Precast concrete by noidarocker

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									                                                                                                                 WINTER 2005/2006




Precast concrete                                                                     –
                                                                                                            required. The common theme is
                                                                                                            to adopt modular construction
                                                                                                            wherever possible, to increase
                                                                                                            speed and keep down costs.
                                    the backbone of construction                                            A good example is precast
                                                                                                            crosswall construction, which
by SPA Chairman John Milner                                                                                 offers many benefits. By design,
                                                                                                            the method provides flat soffits
                                                                                                            with no intruding downstand
                                                                                                            beams and also solves the
                                                                                                            increasingly onerous acoustic
                                                                                                            requirements of the Building
                                                                                                            Regulations. As with all precast
                                                                                                            concrete solutions, elements are
                                                                                                            produced in a factory-controlled
                                                                                                            environment and quality is not
                                                                                                            compromised as a result of fast-
                                                                                                            track programme pressures. In
                                                                                                            addition, wet trades are usually
                                                                                                            eliminated, permitting early
                                                                                                            follow-on of other trades such
                                                                                                            as cladding and M&E fit-out.
                                                                                                            Depending on finish required,
                                                                                                            paint can often be applied
                                                                                                            directly to the concrete walls,
                                                                                                            providing a robust and first
                                                                                                            class finish.

                                                                                                            The careful design and
                                                                                                            identification of individual


T     he demand for off-site construction is on the up and
      momentum is building. Many ascribe this growth to
two things – the increase in construction in general and the
                                                                     This higher density poses
                                                                                                            precast elements enables
                                                                                                            accurate planning of the works,
                                                                                                            while just-in-time deliveries
                                                                     challenges such as noise
                                                                                                            ensure that coordination with
ever-growing shortage of skilled labour on site. But there           transmission, as a result of           other trades on site is precise –
are three other, and perhaps more valid reasons, namely              which concrete is increasingly         essential on busy and congested
the faster erection time, the superior quality of the result         becoming the construction              sites. Further value is added by
and the lifetime energy reductions from the thermal mass             material of choice, both for           providing typical programme
of the concrete. As a result, techniques such as crosswall           builders and home owners,              gains over traditional and
construction, modular construction and so-called flatpack                                                    lightweight methods of between
                                                                     who appreciate its durability,
construction – all making use of precast concrete – are                                                     30% and 50%.
                                                                     robustness and energy-
being adopted for a wide range of projects such as hospital,         saving features.
hotels, residential and high-rise apartments, social housing,                                               Safety by design
                                                                     Within the Structural Precast
high-security accommodation, and student accommodation
                                                                     Association, member companies          Buchan Concrete Solutions,
schemes. At the same time, latest Government statistics show         are approaching this market in         for example, have developed
that the average density of new homes has increased from             various ways, each technique           over the years a comprehensive
25 dwellings per hectare in 1997 to 40, an increase of 60%.          suited to the type of structure
                                                                                                                               continued on page 2

                                STRUCTURAL PRECAST ASSOCIATION 60 Charles Street, Leicester LE1 1FB. Tel: 0116 253 6161. Fax: 0116 251 4568

                                P A G E    O N E
                                                                           Although precast crosswall construction is often seen as being most
                                                                           appropriate and economic in buildings of regular plan, such as
                                                                           hotels and student accommodation, it can very easily accommodate
                                                                           less regular plan details. At Erdington, for example, the building
                                                                           turns through 90º, a change of direction easily and aesthetically
                                                                           accommodated.



                                                                           Experience counts

                                                                           Track records often play a large part in contract awards. Having
                                                                           completed Ibis Hotels at Manchester, Liverpool, Gatwick,
                                                                           Birmingham and Leicester, Bell & Webster Concrete was selected
                                                                           by design-and-build contractor Jarvis Construction to build a
                                                                           14-storey, 210-bedroom hotel in Wembley using the company’s
                                                                           ‘Fast Build Rooms’ system. The building has been erected above a
                                                                           single-storey in-situ concrete structure, with mezzanine floor. Built
                                                                           on a first-floor transfer slab, factory-engineered concrete was used
                                                                           for all walls, floors and the inner skin of the external walls, stair
                                                                           and lift areas and with the window openings cast-in. All concrete
                                                                           surfaces within the rooms were ready for direct decoration with
                                                                           minimum preparation.

