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High Performance Hospitals SMALL HEADLINE
USING CONCRETE FRAMES AND CLADDING
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Good hospital design can provide more efcient facilities and a better environment for both staff and patients. Concrete construction presents great opportunities for the project team to meet the needs of the client by helping to improve the function, value and whole life performance of the facility. By checking that the design and construction process gives timely consideration of the benets discussed in this publication, decision makers in the procurement process can ensure that extra value is added to the building, building , often at no or little additional cost.
Front cover (left to right) Photography: y: Gillian Bond. • The Great Western Western Hospital, Swindon: in-situ in-situ at slab concrete frame with precast cladding. Photograph • Central Middlesex Hospital ACAD Centre: Centre: a concrete framed structure which is exposed in public areas. Photography: Nicholas Kane.
This page Photo captions to West go hereMiddlesex University • The University Hospital: concrete walls clad in timber, render and brick. Design: Nightingale Associates; Photography: Charlotte Wood.
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BUILDING BETTER HEALTHCARE Hospitals are facilities that help medical staff in the efcient delivery of quality healthcare and provide a positive environme environment nt for speedy patient recovery. recov ery. Good building design can provide more efcient facilities and a better environment environment for both staff and patients. This publication examines the role of concrete construction in the current hospital development programme to provide additional effective, high quality healthcare to meet the nation’s growing and changing needs. It aims to inform decision makers in the procurement process about areas where concrete construction can help improve the function, value and whole life cost of the facility. A major government initiative is underway to provide 100 new hospital buildings by 2010. To meet this ambitious target and also ensure best value, the plan is being funded by a mixture of public, private and local NHS trust capital, with procurement under the Private Public Partnership, often involving ProCure21, PFI and DBFO. These aim to promote better capital procurement and improve the service to patients through a partnering programme between the NHS and the private sector. Construction partnerships will often design the facilities and be nancially involved with their operation and maintenance. This will help secure highquality designs and earlier access to new facilities, and ensure best value, both from initial and whole life cost perspectives. Recent research has conrmed that good design creates the best environment for patients, staff and visitors, which promotes effective services and speedier recovery, resulting in more efcient use of resources. The design, construction and operation of new facilities is now formally assessed using a variety of measures – not just nancial – encouraging more considered and holistic design and construction processes and better value solutions. The new buildings will have to satisfy a range of complex and often conicting needs, including the exibility to accommodate not only changes in demand, healthcare procedures, IT and working methods but also newly emerging issues such as cross-infection and MRSA, daylighting, natural ventilation and sustainability.
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The benets of using concrete: • Reduces initial and running costs • Speeds construction • Minimises vibration
CONCRETE FOR HOSPITAL CONSTRUCTION Well-designed and effectively managed hospital buildings help support the work of frontline staff, provide an appropriate environment for patient recovery, and so improve efciency. The choice and design of a building’s frame and cladding can have a surprisingly large inuence on the performance of the nal building. An important example of this is the effect on the provision of M&E services, which are generally the most critical item in cost and construction time, and are a major factor in the costs of running, maintaining and refurbishing a building over its life.
• Accommodates Accommodates future changes
Although every new facility has specic requirements, a typical list of needs to be considered might be:
• Facilitates partition wall sealing s ealing
• Value/cost – how well well it performs its its function in terms terms of helping staff and and patients in relation to initial and running costs and residual value
• Caters for easy services installation
• Speed – how quickly it can be brought into use • Flexibility – how easily easily it can accommodate accommodate or be adapted adapted for changing needs • Sustainability issues – both both during construction construction and in in use.
• Enhances sustainability s ustainability
Behind these requirements lie some particularly important considerations, considerations, some of which are specic to healthcare buildings, and include:
• Promotes Promotes a good work environment
• Vibration – operating theatres theatres and night wards wards require the designer designer to pay special special attention to reducing vibration
• Resists spread of re re and sound
• Partition walls walls – installing installing and sealing literally literally miles of these to to the frame
• Improves Improves air quality
• Further issues such as sound, re resistance resistance and air air quality.
