge designers, but often that clients are
it is made from and how it is built. Procurement choices can also govern
not prepared to do what it takes, or don’t
adds Marwan Nader, Nader, senior vice president at TY Lin International.
the degree of receptiveness to innovative
intended result. The procurement method is
starting to open up a new option for clients
approaches, whether involving the use of the
often the problem, Jensen feels. The decline in the traditional approach
in this regard, enabling them to lock-in the
latest high-strength materials or by looking for better ways of addressing issues such as
of completing design before construction
Champlain Bridge in Montreal, Canada – also
vulnerabilities.
tenders are invited has been accompanied by
known as the New Bridge for the St Lawrence
But on all too many projects, price turns
18
“If you want to be fairly protective of what
Mellier. In addition, the bridge is quite flexible and so there were issues during the design
understand what it takes, to achieve the
However Howev er the use of definition designs is
appearance they want from the start. The new
a corresponding increase in formats where the
– is a current illustration. “We ended up with a
out to be the only thing that matters in the
contractor’s contractor’ s team is given responsibility for
definition design that was mandatory for the
end, says Poul Ove Jensen, bridges director at
much of the design. In design and construct
bidders,” explains Jensen. The Oresund Bridge,
Dissing & Weitling. He is surprised that there
tenders, the bidders often see no reason to
which opened in 2000, was an early example
is so little focus on the appearance of major
make an effort because they assume only the
of this process, which is still only rarely used.
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LONG-SPAN BRIDGES
for the long-span bridges that are often critical infrastracture links and the choice of procurement method can also affect how such risks are addressed. At the advent of privately-funded bridges, financial backers were mostly concerned with the seismic risk. Earthquakes had certainly been considered before then, but it had not been such an overriding issue, says TY Lin International senior vice president David Goodyear. “The same is now becoming true for vulnerability assessments,” he says. Someone financing a project for several decades needs to weigh up risks and revenue implications, not just of terrorism but of all kinds of major incidents - perhaps a tanker Some see such an approach as beneficial,
terms of making things look better but it’s
catching fire. “My personal belief is that
others less so, feeling that it does not really
not just how it looks – it’s making sure it
there is a lot of good thinking generated by
engage the creativity and resourcefulness of
works better as well,” says Withycombe.
having private financing step in front of public
the private sector. There can also be situations
Aspects such as durability and choice of
financing, because with private financing there
where the ambitions of the architect ambitions
materials are important. “It’s important to
seems to be more ‘ownership’ of the funding
and the engineer don’t really converge.
fix the requirements so that you don’t rule
stream,” says Goodyear.
In Montreal, client Infrastructure Canada
out contractors coming along with their
Blast protection is increasingly a key issue
was determined that the new bridge should
most creative and best ideas for how to
for long-span bridges, though this tends not
meet local expectations of a landmark bridge.
build it. Contractors bring important areas of
to be widely discussed in public for fear of
However, the project has an exceptionally
innovation to the project.”
raising awareness about vulnerabilities. At the
tight time schedule, particularly because
This influence also extends to maintenance: concession projects run for perhaps 30 or 35
to the issue of fire protection both in service
bridge, which is in poor condition. A design
years and clearly the structure needs to be in
and during construction. Various incidents
competition would have delayed the 2018 target completion. Use of the mandatory
a certain condition when handed back to the client. This means designing for a particular
have made owners more concerned about
definition design was a good solution, Jensen
measure of performance 30 years from now,
a main suspension cable, hangers or stay
believes; it would have been impossible
or risking expensive repairs before handover.
cables. In one instance a few years ago, a truck
to describe the architectural treatment,
“There have been changes in our world
caught fire by the low point of a main cable of
the potential consequences of fire affecting
proportions and so on sufficiently well in
because of the advent of PPP.” says Mike
words. The owner effectively had a guarantee
Cegelis, senior vice president at American
new Little Belt Bridge in Denmark and direct lightning strikes of bridges such as the Rion
that it would get what was envisaged.
Bridge. “There is a much greater focus on
Antirion Bridge in Greece, which damaged
The public-private partnership agreement
the operational and maintenance costs of
a cable and a similar incident in Korea have
with the government of Canada was won
components of the bridge than there was in
raised this as an issue. Cable and hanger
by Signature on the Saint Lawrence Group,
former times.”
suppliers are developing systems to provide
which includes designer TY Lin International.
There is increased interest in health checks
some fire protection.
The aggressive schedule could never have
for the bridge, particularly as the cost of
been achieved under a design-bid-build
instrumentation falls. “It is very fashionable to
design,” reveals Tina Vejrum, vice president
environment, according to Nader. “What the
equip all your bridges with all kinds of sensors,”
of international bridges at Cowi. Replacing
client is getting is the best of both worlds,” he
says VSL International group technical
hangers or stay cables is one thing, but would
says. The project can meet the schedule, and
officer Max Meyer. But there is no point in
be a different matter if the main cable of a
will be the bridge that was envisioned. The Mersey Gateway in the UK (see page 42)
collecting extensive data unless it can be used,
suspension bridge was affected, she says.
took an intermediate approach, partly using
clients to come up with a system that gives meaning to the data and enables maintenance
fire damaging cables on ong-span bridges,
the planning process to provide that definition, says Withycombe, with some rules for what the
interventions to be well planned.
where fire broke out when welding was taking
he stresses. Adding value involves helping
structure would look like. “That took a high-
“We are beginning to see a requirement in
Meyer is aware of five or six cases of including a recent one at a bridge in China place inside a tower. Nine cables were lost,
level view that nevertheless was very careful in
Checking for vulnerabilities
snapping one after the other; luckily the site’s
terms of how it defined visual quality,” he says.
Risks such as accidents and the potential
tower cranes were able to drop water into the tower from above to put the fire out.
“We’re getting better as designers in
20
same time, increased attention is being paid
of the urgent need to replace the existing
of terrorism have a significant impact
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LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES
The Post-Tensioning Institute has
A difficulty with high-strength materials
acknowledged the risk of fire and has
arises in relation to codes and standards, says
formulated test requirements. Details of
Vejrum. “At the moment we can’t go higher
Advanced materials like high-strength
fire resistance qualification testing were
than the grades we are using.” For instance,
steel are not necessarily straightforward to
among the significant additions and updates
manufacturers can produce 2,200MPa steel
use. Issues can arise when using this kind of
introduced in its 2012 edition. “If you want to
but this is far outside codes that only allow
material under high tension in bridges exposed
supply a system you need to be able to pass
values of perhaps 1,860MPa or 1,960MPa.
to chlorides and water. For example American
this test,” says Meyer.
There is a similar situation for high-strength concrete; it all boils down to who takes
Bridge has had to deal with high-profile failures of a small proportion of the tension rods on
project is what level of protection is really
responsibility. Without the backing of codes,
the self-anchored suspension span built as part
necessary. Once the bridge is in service,
it’s difficult to get the materials introduced as
of the new East Span of the San Francisco-
tankers pose a particular risk and Meyer
standard on projects, she says; consultants
Oakland Bay Bridge. There have also been
suggests that a rule of thumb might be to
wouldn’t take the responsibility if the client
some rod issues on other projects.
take the protection to double the height of the
doesn’t want to.
vehicles that will be crossing the bridge. It is not only heat that poses a risk: cold and
that such materials find a home on PPP
lot of other issues in an economical manner.
in particular the build-up of ice are potentially
projects where the contractor is responsible
“But we are now highly dependent on the
damaging. High-profile cases such as Canada’s
for subsequent of maintenance. This could
success of this material. It has obviously
Port Mann Bridge have highlighted the
been proven in a test environment that it can
dangers and cable companies are developing
be a likely way forward, says Vejrum, as the contractor will benefit from a saving on initial
prevention or removal technologies.
costs and would deal with any subsequent
the question is whether it can withstand the
issues. However, agreement would also be
environmental attack.”
One of the key questions to address on a
The devastating tsunami of 2004 highlighted
Perhaps it is more likely in the meantime
a further risk that major bridges can be
needed with the independent checkers about
exposed to. Awareness of disaster prevention
going outside the codes.
was heightened in the aftermath, points out
Introducing innovations is certainly
the fact that the larger schemes are closely examined by top consultants.
Such materials are now part of the bridgebuilding world, says Cegelis, and they solve a
meet the stresses that are imposed on it – but
Samples of any new material tested in the lab are checked over by the manufacturer in tremendous detail, points out Cegelis. But
Aecom director Robin Sham, the company’s
becoming more difficult, feels Mellier, partly
fabrication of these one-off test pieces is not
global leader of long-span bridges. This has
for reasons to do with issues like CE marking
the same as for general production and normal
fed into projects such as the Second Penang
and norms. “I believe that most clients are
Bridge, where a study of the likelihood of a
increasingly reluctant to be the first,” he says.
handling on site in the real world. Such elements may have their benefits but
tsunami event and the resulting soil liquefaction
You really need large projects, such as the
American Bridge has certainly become quite
phenomena was carried out. The bridge,
Third Bosphorus Bridge, in order to move
wary about them. Cegelis observes that the
which opened in 2014, consists of precast
forward. The technology can then be used on
company asks a lot more questions about jobs
segmental concrete marine viaducts and a
smaller projects, as clients are less reluctant
that will use them. However, he regards the
475m-long cable-stayed bridge. The study sought to determine the risks and magnitudes
once someone else has demonstrated that
issues as part of a natural process - inherent
it works. They can also take confidence from
problems have to be overcome whenever
of tsunami-generated waves on the bridge, says Sham. A simulation was then calibrated with records to allow a predicted wave height to be accommodated in the bridge design. Advanced materials
There is correlation between advances in materials and increases in maximum span length over time, says Nader. But such increases have now tapered off, he feels. “In my opinion, we are now on the cusp of starting to look at ultra-light high-strength concrete and what that will bring to the equation.” It is a major factor when spanning longer distances. “I don’t think at this point that somebody is going to dream up structural systems that give us the ability to go longer - it’s going to have to be through the materials,” he says. Ultra-highstrength steel, fibres and ultra-light highstrength concrete will all play their parts.
LONG-SPAN BRIDGES SUPPLEMENT 2016
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21
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LONG-SPAN BRIDGES
isolating the anchorage of a suspension
time-dependent behaviour, and the required
bridge. Arup toyed with trying to keep the
pre-cambering in order to achieve the design
technique as secret as possible – though the
shape once construction has been finished,
information had been included in the bid – or
she says.
patenting it. “But at Arup we’re not trying to
However, different challenges face engineers
patent too much construction technology,”
when designing ultra-long-span bridges, such
says Carter. “We are a relatively patent-free
as stay cable or suspension bridges with
industry. We don’t want to be a market leader
high pylons and slender steel or concrete
in taking us to a place where engineering
decks. Here the challenges are mainly related
consultants are suing each other for patent
to optimising the stressing sequence of
infringements.” Instead, the decision was
the cables to the geometrically non-linear
taken to publish. He regards it as very positive
behaviour of the structure, and to dynamic
that the sector promotes a collaborative
problems such as wind-induced vibrations
environment, where people want to discuss
and seismic events. It is natural that wind-
and share the work they’ve done.
load effects would be greater on longer span lengths of cable-supported bridges, she says.