                                                                           More than 1200 precast concrete components, some weighing up
                                                                           to eight tonnes, were delivered by road and craned directly into
continued from page 1                                                      the structure; at the same time, fully-finished bathroom pods were
                                                                           craned into place. Because of the design, external cladding was
range of FASTCAST solutions. This system is especially finding
favour on projects over two to three storeys where lightweight
systems can suffer movement problems. Robustness is achieved
through horizontal and vertical ties. For sound insulation, Buchan
provides 180mm-thick separating walls between living areas which
satisfies the requirements of the new Part E.

One of the UK’s most modern business hotels, the Crowne Plaza
in London Docklands, is a recent Buchan project, the company
being asked to provide a suitable modular concrete solution for
the accommodation floors.The in-house design team devised a
method of providing stability by using the diaphragm action of the
floors spanning between the wall panels, which in turn act as shear
walls. Like all other wall units in the system, the shear walls were
structurally connected by in-situ concrete stitched joints that ensure
transfer of all forces acting on the structure and thus allow transfer
of loads to the first-floor in-situ slab.



High-rise construction

SPA member Bison Concrete Products is another company
promoting and benefiting from the upsurge in concrete off-
site construction. On the site of the former Highcroft Hospital
at Erdington, Birmingham, the company is erecting a high-
quality residential development above an in-situ concrete podium
over basement car parking. Bison was awarded the contract
by the main contractor George Wimpey West Midlands Ltd to
design, manufacture and erect the precast concrete structure. This
comprises crosswall panels, 200mm-deep prestressed hollow-core
flooring and precast staircases. Manufacture of all the precast
components for the project was undertaken at a nearby Bison
factory. Altogether, 4500m2 of prestressed hollow-core floors,
850m3 of wall units and precast staircases were produced.


                                     STRUCTURAL PRECAST ASSOCIATION 60 Charles Street, Leicester LE1 1FB. Tel: 0116 253 6161. Fax: 0116 251 4568

                                     P A G E    T W O
effectively off the critical path. With the windows installed as the
concrete is erected, the structure has inherent weather-tightness
and so other trades can begin much earlier than on a traditional
build programme.



The modular approach

Precast Cellular Structures Ltd (PCSL), a joint venture between
Tarmac Ltd and Composite Limited, has been concentrating
on modular projects, especially for prisons. Including PFI and
contracts for the English and Scottish Prison Services as well as
the States of Guernsey, the total exceeds 3670 modular cells. The
experience gained has enabled the company to establish precast
concrete as the preferred modular solution for the prison house-
block market.

The house-blocks come in the form of pre-fitted cells, cast at
Tarmac’s factories. Their modular nature means that they can be
erected five times faster than in-situ construction methods, allowing
progression from a greenfield site to a structural prison frame in
11 days. From cutting the first turf to completion, a 120-cell house
block with core area can be completed in 30 weeks.

A recent example of PCSL’s work is for HMP Wellingborough.
Units were manufactured using state-of-the-art steel moulds.             All these projects carried out by SPA member companies
Cells are cast as a five-sided box with four walls and a roof in a        demonstrate the significant benefits of precast concrete
monolithic four- or two-cell unit: a standard four-cell block weighs     construction for medium- and high-rise accommodation on
around 39 tonnes.                                                        inner city and brownfield sites.




Insulated panels given Lantac approval
                                                                         R      oger Bullivant Concrete Products has secured Lantac
                                                                                approval for its insulated HighWall® building panels.
                                                                         Said Steve Parker, RB Group production director, “The certificate
                                                                         which has been awarded by Dudley Metropolitan Borough Council
                                                                         was the result of many months of hard work by the RBCP pre-order
                                                                         team and Dudley MBC.”