• Services – often often the most expensive and and slowest element element to construct construct • Work environment environment – proven proven to affect staff staff morale and patient patient recovery
Today’s concrete frames are ideally suited to support the requirements of modern hospital Today’s buildings; and by playing an important background role in the operation and performance of the building, concrete frames can help reduce running costs and maintenance. Exposed concrete walls look good and provide fabric energy storage (European Institute of Health and Medical Sciences). Courtesy of The Concrete Society. Society.
The following sections consider these issues fur ther and discuss how concrete’s properties can help resolve them.
SPEED AND PROGRAMME The use of concrete is highly compatible with fast programme programme construction due to easy mobilisation at the start and the use of modern methods of construction, including sophisticated formwork systems, post-tensioning and precast elements. With traditional methods of construction, concrete frames were erected on a oor-to-oor cycle of two to three weeks. With modern methods it is common to achieve this in one week. Concrete frames normally require no disruptive re protection after erection, and can be made sufciently watertight for early installation of M&E services (the longest phase of construction in hospitals) and other follow-on trades. The use of concrete at slab oors provides ush softs that simplify service provision. This encourages the swift installation of prefabricated services, where major savings in cost and time come f rom factory-tested assemblies and fewer joints on site. Prefabricated bathroom pods can be installed and set ush by recessing them into the oor slab.
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VIBRATION VIBRA TION CONTROL Vibration control is especially important in areas Vibration such as operating theatres, night wards and intensive care units, and is an important factor in the design and specication of building frames. Concrete Concrete can easily be designed for the most complete control of vibration over whole areas, often without the need for signicantly thicker oor slabs, giving great exibility for change in use. A recent independent study* into the vibration performance of different structural forms has provided new insight into the additional mass and stiffness required to upgrade a basic ‘ofce‘ structure to meet the higher criteria of hospitals. This is summarised in the diagram opposite. The concrete solutions can meet vibration criteria with only small increases in mass and depth and hence cost, compared with steel frame solutions. They also help the D&B team avoid the risks, often associated with other materials, of having to seek modications to NHS vibration criteria. This is done to avoid the cost penalties of providing this extra mass and stiffness.
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FLEXIBILITY AND ADAPTABILITY Healthcare methods, provision of IT, patient expectations, and standards of environment and equipment are all changing rapidly; so exibility of use of new buildings is a major design requirement. For instance, less invasive surgery is likely to continue to change the required proportions of theatre, recovery and ward space. The use of concrete construction automatically ensures many of the qualities that aid exibility. For services and future stairs or lifts, holes in both normal and post-tensioned slabs can easily be designed-in and either formed during construction or cut out later as required. For vibration, larger areas can be designed to meet stringent criteria for operating theatres at little extra cost, permitting future exibility.
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The above diagram shows the increases in mass and construction depth needed to upgrade an ofce frame to hospital vibration criteria for night wards and operating theatres.
PARTITION WALLS Hospitals require literally miles of partition walls and their construction is a major factor in cost, time and the consequent disruption to other construction procedures. Sealing walls at the softs of the oor above is particularly important. The use of at slabs simplies this, reducing partition costs by up to 4% of the frame cost before considering additional programme savings.
Early consideration of these benets during design can optimise exibility at little or no extra expense. Concrete structures reduce vibration cost-effectively. cost-effectively. Courtesy of the National Society for Epilepsy.
SOUND It has been shown that patient comfort is an important factor in recovery. Concrete’s mass and damping qualities are easily used to achieve the required acoustic performance, which provides a restful and productive environment that is isolated from the noise and vibrations resulting from normal hospital routines. In concrete buildings, oor and ceiling nishes are rarely dictated by acoustic requirements; these are delivered by the performance of the concrete slab.
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In a building, the environmental impact of construction materials is typically one tenth of that caused by operation over its life.
SERVICES The choice of material and design of a building’s frame and cladding can have a surprisingly inuential role on the services, which are generally the most critical element in construction cost and time. Concrete at slabs are ideal for highly serviced areas in h ospitals, such as operating theatres and intensive care units. They allow complete freedom to prefabricate, install and maintain services without having to thread ducts under or through intrusive downstand beams. Openings Openings in the slab for service risers can be simply accommodated during design; they can be formed during casting or cut later to suit. For the longest spans, wide shallow beam solutions provide large areas uninterrupted by secondary beams and the freedom to route ducts under the shallow main beams. For the less h eavily serviced areas, designers are now encouraged to use concrete’s thermal mass properties to reduce air-conditioning. air-conditioning. This then reduces capital, refurbishment and running costs.