Technology As bridge engineers design ever longer spans,
These phenomena include vortex shedding and the lock-in, across-wind galloping and wake
they typically depend on highly sophisticated
galloping, torsional divergence, flutter, and
strength steel than the current 1,860MPa:
analysis models to use in the process. Vanja
wind buffeting.
there are fabricators who want to push this to
Samec, global director bridges at Bentley
something like 2,200MPa. The steel is harder
Systems, points to the issues involved for large
printing. “It’s going to change our industry in
to produce - and more expensive - but for the
prestressed concrete and composite bridges
a very big way,” predicts Nader. Being able to
big bridges, wind is more of a controlling factor
built using the incremental launching or free
go from the computer to printing the bridge
and there is definite interest in keeping the
cantilevering methods. The challenge is to
would bypass a major part of the contracting
diameters of cables down, he says. However,
model accurately the erection process, while
process. It may not happen within our lifetimes,
the product would need to be economical,
considering different construction stages,
but could happen someday.
technology advances.
Meyer too is seeing a move to go for higher
Another area of IT development is in 3D
which may not be possible if the volume is not there.
TYPE TALK
Patenting ideas The long-span bridge engineering fraternity has traditionally been very open with regard to sharing details of innovations developed for projects. Deciding what to patent is difficult. “We are patenting technology – but we are being quite careful about it,” says Matt Carter, Americas long-span bridge leader at Arup. “We are not going down the line of patenting everything in sight.” One idea on which Arup does have a patent, jointly with GS Engineering, involves earthanchored cable-stayed bridges. The system enables thinner steel plates to be used for very long spans. “We felt there were good arguments for cable-stayed bridges up to the 1,400m kind of range, and we felt that the technology that really works well at that range was to build partially earth-anchored cablestayed bridges,” says Carter. But publishing rather than patenting was the choice for an innovative idea that was developed at the time of bidding for the Izmit Bay Bridge (see page 30), which Arup didn’t
W
hat counts as a long span naturally depends on the type of the bridge. Acrow Bridge recently supplied two bridges to a flood-damaged area in the Himalayas. The bridges were customised with modular components to address local conditions and had clear spans of 60m and 80m. Such bridges can be operational in days, with minimal construction machinery and using unskilled labour, says Acrow Bridge president Bill Killeen. “In remote areas such as this, building a modular steel bridge on site is often the best option, since constructing a conventional bridge of a long length in-situ is most likely not feasible due to challenging topography,” he says. Substandard road conditions also make it difficult to transport heavy highway construction equipment or materials to site. In contrast, the components for the Acrow structures were shipped in standard ocean containers, which were then loaded onto compact trucks with a length of 6.5m.
win. The concept involves a way of seismically
23
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www.acrow.com
[email protected] +1.973.244.0080
For over 60 years, Acrow has been creating and restoring transportation lifelines under extreme circumstances. In the spectacular foothills of the Himalayas, pilgrims make the annual trek to a Temple at 3,700 meters. Damaging floods cut off the route to the temple. Acrow supplied a clear span modular bridge with components customized for local conditions. Installed in a matter of days, with minimal construction machinery and unskilled labor, locals are able to make the pilgrimage again.
©2016 Acrow Corporation of America
LONG-SPAN BRIDGES
HÅLOGALAND BRIDGE, NORWAY Norway’s low traffic
volumes and local topography have led to creation of a stunningly slender structure
A
new suspension bridge with distinctive A-shaped towers and an unusual cable arrangement is taking shape over the Rombak Fjord near Narvik in northern Norway. Hålogaland Bridge’s 1,145m main span will
26
make it one of the longest in Europe, though it is certainly not among the widest of the world’s major suspension bridges as the main span’s steel box girder deck measures just 18.6m across. It is also notable for its A-shaped towers, the form of which has
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governed the unconventional arrangement of the cables and hangers. As a result, the bridge will be the longest in the world with a spatial cable system: its main cables will follow an oval shape in the horizontal plane and the hangers will be slightly inclined in the vertical plane. Client for the scheme is the northern region of the Norwegian Public Roads Administration, Statens Vegvesen. The bridge is typical of Norway’s crossings of deep and wide fjords, in that traffic levels are relatively low and so it will carry just a single traffic lane in each direction, as well as a 3.5m-wide walkway. The towers have been designed very much with aesthetics in mind. “What we always try to do is to take advantage of the special conditions at the site and in this case it was natural for us to choose an A-shaped tower,” says architect Poul Ove Jensen, bridges director at Dissing & Weitling. The choice suited the requirement for an attractive structure, but decisions aren’t taken for aesthetic reasons alone, he stresses. Design should take account of a site’s specific requirements, rather than trying to invent some dramatic forms, which often lead to very contrived results. “In this case – a long span bridge with an extremely narrow deck – it was quite a logical concept.” It is not a solution that would work everywhere. “For a conventional suspension bridge, it would be difficult to have A-shaped towers because of the very wide deck,” says Assad Jamal, chief project manager for international bridges at Cowi. At the start of design, members of the team went to visit the site. “By the end of the week, we had the concept,” recalls Jensen. An H-shaped tower didn’t look very good, given the tall height and narrow width needed; and a central tower between traffic lanes was out of the question with the twolane road. The design team quite quickly came to the conclusion that the A-shape was right. Two separate contractors are building the bridge, with Sichuan Road & Bridge Group responsible for the steelwork – deck
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and cables – and NCC for the concrete.
By March 2016, construction of both of the concrete towers had been completed, and the catwalk installation, which will take about three months, had just begun. Installation of the prefabricated main cable is due to start at the end of July. The tower design has dictated the layout of the rest of the structure, in particular the unusual spatial arrangement of the cables and hangers. The two main cables meet at saddles on a narrow support on the top of the towers, splaying out at the centre of the bridge. As a result of this alignment of the main cable, the bridge’s hangers are slightly inclined. In terms of stability of the bridge subjected to traffic load, this has minor but beneficial effect in regards of wind stability, says Jamal – though it did mean that additional load cases had to be considered. Having the A-shaped towers poses extra challenges for installation of the cable system; a special construction sequence is needed to obtain the correct shape, beginning by allowing the two main cables to hang vertically during air spinning. Initially,
28
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there will be a single common catwalk between the two main-span cables. The next step will be to displace the main cables horizontally using an hydraulic strut system to create the oval shape, with struts at 16m centres. “The struts need to span approximately 16m at the centre of the main span, and they need to be able to telescope outwards by using a hydraulic system,” explains Jamal. The hangers can then be installed and the deck erected, before the struts are removed. The saddles are at the top of the towers, and the shape of the towers means that the saddles are very close together. As they are so close together, there is an influence on how the loads are distributed between the side span and the main span cables: where a conventional suspension bridge tower will twist for uneven main cable loading in the main span, this is not the case for Hålogaland Bridge. The towers do not twist, which means that the loads of the back span cables are shared evenly. The ratio of span length to tower height above deck for the bridge is 1:9; the ratio of
LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES
main span length to the distance between the cables is 90, while typical values for suspension bridges are in the range 5560, explains Jamal. This combination of a slender bridge with a long main span posed considerable design challenges in order to fulfil the requirement of ensuring aerodynamic stability at 63m/s at bridge deck level. The aerodynamic stability was verified through numerical analyses and wind tunnel tests; this showed a critical wind speed of 68m/s. The bridge’s box section deck is arranged with a slope of 15.8° of the lower inclined side plates relative to the horizontal bottom plate, says Jamal. Wind tunnel tests carried out in smooth flow proved that there will be no vortex-induced vibrations, thus saving the potential costs of installing and maintaining any mitigation measures.
be an architectural feature; their internal lighting will be the only strictly nonfunctional feature on the bridge, admits Jensen.
Each tower is topped with a ‘tower house’; a naturally-ventilated structure designed to enclose them the cable saddles and give extra protection. They will also
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LONG-SPAN BRIDGE SUPPLEMENT 2016
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29
LONG-SPAN BRIDGES
IZMIT BAY BRIDGE, TURKEY One of two major bridges currently being built in Turkey is a long-span suspension bridge which forms part of a new 420km-long motorway in the north of the country
deck of the new bridge. The 235m-tall towers have two legs and two cross beams; and the legs measure 7m by 8m in cross section at the base. The suspended deck is a single, orthotropic box girder that is 30m wide and 4.75m deep and has a 2.8m-wide inspection walkway attached to each leg. The main cables on the main span have been formed from 110 prefabricated parallel wire strands each made of 127, 5.91mmdiameter cable wires with a breaking strength of 1,760MPa. The main cable on the side spans has two extra strands of the same size. Hanger ropes are of parallel wire strand, typically formed of 133, 7mm-diameter wires with a breaking strength of 1,760MPa. They are connected to a cable clamp at the top and hanger anchorage at the bottom. The side spans flanking the 1,550m main span are each 625m long, giving a total suspended deck length of 2.8km, which is continuous between the two side-span piers. A key design change was made early in the project following ground investigations by Fugro that showed a potential fault at the planned location to the south anchorage. This led to the anchorage being moved 138m to a safe zone, reducing the main span from the originally planned 1,688m. The structure is a central part of the 420km-long Orhangazi-Izmir motorway project, which is being developed by Nomayg,
longest suspension spans is nearing
A
very active and where a major earthquake
carry the new link across the Sea of Marmara
completion in Turkey. Izmit Bay Bridge,
occurred on the North Anatolian fault in 1999.
at the Bay of Izmit in northern Turkey.
which has a 1,550m main span, is being built
Seismic issues have placed considerable
by IHI Infrastructure Systems and Itochu.
additional demands on the design.
The team was given notice to proceed in September 2011 and the bridge is set to open
year with the erection of three 51.2m-long
in May this year – a very short period for such
segments at each of the towers. A floating
a major crossing.
crane was used for installation of the initial
new bridge with one of the world’s
The project had been on track for completion in the first quarter of this year, but
30
The bridge is in a region that is seismically
Deck erection began at the start of this
a consortium of six companies. The bridge will
Read our full feature about Izmit Bay Bridge in Bd&e issue no 83
segments at locations including the towers
suffered a setback last year when the catwalk
and the ends of the side spans, with the remaining deck segments positioned by a
collapsed in March just as the contractor was
lifting device mounted on the main cable.
preparing to start erecting the main cable.
Detailed design of the bridge has been
Luckily bad weather had halted work that
carried out by Cowi, with Dissing & Weitling
day and no-one was injured; the catwalk was
as the project architect. CH2M performed
completely reconstructed and ready for use
the independent design check. Steel has
by August.
been used both for the main towers and the
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LONG-SPAN BRIDGES SUPPLEMENT 2016
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LONG-SPAN BRIDGES
QUEENSFERRY CROSSING, UK The world’s longest three-tower cable-stayed bridge is reaching completion in Scotland
A
Queensferry when it opens.
over the Firth of Forth near Edinburgh in
viaducts, the bridge has a total of 14 spans, three concrete single-leg towers which
Scotland. Design and construction of the
are on the centre-line of the transverse
reinforcement and embedded into the massive 25,000m3 concrete bases formed
new Queensferry Crossing began almost five
cross-section, two planes of stay cables
by using 1,219t steel caissons sunk to the
years ago and the bridge is on track to be
anchored along the centre of the structure
Forth’s seabed (Bd&e issue no 70) .
completed by spring 2017.
and a composite steel and concrete deck
landmark cable-stayed crossing is in its final year of construction alongside two other famous bridges
The new bridge will take the record for the world’s longest three-tower cable-stayed
superstructure.
at the base to just 5m by 7.5m the top. The towers are integrated onto structural foundations through heavy vertical
The focal point of the visible bridge is the cable-stayed section which makes up just
The three bridge towers reached
over 2km of the total 2,638m of the main
bridge and it will also be the UK’s tallest
full height at the end of 2015, marking
crossing, including the twin main spans of
bridge. Queensferry Crossing will itself
a key milestone for the project team.