                                                                         The insulated panel forms the basis of both the RB ProWall®
                                                                         system, which is being used throughout the UK on numerous
                                                                         distribution units, and the new ‘HighWall®’ frameless building
                                                                         system, which has been installed on projects in both the public and
                                                                         private sectors.

                                                                         The new panels can either be manufactured in volume from the
                                                                         standard grey product, which RBCP regularly supplies and installs
                                                                         throughout the UK, or have bespoke finishes applied to order.

                                                                         “Both our current customer base and new clients can benefit from
                                                                         the Lantac approval in the knowledge that the product has been
                                                                         checked and approved by a recognised authority,” added Trevor
                                                                         Howells, national sales manager for RBCP.

                                                                         The Lantac approval of the HighWall® panels follows the previous
                                                                         certificate gained for the award-winning Quickwall® panels now
                                                                         used extensively on new construction developments nationwide.



                                    STRUCTURAL PRECAST ASSOCIATION 60 Charles Street, Leicester LE1 1FB. Tel: 0116 253 6161. Fax: 0116 251 4568

                                    P A G E    T H R E E
Moving the industry forward
H     anson Building Products received
      an innovation award at the British
Precast Best Practice Awards 2005 for the
Hanson innovative house. The building
was constructed as a demonstration
project specifically for the BRE Offsite 05
event, but remaining on site for a period
of two years, for display, training and
developmental purposes.
                                                      From left to right Mike Eberlin, sponsor; Lord Hunt OBE; Gerry Feenan commercial director Hanson Floors & Precast;
                                                      and judges Dr Jacqui Glass and Richard Ogden

                                                                                                      The load-bearing elements of the structure
                                                                                                      were constructed using prefabricated panelised
                                                                                                      concrete, masonry wall and floor units with the
                                                                                                      roof formed from prefabricated insulated panels.
                                                                                                      The overall objective of the construction is to
                                                                                                      promote Hanson’s range of building products and
                                                                                                      services while reinforcing Hanson’s commitment
                                                                                                      to product development.

                                                                                                      Although the house looks and feels both solid
                                                                                                      and conventional it has been constructed using
                                                                                                      a mixture of building systems and products that
                                                                                                      can be assembled more quickly, produce less
                                                                                                      waste and prove safer than some traditional
                                                                                                      methods, since the erection process precludes the
                                                                                                      involvement of untrained personnel.

                                                                                                      Hanson also received the first place award for
                                                                                                      health and safety at the British Precast Awards.




SCC receives top health and safety award
S   CC Ltd’s health and safety achievements were
    acknowledged by the British Safety Council and the
Health and Safety Executive during an awards ceremony at
                                                                              how we can improve
                                                                              further on our
                                                                              health and safety
                                                                              record. One topic
London’s Grosvenor House Hotel. Picture shows Sir Frank
                                                                              was the disposal of
Davies (right) presenting the International Safety Award to                   food and material
Peter Crofts (left) SCC’s design and build manager; centre is                 waste,       which
John Grimshaw, the company’s health and safety manager.                       led to a marked
                                                                              improvement       in
“The statistics we had to improve on are the Accident Incident
                                                                              tidiness within the
Rates (AIR) published by the HSE” said John Grimshaw. “We also
                                                                              workshops and a
had to illustrate significant progress of two initiatives during the
                                                                              dramatic reduction
qualifying year. Firstly regular meetings with foreman and charge
                                                                              in trips and falls.
hands that have a ‘no name-no blame culture’ to enable open and
                                                                              At the request of employees, more bins were situated in relevant
frank discussions on health and safety matters affecting them and
                                                                              locations and ‘tidy up days’ are a thing of the past. The
the operatives under their control. All information is referred to the
                                                                              focus on health and safety has stimulated employer/employee
directors’ monthly meetings, which I attend as safety manager.”
                                                                              communication across all operational areas, principally because
Continued John, “The second initiative is the publication of a safety         suggestions are acted upon. These advances assist in reducing the
bulletin with contributions from all levels within the company on             mystery surrounding the subject of health and safety.”


