Lecture 7 - Steel Application

7.1 Introduction Introduction

7.1 Introduction Introduction 5

6 http://skyscraperpage.com

http://skyscraperpage.com

“Megatall”

“Supertall”

Figure 7.2 Skyscrapers currently under-construction around the world (2015)

Figure 7.1 World's Ten Tallest Buildings (2015) ARBE3100 Construction Technology 3

ARBE3100 Construction Technology 3

7.1 Introduction Introduction

7.1 Introduction Introduction 7

8

skyscraperpage.com

Where is Petronas Twin Towers???

geekologie.com

 Inspired

by Mount Fuji  Designed by Taisei Construction Corporation  Height: approximately 4 km, 200 m taller than the real Mount Fuji.  6,000m in diameter at the base and contains 800 floors, and be capable of housing housing between between 500,000 500,000 and 1,000,000 1,000,000 people. http://www.youtube.com/watch?v=SRjEtTlq7kk

Figure 7.4 The X-Seed 4000

Figure 7.3 World's Ten Tallest Buildings in 2020 ARBE3100 Construction Technology 3


archrecord.construction.com

7.1 Introduction

7.1 Introduction 9

www.geekwidget.com

10

mostbeautifulplacesintheworld.org

http://kientrucinfo.vn/266-crystal-island.html

 The

Shimizu Mega-City Pyramid is a hypothetical project for construction of a massive pyramid over Tokyo Bay in Japan.  The structur e would be 2,000 meters high.  Would house 1,000,000 people.  The proposed structure is so large that it cannot be built with currently available materials, due to their weight. The design relies on the future availability of superstrong lightweight materials based on carbon nanotubes. http://www.youtube.com/watch?v=aS2ob2wAnmU

Figure 7.5 Shimizu Mega-City Pyramid

   



World’s biggest building (to be built within next 5 years) Designed by Sir Norman Foster Height: 450 m. Floor space of 2.5 million square metre will feature 900 apartments, 3000 hotel rooms, an international school for 500 students, cinemas, a theatre, sports complex and much more. There will also be a 16,500 space underground parking lot for all the visitors.

Figure 7.6 Crystal Island Moscow, Russia



7.1 Introduction

7.1 Introduction 11

Table 7.1 List of tallest buildings in the world

12

In the era of super high rise buildings the need for lightweight and cost effective construction is continuously increasing. Along with this durability is also an increasing concern. Thus the solutions reached upon were steel structures with calculated detailing. Problem like building height, fire resistance, earth-quake resistance etc. could be dealt with in these constructions. The properties of steel like capacity to withstand high tension as well as compression helps engineers to use it in varied permutations and combinations.


en.wikipedia.org


7.1 Introduction

7.1 Introduction 13

7.1.2 General Properties of Steel Steel is an alloy consisting mainly of iron, with a carbon content normally between 0.2 to 2.1 % by weight, depending on grade. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another.

14

Steel has the following properties, that makes it one of the most efficient materials for use in building construction.

knol.google.com

Varying the amount of alloying elements controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but is also less ductile. ARBE3100 Construction Technology 3

Favourable properties

Some drawbacks



Strong: has a high strength/weight ratio



Heavy and lengthy, not easy to handle



Versatility: adaptable and ductile



Loss strength under higher temperature



Cheap and plentiful





Easy to cut, connect and fabricate

Easily get rust if not properly treated



Deflect under loads


7.1 Introduction

7.1 Introduction 15

7.1.3 Steel Design Standards Loading codes 

AS 1170.0 General principle



AS 1170.1 Permanent, imposed and other actions



AS 1170.2 Wind Actions

16

Steel reinforcement 

AS 4671 Steel reinforcing materials supersedes the following Standards - AS 1302 Steel reinforcing bars for concrete - AS 1304 Welded wire reinforcing fabric for concrete - AS 1554.3 Part 3: Welding of reinforcing steel

Steel structures 

AS 3679



AS 4100:1998



HB 2.2 - 2003 Australian Standards for civil engineering students Structural engineering


infostore.saiglobal.com


which

7.2 Steel Production

7.2 Steel Production 17

7.2.1 Global Demand of Steel

18

7.2.2 Steel Production in Australia

The World Steel Association (worldsteel) reports the world crude steel production has reached about 1.64 billion tons for the year of 2014. This is an increase of 3.8% compared to 2013.