SUSTAINABLE SUST AINABLE CONSTRUCTION Concrete has much to offer those who aim for sustainable construction. It has the potential to reduce both the initial cost and running expenses by: • Reducing the need for air-condi air-conditioning tioning through fabric fabric energy storage, storage, and the use of of daylighting and natural ventilation. ventilation. Concrete has an excellent track record in passively passively cooled buildings. • Reducing the need for heating through airtight construction. construction. • Reducing maintenance maintenance through providing providing durable walls, columns and cladding. Other sustainable aspects of concrete construction include: • UK manufactured reinforcing reinforcing steel is made from 100% recycled scrap, unlike structural steel. • Cement manufacture manufacture is increasingly increasingly using waste-derived waste-derived fuels (such as scrap scrap tyres), thereby saving energy and relieving pressure upon landll facilities. • Replacement materials, materials, which which would otherwise go to landll, are being being incorporated incorporated into both cement and concrete to reduce their environmental impact. • Aggregates are often extracted extracted locally, locally, and ready-mixed ready-mixed concrete is typically made no more than 15 miles from any project. This reduces the environmental impacts associated with transportatio transportation. n.
Concrete at slabs are ideal for highly serviced buildings.
• Unlike some materials, impacts arising from reinforced concrete generally occur in the UK, rather than being ‘hidden’ abroad, and so are recognised and minimised for global benet. • The energy and carbon dioxide emissions ‘embodied’ in a concrete frame are slightly less than those in a steel frame. More importantly, however, the energy used and CO 2 emitted during a building’s operation are some 50 times greater than those embodied in its structural frame. By using the excellent thermal properties of concrete it is possible to make signicant whole life savings in energy, carbon dioxide emissions and operating costs. • On demolition of a building, concrete and reinforcement can be recycled. • Concrete buildings buildings are adaptable, adaptable, durable and and have many inherent inherent qualities (sound, (sound, re and vibration performance), performance), and hence are ‘long life, loose t’ sustainable buildings.
By the use of thermal modelling, solar shading and passive ventilation techniques to complement its concrete frame, the designers of Derby PFI hospital are aiming for an annual energy target of 55 GJ/100 m 3 p.a. – making it one of the most energy-efcient acute hospitals in the UK.
An environmental review of design and construction of the Great Western Hospital Swindon by environmental award award winner, Carillion, achieved a cost saving of £1.8m. £1 .8m. This considered materials used, waste targets and energy in use. The hospital incorporates a high thermal mass concrete frame and concrete cladding. Excavated clay material was treated with lime and cement to provide a sub-base for the roads and car parks, saving the costs of removal from site. The building is designed to consume
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WORK ENVIRONMENT The look and feel of a hospital is known to affect patient and staff well-being and hence healthcare performance. Uplifting Uplifting architecture in public areas, involving the use of exciting structurally efcient exposed softs, columns and walls can all add to the character and ambience of a building. This avoids having to develop an ar ticial architectural veneer that adds to rst costs, maintenance, and refurbishment. Concrete is inert with no harmful off-gassing, and its structural form is commonly associated with enhanced natural ventilation and daylighting. It provides robust surfaces for walls, partitions, columns, softs and cladding that are easily sealed for cleaning where required. Aesthetics, ease of cleaning and a healthy atmosphere all lead to enhanced user satisfaction of concrete hospitals.
FIRE Concrete is inherently re resistant, and unlike some materials normally requires no added re protection. This avoids the delays and disruptions of follow-on trades caused by site applied protection or repair on site of damaged off-site applied protection. Concrete’s re protection is provided at no extra cost and does not require the use of intumescent paints. The inherent re resistance results in concrete often performing in excess of design requirements for occupant safety. This over-performance benets the building ‘owner’ as repairs and the period before re-use following a re are minimised.
MAINTENANCE AND REFURBISHMENT Whole life costs can be reduced by the use of concrete which provides long life cladding, durable walls and columns with direct nishes, and easily accessed services under at softs. Cladding can be designed to last the nominal design life of the building, with only periodic inspection of the external seals. By using the exposed softs, suspended ceilings and air conditioning may be reduced or avoided, lowering lowering maintenance and refurbishment costs.