650m supported by the three main towers.
provide reasons enough for people to visit
The reinforced concrete towers start at
the area when it opens next year - but it also
bedrock nearly 40m below the water. The
The bridge has a multi-cell steel box girder design with a composite reinforced and post-
stands alongside one of Europe’s longest suspension spans, the Forth Road Bridge,
middle tower is a height of 210m, while
tensioned concrete deck; a parallel strand
the flanking towers are each 207m tall.
system is used to anchor the deck girders to
and close to the historic Forth Bridge, which
The towers are roughly rectangular in
the towers.
carries railway traffic.
cross-section, with the east and west sides
Forth Crossing Bridge Constructors,
33
Including the north and south approach
Deck construction began with the erection
curved and the north and south sides
of temporary falsework at each tower to
a joint venture of Hochtief Solutions,
(where cable anchorages are located)
accept four starter segments. The starter
American Bridge International, Dragados
inclined. They were built in 4m sections
segments contain more steel and concrete,
and Morrison Construction, is responsible
using climbing formwork, with a total of 54 lifts per tower. Each of the 54 tower
making them heavier, and so were erected
for designing and building the cablestayed bridge which will create a new link
lifts had a slightly different profile, as the
the concrete decks to be cast in situ. For the
between South Queensferry and North
hollow structure tapers from 16m by 14m
rest of the units – the typical segments –
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on the temporary falsework in order to allow
LONG-SPAN BRIDGES SUPPLEMENT 2016
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LONG-SPAN BRIDGES
the concrete deck is cast onto the steel tub
bridge construction. This achievement will be
segments. The temporary tie-downs will be
girders at the casting yard in nearby Rosyth
assisted by the use of a system of temporary
disengaged after the flanking tower fans are
Docks. Segments are then fitted out with
tie-down cables beneath the superstructure.
closed to their anchor piers and the central
mechanical, electrical, and inspection walkway
The temporary tie-downs comprise four
tower fan is fully erected. When the central
components, before being transported on to
stay-cable pipes and strands similar to the
tower is at full cantilever it is fully balanced and
the ballasted delivery barges. The two delivery barges, which can each
bridge’s permanent stay system. There are four tie-down cables at each tower with their lower
the tie-downs will no longer be required. When the temporary tie downs are removed, the
carry three completed deck segments,
anchorages located behind a mass concrete
holes in the segment soffits will be closed with
are towed approximately 3km from the
block anchorage chamber that was cast into
welded plate and the tower penetrations - along
yard to the site. The barges are anchored
the bottom of the towers during the initial lifts.
with the anchor chamber – will be filled with
into position below the specially-designed
The tie-downs penetrate the tower walls and
concrete.
erection travellers, which lift the segments
run up through the soffit of the deck segments
– weighing on average 750t - to an elevation
approximately 90m and 106m from the tower
See our full article about the bridge
of approximately 60m above the water. Once
centre-line. They anchor into temporary
construction in issue 83 of Bridge design &
the segments reach road elevation, the global
anchor beams fabricated into the permanent
engineering.
geometry is established and fixed, allowing the welders to begin work. As soon as the top flange welds of the steel girders have been approved, the in situ concrete stitch can be formed and poured. The stay-cable pipes can be lifted at the same time as the stitch pour, with strand installation following. The segments must be erected at each tower following the balanced cantilever method, so that each side is never more than one segment ahead of the other. The 12 starter segments at the towers were erected in autumn 2014, while erection of the 110 typical deck segments began in September 2015. In their most extended position, the central tower fans will create what is claimed to be the world’s longest balanced cantilevered
LONG-SPAN BRIDGES SUPPLEMENT 2016
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35
LONG-SPAN BRIDGES
GERALD DESMOND BRIDGE, USA
Long-span bridges in earthquake zones pose specific challenges as demonstrated by a cablestayed bridge in California
Every shear link needed a diaphragm connecting into it; small, confined spaces result. After an earthquake all the shear links would have to be replaced. “In the tender, we came up with an alternative, which was to seismically isolate the superstructure and make the tower a fairly standard reinforced hollow section,” he says. eismic issues have been influential in the In an earthquake, each 152m-tall tower “pretty design of the Gerald Desmond Bridge, much does its own thing,” Carter says. It is which is under construction in the US state very tall, quite slender and flexible; during an of California. earthquake the tops are designed to deflect up The US$1.467 billion project is sponsored by to 1.8m. Meanwhile, the superstructure is isolated Caltrans and the Port of Long Beach, a major and would more or less remain unmoved. This container facility. It is a replacement for the approach reduces the cost and makes it easier to existing bridge which has the typical litany of construct, he says. After an earthquake, all that woes; not having enough traffic lanes, severe needs to be done is to reset the viscous dampers. maintenance problems and seismic deficiency, as Such design and build contracts challenge well as being too low for post-Panamax ships. engineers to innovate, says Carter. Seismic The replacement will be 3.2km long, isolation is not new – but bridge codes do take including the 610m-long cable-stayed bridge time to evolve. The seismic codes are written that will improve clearance both vertically and assuming a traditional ductile approach, with horizontally. controlled damage. A design and build contract was awarded in July A project-specific test specification was 2012 to Shimmick Construction, FCC Construction needed for the system. At each tower, there and Impregilo, with Arup as design lead. The need to be dampers in both longitudinal and towers are currently under construction, having transverse directions, and also at the piers at the reached about 37m in height as of March 2016. end. Everything was sub-divided into multiple The reference design was carried out by a parallel units to cater for the large forces. “If you Parsons/HNTB team that included Dissing & just did it with a single damper it would be too Weitling. The concept fits the proportions of big for any test facility,” says Carter. The solution the site very well and is a good solution, says was to split it into six longitudinal dampers at Americas long-span bridge leader at Arup, Matt each tower, and three transverse. At the end Carter. The key question was how to make the bents, there are four longitudinal and two towers seismically safe. The reference design transverse, giving 30 dampers in total. had multiple elements, with shear links between Catering for the design earthquake wasn’t the them. The difficulty was that it would have been end of the process. “In seismic isolation there expensive and time-consuming to build, he says. is always the question of what would happen if
S
36
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the earthquake is a bit bigger,” adds Carter. To address this, structural stops will prevent the dampers from reaching the end of their stroke even if ground motions exceed design values. An earthquake would have one or two big peak cycles at the start, then maybe half a dozen secondary cycles. “If you had a situation where the damper bottomed out and got damaged it might not perform properly in the rest of the earthquake,” says Carter. A complex fully non-linear time-history model has been run to prove that the superstructure doesn’t hit the towers and the dampers all stay within their operating limits under the 1,000-year design earthquake – the safety evaluation event. But if a bigger earthquake comes along, the system has been deliberately engineered so that the superstructure actually hits the tower. The gap between the tower and superstructure is 760mm but the dampers are given 810mm of stroke capacity. There would be some localised damage of the concrete, but the impact would protect the dampers, says Carter. Arup increased the ground motion by 25% in its time-history analysis model and saw this behaviour happening – some repairable damage, but adequate global performance. Tell-tale strips on the outside give an instant visual check on whether the damper has stroked or not for the post-earthquake inspection. In addition, the dampers are fused with bolted O-rings that transfer the wind load when there is no earthquake. In an earthquake, the O-rings are designed to shear, allowing movement. The design also has to ensure that the bridge is safe for traffic without the fuses, so that it can be reopened straight after an earthquake.
LONG-SPAN BRIDGES SUPPLEMENT 2016
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LONG-SPAN BRIDGES
E39 ROUTE, NORWAY
Ideas for super-span and new types of bridges are being explored by engineers working on the ferry-free E39 project in Norway
ne project currently attracting much
O
Bergen, where water depths are up to 550m.
such as aerodynamics and hydrodynamics
interest in the long-span bridge sector
It could be crossed by a floating suspension
will be in demand. “We will use these studies
is the E39 route in Norway, which will
bridge, another style of floating bridge or by
as a way of building up the competence in the
require enormous investment to replace eight
a submerged tube tunnel, suspended perhaps
consultant market,” adds Eidem. “Nobody has
ferry services with fixed links over fjords.
20m or 30m below pontoons at the surface.
built structures like this before. It’s a first both
Creating the 1,100km ferry-free route from
for us and for the consultants.”
part of a plan that is being developed. “In
reduce journey times by up to nine hours. But
that plan we will make a proposal to move
with offshore engineering in areas such as
the fjords pose daunting barriers; in places the
forward with one or two concepts,” says
anchoring in deep water. “For us it is absolutely
water is 1,200m deep and they are typically several kilometres wide. Potential options
Mathias Eidem, project manager for the fjord crossing project at Statens Vegvesen – the
necessary to adapt things from the offshore industry – we don’t want to reinvent the
for crossing them include floating bridges
Norwegian Public Roads Administration. Costs
wheel,” says Eidem. Bridge concepts include
that introduce many new challenges in both
for the construction, as well as operation and
a multi-span suspension bridge supported by
analysis and construction.
maintenance of each option, are now being
tension leg platforms, used by the offshore
firmed up. “We should be able to make an
industry in great water depths.
informed decision over the next two months,” he says.
concepts under consideration for Bjørnafjord.
The dates for the project are still to be confirmed but should become clearer during the approvals process for Norway’s latest transportation plan, which was published in draft form in late February. One of the most challenging crossings along the route is the 5km-wide Bjørnafjord south of
38
The options will soon be narrowed as
Kristiansand to Trondheim is expected to
Ahead of design contracts, Statens
The work combines bridge engineering
Cowi is involved with two of the three Tina Vejrum, Cowi’s vice president for
Vegvesen will be issuing tenders for further
international major bridges, says that the
studies to develop areas of engineering that
project raises a lot of interesting issues such
need to be understood. Specialists in fields
as how to combine wind loading and wave
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LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES
loading, and how to deal with construction challenges, durability in the harsh environment and the deformations of these flexible structures. A primary requirement is to have a navigation span – a first for floating bridges, says Vejrum. So far, floating bridges have only been built close to the water but for Bjørnafjord there will need to be a clearance of perhaps 45m to 50m. A wide field of expertise is needed to address the challenges and Cowi is working in a group consisting of both bridge and offshore engineers, as well as specialists in geotechnics and architecture. The team includes AasJakobsen, Johs Holt, Global Maritime, NGI, Skanska and L2 arkitekter together with Cowi. The key challenge in designing the bridge is
the combined effect of waves and wind, says Sverre Wiborg, Cowi’s chief specialist/project
manager for bridges and construction. The bridge has a large number of eigenmodes
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LONG-SPAN BRIDGE SUPPLEMENT 2016
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39
LONG-SPAN BRIDGES
projects commissioned by Statens Vegvesen, looking at everything from ship impact to the potential use of fibre-reinforced concrete or graphene. “One of the main challenges of designing long floating bridges, such as the crossing in Bjørnafjord, is the dynamic response due to wind and wave loading,” says Vanja Samec, global director bridges at Bentley Systems. “This response can be predicted in the timedomain using newly developed functionality in RM Bridge.” She adds that Bentley Systems Austria and TDA Cowi have collaborated to develop the project (Bd&e issue no 82). Non-linear time-domain analyses are needed to predict the bridge response from wind and wave loading with sufficient accuracy. This is due to the non-linearity of the structural system and the coupling between wind and below 1Hz, and several of them are in
the vessels visiting the fjord is limited, says
wave loading, which is challenging to model
the same area as the periods of the waves,
Wiborg, but still the bridge has to withstand
correctly in the frequency-domain. “A time-
both swell and wind-generated. As a result,
substantial impact loads. “We have executed
domain analysis model of the bridge has
calculating the dynamic response of the bridge
both local design calculations of pontoons and
been developed, which includes both the
is particularly challenging. Another issue is ship collision. The size of
girders as well as global response calculations of the entire bridge,” he adds.
hydrostatic and hydrodynamic properties of
Analysis of the construction phase and HIGH IN FIBRE The E39 project has certainly captured the imagination of the engineering community. A team from Royal Haskoning DHV and IGWR worked in their own time to explore whether fibre-reinforced polymers could be used on a project of this scale. The team looked at whether it would be possible to use FRP for the cables and deck of a 3,700m-span suspension bridge with floating piers. The work, which was presented at the IABSE conference in Geneva in September 2015, was not commissioned by the Norwegian government. “We did it to promote fibre-reinforced polymers,” says Kees van IJselmuijden, infrastructure advisor at Royal Haskoning DHV. “We wanted to show that it was possible.” The team concluded that such a bridge would indeed be possible; that the concept would work, once practice catches up with the theory. Clearly the result of the project is not a full design; it has not been optimised and nor has it been subjected to a full dynamic analysis. “We tried to do as much as possible in FRP - but it doesn’t mean we have to do it all in FRP,” adds van IJselmuijden. For instance, it was decided to exclude the cross-beams, opting instead for 30m-long sections of FRP deck, supported by a steel cross-beam.