According to Australian Steel Institute (ASI) steel indicators, the annual capacity of Australian steelmakers is 8 million tonnes of which approximately 20 % (i.e. 1.6 million tonnes) is structural steel. bokertov.typepad.com

Mainly used for industrial, commercial and residential buildings, bridges, towers and masts, maritime structures, mining and materials handling projects.

China, the largest steel maker in the world, its output of crude steel in 2014 was about 822 million tons, which was a half of the world annual production!

There are estimated to be 50,000 tonnes of structural steel stock in the distribution chain at any one time.

For more details about steel production statistics, please see http://www.worldsteel.org/ ARBE3100 Construction Technology 3




Table 7.2 Approximate segmentation of steel usage in Australia Agriculture

8%

Dwelling Construction

6%

Non Dwelling Construction

13%

Engineering Construction

21%

Manufacturing Plant and Equipment

14%

Vehicles and transport

13%

Mining

17%

Other

8%

Figure 7.7 Current steel usage in Australia ARBE3100 Construction Technology 3

http://steel.org.au/about-our-industry/steel-indicators/

20

7.2.3 Steel Production Process When iron is smelted from its ore by commercial processes, it contains more carbon than is desirable.

cascadesteel.com

To become steel, it must be melted and reprocessed to reduce the carbon to the correct amount, at which point other elements can be added. The molten steel is then continuously cast into long slabs or cast into ingots. ARBE3100 Construction Technology 3

brocksolutions.com

Figure 7.8 Steel melting and continuous casting



22

The ingots can be heated in a soaking pit and hot rolled into slabs, blooms, or billets. Rollers alfadux.com

Figure 7.9 Steel and Gold ingots

Figure 7.11 Steel billets

stainlesssteelseamlesspipe.net alfadux.com

Hot rolling of steel at a temperature above re-crystallization (above 1000 C) makes the individual crystals being reduced in size after each rolling ‘pass’. The rolling of hot steel has two important purposes: commodityforsale.com

Figure 7.10 Steel long slabs ARBE3100 Construction Technology 3

brocksolutions.com

 to

get the steel into a desirable shape, and

 to

improve the quality of steel




Slabs are hot or cold rolled into sheet metal or plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into structural steel, such as I-beams.

fulcrumsteel.com

Figure 7.12 Deformed steel bar ARBE3100 Construction Technology 3

oursbiz.com

Figure 7.13 I beam

24

Because of the cold ductility of metal, they can be shaped below re-crystallization temperature (usually at room temperature). In cold rolling, steel passes between the rolls. The metal coming from the rolls consists of the same crystals but are now elongated.

www.vinssco.com

Figure 7.14 Cold rolled steel

An elongated and distorted crystal structure of this kind has greater hardness and tensile strength than the original structure but is less ductile and in addition makes the steel more resistant to further cold work. This effect is known as work hardening. ARBE3100 Construction Technology 3


7.3 Steel Reinforcement 25

In modern foundries these processes often occur in one assembly line, with ore coming in and finished steel coming out.

26

7.3.1 Application of Steel Reinforcement Steel reinforcement is commonly used in in-situ reinforced concrete and reinforced masonry structures. It is usually formed from carbon steel, and is given ribs/indentation for better mechanical anchoring into the concrete. It can also be described as reinforcement or reinforcing steel. In Australia, it is commonly known as reo. The resulting reinforced concrete or other material is an example of a composite material.

eng2mfg.co

Figure 7.15 Steel manufacturing Process ARBE3100 Construction Technology 3

shotcreteconcrete.com

Figure 7.16 Steel RC


7.3 Steel Reinforcement


personal.cityu.edu.hk/~bswmwong/

Figure 7.17 RC Wall ARBE3100 Construction Technology 3

personal.cityu.edu.hk/~bswmwong/

Figure 7.18 RC Column

28

encompass-engineering.co.uk

Figure 7.19 RC Slab ARBE3100 Construction Technology 3

rom-tech.co.uk

Figure 7.20 RC Beam



30

7.3.2 Reinforcing Steel Manufacturing Control In compliance with AS4761, manufacturing control shall apply to all aspects of production, from steel melting to the dispatch of end products to the purchasers (steel processors or customers). In Australia, all the major steel reinforcement processors are Members of the Steel Reinforcement Institute of Australia (SRIA), operating material supply centres throughout Australia. http://www.sria.com.au/