ANCILLARY BUILDINGS The use of techniques such as ‘tunnel form’ form’ and precast wall and oor panels introduces further mass production methods into concrete construction. Both are fast, economic, highly-mechanised and increasingly popular. For repetitive room layouts, such as staff residences, they are ideal because of excellent sound and re properties and low maintenance durable nishes. Concrete is also ideal for car parks due to its robustness and corrosion resistance. It is a popular choice with users, with modern design taking advantage of concrete’s clear span capabilities to provide easy access/parking, and bright clean softs that help security and boost user condence.
Exploiting the benets of concrete is simple and comes at little or no added cost. It just requires early awareness and consideration of the
AIR TIGHTNESS
potential gains and for decisions to be made at the correct stage in the design process.
With concrete, the at softs enable the partitions between rooms to be sealed easily, helping prevent airborne cross contamination between compartments. Large panel external cladding reduces the number of external joints and so cuts air loss and saves energy. The light and airy reception at the Great Western Hospital, Swindon. Photography: Gillian Bond.
Modern methods of concrete construction are ideal for staff accommodation.
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Flat slab concrete
DESIGN
construction is the
Concrete frames are available in a broad range of structural forms to suit all needs and can be constructed in precast or in-situ concrete, or a combination of the two, known as hybrid concrete construction.
preferred framing option for many hospitals as it provides speed and exibility.
Currently, at slab construction, typically on grids of 7.2 to 8.4 m on a 1.2 m module, Currently, is the preferred choice for many hospitals with its speed, vibration performance and ability to best facilitate the installation of services and partition walls. Increasingly, the at slabs are post-tensioned to reduce slab thickness and provide potential for longer spans of up to 12 m if necessary. Some alternatives to at slab construction are shown below. • Prestressing of of concrete beams and oor units provides provides fast, light and economical economical solutions. • Ribbed in-situ slabs slabs on wide shallow beams beams are lighter than at slabs, but but not so versatile and take longer to construct. • Hybrid concrete construction construction combines combines the best qualities qualities of precast concrete concrete (accuracy, high quality nishes, off-site manufacture) with those of in-situ construction (exibility for late changes, mouldability, robustness, two-way spanning, local manufacture). For each hospital the most effective solution can be determined only after considering all design, construction and use parameter parameters. s. The benets of using concrete discussed in this publication provide a useful guide for designers when comparing construction types. For the structural engineer, assistance assistance is available from the design tool, Concept (see back cover). Design loadings need to be agreed between client, architect and structural engineer early in the design process. Allowances Allowances for larger point loads for ceiling-hung equipment and heavy-weight blockwork partitions are often required. Vibrati Vibration on criteria for operating theatres and night wards will often dictate structural design. The client may choose to have larger areas designed to these tighter criteria to permit future space planning exibility.
Concrete options for hospital frames.
Solid at slab (may be post-tensioned)
When considering penetrations through slabs for services, the needs of the services engineer must be co-ordinated with those of the structural engineers, who should incorporate them into their design. Working with the design team, the client will need to decide how much exibility it is reasonable to build in. For future exibility, ‘soft spots’ are generally designed in; polystyrene knock out slots, cast-in lightweight blocks or cast-in markers are all commonly used. These, together together with the design drawings, aid those making future modications modications.. In reinforced concrete, holes near columns can be situated at the faces of the columns, rather than being restricted to the corners so as not to clash with beams. This avoids the need to offset pipe work back to column faces or use oversized clad columns to hide pipe work on column corners. Off-site manufactured bathroom pods are commonly used. To incorporate these with the required falls, pods may be set on the slab with a traditional screed used elsewhere. elsewhere. However, it is common common to omit the thick screed and at most have a thin bed levelling screed. To obtain the falls into the wet area, the slab is locally cast with a recess of 30 to 50 mm into which the pod is placed.
Ribbed slab with integral beams
In line with Government policies, various hospital design guides* promote important, non-nancial aspects to consider. These include: • Air quality (optimisatio (optimisation n of natural ventilation) • Daylighting (improving (improving natural light penetration penetration and minimising minimising solar gain) gain) • Integration of passive cooling cooling and sustainable sustainable construction construction into design • Aesthetics.