40
the floating elements,” she says. Wave loading is represented as force-time histories in all six
marine operations is the focus of the third
degrees of freedom for each floating element.
major challenge. In particular, assembling
Wind loads are modelled using wind speed
the floating part of the bridge on site will be
time histories as input.
difficult.
“The results of this study show the
For a floating suspension bridge with
importance of coupled aerodynamic and
tension link platforms, the links would need
hydrodynamic analyses of floating bridge
to be anchored to the bottom of the fjord and
concepts,” says Samec. “Many of the load
the geotechnical conditions are challenging.
effects and responses considered in this
The other bridge idea would have a navigation
project would not be possible to analyse in
span about 450m wide. A cable-stayed bridge
frequency domain. With this in place, RM
is probably the most likely, says Vejrum.
Bridge will be able to analyse suspension
The crossings are very different to what
bridges in time domain, with all important
has gone before and not surprisingly the E39
structural, functional and environmental load
project is supported by a range of research
effects included.”
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LONG-SPAN BRIDGES SUPPLEMENT 2016
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LONG-SPAN BRIDGES
MERSEY GATEWAY, UK
Multi-span cable-stayed bridges make it possible to build longer crossings with more modest spans, but articulation is an issue that must be addressed
T
he Mersey Gateway project is a 2.3km long, six-lane tolled crossing of the Mersey River, which will create a new link to Liverpool, north Cheshire and the north west of England. The main crossing will be a four-span, three mono-tower, cable-stayed structure with a total cable-supported deck of 998m carrying six lanes of traffic. The 80m-high central tower will be shorter than the two outer towers, which will be 110m high and 125m high. A central plane of cable stays will support the single post-tensioned concrete box – which has a structural depth of approximately 4.6m – at 6m centres. Deck forces are transferred to the stays by way of internal steel bracing system and integral/monolithic horizontal shear connections. The client for the project is Halton Borough Council, operating through the Mersey Gateway Crossings Board. The bridge is being designed, built, financed and operated by Merseylink, whose contractors are FCC Construcción, Kier Infrastructure & Overseas
42
and Samsung C&T Corporation. Flint & Neill is leader of the design joint venture, working with URS. CH2M is technical and contractual advisor to the MGCB for the delivery. There has been close collaboration between the designers and the concession company that will operate the bridge for the first 30 years of its life, says Paul Sanders, a director of Flint & Neill. Designers always want to consider operation, he says, but don’t always have the operations and maintenance company available when developing the detailed design. The choice of a concrete deck was mainly dictated by two factors - speed of construction and the difficulties of access over the estuary. But elimination of repainting was another factor considered as regards future maintenance. The bridge will have an integrated structural health monitoring system, which will also include measurements carried out using optical survey and manual techniques to supplement the inspection regime. The
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system will provide data on the day-today in-service behaviour of the structure incorporating stable long-term baselines for measurement. Furthermore, it will permit the early diagnosis of any problems. Close integration between design and construction has also been a feature of the project. “A lot of money goes into the ground on a project like this and you need to spend a lot of time looking at the foundation solutions to make sure that you pick the right option,” says Sanders. The solution adopted for the estuary foundations of the three towers involves large spread footings. It is a simple solution, but quite ambitious, he says, and each of the foundations is about 20m in diameter. Structurally, it is a very efficient solution and it allows open excavation - in this case inside a substantial, double-skinned temporary cofferdam (Bd&e issue no 81). Earlier studies indicated that the estuary’s primary channels have been moving back and forth over the decades; it was important not to restrict this. A key benefit of the chosen spread footings is that they are buried beneath the lowest bed level, so there is only a minimum cross-section of column projecting into the water. This minimises the possibility of the water channel ‘latching on’ to the bridge supports and losing its natural tendency to move over time. The location of foundations was restricted to three specified zones, allowing the precise configuration to be optimised to suit the design and construction methods. “We wanted to make sure that we could have a balanced cantilever extending out from each tower,” explains Sanders. “That effectively dictated the span arrangements.” The main spans are 318m and 294m while the back spans are 181m and 205m. Any cable-stayed bridge with a three-tower arrangement will give rise to some challenges in terms of anchoring the back spans, says Sanders. The constraints on the positions of the foundations in the estuary made it more challenging, as anchor piers couldn’t be introduced. As a result, large bending effects in the deck have had to be dealt with.
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SPONSORED PROFILES Contents
Advertisers' index
Page
Company
Website
Page Company
Website
44-45
Acrow Corporation of America
www.acrowusa.com
02
Arup
www.arup.com
46
American Bridge Company
www.americanbridge.net
07
American Bridge
www.americanbridge.net
47
Arup
www.arup.com
09
Deal S.R.L.
www.deal.it
48
BSI Group
www.bsigroup.com
13
TENSA
www.tensainternational.com
49-51
Bentley Systems
www.bentley.com/bridges
17
Barin
www.barin.it
52
DYWIDAG Systems
www.dsi-posttensioning.com
19
Bentley Systems
www.bentley.com/bridges
22
Cimolai
www.cimolaitechnology.com
International GmbH 53
Soletanche Freyssinet
www.freyssinet.com
24-25
Acrow
www.acrowusa.com
54
Lindapter International
www.lindapterusa.com
27
Soletanche Freyssinet
www.freyssinet.com
55
Mabey Bridge Ltd
www.mabeybridge.com
29
Redaelli Techna S.p.A.
www.redaelli.com
56
Maurer Söhne
www.maurer.eu
31
Maurer Söhne
www.maurer.eu
57
PERI
www.peri.com
32
DYWIDAG Systems
www.dsi-posttensioning.com
58
LARSA
www.larsa4d.com
LONG-SPAN BRIDGES SUPPLEMENT 2016
International GmbH 34
Bridge design & engineering
www.bridgeweb.com
37
Mabey Bridge Ltd
www.mabeybridge.com
39
BSI Group
www.bsigroup.com
41
FIP Industriale S.p.A.
www.fipindustriale.it
59
LARSA
www.larsa4d.com
60
PERI
www.peri.com
www.bridgeweb.com
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LONG-SPAN BRIDGES SUPPLEMENT
S E L I F O R P Y N A P M O C
ACROW BRIDGE 181 New Road Parsippany, New Jersey 07054-5645 USA t: +1 973-244-0080 f: +1 973-244-0085 e:
[email protected]
Building Bridges. Connecting People.
www.acrow.com
ACROW For over six decades, Acrow has provided cost-effective permanent and short-term modular prefabricated bridging solutions that ensure fast and easy bridge assembly and installation, requiring minimal heavy equipment, from rural towns and villages to large cities and urban centres in the US and around the globe Infrastructure development
A
crow’s prefabricated steel bridges offer a number of advantages over other bridges. First, the steel parts are galvanised to withstand severe weather conditions and are virtually maintenance free. Second, their modular design allows for easy customisation to meet specific requirements as well as fast installation - in one to four weeks - using minimal equipment. Both factors allow Acrow bridges to be erected in environmentally-challenging locations. Internationally, Acrow’s training of local labour provides a transfer of knowledge and skills that help with the creation of a country’s next generation of engineers and technicians. With a North American customer base ranging from federal agencies to state and provincial transportation departments as well as highway contractors, and an international customer base of government agencies along with a wide spectrum of extractive and utility companies, Acrow has deep experience in designing and engineering bridge solutions to meet even the most complex site constraints.
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The demand for Acrow’s modular bridges is truly global On the African continent, over decades, Acrow has been involved in the design, supply and construction of more than 1,000 bridges – across more than 20 countries – that connect people in rural and urban communities while facilitating regional and international trade. In Peru, Acrow has worked extensively with government partners to provide permanent replacements for aging structures as well as new connections. In the past two years, Acrow has supplied some 300 bridges as part of a major presidential initiative to improve the country’s bridging network, connecting regional communities to the main arteries of transport. Financed development projects Acrow understands that funding for infrastructure development projects is often a key issue, particularly for international projects. As a recognised project leader, Acrow is able to leverage its relationships with major international financial institutions, as well as export credit agencies, to facilitate the process of structuring competitive financing that not only covers the Acrow bridging, but also assists with the local civil works and installation activities associated with the successful implementation of the project. North America As the need for infrastructure maintenance and replacement has increased
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America, engineering drawings in compliance with owner specifications, on-site engineers to oversee bridge installation and return delivery upon completion of a project. Acrow maintains a substantial stock of bridge components for assembling any size bridge up to four lanes wide, with service and storage facilities strategically located for rapid response and service to customers in North America. For a recent project in Wyoming, an Acrow bridge replaced an overpass that had collapsed onto railroad tracks below during heavy flooding of a nearby river. The collapse created an immediate stop to the passage of daily train and vehicular traffic. Because of the easy assembly and installation of the Acrow bridge, the project was completed in three weeks. Increasingly, governments are planning ahead for natural disasters. In addition to the structures supplied to Peru under the president’s initiative, 41 Acrow bridges were ordered ahead of the anticipated impact of a particularly damaging El Niño rainy season. In the US, Florida maintains many Acrow bridging components for use during planned construction and to improve traffic flow in the event of an emergency evacuation due to hurricanes. dramatically in North America, Acrow’s prefabricated modular bridging is seen as an ideal cost-effective solution for permanent applications as well as detours to maintain traffic flow during construction or repair of existing structures. The structures can be engineered to support heavy loads, including rail traffic, and constant truck traffic year in and year out. Because they can be assembled and installed quickly, they are also a perfect solution for emergency projects. The use of detour bridges has grown significantly as more contractors use them to stay on or ahead of schedule and control costs, while providing a safe and dependable route for traffic. Acrow bridges, rented and used as temporary detours, address many important issues during highway and road construction. By providing a temporary roadway that is predictable and unchanging, traffic disruptions are significantly reduced while the safety of motorists and construction workers is greatly improved. This is a safer, faster and more economical alternative to ‘phased’ construction in which lanes are moved as needed to divert traffic through work sites. During a 2015 culvert replacement in Ryegate, Vermont, for example, two Acrow bridges were rented to enable uninterrupted traffic flow during the construction. Without the interim structures, both vehicular and railroad freight traffic would have faced unacceptably long detours.
Emergency projects/emergency preparedness Acrow’s rental bridge services include quick delivery to most points in North
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Aging infrastructure A significant challenge during the repair and maintenance of aging infrastructure is maintaining the flow of traffic, and a cost effective and efficient way to do this is by installing temporary detour bridges. Acrow’s modular prefabricated bridges are ideally suited to this and can be either rented as needed or purchased for unlimited repeat usage. In addition to bridges, Acrow’s Superprop shoring systems are an excellent choice to consider for projects such as bridges undergoing seismic retrofits or to support excavations. Acrow’s shoring components can support up to 270t on a single leg.