                                      STRUCTURAL PRECAST ASSOCIATION 60 Charles Street, Leicester LE1 1FB. Tel: 0116 253 6161. Fax: 0116 251 4568

                                      P A G E    F O U R
                                                                           crane operation led to long-span lightweight construction

Efficient building                                                          with a total building height of 14m.
                                                                           The new factory is adjacent to an existing Milbank factory able
                                                                           to produce large precast components and this, together with the


W     hen Milbank Floors decided to build a new production                 potential saving in transport costs, suggested the precast concrete
                                                                           columns be produced close to the site. Wall construction was
      facility at Brandon, the type of construction was a key
                                                                           determined by three factors – sound insulation, robustness and
element in the economics and efficiency of the building. The
                                                                           economics – and so precast concrete cladding panels were the
requirement for an uninterrupted working area and two-tier                 obvious choice, again manufactured in the existing factory.

                                                                           As production required a 16-tonne high-level crane, bullet skip
                                                                           distribution system and low-level production cranes, considerable
                                                                           vertical and horizontal loads were induced in the main columns.
                                                                           Therefore, precast concrete columns cantilevered from the
                                                                           foundations were adopted, to restrict sway and cope with the high
                                                                           stresses and wind loading. To minimise crane loading and allow
                                                                           twin-span crane beams to reduce construction time, 12m-long steel
                                                                           crane beams were supported from corbels on the precast concrete
                                                                           columns. The longitudinal stability of the frame is achieved by
                                                                           vertical K- bracing at four points down each side of building,
                                                                           placed to coincide with the construction phasing of the building.




Thorp no stranger to paradise
K     nown as the Paradise project, Liverpool’s new multi-
      storey car park and bus layover for client Grosvenor
has provided an interesting challenge for Thorp Precast
                                                                           incredibly fast in a busy section of the site. The quality was ensured
                                                                           as each brick was cut off-site and carefully cast into a uniform mould.
                                                                           The move from a traditional brick wall and wind-post construction
                                                                           to a precast solution meant that structurally the construction depth
on behalf of main contractor Laing O’Rourke. The work
                                                                           was reduced to a minimum and that one subcontractor could take
involved casting 34 brick-faced precast concrete feature walls             responsibility for the entire job.
to screen the bus layover area, delivering to site fully pointed
and finished and erecting over five days. The 6m-tall and
3m-wide units weigh 10 tonnes and are faced with smooth
grey 270×52mm bricks sourced from Germany.
Brick specials were water-jet cut to achieve a fold in the wall which
gives the appearance of depth and LED light bars were cast into each
unit to enhance the architectural features by throwing light across
the top triangles. An integral monolithic coping eliminated the need
for further trades and work at height.

The 4.5m-high wall provides both a visual and secure boundary
around the new bus layover. Owing to the site restraints imposed
by the internal bus turning circles, the wall had to be as narrow as
possible while simultaneously giving the impression of mass. In this
it provides a modern interpretation of the sturdy Victorian dock
walls found all over Liverpool. The fold in the panels allowed the
vertical plane to be articulated and broken down along its length
but also reveals a depth that is highlighted by the inclusion of
linear light fittings. The brick at street level was chosen to allow the
wall to relate to the context of the adjoining Victorian buildings.
The colour and texture of the brick and simple composition of
the panels also allow the wall to sit comfortably at the base of the
imposing structure of the over-sailing car park.

There were many advantages to using a precast system – most
notably that the panels came to site pre-finished and were erected

                                       STRUCTURAL PRECAST ASSOCIATION 60 Charles Street, Leicester LE1 1FB. Tel: 0116 253 6161. Fax: 0116 251 4568

                                       P A G E    F I V E
First of seven apartment
blocks at Dublin development

T    rent Concrete was awarded the combined structural
     and architectural precast concrete package for the first
phase in a major new seven-block apartment development
on Finglas Road in Dublin.
The contract of approximately 14m Euros covers a 30,000 m2 cross
wall frame system covering a total floor area of around 37,000m2,
7300m² of external cladding, 2400 linear metres of external party
walls and 2700 linear metres of balconies.