Figure 7.21 The Lucia Apartments in South Yarra, Melbourne using RC structural frame

sria.com.au

http://www.edgearchitectural.com.au/





These processors act as the main link between the major steel manufacturers in Australia and overseas, and the end user of reinforcing materials by providing a one-stop shop for reinforcing material. The SRIA processor members aim to produce products of a high standard in compliance with the relevant Australia Standard AS/NZS 4671:2001 Steel reinforcing materials. How the steel products be certified ARBE3100 Construction Technology 3

http://www.reinforcing.com/

32

The Australian Certification Authority for Reinforcing Steels (ACRS) administers an independent voluntary product certification scheme to provide an audit of the manufacturing processes for reinforcing steels as supplied to the Australian market to ensure their compliance with Australian Standard, AS 4671.

acrs.net.au

ACRS mission “The continued manufacture and supply of reliable, safe, consistent-quality steel reinforcement and prestressing strand to Australian Standards” ARBE3100 Construction Technology 3



7.3.3 Steel Storage The steel must be stored above the surface of the ground upon platforms, skids, or other supports and shall be protected from damage and deterioration. This prevents excessive rusting that would occur if sitting directly on the ground.

34

Does rusting affect the performance of reinfor cement? Surface rusting of reinforcing bars or mesh does not affect the performance of the steel unless the physical properties of the suspected steel are below the minimum requirements of AS4671. alaglobal.com

What are the min requirement?

Figure 7.22 Steel batch

When placed in the work, reinforcement shall be free from dirt, paint, grease, oil, or other foreign materials, and shall be free from defects such as cracks and lami nations.

Figure 7.23 Surface rusting of steel

In fact, surface rusting can increase the bond of the steel to the concrete. However, prolonged surface rusting can eventually lead to pitting of the steel and this may lead to a weakening of the steel section.





7.3.4 Reinforcing Steel Characteristics

36

Reinforcing steel abbreviation

Grade strength 

Only three strength Grades have been considered, i.e., those having lower characteristic yield strengths of 250 MPa, 300 MPa and 500 MPa respectively.

Deformed steel

Grade 500 yield bars; yield strength = 500 N/mm2

Ductility 

D 500 N

Three ductility classes. These are distinguished in requirements by the letters ‘L’ (low), ‘N’ (normal) and ‘E’ (earthquake), placed immediately after the strength-grade number.



Ductility class, N = normal



38

Brittle failure and ductile failure Importance of Ductility  Large displacements before collapse (as opposed to a brittle material, which fails suddenly)

Brittle Ductile



Energy dissipation as the steel yields (important for resisting earthquakes and other overloading) Elongation Al: > 40% High strength Al alloy: 10-15% High strength steel: < 10% Ceramics: ~0

, ) A / F ( s s e r t S

Figure 7.24 Ductility among different materials

hsc.csu.edu.au

O

’

’’

Strain (l /l ),

Figure 7.25 Brittle failure vs ductile failure ARBE3100 Construction Technology 3




Size of reinforcing bars

40

Bond mechanism

Table 7.3 Preferred nominal diameters, cross-sectional areas and masses for reinforcing steels (AS 4617)



Bonds refer to transfer of stress along the length of the bar.



Deformed bar increase surface area, thus more effective bonding with concrete.

Nominal diameter mm

Cross-sectional area mm2

Mass per metre length, kg/m

12.0

113

0.888

16.0

201

1.58

20.0

314

2.47

24.0

452

3.55

Concrete

28.0

616

4.83

Interfacial bonding

32.0

804

6.31

36.0

1020

7.99

Deformed Steel Figure 7.26 Bond between concrete and reinforcement

NOTE: The values for the mass per unit length given in Table 7.3 have been calculated from the values for the nominal diameter using a density value of 7850 kg/m3. ARBE3100 Construction Technology 3




Geometry of ribs and indentations

42

7.3.5 Examples of Steel Reinforcing Materials Grade D500N hot-rolled deformed bars 

Rib flank inclination (α) and rib height (h)

Figure 7.27 Example of rib geometry

AS/NZS

Straight lengths up to about 12 metres.



