high performance hospitals - using concrete frames and cladding
TRANSCRIPT
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SMALL HEADLINEHighPerformanceHospitals
USING CONCRETE FRAMES AND CLADDING
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Good hospital design can provide more efficient 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 benefits discussed in this publication,
decision makers in the procurement process can ensure that extra
value is added to the building, often at no or little additional cost.
Front cover (left to right)
• The Great Western Hospital, Swindon: in-situ flat slab concrete frame with precast cladding. Photography: Gillian Bond.• Central Middlesex Hospital ACAD Centre: a concrete framed structure which is exposed in public areas. Photography: Nicholas Kane.
This page• The West Middlesex University Hospital: concrete walls clad in timber, render and brick. Design: Nightingale Associates; Photography: Charlotte Wood.
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BUILDING BETTER HEALTHCAREHospitals are facilities that help medical staff in the efficient delivery of quality healthcare and provide a positive environment for speedy patient recovery. Good building design can provide more efficient facilities and a better 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 financially involved with their operation and maintenance. This will help secure high-
quality designs and earlier access to new facilities, and ensure best value, both from initial and whole life cost
perspectives.
Recent research has confirmed that good design creates the best environment for patients, staff and visitors,
which promotes effective services and speedier recovery, resulting in more efficient use of resources. The design,
construction and operation of new facilities is now formally assessed using a variety of measures – not just
financial – 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 conflicting needs, including the flexibility
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.
Romford New Hospital: floor plan (level 3) showing the central core servicing the ward towers. Concrete framed ward tower under construction.
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The benefits of
using concrete:
• Reduces initial and running costs
• Speeds construction
• Minimises vibration
• Accommodates future changes
• Facilitates partition wall sealing
• Caters for easy services installation
• Enhances sustainability
• Promotes a good work environment
• Resists spread of fire and sound
• Improves air quality
CONCRETE FOR HOSPITAL CONSTRUCTIONWell-designed and effectively managed hospital buildings help support the work of
frontline staff, provide an appropriate environment for patient recovery, and so improve
efficiency. The choice and design of a building’s frame and cladding can have a surprisingly
large influence on the performance of the final 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.
Although every new facility has specific requirements, a typical list of needs to be
considered might be:
• Value/cost – how well it performs its function in terms of helping staff and patients in
relation to initial and running costs and residual value
• Speed – how quickly it can be brought into use
• Flexibility – how easily it can accommodate or be adapted for changing needs
• Sustainability issues – both during construction and in use.
Behind these requirements lie some particularly important considerations, some of which
are specific to healthcare buildings, and include:
• Vibration – operating theatres and night wards require the designer to pay special
attention to reducing vibration
• Services – often the most expensive and slowest element to construct
• Partition walls – installing and sealing literally miles of these to the frame
• Work environment – proven to affect staff morale and patient recovery
• Further issues such as sound, fire resistance and air quality.
Today’s concrete frames are ideally suited to support the requirements of modern hospital
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.
The following sections consider these issues further and discuss how concrete’s properties
can help resolve them.
SPEED AND PROGRAMME
The use of concrete is highly compatible with fast 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 floor-to-floor cycle of
two to three weeks. With modern methods it is common to achieve this in one week.
Concrete frames normally require no disruptive fire protection after erection, and can be
made sufficiently watertight for early installation of M&E services (the longest phase of
construction in hospitals) and other follow-on trades.
The use of concrete flat slab floors provides flush soffits that simplify service provision.
This encourages the swift installation of prefabricated services, where major savings in
cost and time come from factory-tested assemblies and fewer joints on site. Prefabricated
bathroom pods can be installed and set flush by recessing them into the floor slab.
Exposed concrete walls look good and provide fabric energy storage (European Institute of Health and Medical Sciences). Courtesy of The Concrete Society.
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VIBRATION CONTROL
Vibration control is especially important in areas
such as operating theatres, night wards and intensive
care units, and is an important factor in the design
and specification of building frames. Concrete can
easily be designed for the most complete control of
vibration over whole areas, often without the need for
significantly thicker floor slabs, giving great flexibility
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 ‘office‘
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 modifications to NHS
vibration criteria. This is done to avoid the cost penalties
of providing this extra mass and stiffness.