Historial bridge rehabilitation Although a very small part of the bridge repair market overall and often posing particularly difficult engineering challenges, Acrow is proud to have been involved in many projects to restore historically significant bridges. In addition to having been used during renovations on wood covered bridges, in 2015, for example, an Acrow bridge was installed as a detour structure in Hawaii during repairs to a century-old steel girder bridge, and more recently, three Acrow support and bridge structures are being used innovatively during the on-site restoration of a 96-year-old truss bridge in Minnesota.
www.bridgeweb.com
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LONG-SPAN BRIDGES SUPPLEMENT
S E L I F O R P Y N A P M O C
AMERICAN BRIDGE COMPANY 1000 American Bridge Way Coraopolis, PA 15108, USA t: +1 412-631-1000 f: +1 412-631-2002 e:
[email protected] www.americanbridge.net
AMERICAN BRIDGE
S
ince its inception in 1900, American Bridge Company has held a laser focus on delivering the world’s most challenging bridges, marine works, and complex structures. The company’s central cultural tenet is to relentlessly develop and apply advanced construction engineering and methodology that supports safer, more efficient delivery. Throughout the company’s history, self-performing critical construction and erection work components in the field has become a hallmark of a true ‘AB project’. American Bridge has constructed many of the world’s notable bridges including the San Francisco – Oakland Bay Bridge (1936), the Mackinac Straits Bridge in Michigan (1957), the Verrazano Narrows Bridge in New York (1964), The Angostura Bridge over the Orinoco River in Venezuela (1966), the 25th of April Bridge in Lisbon, Portugal (1967), and the Sunshine Skyway (cable stay) Bridge in Tampa Bay, Florida, (1987). Founded as a JP Morgan-engineered merger of 28 bridge and structural companies, AB immediately operated on an unprecedented scale. American Bridge established the practicality of steel as the basic product in large scale infrastructure including bridges, buildings, power and water transmission, and military facilities. As a result, its dozen or so factories, hundreds of construction engineers, and thousands of skilled workers played a dominant role in the development of the infrastructure of the United States and many other countries. Operating as a part of United States Steel Corporation from 1901-1987, American Bridge had significant roles in the establishment of the railroad networks of the United States, Kenya, Alaska, Brazil, Norway, Korea, Panama, Peru, Mexico, Japan, Columbia, Guatemala and the Philippines. It supplied more than 607,000t of fabricated steel for the
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construction of New York City’s subway system between 1913 and 1931 – an average of 33,000t per year. In the early 1980s AB’s parent (US Steel) split the fabrication and construction operations, with the construction company retaining the name. In 1987, US Steel sold American Bridge to two investors, who focused mainly on equipment divestiture and high rise structural steel erection. In 1989, the current ownership purchased the company. By the early 1990s, American Bridge had become a shadow of its former self. Negatively affected by difficult economic conditions and a series of new CEOs with different strategic directions, revenues had dropped to about US$30 million by 1993. Ownership recruited the current company leadership in 1993 and has steadily rebuilt the brand. Major bridge project successes (Williamsburg Bridge reconstruction, Tagus River Bridge reconstruction, Lions Gate Bridge reconstruction, Woodrow Wilson Bascule Bridge) combined with numerous smaller ones were instrumental in this rebuilding. Moreover, the successful entry into marine construction and the greater involvement in complex concrete construction have diversified and modernised the company. Through this rebuilding period the company consistently operated profitability. The company today has fully rebuilt its technical capability, and is financially strong. Currently, American Bridge has numerous technically challenging bridge construction projects underway. This includes the recently completed US$1.7 billion main span of the new San Francisco Oakland Bay Bridge; the new US$1.3 billion Queensferry Crossing near Edinburgh, Scotland; and the ‘New NY Bridge’ – the Tappan Zee Hudson River Crossing. Today, American Bridge continues to build on more than a century of engineering and construction experience, and celebrates that history. AB’s business focuses on new construction and rehabilitation of movable bridges, steel truss bridges, cable-supported bridges, steel and concrete girder bridges, heavy marine, military, government and security infrastructure, and other structural projects that benefit from advanced construction engineering capabilities. Additionally, the company owns and designs equipment for a wide variety of heavy civil construction tasks. As American Bridge looks to the future, we will continue to develop our world-class in-house engineering, safety-first attitude, and unmatched culture of innovation to deliver legendary construction projects throughout the world.
www.bridgeweb.com
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ARUP 13 Fitzroy Street, London W1T 4BQ, GB t: +44 020 7636 1531 e:
[email protected] www.arup.com
ARUP
A
rup is a wholly independent firm of designers, planners, engineers, consultants and technical specialists offering a broad range of professional services principally in the built environment. Founded in 1946 by Sir Ove Arup, Arup has more than 13,000 people working in 92 offices in 40 countries and projects have taken Arup to more than 160 countries offices. Owned in trust on behalf of its employees, Arup is able to retain its independence, which sets it apart from other organisations. Ove’s background in contracting and first-hand experience with disparate and uncoordinated construction delivery systems led him to advocate the use of integrated multi-disciplinary design and construction teams, and this ethos is the driving force in the Arup approach to project delivery. Working in multi-disciplinary teams ensures coordination between the disciplines. Arup operates formal quality management systems, routinely reviewing and auditing the work. The project teams are structured to achieve clear lines of responsibility and communication with clients and others. Arup provides engineering and related consultancy services necessary to every stage of the project lifecycle. These are available to clients singly or in combination, to suit the particular circumstance of the project. Arup is committed to sustainable design, to its increasing incorporation in projects that it undertakes and to industry-wide sustainability initiatives. Throughout the world Arup provides a consistently excellent multi-disciplinary service, which also addresses the concern for the environment. In the field of bridge engineering Arup has worked for government and public procurement agencies, private developers and contractors and has experience in the design of new build, independent design checking and rehabilitation of all types of bridges; movable bridges, boutique footbridges, steel truss bridges, steel concrete and composite girder bridges, arch bridges, extradosed bridges, cable stayed bridges, suspension bridges. Known for innovation, creativity and pioneering, Arup has designed some of the world’s most recognisable and renowned bridges. Arup designed the award winning Hulme Arch Bridge in Manchester England which is the world’s first diagonal arch bridge and has been described as a ‘show-piece for the civil engineering profession’. For this work, Arup was awarded the UK Millennium Product Status. Arup has expertise in design of concrete, steel and composite cable-stay bridges and has designed award-winning bridges such as the double decker road and rail Oresund
LONG-SPAN BRIDGES SUPPLEMENT 2016
Crossing between Denmark and Sweden, and the twin-box Stonecutters Bridge in Hong Kong with its span of 1,018m which was record-breaking at the time. Arup has also designed cable-stay bridges on the Brunei Temburong Sea Crossing; Hong Kong Macau Bridge; Jizhou Bridge; the triple-tower Queensferry Crossing in Scotland with its world-record 2 x 650m spans and unique crossed cables; Gerald Desmond Bridge in Los Angeles, and Champlain Bridge in Montreal, all of which are currently under construction. In the last decade Arup has carried out detail tender designs for contractors on a number of suspension bridges including the 800m-span JeokgeumYeongnam Bridge and the 1450m-span Gwangyan Bridge, both in Korea, and the 1,550m-span Izmit Bay Bridge in Turkey. With significant expertise in designing for extreme events caused by seismic, wind and ship impact, Arup has pioneered the use of many new world-first technologies. On Stonecutters Bridge, Arup designed twin decks to cope with extreme typhoon winds and also developed centrifugal model tests to design for ship impact. On the Queensferry Crossing, Arup saved the bridge owner US$120 million by introducing the ‘As Low As Reasonably Practical’ (ALARP) approach to ship impact. This methodology set the risk acceptance criteria based on cost-benefit analysis comparing the quantified consequences of failure against the increased capital costs and environmental impact that would result from structural strengthening to mitigate risk. And at Gerald Desmond Bridge, Arup’s seismic and foundation design contributed significantly to the contractor’s competitive edge that secured the design and build contract for the first major cable-stayed bridge in California. The Arup team of bridge engineers is supported by in-house experts in highway and railway engineering, traffic engineering, marine engineering, off-shore engineering, aviation, geotechnics, fire engineering, electrical and mechanical engineering, materials technology, acoustics, environmental, feasibility and financial evaluation, quantity surveying, contract compilation, construction supervision and legal advice. This depth of global experience combined with local presence and holistic approach can help owners realise bridge projects that meet their unique aesthetic desires, environmental needs and economic considerations.
www.bridgeweb.com
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S E L I F O R P Y N A P M O C
BSI Group 389 Chiswick High Road London W4 4AL, United Kingdom t: +44 345 086 9001 f: +44 208 996 7001 e:
[email protected]
www.bsigroup.com/eurocodesplus
BSI GROUP Eurocodes: How to use them and how to realise their potential for your business Excerpts from the BSI white paper by Owen Brooker, technical director, Modulus. The paper is intended to address the challenges the Eurocodes presents and to provide useful insights and assistance in making the transition to using them
T
he introduction of the Eurocodes to the UK is a major change for engineers working in structural and civil engineering. The codes were introduced to eliminate technical obstacles to trade and harmonise technical specifications, thus creating a more open marketplace. The drive towards implementation of the Eurocodes has differed between the civil and structural markets. Civil engineers have been relatively early adopters because their clients are mainly public bodies, and they are under an obligation through the EU Public Procurement Directive (2014/24/EU) to use designs that conform to the requirements of the Eurocodes. By contrast, structural engineers undertake considerably more work for private clients and there is less incentive to make the transition because the Eurocodes are seen as just one way of demonstrating compliance with the UK Building Regulations. Due to their less prescriptive nature, the adoption of the Eurocodes offers opportunities for flexibility in design, as well as opportunities for increasing market share across the European Union.
Language and symbols
To the native English speaker the use of some words in the Eurocodes is not familiar. For example, the term ‘actions’ has been adopted when most engineers would think that ‘loads’ is more appropriate. Particular words have been adopted for specific reasons; it could be that they translate more easily into other languages, or because they are more precise. ‘Actions’ has been used so that it can cover the effect of temperature changes, which are not strictly speaking ‘loads’. The symbols in the Eurocodes can also be confusing to the newcomer. There are a lot of them, and some of them do differ from those used in British Standards. However, there is a system, which on the whole has been adopted across all of the Eurocodes. Therefore, once they become familiar it does become easier to turn to a new material Eurocode and have a grasp of the symbols. The symbols are also quite precise, so they should be used accurately. However, the precision and consistency should mean that less time is devoted to scouring a Eurocode to find the definition of the symbol. Eurocodes are standards – not design guides
The Challenges facing engineers Complexity The number of standards, some of which have many parts. The references to separate product and material standards. The need to accommodate the requirements of many different countries – giving
rise to the National Annexes (NA). They are claimed to be the most technically advanced construction standards in the world.
To the user of a BS, the Eurocodes have a very technical feel to them. This is because they are written to give the basic design requirements; setting out the rules which should be adopted. The former British Standards go a step further and provide design guidance, design aids and are in fact far more like design manuals; Europeans would expect this information to be found in textbooks or design manuals. This approach means that it is often necessary to have a Eurocode and some guidance, such as the relevant published documents, open at the same time. Uncertainty of member resistances
To the first-time user, navigating through the Eurocodes and the supporting standards can be confusing. Volume of changes
For the typical practising engineer, changing from using the BS (British Standard) system to the Eurocode system requires an understanding of the new requirements for all construction materials at the same time. In the past, changing to a new standard for a single material was more manageable. For many it is the extent of the changes that appears to make the transition an insurmountable barrier.