Standard diameters 12 mm, 16 mm, 20 mm, 24 mm, 28 mm, 32 mm and 36 mm.




to



( AS 4671)

The rib height (h) shall be 0.05d to 0.10d and the longitudinal spacing (c ) of the ribs shall be between 0.5d to 1.0d. The crest width of ribs (w c ) shall be not greater than 0.3c . For more details, please refer to AS 4671.

Manufactured 4671.

acereinforcements.com.au

Figure 7.28 D500N Deformed bars

Mainly for moment resistance purpose.




Grade D250N deformed bars 



44

Resistance-welded reinforcing mesh

More-easily bent into complex shapes, hence preferred in concrete swimming pool construction. Not allowed for foundation purposes.



Made from Grade 500L cold-drawn wires



Square or rectangular



Available with reduced side laps



Standard sheets 6.0 x 2.4 m

gharexpert.com

Figure 7.29 D250N Deformed bars 


May be cut and bent


mcmahons.ie

Figure 7.30 Steel mesh



Reinforcing accessories - Mechanical Splices

46

Reinforcing accessories - Bar Chairs



Compression and tension splices



Plastic-tip wire chair



Tapered screw-thread couplers



Metal bases



Swagged/screwed couplers



Bottom and top reo support



Single-part couplers



Clip-fast plastic chairs



Slab-on-ground plastic chairs



Plastic fastwheel chairs

sria.com.au

sria.com.au

sria.com.au

photographersdirect.com

Figure 7.32 Bar chairs hotfrog.in

bikudo.com

edingaps.com

Figure 7.31 Rebar splicing ARBE3100 Construction Technology 3




Reinforcing accessories - Bar Safety Guards 

Place on starter bars



Site safety and protection



Bright colours



Many types and sizes

Maintaining steel continuity in the longitudinal direction is important in ensuring good performance of the long span structural elements.

sria.com.au

Figure 7.33 Safety Guards


48

7.3.6 Steel Lapping

The continuity of the longitudinal steel is achieved conventionally by overlapping individual steel bars.


onlinemanuals.txdot.gov

Figure 7.34 Example reinforcing steel

of

lapped



Extensive testing shows that as long as the overlapping is more than 33 times bar diameter , stresses in one steel is effectively transferred to the next steel via surrounding concrete.

50

Steel lapping or splicing? Lapping Advantages   

For example, bars of 10 mm diameter would need a 330 mm splice for effective stress transfer. Steel splicing using couplers becomes more popular.

More flexible Require less prefabrication work Cheap



Increase resistance of bending/buckling



Traditional method

Splicing Advantages  


Reduces rebar congestion More no of rebars can be added within same crosssection



Direct load path continuity



Develops rebar splice strength independent of concrete strength & conditions



Huge steel saving due to overlap length (50d), nearly 30-40% saving compared to lap length

barsplicing.tripod.com




7.3.7 Sampling and Testing of Reinforcing Steel The sampling and frequency of testing of the various types of reinforcing steel shall be in accordance with Appendix B of AS 4671.

52

Tensile properties 

The tensile properties include the yield strength, maximum tensile strength and ductility of a metal can be characterized by performing the longitudinal tension test in accordance with AS 1163.



For reinforcing bars, one test for each 50 tons of product or part thereof, but not less than three tests per batch shall be performed.

The following material properties are required to test:    

Chemical composition Yield stress and tensile strength Uniform elongation Mass per unit length



Bending and rebending properties



Geometric properties



Bond strength


Figure 7.35 Tensile test machine ARBE3100 Construction Technology 3



Tensile stress-strain curve D

C

54

Bond test 

The bond test in Appendix C of AS 4671 has been introduced.



An alternative means for demonstrating the ability of deformed reinforcement to develop sufficient bond to achieve its characteristic yield strength when embedded in concrete.

B

, ) A / F (

A

Fracture

s s e r t S

O

<1%

Strain (l /l ),

<30 %

Figure 7.37 Schematic arrangement of bond test equipment and test specimen ( AS 4671)

Figure 7.36 Stress-strain diagram by tensile test ARBE3100 Construction Technology 3


7.4 Structural Steel

7.4 Structural Steel 55

56

7.4.1 Application of Structural Steel Increased demands for efficient use of space and cost-effective building practices have resulted in the adoption of structural steel frame allows the maximum provision of usable space with the minimum space taken up by the structures.