FLEXIBILITY AND ADAPTABILITY
Healthcare methods, provision of IT, patient
expectations, and standards of environment and
equipment are all changing rapidly; so flexibility 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
flexibility.
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 flexibility.
Early consideration of these benefits during design can
optimise flexibility at little or no extra expense.
SOUNDIt 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, floor and
ceiling finishes are rarely dictated by acoustic
requirements; these are delivered by the performance
of the concrete slab.
PARTITION WALLSHospitals 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 soffits of the floor above is
particularly important. The use of flat slabs simplifies
this, reducing partition costs by up to 4% of the frame
cost before considering additional programme savings.
* Hospital floor vibration study. Comparison of possible floor structures with respect to NHS vibration criteria. Research Report, Arup, 2004. Available for download from www.concretecentre.com
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The above diagram shows the increases in mass and construction depth needed to upgrade an office frame to hospital vibration criteria for night wards and operating theatres.
Concrete structures reduce vibration cost-effectively. Courtesy of the National Society for Epilepsy.
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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.
Concrete flat slabs are ideal for highly serviced buildings.
SERVICESThe choice of material and design of a building’s frame and cladding can have a
surprisingly influential role on the services, which are generally the most critical element
in construction cost and time.
Concrete flat slabs are ideal for highly serviced areas in hospitals, 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 down-
stand beams. 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 heavily serviced areas, designers are now encouraged to use concrete’s
thermal mass properties to reduce air-conditioning. This then reduces capital,
refurbishment and running costs.
SUSTAINABLE CONSTRUCTIONConcrete 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-conditioning through fabric energy storage, and the use of
daylighting and natural ventilation. Concrete has an excellent track record in passively
cooled buildings.
• Reducing the need for heating through airtight construction.
• Reducing maintenance through providing durable walls, columns and cladding.
Other sustainable aspects of concrete construction include:
• UK manufactured reinforcing steel is made from 100% recycled scrap, unlike structural steel.
• Cement manufacture is increasingly using waste-derived fuels (such as scrap tyres),
thereby saving energy and relieving pressure upon landfill facilities.
• Replacement materials, which would otherwise go to landfill, are being incorporated
into both cement and concrete to reduce their environmental impact.
• Aggregates are often extracted locally, and ready-mixed concrete is typically made
no more than 15 miles from any project. This reduces the environmental impacts
associated with transportation.
• 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 benefit.
• 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 CO2
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 significant whole life savings in energy, carbon dioxide emissions and operating costs.
• On demolition of a building, concrete and reinforcement can be recycled.
• Concrete buildings are adaptable, durable and have many inherent qualities (sound,
fire and vibration performance), and hence are ‘long life, loose fit’ 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 m3 p.a. – making it one of the most
energy-efficient acute hospitals in the UK.
An environmental review of design and construction of the Great Western Hospital
Swindon by environmental award winner, Carillion, achieved a cost saving of £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
30% less energy in use and generate 50% less construction waste than a typical
hospital: it is discussed in detail on page 8.
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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 architecture in public areas,
involving the use of exciting structurally efficient
exposed soffits, columns and walls can all add to
the character and ambience of a building. This
avoids having to develop an artificial architectural
veneer that adds to first 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,
soffits 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.
FIREConcrete is inherently fire resistant, and unlike some
materials normally requires no added fire 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
fire protection is provided at no extra cost and does
not require the use of intumescent paints.
The inherent fire resistance results in concrete often
performing in excess of design requirements for occupant
safety. This over-performance benefits the building
‘owner’ as repairs and the period before re-use following
a fire are minimised.
AIR TIGHTNESSWith concrete, the flat soffits 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.
MAINTENANCE AND REFURBISHMENTWhole life costs can be reduced by the use of concrete
which provides long life cladding, durable walls and
columns with direct finishes, and easily accessed
services under flat soffits. 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 soffits, suspended ceilings and
air conditioning may be reduced or avoided, lowering
maintenance and refurbishment costs.
ANCILLARY BUILDINGS The use of techniques such as ‘tunnel form’ and
precast wall and floor 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 fire properties and low maintenance
durable finishes.
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 soffits
that help security and boost user confidence.
The light and airy reception at the Great Western Hospital, Swindon. Photography: Gillian Bond.
Modern methods of concrete construction are ideal for staff accommodation.