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Another challenge is knowing what sizes are appropriate at the start of the design process and here an experienced engineer needs to know if their existing ‘rules of thumb’ are still appropriate. Whichever code of practice is used, the end result should be a design which gives more or less the same sizes. The Eurocodes represent an evolution, rather than a revolution and therefore some reduction in member sizes might be an outcome, but any reduction of more than 10–20% should be a warning sign. An experienced engineer will still be able to use their rules of thumb and over time may modify them. To get your free copy of the white paper go to: http://shop.bsigroup.com/ecwpbd
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LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES SUPPLEMENT “The tools provided by Bentley allow us to follow the technological evolution necessary on today’s challenges.” – Pedro Pereira, Engineer, LCW Consult SA –
BENTLEY SYSTEMS, INC. 685 Stockton Drive Exton, PA 19341 USA t: 1-800-BENTLEY (1 800 236 8539) t: +1 610 458 5000 e:
[email protected]
www.bentley.com/bridge
BENTLEY
B
entley’s bridge applications are purpose-built for bridge designers and contractors who need to create, construct, maintain, and document bridge information throughout the lifecycle of the asset. Sharing information in an information-rich 3D model increases data quality, collaboration, constructability, and operational aspects including asset management. Bentley’s bridge applications provide the ability to interoperate with all stakeholders during design, construction, and beyond on bridge projects of all sizes. There are tremendous advantages in connecting the project team members with a 3D approach and the technology that supports it. Having geometry that is relevant and current ties the roadway and bridge engineers together from the onset of a project and throughout design revisions in a bi-directional manner. Not only are they working in a connected manner, they are working geospatially for improved accuracy. With Bentley applications, bridges can be modelled in a real-world manner referencing existing conditions in a meaningful way. Models become the immediate mechanism for design and analytics. Imagine the time and cost savings of easily developing an intelligent model in the preliminary stages of a project – and carrying this through to design and analysis without the time or expense of re-engineering. Most 3D modelling technology does not allow for a direct link to analytics without some re-entry of data; nor “Finally, a purpose-built do these models contain the level of bridge modelling software detail required for today’s projects. that is parametric and However, with Bentley’s OpenBridge easily editable. In just minutes, I had results with Modeler, RM, and LEAP interoperability, OpenBridge Modeler that the physical model can be linked would have taken at least directly to the analytics. It allows for a half hour in other civil alternate design options, previewing engineering programs.” alternatives, constructability – André Tousignant, PE, issues, and conflicts in the earliest Construction engineer, PCL development of the bridge. Civil Constructors, Inc – Visualise, render, perform clash
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detection, generate quantities, and evaluate clearances with the information-rich model, and be assured of reliable construction methods from the onset. Directly connect and reference existing and proposed conditions, as well as civil data to perform constructability analysis – key to maintenance of traffic – facility over facility. Bentley’s OpenBridge Modeler addresses the challenges we face with complex geometry needs, parametric updating of changes, and evaluating constructability early in the process, including conflicts not seen in a 2D workflow. Bentley applications allow you to easily share engineering-rich data, and make more informed decisions within a 3D model of the bridge project. The advantage of all disciplines (roadway, utilities, bridges, existing conditions, and so on) operating in a single modelling environment with no need to recreate critical project data helps stakeholders meet the challenges of the 3D deliverable by industry standards. OpenBridge Modeler provides a workflow specific to the needs of the bridge engineering software that model bridges not buildings, yet facilitates collaboration and integration with other disciplines, such as civil engineers, utilities, and others to ensure everyone has the data they need when they need it. 3D bridge models provide the ability to reference related designs that connect or affect the project. Subsurface utilities, rebar detailing, bridge element placement, and traffic maintenance are all key construction issues that, in an integrated and interoperable workflow, can be detected and resolved upfront in the office rather than in the field. Bridge design and construction processes are evolving and 3D deliverables are imminent. Interoperability and collaboration are keys to the success of bridge projects of all sizes and construction methods. Leveraging complex geometry from the beginning to generate physical bridge models and preparing the design and analytical requirements is essential to moving to a more fluid and seamless reality modeling workflow. With intelligent as-designed models and as-built data, engineers can provide operations and maintenance value for the entire life of the asset. Address complex modelling, design, and analysis of all bridge types on both existing and new structures. Experience enriched problem solving at every stage of the project delivery process, from planning, design, and engineering to construction simulation and analysis with Bentley’s bridge applications. Your result – remarkably better engineered bridges.
www.bridgeweb.com
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LONG-SPAN BRIDGES SUPPLEMENT
S E L I F O R P Y N A P M O C
BENTLEY SYSTEMS, INC. 685 Stockton Drive Exton, PA 19341 USA t: 1-800-BENTLEY (1 800 236 8539) t: +s1 610 458 5000 e:
[email protected]
www.bentley.com/bridge
BENTLEY RM Bridge enables Armando Rito Engenharia to improve quality of life in Angola Bridge reduces river crossing time from two hours to less than one minute
I
In the aftermath of a devastating civil war, the Republic of Angola faced the daunting task of rebuilding its infrastructure. As part of this effort, Armando Rito Engenharia SA Lisbon, Portugal, was retained by the Road Institute of Angola on behalf of the Ministry of Public Works to design the 4th of April Bridge over the Catumbela River. The EUR 26 million cable-stayed bridge replaced an antiquated one-way bridge, which turned a two-hour-or-more journey between the cities of Benguela and Lobito into a 30-minute drive. Rebuilding post-war infrastructure The project team used RM Bridge, Bentley’s comprehensive software for bridge design and analysis, to develop the impressive cable-stayed solution, which not only improved the quality of life in this community, but also marked a remarkable engineering achievement that was able to benefit from a comprehensive 3D model for analysis. RM Bridge helped the team achieve technical innovations in pylon geometry, cable-stay design, and optimisation of cable-stay tensioning through all construction stages, enabling the team to design a structure that has a modern aesthetic, as well as an impressive engineering design. The bridge symbolises the end of war and the freedom of the Angolan people. One-way bridge replaced with innovative cable-stayed bridge A former Portuguese colony, Angola is an African nation that was for decades torn by war. The civil conflict took a toll on both the people and the built environment. During those years, the road system along with a vast number of bridges ended up being destroyed or heavily damaged. Since the end of the armed conflict, the country has been rebuilding, and Armando Rito has worked in Angola since 2000 constructing about 30 bridges as part of that rebuilding. The 4th of April Bridge is part of the highway between Benguela and Lobito, crossing the Catumbela River approximately 7km north of the Atlantic coast. Previously, the crossing was made using a single-lane bridge built in the early 20th century. Crossing the river seldom took nearly two hours. To address that problem, Armando Rito proposed a new bridge that would be an aesthetically pleasing landmark, and yet demonstrate the technological advancement that symbolises Angola’s will to rebuild itself in the modern era. The bridge geometry and technical solutions, from deck to pylons, reflect not only
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modern structural concepts but also the country’s forward-looking vision for form and function in infrastructure. Several constraints influenced the design of the replacement bridge. Its location in the heart of the city of Catumbela required the road profile to be low, with pronounced curves. The deck had to be slim to allow for local circulation underneath the bridge. Also, the tight schedule and seasonal flooding dictated that the piers be located outside the river, which impacted the bridge’s main span. 3D model analysis used from design to constrction While Armando Rito has used RM Bridge since 2003, this was its first opportunity to use the software for the analysis of a cable-stayed bridge. The bridge’s complex geometry made the construction stage analysis and determination of optimised tensioning cable stay forces quite challenging. With help of the RM Bridge professional services team, the project engineers were able to accelerate the process and meet the required timeline.
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“The team is proud to have been able to successfully build this important bridge, and the measure of our success is the opportunity to design two more cablestayed bridges in Angola. RM Bridge will undoubtedly be an important part of the process.” – Pedro Cabral, Armando Rito Engenharia SA
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Fast fact s: RM Bridge was used to create a 3D structural model of the cablestayed bridge, including pylon geometry and cable stays. The team used RM Bridge to perform construction stage analysis, considering time dependent functions. RM Bridge was used to determine optimised cable-stay tensioning forces during construction stages.
construction stages of the bridge, considering timedependent functions (creep, shrinkage, and relaxation), and all stressing operations. The innovative saddle design for the bridge provided an immediate savings of almost 15%. A more conventional solution would have resulted in an increase of concrete and reinforcement quantities of 10-15% plus an estimated 25 metric tons of structural steel for the anchorage caisson.
ROI:
RM Bridge delivers technical innovation and smarter design The bridge is a cast in-situ cable-stayed bridge with a semi-fan arrangement of stays. The main span of the bridge is 160m, and the two side spans are both 64m long. The approach viaducts have multiple 30m spans. Together with the approach viaducts, this bridge forms a 438m-long, continuous structure with only two expansion joints located at the abutments. The prestressed concrete pylons are U-shaped and approximately 50m high. They were designed in such a way as to allow them to work without the usual transverse bracing system, giving them the U-shaped configuration that contributed to the aesthetics of the bridge design. The total suspension 24.5m-wide deck is composed of two prestressed hollow-beam concrete girders. The two beams are connected transversally by the reinforced concrete top slab and by prestressed cross beams placed every 4m. The bridge design led to some technical innovations, such as the saddle developed for the stays to allow a reduction in steel quantities and slimmer concrete masts. The stays are arranged in two planes and are constituted by bundles of individual pre-stressed steel strands. They connect to the pylons by crossing through the saddles, except on the first three stays where traditional anchorages are used. The deck anchorages are positioned at 8m intervals except for the four backstay cables, which are spaced at 4m.
The innovative saddle design developed for the stays, allowed a reduction in steel quantities and slimmer concrete masts. A more conventional solution for the pylon anchorages would have resulted in an increase in concrete and reinforcement quantities of 1015% plus an estimated 25 metric tons of structural steel for the anchorage caissons.
Armando Rito also used RM Bridge to model the 3D cable-stayed bridge and analyse the geometric attributes and design challenges within the model. This allowed the team to make more informed decisions throughout the construction process, saving time and money. “This was an investment that not only provided important knowledge of the software usage, but also permitted an interesting exchange of ideas and concepts between developers and end-users,” said Pedro Cabral, head of the bridge department at Armando Rito Engenharia SA. “It also improved the experience and know-how about the behaviour of this kind of structure.” The team used RM Bridge to compute the complete construction sequence, solving structural problems in the 3D model before construction began. In addition, the team used Microstation to produce construction drawings. The RM Bridge optimisation module for cable-supported bridges allowed the project team to efficiently evaluate the optimal cable stay tensioning forces during all
Organisation: Armando Rito Engenharia SA Solution: Bridges Location: Catumbela, Benguela, Angola Project objective: Design a cable-stayed bridge to replace the antiquated one-way bridge over Catumbela River. Create an aesthetic form that symbolises the end of war and the freedom of the Angolan people. Provide a low profile, slim deck, with piers outside the main river channel to minimise impacts on the urban setting. Products used: RM Bridge, MicroStation
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Symbolic aesthetics – a bridge between two nations, celebrating freedom The new bridge dramatically shortened the time to cross the river and vastly improved the quality of life for those living in the region. The aesthetic of the structure signifies the freedom of Angola’s people, the end of the war, and the pride taken in modern reconstruction. It is also a symbol of the legacy left by the Portuguese to Angola. Besides being a bridge between the two banks of the Catumbela River, it is a bridge between two nations.