Chan, 2012

Advances in construction technology have allowed buildings of great height with great spans to be erected with the engineering.leeds.ac.uk adoption of structural frames. Figure 7.38 Steel frame structure

steelandsite.com

Figure 7.39 A steel frame building ARBE3100 Construction Technology 3


steelhomeplans.com.au

inter-steel.com



skyscrapercity.com

Figure 7.40 New York Times Tower ARBE3100 Construction Technology 3

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skyscrapercity.com

Figure 7.41 Shanghai's World Financial Center

Figure 7.42 Steel roof

Chan, 2012




60

7.4.2 Structural Steel Advantages and Disadvantages The choice of structural steelwork system as an alternative to reinforced concrete structures has many advantages. Speed of construction 

Building can be occupied sooner.



Less disruption to public.

Low construction depth 

Reduce overall height of structure.

Long spans  Few

columns.

 Flexible Chan, 2012

Figure 7.43 Steel stair ARBE3100 Construction Technology 3

Chan, 2012

occupancy.

 Cheaper foundation. ARBE3100 Construction Technology 3

braemarbuildings.com

Figure 7.44 Clear-span steel structure



Permanent slab formwork 

62

There are some drawbacks construction.

Falseworks are eliminated.

Lower weight of structure

structural steel

Fire performance



Fewer piles and size of foundation.



Typical 50% weight reduction over concrete.

 Weaker

in fire resistance for steel will lose strength and deform serious at higher temperature (at 600oC or above).

www.core77.com

Prefabrication in workshop 

using

Figure 7.45 Lightweight steel

 This

can be improved by applying fire resistant plaster.

Quality control in good conditions avoiding sites affected by weather.

Other benefits

High deformability

 Adaptability,



future extension, predictable maintenance costs, lightweight units for erection, options for site joint locations, aesthetics, etc.


farm3.static.flickr.com

Figure 7.46 Fire bent steel construction

Produce larger deflection & deformation (Bend) under wind - this will cause discomfort to users of building.




64

Rusting or corrosion problems

Hoisting and handling





Very strict anti-corrosion treatment has to be applied.

Demand greater transportation or cranage provision.

 Large

member delivery to site waiting to hoisting up for erection.

 Huge

amount of structural members make erection very complicated.

rollanet.org

superstock.com

farm4.static.flickr.com

Figure 7.47 Serious structural problem due to r usting asc.llnl.gov ARBE3100 Construction Technology 3


Figure 7.48 Crane hoisting steel beam to top of building



66

Connections Assurance 

Longer and highly coordinated planning – require long time to make structural design, fabrication, delivery and connection.



Complicated quality assurance procedures especially in the control of welding connection.

Roof truss and the decking not on the same level www.tboake.com

Figure 7.49 Complicated connections  Difficult

to make connection with rigid structures – especially in composite structure in which RC core structure is involved.

 Connecting

large and complicate shaped components can be very

difficult.

Concrete has to be trimmed to allow steel to pass through personal.cityu.edu.hk/~bswmwong/

 Unmatched

Figure 7.50 Examples of location where unmatched dimension causing problem

dimension causing problem.





68

Work at higher altitude  More

complex when building become more gigantic and taller which may induce more works at higher altitude

appletreeblog.com

cache.boston.com

Figure 7.52 Structural steel workers elegantchic.wordpress.com

Figure 7.51 Workers work at high altit ude (upper floor of Burj Khalifa) ARBE3100 Construction Technology 3

cartoonstock.com

World’s 10 most dangerous jobs: The risk of falling is high for structural iron and steel workers who work at extreme heights in a variety of weather conditions. ARBE3100 Construction Technology 3



7.4.3 Principle Factors Affecting Choice of Structural Frame Structural design considerations  Foundation

 Strength

consideration

 Standardization

of members or design

 Span  Fire

Floor structure



resistance requirement

Durability and maintenance

freedom

from

e.g. corrosion resistance

consideration

 Fire

Foundation

Integration of architectural & structural elements

and stability

e.g. yield strength of steel and rigidity of connections and stability against various loads