Exploiting the benefits of concrete is simple and
comes at little or no added cost. It just requires
early awareness and consideration of the
potential gains and for decisions to be made at
the correct stage in the design process.
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DESIGNConcrete 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.
Currently, flat slab construction, typically on grids of 7.2 to 8.4 m on a 1.2 m module,
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
flat slabs are post-tensioned to reduce slab thickness and provide potential for longer
spans of up to 12 m if necessary.
Some alternatives to flat slab construction are shown below.
• Prestressing of concrete beams and floor units provides fast, light and economical
solutions.
• Ribbed in-situ slabs on wide shallow beams are lighter than flat slabs, but not so
versatile and take longer to construct.
• Hybrid concrete construction combines the best qualities of precast concrete
(accuracy, high quality finishes, off-site manufacture) with those of in-situ
construction (flexibility 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 parameters. The benefits of using concrete discussed
in this publication provide a useful guide for designers when comparing construction
types. For the structural engineer, 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 for larger point loads for ceiling-hung
equipment and heavy-weight blockwork partitions are often required. Vibration 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 flexibility.
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 flexibility it is reasonable to build in. For future flexibility, ‘soft spots’
are generally designed in; polystyrene knock out slots, cast-in lightweight blocks or
cast-in markers are all commonly used. These, together with the design drawings, aid
those making future modifications.
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.
However, it is 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.
In line with Government policies, various hospital design guides* promote important,
non-financial aspects to consider. These include:
• Air quality (optimisation of natural ventilation)
• Daylighting (improving natural light penetration and minimising solar gain)
• Integration of passive cooling and sustainable construction into design
• Aesthetics.
Flat slab concrete
construction is the
preferred framing
option for many
hospitals as it
provides speed
and flexibility.
* NEAT evaluation toolkit (NHS Estates); Better health buildings (Centre for Healthcare Design); and Design
evaluation toolkit (Department of Health).
Concrete options for hospital frames.
Solid flat slab (may be post-tensioned)
Ribbed slab with integral beams
Hybrid – precast floor units on in-situ beams and columns
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PROCUREMENTThe specialist frame contractors should be involved
early in the procurement process to allow the design
to reflect 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
prestressing firm (or preferred partner), allowing
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
programme and economies through repetition of
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,
rather than the traditional separation, of the design-
construct 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 and
forming methods, and deliveries can be adapted to
suit congested areas, and precast or self-compacting
concrete can be used where construction noise is an
issue.
CLADDING IN CONCRETEPrecast concrete cladding can be designed with a wide
range of finishes, 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 fitted 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
significant 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 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 fixing/interface
details with the frame.
The Great Western Hospital case study on page 8
illustrates the use of concrete cladding.
Concrete sandwich panel being hoisted into position.
700
500
300
100
Inde
x o
f co
st
Labour content & cost
1 10 20 30
Cost of precast units drops with repeated use of moulds – Cast in concrete, Architectural Cladding Association, 2003.
Casts per mould
The effect of repetition on cost of casting precast concrete structural or cladding units
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Today most hospitals
are built in concrete
because of vibration
performance,
simple services
installation and cost
effectiveness for the
required spans.
Cladding on elevation.
Factory installed glazing avoided the use of scaffolding.
CASE STUDIESTHE GREAT WESTERN HOSPITAL, SWINDON
The Great 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 environmental flagship
project, featuring an in-situ concrete frame and precast concrete cladding.
Concrete frame - strength and simplicity An in-situ concrete flat 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 fire protection and delivered
energy savings through the exploitation of the frame’s thermal mass. Finite element design of the
300 mm deep floors 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 efficient 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, offices and wards,
but also provided flexibility for future changes in use.
Precast cladding - maximising prefabrication Architect Whicheloe Macfarlane HDR (now part of BDP) chose the 7600 m2 of rich cream-
coloured precast concrete cladding to simulate the local natural stone. Its high quality finish
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,
significantly 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 just-in-time deliveries, joints and fixings. Cladding was installed ahead of
programme in only 19 weeks.
The resulting early enclosure provided a dry envelope and allowed the follow-on weather-
sensitive trades to start earlier – especially important in hospital construction with complex
M&E services to install. This, together with the freedom provided by a flat soffit, helped speed
installation and minimise M&E costs that amounted to a third of total construction cost.