For further information:
www.bentley.com 1-800-BENTLEY (1-800-236-8539) Outside the US +1 610-458-5000 +43 316 821 5310
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DYWIDAG-Systems International GmbH Siemensstrasse 8, 85716 Unterschleissheim, Germany t: +49 89 30 90 50 100 f: +49 89 30 90 50 120 e:
[email protected]
partnership. We offer our clients the advantages of an international system supplier with a product range that is tailored to suit individual requirements. Certifications and internatonal organisations International organisations, trade associations and standards committees are becoming more important in times in which products and services seem more and more interchangeable. organisations and trade associations are cross-linked on a global basis and promote the exchange of technology and know-how across borders. We are an active member in many international organisations to drive technical developments.
www.dywidag-systems.com/emea
DSI
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ywidag-Systems International (DSI) is a globally leading system supplier of innovative technologies for the construction industry. The long tradition of DSI reaches back as far as 1865 – the founding year of the German construction firm, Dyckerhoff & Widmann AG (Dywidag). DSI was founded in the year 1979 to market Dywidag Systems and technical know-how around the world and to develop innovative systems resulting from its own research and development activities. DSI technology In more than 90 countries and at 28 regional manufacturing sites, DSI develops, produces and supplies high-quality systems such as Dywidag post-tensioning systems, geotechnical systems and ‘concrete accessories’ for the construction industry. In accordance with our slogan ‘Local Presence – Global Competence’, more than 2,100 specialised and experienced DSI employees ensure that DSI’s technologies and know-how are available around the world. DSI offers quality on all levels – quality that is characterised by creativity, reliability and profitability.
Milestones Dywidag post-tensioning systems and stay cable systems are world renowned for reliability and performance. They embrace the whole spectrum from bridge construction and buildings to civil applications – both above and below ground. The first ever structure built with a prototype Dywidag post-tensioning system using bars was the arch bridge Alsleben (Germany) in 1927. From that time on, Dywidag has continuously improved its systems to keep up with the growing demand of modern construction technology. In addition to traditional post-tensioning systems with bars, DSI offers a complete product line in strand post-tensioning (bonded, unbonded and external) as well as stay-cable systems to fulfill the changing requirements in the industry today and tomorrow. Our stay cable systems have always combined the highest safety and reliability standards with excellent economical efficiency in their research and development. Dependable corrosion protection methods, damper design, fire protection, vibration measurements and the recently developed Dyna Force monitoring system significantly contribute to the longevity of modern construction.
Comprehensive services Our comprehensive services include the conception, design, planning and installation of its systems as well as quality management and on site supervision. Research and development Continued investments in research and development and the resulting patent applications sustainably strengthen the know-how available within the DSI Group. By offering innovative solutions in accordance with superior quality standards, we fulfill the constantly changing requirements of our target markets. It is our declared aim to always be one step ahead. Client orientation The needs and requirements of clients and business partners are always of paramount importance. Our company is characterised by reliability, trust and cooperation based on
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Repair
FREYSSINET
The ageing of structures generates a growing need for renovation, heightened by the increasing stringency of regulatory requirements. As an extension of its new build business, Freyssinet has developed expertise and know-how in structural repair through exclusive solutions under the Foreva label. Foreva solutions incorporate structural design methods, the manufacture of tested, approved products and implementation by trained workers.
280, Avenue Napoleon Bonaparte CS 60002 92506 Rueil Mailmason Cedex France
www.freyssinet.com Twitter: @freyssinet www.linkedin.com/company/freyssinet
FREYSSINET Wing Tip Consol Energy Bridge, USA
Guaranteed turnkey service With Foreva, Freyssinet guarantees quality work and a durable repair as part of a turnkey service. Expertise Repair solution expert Freyssinet offers its expertise to designers and main contractors and supports them at every stage of a project, from assistance in diagnosis through to choice of the appropriate solution and implementation of the works.
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Proven solutions and products With its technical department made up of civil and chemical engineers, materials experts and corrosion specialists, Freyssinet has a proactive policy for the development of repair solutions and products, validated by laboratory trials and feedback from on-site experience. Specialist teams Our specialist teams’ know-how enables Freyssinet to meet its customers’ requirements in terms of quality, schedule, costs, safety and the environment. Its substantial network of locations enables local service and offers customers high levels of responsiveness.
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ounded over 70 years ago by Eugène Freyssinet, the inventor of prestressing, Freyssinet brings together an unrivalled range of skills in the specialist civil engineering sector, offering integrated technical solutions in the fields of construction and structural repair. Freyssinet is involved in numerous projects across five continents, making it the world leader in its specialist areas of: Prestressing, Cable-stayed structures, Construction methods, Structural accessories, Structural repair and reinforcement, Structural maintenance. These activities are performed on a wide range of structures, including civil engineering structures, buildings, skyscrapers, industrial installations, power production plants, offshore platforms, transport and sporting infrastructure, and more.
Commitment to sustainable development Improving, preserving and securing structures helps to save non-renewable resources and reduce greenhouse gases.
Innovation Innovation is in Freyssinet’s blood. Since Eugène Freyssinet invented prestressed concrete in 1928, the company has based its growth on dynamic innovation, as borne out by numerous technological advances that have changed the civil engineering world. To perpetuate the pioneering spirit of its founders, the company implements and invests heavily in an active research and development policy, lead by a Technical Department and a worldwide network of experts working closely with research laboratories and universities. Freyssinet develops exclusive products and processes in all its areas of operation, for which almost 200 patents have been filed over the past two decades.
Construction The product of 65 years of continuous R&D effort, Freyssinet solutions meet the highest standards of modern civil engineering and major building projects. In each of its specialist areas, Freyssinet sets itself exacting performance criteria generally positioned above the usual industry standards. This demand for quality applies not just to products developed in the company’s factories and laboratories, but also to implementation, adherence to deadlines and sustainability. Freyssinet’s aim is to provide the best possible responses to clients’ major challenges in terms of technical and economic performance, reliability and durability.
LONG-SPAN BRIDGES SUPPLEMENT 2016
Agigea Bridge repair, Romania
www.bridgeweb.com
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LINDAPTER INTERNATIONAL 1512 Yellow Springs Road, Chester Springs 19425 Pennsylvania, USA t: 610 590 2160 f: 610 590 0457 e:
[email protected] www.lindapterusa.com
LINDAPTER
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indapter is the pioneer in the design and manufacture of steel connection solutions, providing a faster alternative to drilling or welding, ultimately saving contractors’ time and money. With over 80 years’ experience, Lindapter has an extensive range of products for the bridge industry, including connections for hollow steel section, steel-tosteel, concrete decking, pipe supports and metal flooring. Lindapter products are used in multiple prestigious long span bridges, including the Goethals Bridge and Alexander Hamilton Bridge in New York and the Walt Whitham Bridge and Ben Franklin Bridge in Philadelphia, PA. Typical applications include securing metal flooring, pipework, and steel framework while bespoke applications include bridge strengthening applications. The below case studies show the versatility of Lindapter connections.
Lindapter Support Fixings are often specified for securing pipework due to the ease of installation and high adjustability. In this case, Lindapter Type F3 clamps secured a 100mm-diameter pipe carrying fibre optic cable along the entire length of Manhattan Bridge. Using just simple hand tools simplified the installation across the iconic bridge and allowed the contractors to finish on time and on budget. During the major upgrade of the 150-year-old Arnside Viaduct (pictured right) , chequer plate flooring was secured to supporting box girder sections along the length of the new deck using 8,000 Lindapter Floorfast connections. The ease of installation allowed the flooring to be fitted as the deck units were removed, helping the major renovation to be completed on schedule. Lindapter often designs and manufactures customised connection assemblies, which can include the supporting steel. In a bespoke application for Tower Bridge in London, the Type A clamps were used to attach the new glass walkways’ supporting steel frame to the original steel structure.
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The new viewing platform spans the River Thames at a height of 42m and features a glass floor to reveal the bridge deck and water below. The floor consists of several 530kg glass panels supported by a carbon steel framework weighing 1000kg. The frame was safely secured with Lindapter’s CE marked clamps using just simple hand tools. The simple installation process ensured that the iconic structure was not damaged and helped the contractors to complete the installation within six weeks. Whether securing a new walkway, adding pipework or building a new steel-framed bridge, Lindapter has a proven and accredited connection solution. As a premium manufacturer, Lindapter has an extensive range of product approvals and all our products have independently approved safe working loads.
For further information, visit www. LindapterUSA.com to download a bridge application brochure which includes more prestigious bridge projects and the popular Hollo-Bolt, which is the only blind fastener to be recognised for primary structural use by SCI and BCSA. The Hollo-Bolt is also the only expansion bolt for structural steel that has full seismic approval (A-F) from California based ICC-ES and COLA (City of Los Angeles) approval.
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LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES SUPPLEMENT
MABEY BRIDGE LTD Unit 9, Lydney Harbour Estate Harbour Road, Lydney, Gloucestershire GL15 4EJ UK t: +44 (0)1291 623801 e:
[email protected] www.mabeybridge.com
MABEY
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abey is a leading international provider of high quality bridging and infrastructure solutions. We specialise in rapid-build, pre-engineered modular bridging solutions to develop, improve and repair essential infrastructure in urban and rural areas. We also deliver permanent and temporary bridging solutions for transport, oil and gas, and mining applications.
A unique heritage of British engineering expertise Mabey is a company of engineers. We have a tradition of innovation which dates back to 1848 with the construction of Isambard Kingdom Brunel’s Railway Bridge over the UK River Wye. Since then, we have built on the engineering success of our founder, Bevil Mabey, to invest in new product development, advanced production equipment and new ventures to become a market leader in the development of modular bridging systems now found all over the world. A track record of innovation in modular bridging We are proud of the contribution we continue to make to innovation in modular bridging. As an original manufacturer of the Bailey Bridge developed in WW2, Mabey retains outstanding knowledge and expertise in their design and manufacture. We have drawn on this to develop a range of proprietary, pre-engineered bridging solutions which are entirely modular, easily transportable and rapid to deploy. Innovation features prominently throughout the range; innovative developments include backward launch mechanisms and cost-effective replacement bridging solutions, as well as elaborate flyovers and robust military systems, serving a wide range of both permanent and temporary applications. An established provider of long-span modular bridging Mabey is a long-span bridging specialist. Launched in 2003, the Mabey Delta is a permanent, lightweight, modular steel bridge which features standardised, interchangeable steel components with full highway loading capability. The Delta can be configured as a single or multiple span bridge for clear spans of up to 90m. It can also be supplied in multiple spans, supported on intermediate piers, meaning that there is no limit to the length it can bridge. Mabey has supplied the Delta to numerous customers around the world, from Canada to Chile and from the Philippines to Pakistan; a 328.5m Delta, the Gammon Bridge, was installed in
the Swat Valley following severe flooding in 2010. More recently, in December 2015, Mabey installed its first Delta in Latin America, in the Arauco region of Chile. The installation replaced infrastructure which had previously been destroyed by a severe earthquake and has since had a beneficial impact on the region’s economy.
