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concrete

21

SCHOOLS, HOSPITALS

The structural frame

An evaluation was made to determine the

optimum construction technique for the

structural frame. Based on cost, efficiency,

sustainability and design adaptability, this

proved to be a precast composite flat slab

supported by precast columns on a typical 8.1

× 8.1m grid.

The perimeter façade was integrated with

approximately 1265 precast concrete load-

bearing sandwich panels, designed to look

like the red sandstone rock strata prevalent

in Liverpool. These panels distributed loads

to the foundations, removing the need for

conventional columns, and consisted of

200mm load-bearing solid concrete with

100mm rigid insulation and 100mm concrete

architectural facing panel.

Principal columns

Principal columns were designed byWSP–

PB and precast off-site by the specialist

subcontractor (approximately 1025 in

number). The suspended upper-floor slabs

constructed of 350mm-thick two-way-

spanning precast composite (filigree) slabs,

designed using RAMConcept, enabled

clear spans over the concrete frame, with

the slabs enabling reduction in the building

height. The slabs generally consist of in-situ

concrete topping (275mm thick) cast upon

75mm-thick precast concrete units fabricated

off-site (approximately 5325 units).

Reinforced concrete ‘twin-wall’shear

walls (approximately 1545 panels) to resist

lateral loads, were located around lift shafts,

stair cores and at strategic locations. These

walls consisted of two panels of precast

reinforced concrete joined to each other

via lattice girders and infilled on-site with

in-situ concrete to create virtually monolithic

concrete walls.

Movement joints, positioned to avoid

clinical areas, were provided to control

the effects of building and thermal

movements during curing, drying shrinkage

and long-term creep.Where the concrete

frame interfaces with other materials,

movement joints were provided to avoid

damage to the finishes.

Using newly designed concrete columns,

precast composite floor slabs and special

reinforced concrete shear walls meant

improvements in thermal mass, energy

efficiency and maintenance requirements.

These elements also reduced the build time,

contributing to what was Laing O’Rourke’s

fastest hospital build – completed in 130

weeks and 20% faster than any previous

healthcare project.

Key designbenefits

The new hospital buildings benefited from

bespoke, flexible design solutions, with

extensive use of design for manufacture and

assembly (DfMA). This, in turn, led to

further benefits:

high-quality, robust and durable products

providing certainty in performance

low environmental impact construction

methods and reduction of waste to

landfill

safe and tidy construction methods

reduction in programme and traditional

labour

low-maintenance building fabric and

simply controlled services providing

year-round comfort

maximising environmental conditions

such as acoustic separation, natural light

and ventilation

low whole-life-cycle cost

sustainable, energy-efficient solution –

thermal mass.

Sustainability

Alder Hey is one of the most sustainable

hospitals ever built, with over 50% of its

energy generated on-site, rainwater-capture

systems and a renewable heating plant. The

system includes boilers, combined heat and

power (gas and biofuel), an air source heat

pump, ground source heat pumps, absorption

chillers and air-cooled chillers to achieve a

range of targets based around GJ/100m

3

,

carbon, on-site power generation and site

renewables.

A dedicated community and regeneration

officer maintained good relations with local

people and ensured that the surrounding area

benefited from the work. Close relationships

were fostered with ‘Liverpool inWork’

and local schools and colleges, supporting

80 apprenticeships, 1800 hours of work

experience and the involvement of 900

students in the project. The project teams

themselves gave 1100 voluntary hours to local

causes and raised £30,000 for the Alder Hey

Children’s Charity.

Alder Hey Children’s Hospital, Liverpool

Client

Alder Hey Children’s NHS

Foundation Trust

Lead designer/architect

BDP

Consulting engineer – structural

WSP–Parsons Brinckerhoff

Consulting engineer – MEP

Hoare Lea

Contractor

Laing O’Rourke

Piling subcontractor

Expanded Piling

Precast manufacturer

Explore Manufacturing

M&E subcontractor

Crown House Technologies