Framework

and floor loads

 Maintenance 

70

The functional requirements of a structural frame are:

fgg.uni-lj.si

safety

e.g. fire resisting period and strength retention

Figure 7.53 Typical layout of multi-storey steel building


exponent.com

Figure 7.54 Collapse of steel structure




72

7.4.4 Standard Forms of Structural Steel The availability of steel sections in a variety of dimensional ranges provides the designers with a wide variety of design options. These sections are manufactured in convenient shapes, sizes and thickness. They can be readily fabricated, combined and connected to form unlimited possibility of designs. ARBE3100 Construction Technology 3

Angles

Channel

S.H.S

Tee

H-section

R.H.S

Beam

C.H.S

Figure 7.56 Steel section terminology

corusconstruction.com

Figure 7.55 Common sections used for structural steelwork. ARBE3100 Construction Technology 3



Structural steel members, such as I-beams, have high second moments of area, which allow them to be very stiff in respect to their cross-sectional area.

74

Cellular beam is an advanced development of the castellated beam design. Castellation is a technique used to expand a standard section steel beam (~1.5 times) without adding any weight or wastage.

neo-techsys.webhop.net 

High fabrication cost



Less deflection  Long span

Figure 7.57 Examples of hot-rolled steel sections What kind of sections can u see?

Chan, 2012



Figure 7.58 Cellular beam


Good for housing electrical and mechanical services




76

Steel strength grades commonly used in structural applications in Australia are “ 300PLUS”, conforming to AS 3679.1, AS 3679.2 and mainly hot rolled sections. Table 2.1 (HB 2.2 page 153) provides yield stresses and tensile strengths of the above strength grades. E.g. 300PLUS sections exceeds the min. requirements of AS/NZS 3679.1:1996 grade 300 (yield strength of 280 300MPa depending on thickness, HB 2.2 page 155) The above steel grades ensure ductility permitting plastic design criteria. NB: Steel members are generally slender and susceptible to buckle in and out of plane. ARBE3100 Construction Technology 3

http://www.onesteel.com

Figure 7.59 BHP Catalogue ARBE3100 Construction Technology 3



7.4.5 Structural Connections Design consideration for cost-effective connections  Carry

and distribute the load required

 Easy

fabrication

 Easy

transportation

 Easy

erection and assembly on site

 Do

78

Bolting or Welding ? Preferred methods of connections Bolting on site 

AS 1252 high strength steel bolts

 Fast

and economic. imghost.indiamart.com Strength Friction Grip bolts (HSFG) provide extremely efficient connections and Figure 7.61 HSFG bolt perform well under fatigue load conditions.

 High

Welding in fabrication shop

not hold water

Connections in structural steelwork are classified as either shop connection or site connection, and can be made by using bolts, rivets or by welding.

 AS

1554 Welds

 Difficult

and expensive to do site welding at heights.

gdengineers.net

Figure 7.60 Structural connections




Easily controlled and hence quality assured.

squarehouseinfo3.blogspot.com

Figure 7.62 Beam welding on site




Common types of structural connections:  Beam 

splices (A)

Simple connection (A)

 Column 

A

C

Continuous beam-column connections (C) base connection (D)

 Bracing

connections (E)

Connection core (F)


with

Beam splices either bolted or welded typically resist large bending moments and shear forces. It is usually assumed that the flange splice carries all the moment and the web splice carries the shear.

E

D

 Column





B

beam-beam

splices (B)

80

Beam splices connection

F

concrete

Chan (2012)

Figure 7.63 Beam bolted splices

http://www.fgg.uni-lj.si/


csihellas.gr



82

Beam-beam connection

Slab-beam connection



Usually secondary beams are simply supported on main beams and only shear force is transmitted.

 General



Fastening to the plate bolted to the flanges/webs.

kurowski.com

profile steel floor deck with insitu concrete cast over the deck.



Primary and secondary beams in composite steel frames are connected by shear studs.

bignews.biz

 Floor

steelesolutions.com

slab and the beams beneath act compositely.

fgg.uni-lj.si

img.tfd.com

Figure 7.65 Slab-beam connection

Figure 7.64 Beam-beam connection ARBE3100 Construction Technology 3




84

Beam-column connection 

Simple beam, either thin plate and end plate connection.