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A thought leader in long-span bridge innovation Mabey is a master of long-span bridging design. The uniqueness of our Delta bridge is the intellectual property that sits behind its unique jointing and load sharing system. This means that special load requirements can easily be accommodated, as can sitespecific topography, high wind loads and seismic requirements. Important too is the simplistic modularity of our designs. The long-span Delta features an innovative proprietary steel decking system, which transfers wheel loads to the transom and then on to the trusses. These, in turn, carry the load to the abutments and onto the intermediary piers, enabling multi-span configurations for a wide range of applications. Extremes of temperature are also taken into consideration; Mabey designs using certified high-grade steels to provide a physically strong and durable product, which is hot-dip galvanised to international standards to protect it from corrosion. Additionally, full-scale testing, to verify design calculations and fatigue characteristics and to prove structural integrity, features as an integral process in our design statement methodology. It is the versatility and robustness of the Delta’s design, combined with its aesthetically pleasing triangular-shaped panels, which differentiates it as a superior high-quality product in the long-span market. A world leader in speed of installation Mabey’s expertise goes far beyond design and manufacture. We pride ourselves on the comprehensive bridge installation advice we offer our customers in support of their project to ensure their bridge installation is rapid, safe and trouble-free; our qualified bridge installation advisors are experts in site reconnaissance, planning, logistics, infrastructure development and installation, and have overseen the installation of thousands of bridges worldwide. The Delta combines the best of off-site fabrication with high speed construction and rapid installation, offering significant advantages over more traditional construction techniques which involve major site work. Delta components can be transported to remote sites easily in ISO containers and bridges can be erected quickly using locally sourced labour and a minimum of specialist equipment. Installation times are impressive; a 90m single-span Delta was recently built in Chur, Switzerland, in 16 days. A globally trusted partner for the future of long-span bridging There is more to Mabey. Product development work at Mabey continues to push Delta bridge developments: to continue to strengthen it so as to respond to industry’s demand for longer spans; to incorporate new, stronger and more cost effective materials and to identify new markets and applications. For help with your project, visit www.mabeybridge.com or email us on sales@ mabeybridge.com. We look forward to hearing from you.
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MAURER AG Frankfurter Ring 193 80807 Munich, Germany t: +49 89 323 94 0 f: +49 89 323 94 306 e:
[email protected] www.maurer.eu
MAURER AG
B
ridges, buildings, ferris wheels: MAURER AG in Munich, Germany is known worldwide for its spectacular constructions. Each of us has probably seen one of the components built and installed by MAURER – but often without knowing it. The support of the 34,000m2 large movable roof construction of the Allianz Arena in Munich comes from MAURER as does the entire bridge equipment for the Russky Bridge in Vladivostok. In steel construction, the BMW Welt and the Airport Terminal II in Munich are among the showpieces. The most relevant MAURER products are components that transfer loads or convert energy. These include expansion joints as well as structural bearings, seismic control devices and vibration absorbers. For each building project – whether they be filigree pedestrian bridges or skyscrapers – measures to compensate vibration are designed individually. Continuous research ensures the adaptation of new products to prevailing conditions. For instance, MAURER developed a solution for low-noise expansion joints for road bridges as well as permanent bridge bearings which protect the respective building for much of its life. The possibility to selectively generate and utilise accelerations and movements characterises a further business segment. Professional rollercoasters and ferris wheels are planned, designed and built for amusement parks. Among the most impressive of MAURER rides is the Rip Ride Rockit rollercoaster at Universal Studios in Orlando and the Fiorano GT Challenge
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in Abu Dhabi. A common feature of all business activities is that they focus on mastering forces or directing them in a controlled manner, which is reflected in the company slogan ‘forces in motion’. Services such as providing individual building-specific advice, training external personnel for the installation of products or ongoing monitoring complement the portfolio. MAURER’s resourceful engineers developed a roadway expansion joint made of steel and rubber to bridge the expansion gap using the accordion principle. Expansion joints adjust depending on the temperature and can absorb up to 5m of movement. Waterproof expansion joints in particular were developed to address a gap in the bridge construction market. Having laid more than 1,000km of expansion joints in roads and bridges, this Munich family enterprise became a world market leader in the field; this milestone also marked the beginning of international activities. After plants were established in Turkey and China in 1999, additional branches followed in Russia, France and India in 2004. The company now maintains a global network of subsidiaries and agencies in over 60 countries. The change in the company’s name in December 2014 marked a milestone in strategy. Maurer Söhne GmbH & Co. KG was renamed MAURER AG and the change of legal form, representing a further step in terms of internationalisation, was accompanied by a new, clearly-focused brand identity. Thus both the website as well as the company logo, which bears the name MAURER, were given a contemporary and distinctive makeover. In addition to these visible changes, the reorientation also involved presenting the company as a ho mogeneous unit. Former managing directors Dr Holger Krasmann (CEO) and Dr Christian Braun were appointed members of the board of MAURER AG. The company is still owned by the Beutler and Grill families, represented on the board by chairman Jörg Beutler. A high capacity for innovation based on extensive competence in technical development, excellent product quality, vast experience in handling sophisticated projects as well as first-class service have been the cornerstones of MAURER AG for almost 140 years. The company also sees itself well prepared for the future. By producing more sustainable and energy-efficient products, it takes into account the higher building requirements caused by changing climatic conditions and the scarcity of resources. Thus MAURER will make our world safer in the future – despite increasingly elaborate construction – in a positive sense completely unnoticed.
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LONG-SPAN BRIDGES SUPPLEMENT 2016
LONG-SPAN BRIDGES SUPPLEMENT
Harpe Bru Bridge, SørFron (Oppland), Norway: Simple connecting means the compatibility of the VARIOKIT engineering construction kit with the PERI UP Modular Scaffolding have facilitated safe access and working platforms in all areas. ( hoto: Peri GmbH )
PERI GROUP Rudolf-Diesel-Strasse 19, 89264 Weissenhorn, Germany t: +49 (0)7309.950-0 t: +49 (0)7309.951-0 e:
[email protected]
www.peri.com/en
PERI Formwork, scaffolding and engineering from one source
Expertise in bridge construction – successfully active on the market for over 45 years
P
eri is one of the leading providers of formwork and scaffolding technology worldwide. The company’s great innovative strength and early international expansion have been the cornerstones of its global success and steady growth. Its high level of customer orientation, innovative systems and expertise have created the trust that has turned the company into a leading international brand. Worldwide, Peri employs more than 7,700 people at more than 60 subsidiaries together with a large number of branches and locations. With around 120 efficiently-run rental parks, Peri ensures sufficient and rapid material availability as well as close proximity to the projects of its customers.Through the experience gained from a wide range of market and project requirements, Peri supports its customers, for example, with the preparation of the most suitable technical solution, providing the appropriate system equipment along with the most cost-effective and safe execution, through to the return delivery of materials. A Peri solution always results from the combination of product, concept and execution. Peri engineers work hard every day to efficiently streamline construction processes and to make rationalisation reserves usable. For complex projects in civil engineering bridge construction, eg balanced cantilever solutions, Peri now provides even better support for its customers. The
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close collaboration of sales engineers with a newly-founded specialist group for technical advice and planning strengthens our ‘single point of contact’ sales and marketing concept. Peri customers benefit from project management available from one source throughout the project along with the best solution competence. Peri development has therefore focused on modular construction kit systems with standardised system components and maximising benefits for the users: VBC VARIOKIT balanced cantilever carriage Suitable for large spans, deep valleys and inaccessible terrain. Section weights during pouring up to 250t using a standard application with two main frames. Section lengths of up to 5.75m are possible. Achievement of dimensionally-accurate concrete sections with help of independent assembly operations by means of integrated hydraulics. VRB VARIOKIT heavy-duty truss girder Maximum span of 40m. Longitudinal inclination and cross-fall of up to 7% . Span lengths can be continuously built. Coupling joint suspensions are also possible. VST VARIOKIT heavy-duty shoring tower Leg loads of up to 700kN. Continuous height adjustments and variable layout . Head spindle can be operated hydraulically when fully loaded. Easily integrated access technology.
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LARSA INC 68 S. Service Road, Melville, NY 11747, USA t: +(800) LARSA-01 t: +1 212-736-4326 e:
[email protected] www.larsa4d.com
LARSA 4D
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arsa 4D is recognised as the premier software for bridge engineers with the innovative tools necessary to support bridge projects through design, construction, and rehabilitation. It has become the trusted software through Larsa’s team-wide commitment to working closely with its loyal customer base. By coupling structural analysis and design with the latest computing technology, Larsa 4D has become one of the most reliable software packages of its kind for segmental, cable-stay, suspension, stressed-ribbon, steel girder and other bridge forms, as well as other structures requiring geometric or material nonlinearity, complex three-dimensional geometry, or a staged construction analysis.
code check and LRFR load rating, it walks the user through every step and formula of the code. Input parameters include girder locations and skew, horizontal layout, bearings and other support conditions, girder and deck construction sequence, and design vehicle velocity, among many others. But what makes the Steel Bridge Module a production design tool is how the complete model may be revised for design optimisation. Other innovative tools include using bridge alignments as coordinate systems for analytical models and a robust influence surface based live load analysis, providing the ability to load the roadway with standard AASHTO trucks, permit trucks, or any other user-defined custom load patterns. The influence surface solver in Larsa 4D has many advantages including automatic transverse placement of design lanes, distribution of loads across girders and all using a finite element based model. Also coming in Version 8.0 is a powerful new concrete bridge design module, which uses the same parametric approach as the Steel Bridge Module which clients have found to dramatically reduce their time spent on design work. Larsa is also developing a new analysis for the design of structures for high-speed rail projects. At high speeds, resonance and coupling of the vehicle with the natural frequencies of the structure exacerbate structural demands beyond what can be accounted for in a conventional rolling stock analysis. A new vehicle-track-structure interaction (VTSI) analysis has been implemented within the Larsa 4D software package as an extension of the time-history analysis to solve these design problems.
‘4D’ anallysis and design Projects Larsa 4D has led the field of bridge Larsa 4D has been used in many longengineering software with robust span bridge projects including the Gerald staged construction integrated Desmond Bridge replacement which with nonlinear analysis, influencewill be the first long-span cable-stayed based live loading, seismic analysis bridge in California, and the cable-stayed and other complex design needs. Ohio River Bridge-East End Crossing The core is a staged construction which has a 365m-long main span analysis, which models the changes carrying six lanes of traffic and a to a structure over time including Graphics view of LARSA 4D Version 8.0’s new Concrete Bridge Module bikeway. construction activities and timeThe replacements of the Goethals, dependent material effects such as Tappan Zee Hudson River Crossing, and Kosciuszko bridges in the New York creep, shrinkage, and relaxation. Developed for the rigorous needs of metro-area are among the many other major projects extensively using segmental construction and cable-supported structures, Larsa 4D’s staged Larsa 4D for design, construction, and deconstruction. construction analysis has advanced activities, such as hoist, multi-layer concrete pour, and it tracks code-based load classes for load combinations. Innovation in support The ‘analysis scenarios’ option within staged construction analysis Innovation in engineering software pertains not only to the analysis provides the ability to perform a live load, eigenvalue, response spectra, but also to how Larsa suppor ts its clients. ‘Features on Demand’ time-history, or pushover analysis at an intermediate state of construction. allows the Larsa support team to deploy software updates quickly in In Larsa’s upcoming Version 8.0 release, composite construction adds response to users’ technical support needs, outside of the typically new construction activities for multi-layer concrete pours and composite longer software release cycle. And with ‘Larsa Live’, users may preview behaviour of steel girder and concrete deck segments. new versions of the software without needing to uninstall the current The ‘4D’ in the product name refers to the fourth dimension, time, which version. is the basis of staged construction analysis. Figg Engineering, HDR, and many other corporate clients have shaped the development of Larsa 4D. That may be why it has become Innovations for bridge analysis a company standard at Figg, HDR, International Bridge Technologies, Larsa 4D’s Steel Bridge Module is a parametric finite element modelling Parsons Brinckerhoff, Parsons Transportation Group, TY Lin tool that generates ‘4D’ staged analysis based models for I, box, and tub International, and many other leading firms around the world. girder bridges through guided input. With integrated tools for AASHTO LRFD
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