Sustainability Carillion intended The Great Western Hospital to be a flagship sustainability project.
Environmental considerations dictated materials used, construction techniques and waste
handling. At 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 valueWhole life costings and lifetime performance are of critical importance in PFI projects. The
precast cladding not only gave greater certainty in terms of quality, cost and programme time,
but also provided a highly durable, self-finished façade requiring little or no 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 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 AND DERBY PFI HOSPITALS 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 flat slab in-situ concrete floors,
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 flat soffit
to allow uninterrupted services distribution and easy
fixing and acoustic/smoke sealing at wall partition heads.
Arup’s flexible design allowed for up to two holes
in the slab on opposite faces of internal columns
– either cast-in, or post drilled to allow flexibility for
future clinical replanning. Floor finishes 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 floor finishes to falls. Detailed analysis
confirmed that floors could satisfy HTM vibration
criteria without any increase in depth under operating
theatres, further increasing flexibility. 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 m2
of new hospital buildings, including 35 operating
theatres. Like Coventry, a 300 mm flat slab concrete
frame was chosen for reasons of ease of partition
and services installation under a flat soffit, ‘blanket’
vibration control to cover wards and theatres, and
service holes for flexibility 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 columns,
precast in steel moulds, increased speed of erection
and allowed direct paint finishes, so helping reduce
programme time and risk. Arup’s design supported
‘roll-out’ reinforcement mats and contractor detailing
to increase construction efficiency.
ROMFORD NEW HOSPITAL
The in-situ frame at the Coventry Hospital.
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This hospital is being constructed by Carillion Health
for The Hospital Company under a PFI contract with the
Oxford Radcliffe Hospitals NHS Trust. The 45,000 m2
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 flat slab concrete floors that
match existing hospital levels, with stability provided
by the concrete cores. TPS Consult’s flat slab design
approach maximises services zones and flexibility
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 flexibility. 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 soffit).
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.
JOHN RADCLIFFE HOSPITAL, OXFORD
Post tensioning ducts in place for the slab at Romford.
Flat concrete soffits at the John Radcliffe Hospital, showing tendon marking.
Catalyst Healthcare is constructing this new 800-bed
five-storey hospital under a £200m PFI project for
Barking, Havering and Redbridge Hospitals NHS Trust.
Four circular ward towers rise three storeys above two
podium floors that contain administration, diagnostic,
and treatment facilities including operating theatres. A
central service core tower separates staff, patient and
visitor flows, and houses staff facilities.
The in-situ concrete frame supports 250 to 300 mm
thick concrete flat slab floors 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 flat slab
maximises space for services, encouraging their
prefabrication, and giving greater flexibility for routing
and penetration of the slab. It also copes well with the
circular floor plate and irregular cantilever edges of up
to 3 m in length. The flat slab brought savings of
around £800,000 by simplifying the fixing and sealing
of partition wall heads. All five current UK hospitals by
Bovis Lend Lease use concrete flat slab frames for
similar reasons.
Shearheads (steel cruciforms within the depth of
the slab) have been adopted for additional flexibility
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
fireproofing and allowing swift partition installation.
It also meets vibration criteria without seeking
dispensations.
Help and advice on concrete construction for hospitals are available from [email protected] or visit www.concretecentre.com
Ref. TCC/03/13
ISBN 1-904818-25-0
First published 2005
© The Concrete Centre 2005
The Concrete Centre, Riverside House,
4 Meadows Business Park, Station Approach, Blackwater, Camberley, Surrey GU17 9AB
National Helpline 0700 4 500 500 or 0700 4 CONCRETE
All advice or information from The Concrete Centre is intended for those who will evaluate the significance 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 subjectto revision from time to time and should therefore ensure that they are in possession of the latest version.
www.concretecentre.com
Kings College Hospital: feature staircase in the new Golden Jubilee Wing, an in-situ flat slab concrete framed building. Design: Nightingale Associates; photography: Charlotte Wood.
CI/SfB
UDC
69.057.52:728.5
FURTHER READINGEcoconcrete: 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
five 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.
Concrete and fire – using concrete to achieve safe,
efficient buildings and structures.
The Concrete Centre, 2004, 13 pages.
Ref. 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.
CI/SfB
UDC
725.5119.057.52:728.5