 For

moment connection, a stud connection can be used, column is connected by bolting to the end plates welded to beams on site.

Shear Stud

 Steel Chan (2012)

Shear studs are welded onto I-beams

Chan (2012)

Close-up shot of shear studs

Figure 7.66 Slab-beam connection

beam moment connection bolting the beams on both flanges and web.

 Common

for moment transfer joint.

Details will be covered in Lecture 9 Floor, Ceiling and Floor systems





86

Column splices 

Shear connection of using thin plate connection

Columns splices are locations where a column section joins another column section.

Moment connection using bolts and welds

Welded column splice


Chan (2012)

Figure 7.68 Column-column connection

Chan (2012)

Beam to CHS column connection

Bolted column splice

Beam to RHS column connection

Figure 7.67 Beam-column connection




88

Column-base connection  Columns

connect to base.

microstran.com.au

Figure 7.70 Column base (2 channels tied together) at foundations.

Chan (2012)

Figure 7.69 Typical column-base connections



constructiondetails.us.cype.com



Beam and concrete connection

90

Bracing connection E3

E4

E1

E1 E2

E2 Chan (2012)

E4

E3

http://www.fgg.uni-lj.si/

Chan (2012)

Figure 7.72 Different types of bracing connection

Figure 7.71 Beam-concrete connection ARBE3100 Construction Technology 3




92

Wind braces to the steel frame

Chan (2012) eco-logic-systems.com

Plan

Elevation

Beams are represented by single lines only

Figure 7.74 Multi-storey steel frame Figure 7.73 Wind braces to the steel structure ARBE3100 Construction Technology 3




94

7.4.6 Erection of Steel Structures Aims 

To save time, to achieve rapid erection.

 Loads

can be applied immediately to the assembled structure.

Chan (2012)



Does not delay trades following erection.



Stability of the partially erected structure.

Beams are represented by single lines only

Figure 7.75 Steel framing plan

 Safety


of labour.

waltersinc.com

Figure 7.76 Steel erection




96

Site planning & organization

Erection activities

 Competition

 Hoisting

- lifting of members or components.

of resources, e.g. the use of tower crane.



Limited centres.

in

town



Obstruction such scaffolding, shoring.

as

access

personal.cityu.edu.hk/~bswmwong

 Availability

of space in site.

Figure 7.77 Complicated Erection process



Temporary connections - rapid release of crane.



Plumbing & levelling adjustment of position.



Permanent connection to provided connection as indicated on drawings.

-

fine

dubourdieu-inc.com

Figure 7.78 Steel connection

AS 4100 specifies the requirements for the erection of the steel frame including the delivery, storage and handling, assembly and alignment, connections and inspection. ARBE3100 Construction Technology 3




98

7.4.7 Protection Against Corrosion Corrosion of steel costs around 4% of GDP. Every 90 seconds, across the world, one ton of steel turns to rust; of every two tons of steel made, one is to replace rust (MIT open courseware). How to avoid corrosion?  Careful

detailing to protect from

water. 

Use stainless steel.



Protect steel with galvanizing (zinc coating) or other protective coating.

cffstainless.com

Figure 7.79 Stainless I beam

wb8.itrademarket.com

Figure 7.80 Hot dip galvanizing for structural steel

MIT opencourseware, http://ocw.mit.edu/OcwWeb/web/home/home/index.htm. ARBE3100 Construction Technology 3




Additional notes on corrosion protection: 

Good design of members and connections in steel framework is the key to corrosion prevention.

 The

quality of the coatings on fasteners and welds is as important as that on the main framework.



The environments both inside and outside of the building have to be considered.

 Avoid

inaccessible areas in connection.

 Quality

of concrete surrounding steel sections is critical to corrosion.

 Advice

should always be taken from an experienced practitioner.