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PROCUREMENT The specialist frame contractors should be involved early in the procurement process to allow the design to reect the economies of their preferred form of construction, balanced against whole project value. This will depend on the contractor’s previous experience, the availability of equipment and the opportunity to tailor design details to the construction method. For instance, many specialists have their own prestressingg rm (or preferred partner), allowing prestressin them to provide fast and cost effective prestressed frames. Others may have their own stock of special formwork, giving them an edge in another form of concrete construction. Alternatively, precast elements that can be swiftly erected may be best. This needs early involvement of the precaster to obtain the best programmee and economies through repetition of programm components and hence mould use. Partnering, DBFO and modern methods of construction in concrete are highly compatible with the above approaches as they encourage integration, integration, rather than the traditional separation, of the designconstruct process. This minimises construction risk, with its consequences of higher tender prices, extra programme allowances and potential over-runs. Concrete is regularly used for new construction alongside existing working buildings. Construction Construction and forming methods, and deliveries can be adapted to suit congested areas, and precast or self-compactin self-compactingg concrete can be used where construction noise is an issue.
CLADDING IN CONCRETE Precast concrete cladding can be designed with a wide range of nishes, from brick to reconstructed stone. Panels are secure, highly durable, low maintenance and long life; especially compared with lightweight metal alternatives. They can have glazing tted in the factory and be designed for installation without scaffolding. Recently, some new hospitals have been criticised for problems caused by excessive heat or cold. Using concrete cladding to control solar gain and thermal loss can help avoid this. Panels can be large and self-supporting between columns if desired, thereby simplifying the frame and maximising airtightness. Sandwich panels (factory insulated between two concrete skins) provide signicant extra thermal mass due to their solid inner wall and have a durable inner face, suitable for direct decoration. With most cladding systems, hospitals will have to allow for the major cost of recladding – and loss of use of the facilities during this work – within their design life. However, concrete panels can be designed to require only periodic inspection of the external seals, with any replacement of seals to be carried out without scaffolding or closure of the building. Precast cladding panels provide opportunities for rapid construction, just-in-time just-in-time delivery and minimal waste, with low construction risk. Again, for best economy, the cladding should be considered early in conjunction with the specialist supplier. This will ensure best value by optimising repeat mould use and xing/ interface details with the frame. The Great Western Western Hospital case study on page 8 illustrates the use of concrete cladding.
Cost of precast units drops with repeated use of moulds – Cast in concrete, Architectural Cladding Association, 2003.
Concrete sandwich panel being hoisted into position.
700
t s o c f o x e d n I
500 Labour content & cost
300
100 1
10
Casts per mould
20
30
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Today most hospitals
CASE STUDIES
are built in concrete
THE GREA GREAT T WESTERN HOSPITAL, SWINDON
because of vibration performance, simple services installation and cost effectiveness for the required spans.
The Great Western Western Hospital is a £100 million, PFI project on the outskirts of Swindon, providing 55,000 m2 of space for the Swindon and Marlborough NHS Trust. The design and build consortium, which included contractor Carillion, will operate it over the next 27 years, and put great efforts into choosing the most appropriate components on the basis of user needs and whole life cost. The six-storey L-shaped building is an environmen environmental tal agship project, featuring an in-situ concrete frame and precast concrete cladding.
Concrete Concret e frame - strength st rength and simplicity An in-situ concrete at slab frame on a nominal 7.2 by 7.2 m column grid was chosen for speed and buildability. It also maximised the service zones, provided inherent re protection and delivered energy savings through the exploitation of the frame’s thermal mass. Finite element design of the 300 mm deep oors provided for large cast-in and drilled service openings without downstand beams. The frame was constructed ahead of programme in only 38 weeks.
Designing the interface Early involvement between engineers TPS Consult, frame contractor Duffy Construction and precast cladding contractors Trent Concrete, resulted in an efcient and economical system for the concrete cladding panels that then became self-supporting between columns. The design of the cladding and frame accommodated not only operating theatres, ITUs, ofces and wards, but also provided exibility for future changes in use.
Precast cladding - maximising prefabrication Factory installed glazing avoided the use of scaffolding.