100

7.4.8 Fire protection for steelwork If steel is heated beyond 550 oC, its strength would be reduced to 150 MPa (about one-third of its original strength). Structural steel requires external insulation (fireproofing) in order to prevent the steel from weakening in the event of a fire.

www.exponent.com

Figure 7.81 Structure affected by fire

Degree of fire resistance varies according to the function, occupancy, height, capacity, floor area, distance from other buildings ARBE3100 Construction Technology 3



There are four common methods of fire protecting structural steelwork.  Intumescent  Board

AS 4100 specifies the methods of proof tests and prototype tests of complete structures, sub-structures, individual members or connections.

coatings

 Proof

based systems

 Sprayed

fire protection systems

 Concrete

102

7.4.9 Testing of Steel Structures or Elements

dpcltd.co.uk

Figure 7.82 Steel coating

testing - the a pplication of test loads to a structure, substructure, member or connection to ascertain the structural characteristics of only that one unit under test .

 Prototype

testing - the application of test loads to one or more structures, sub-structures, members or connections to ascertain the structural characteristics of that class of structures, sub-structures, members or connections which are nominally identical to the units tested.

encasement or filling

The fire-resistance test specified in AS 1530 applies to all steel building elements. Details will be covered in Lecture 12 Fire Engineering and Fire Fighting Equipment

Both testing methods are used to check for the strength or serviceability limit state compliances.




7.5 Steel and Environment 103

Tensile properties Testing

104

7.5.1 Is Steel a Green Material?

Similar to steel reinforcement, the tensile properties include the yield strength and ductility of a structural element can be characterized by performing the longitudinal tension test in accordance with AS 1163.

Steel manufacturing process consumes lots of resources and produces greenhouse gases inevitably. Steel Brickwork Reinforced concrete Wood

Full section test piece (MIT open courseware).

Portion of test pieces

Figure 7.83 Sections – location of test pieces for tensile testing (AS1391) ARBE3100 Construction Technology 3

Figure 7.84 Ecological profile of materials ARBE3100 Construction Technology 3

7.5 Steel and Environment


However, steel can be recycled and is a good alternative building material that contribute to sustainable construction. 90% of structural steel and 30% of light gauge steel can be recycled.

106

Environmental Impact of Steel Environmental Advantages of Steel

Each ton of recycled steel saves 1200 pounds of coal.



Lower weight reduces foundation requirements



Highly recycled and can continue to be recycled indefinitely



Durable, if protected from corrosion

Environmental Disadvantages of Steel

themetalmuse.com

happyscrappy.co.nz



Very high energy use, predominantly from burning coal → produces pollution



Lightweight, so lower thermal mass compared to concrete → requires more insulation



Is susceptible to corrosion

Figure 7.85 Recycled steel ARBE3100 Construction Technology 3


7.5 Steel and Environment


7.5.2 Future development of using structural steel or composite structures in Australia. The following ways may be adopted in order to achieve more cost effective application of technology in future.  Use

more simple and straight forward design like regular steel frame structure in grid layout.



Use more standardized Chan (2012) components such as Figure 7.86 Regular steel structure universal sections, lattice trusses or prefabricated standard sections.


108



Apply more to other types of building structure/construction as in many developed country like Japan, USA, or even Korea and Taiwan.

 Forming

hybrid structure with other prefabricated elements, i.e. with the mixed use of precast concrete, cast-in-situ concrete and steel composite.


archsd.gov.hk

Figure 7.87 Hybrid structure

7.6 Recommended Study Texts

7.7 Summary 109

Australian Steel Institute, http://www.steel.org.au, accessed on 24 August 2015.

110

After this lecture, be sure you know the followings Describe the general properties of steels and their production process.

Steel Reinforcement Institute of Australia, http://www.sria.com.au/main/main.html, accessed on 24 August 2015.

Chan, W. K. (2012), Structural Steel Introduction, RMIT.

Describe the types of steel reinforcement and their properties and application.

Barry, R. (2001) The Construction of Buildings (Vol 4), 5th Edition, Blackwell Scientific Publications.

Describe the use of structural steel, the connection details and structural steel work.

OneSteel, http://www.onesteel.com/, accessed on 24 August 2015.

Understand the contribution of steel to sustainable construction.



7.8 Self-study Question 111

1. In any particular construction project, either reinforced concrete or structural steel is used as the dominant construction material. Discuss the pros and cons of both materials for construction and determine which is the most appropriate for Australia's construction sector? 2. Please watch “beam-beam connection” video (can be found in the multimedia folder) and then discuss which of the two connections do you prefer?


Lecture 7 - Steel Application

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