Architect Whicheloe Macfarlane Macfarlane HDR (now part of BDP) chose the 7600 m 2 of rich creamcoloured precast concrete cladding to simulate the local natural stone. Its high qu ality nish and careful detailing contributes to the clean and attractive lines of the building. One of the primary reasons for specifying precast concrete was to avoid external scaffolding, signicantly reducing cost and allowing earlier access for following trades. The factory pre-glazed 7.2 m panels were each erected in one movement and the large size minimised the number of ju st-in-time deliveries, deliveries, joints and xings. Cladding was installed ahead of programme in only 19 weeks. The resulting early enclosure provided a dry envelope and allowed the follow-on weathersensitive trades to start earlier – especially important in hospital construction with complex M&E services to install. This, together with the freedom provided by a at soft, helped speed installation and minimise M&E costs that amounted to a third of total construction cost.
Sustainability
Cladding on elevation.
Carillion intended The Great Western Western Hospital to be a agship sustainability project. Environmental Environmen tal considerations dictated materials u sed, construction techniques and waste handling. At Swindon, Swindon, the thermal mass of the concrete frame contributes further to sustainability objectives by maximising its fabric energy storage properties, and the cladding helps moderate solar gain and heat loss.
Whole life value Whole life costings and lifetime performance are of critical importance in PFI projects. The precast cladding not only gave greater cer tainty in terms of quality, cost and programme time, but also provided a highly durable, self-nished façade requiring little or no maintenance maintenance.. Because of early specialist involvement and value engineering it cost only around 55% of the cost for basic curtain walling. Both the frame and cladding at Swindon were erected ahead of programme, and and the Great Western Hospital was delivered on time and on budget in little over three years from start of construction.
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COVENTRY COVENTR Y AND DERBY PFI HOSPIT HOSPITALS ALS A large 127,000 m2 six-storey acute hospital forms part of the £334m Coventry New Hospitals PFI contract with Innisfree. Skanska is constructing the 6000 room building with 300 mm deep at slab in-situ concrete oors, supported on a typical column grid of 7.2 by 7.2 m, increased to 8.5 m in some areas. The structural form was chosen for minimum construction depth, with a at soft to allow uninterrupted services distribution and easy xing and acoustic/smoke sealing at wall partition heads. Arup’s exible design allowed for up to two holes in the slab on opposite faces of internal columns – either cast-in, or post drilled to allow exibility for future clinical replanning. Floor nishes are applied to a 6 mm levelling screed on the as-cast concrete slab, in which 35 mm deep recesses allow for shower and bathroom oor nishes to falls. Detailed analysis conrmed that oors could satisfy HTM vibration criteria without any increase in depth under operating
theatres, further increasing exibility. The frame also supports rooftop plant rooms. Derby PFI Hospital, another six-storey hospital by the same team, will provide 1,159 beds and 128,000 m 2 of new hospital buildings, including 35 operating theatres. Like Coventry, a 300 mm at slab concrete frame was chosen for reasons of ease of partition and services installation under a at soft, ‘blanket’ ‘blanket’ vibration control to cover wards and theatres, and service holes for exibility for clinical re-planning. The design incorporated 15 m wide blocks surrounding courtyards, producing column grids varying from 6.0 by 6.5 m to 8.5 by 8.5 m. Concrete Concrete columns, precast in steel moulds, increased speed of erection and allowed direct paint nishes, so helping reduce programme time and risk. Arup’s design supported ‘roll-out’ reinforcement reinforcement mats and contractor detailing to increase construction efciency. efciency. The in-situ frame at the Coventry Hospital.
ROMFORD NEW HOSPIT HOSPITAL AL Catalyst Healthcare is constructing this new 800-bed ve-storey hospital under a £200m PFI project for Barking, Havering and Redbridge Hospitals NHS Trust. Trust. Four circular ward towers rise three storeys above two podium oors that contain administration, administration, diagnostic, and treatment facilities including operating theatres. A central service core tower separates staff, patient and visitor ows, and houses staff facilities. The in-situ concrete frame supports 250 to 300 mm thick concrete at slab oors on a column grid of 8.1 to 9.0 m span. Columns are mainly circular with a diameter of 400 mm. The post-tensioned post-tensioned at slab maximises space for services, encouraging their prefabrication, prefabricati on, and giving greater exibility for routing and penetration of the slab. It also copes well with the circular oor plate and irregular cantilever edges of up
to 3 m in length. The at slab brought savings of around £800,000 by simplifying the xing and sealing of partition wall heads. All ve current UK hospitals by Bovis Lend Lease use concrete at slab frames for similar reasons. Shearheads (steel cruciforms within the depth of the slab) have been adopted for additional exibility for service penetration at columns – holes can be constructed on all four axes on internal columns. Bathroom pods are recessed into the slab which uses a thin levelling screed. The concrete frame facilitates fast construction, avoiding delay to services associated with site-applied reproong and allowing swift partition installation. It also meets vibration criteria without seeking dispensations.
Post tensioning ducts in place for the slab at Romford.
JOHN RADCLIFFE RADCLI FFE HOSPIT HOSPITAL, AL, OXFORD This hospital is being constructed by Carillion Health for The Hospital Company under a PFI contract with the Oxford Radcliffe Hospitals NHS Trust. Trust. The 45,000 m 2 six-storey frame extends the existing hospital to provide three new sections for the Children’s Hospital, a Head and Neck Centre, and a theatre block with laboratories. Concrete columns, mostly precast, support 250 mm thick post-tensioned at slab concrete oors that match existing hospital levels, with stability provided by the concrete cores. TPS Consult’s Consult’s at slab design approach maximises services zones and exibility within the ceiling voids. Post tensioning was chosen for programme speed and cost. Square precast columns vary between 500 and 600 mm, with larger circular feature columns up to three storeys high in the concourse and entrance. The 250 mm thick post-tensioned concrete slabs span from 6.6 to 9.0 m,
depending on the grid layout of each section of hospital and accommodate 4 by 6 m services riser voids. The slabs are increased to a thickness of 300 mm for theatre, laboratories and plant areas to cater for heavier loadings and vibration control. The post-tensioned slab provides knock out points to accommodate services for future hospital exibility. These will generally provide two holes, situated on opposite or adjacent column faces. All cast-in requirements and post drilled holes are co-ordinated with the tendon layout (which is clearly marked on slab surface and soft). Stairs are mostly precast concrete, housed in the cores, and there is a feature semi-circular in-situ entrance stair. Individual large-diameter bored concrete piles up to 1200 mm across and 35 m long directly support precast columns, avoiding the cost and disruption of pile caps. Flat concrete softs at the John Radcliffe Hospital, showing tendon marking.
CI/SfB
UDC 69.057.52:728.5 725.5119.057.52:728.5 725.511 9.057.52:728.5
FURTHER READING Ecoconcrete: The contribution of cement and concrete to a more sustainable built environment.
British Cement Association, 2001, 21 pages. Ref. 97.381. Economic concrete frame elements – a handbook for
the rapid sizing of concrete frames. British Cement Association, 1997, 128 pages. Ref. 97.358. Concept – an invaluable design tool for the
conceptual design of reinforced concrete frames in ve minutes. The Concrete Centre, 2004. Ref. TCC/03/012. Best practice guidance for hybrid concrete construction.
The Concrete Centre, 2004, 64 pages. Ref. TCC/03/09. Kings College Hospital: feature staircase in the new Golden Jubilee Wing, an in-situ at slab concrete framed building. Design: Nightingale Associates; photography: Charlotte Wood.
Help and advice on concrete c oncrete construction for hospitals are available from
[email protected] or visit www.concretecentre.com
www.concretecentre.com The Concrete Centre, Riverside House, 4 Meadows Business Park, Station Approach, Blackwater, Camberley, Camberley, Surrey GU17 9AB National Helpline Helpline 0700 4 500 500 or 0700 4 CONCRETE
Ref. TCC/03/13 ISBN 1-904818-25-0 First published 2005 © The Concrete Centre 2005 All advice or information from The Concrete Centre is intended for those who will evaluate the signicance and limitations of its contents and take responsibility for its use and application. No liability (including that for negligence) for any loss resulting from such advice or information is accepted. Readers should note that all Centre publications are
Concrete and re – using concrete to achieve safe, efcient buildings and structures.
The Concrete Centre, 2004, 13 pages. Ref. TCC/05/01 TCC/05/01.. Cast in concrete II - a guide to the design of precast concrete and reconstructed stone.
Susan Dawson, Architectural Cladding Association, 2003, 96 pages. Ref. BPCF 1.