“We had an open mind on the structural solution, and as part


                                                                           ICE
of the tender process invited specialist contractors to offer their
ideas,” explains Chris Timmins, contracts manager at McCabe
Builders. “Trent’s solution to precast the entire building was the
simplest and offered several major advantages. Firstly it gave us a
one-stop shop, and minimised the number of trades and operatives           FREE
                                                                           S
on site. This results in a more controllable situation, as well as a           hoppers       leaving
safer site operation. In addition there are big cost savings, as well
                                                                               Doncaster’s extended                      MEMBERS
as safety and operational benefits, in being able to dispense with
                                                                           Frenchgate Centre with its
scaffolding. Trent was the only specialist contractor that could offer                                            Bell & Webster Concrete Ltd
grey, decorative and structural concrete as one package.”                  new integrated transport
                                                                                                                    Telephone: 01476 562277
                                                                           hub will be able to drive
The external cladding includes 4000m2 of terracotta-faced panels                                                  Bison Concrete Products Ltd
                                                                           down the elevated external
featuring a blue/black coloured tile and 1000m2 of reconstructed                                                    Telephone: 01283 495000
Portland stone units. An additional 2300m2 of HardwallTM                   access ramp even in the
                                                                                                                   Buchan Concrete Solutions
insulated sandwich panel cladding is also being used structurally          cold weather.
                                                                                                                    Telephone: 01606 843500
on the gable ends, again featuring a combination of terracotta-
                                                                           The specially prepared                    Roger Bullivant Concrete
faced and reconstructed stone external finishes with the inner faces
                                                                           grooves to the traffic surface                    Products Ltd
acting in the same way as the crosswall panels. The party walls and
                                                                           needed to be both reinforced               Telephone: 01283 525045
balconies are both in a reconstructed Portland stone finish to match
                                                                           and mechanically keyed to
the cladding. Trent started on site in September 2004 on a 60-65                                                         Ebor Concretes Ltd
                                                                           accommodate the electric
week programme. The development will accommodate a total of                                                                    01765 604351
                                                                                                                      Telephone:
                                                                           heating elements, an essential
540 apartments.                                                                                                     Hanson Concrete Products
                                                                           de-icing requirement due to
                                                                                                                     Telephone: 01773 602432
                                                                           the ramp’s external location.
                                                                                                                         Milbank Floors Ltd
                                                                           Because of the exposed
                                                                                                                               01787 223931
                                                                                                                      Telephone:
                                                                           location and close proximity
                                                                                                                                SCC Ltd
                                                                           to the live east coast main
                                                                                                                     Telephone:  0161 432 7700
                                                                           line, full involvement by
                                                                           the whole design team was              Tarmac Precast Concrete Ltd
                                                                           essential which lead to a                Telephone: 01778 381000

                                                                           number of novel features                      Thorp Precast Ltd
                                                                           being incorporated into the                Telephone: 01782 561155
                                                                           precast concrete units.               Trent Concrete Structures Ltd
                                                                           In total Ebor Concretes Ltd              Telephone: 0115 987 9747

                                                                           supplied main contractor,
                                                                           Sir Robert McAlpine via
                                                                           Severfield Reeve Structures
                                                                           with some 180 precast                     A product association of
 Contractor: McCabe Builders (Dublin) Limited
                                                                           concrete     ramp       units,          the British Precast Concrete
 Architect: Anthony Reddy Associates                                       weighing 8 tonnes each, 346                   Federation Limited
                                                                           precast concrete stairflights
 Engineer: WYG
                                                                           and landing units to the main                         Website:
 Precaster : Trent Concrete Ltd                                            fire escape cores.                      www.structural-precast-association.org.uk


                                     STRUCTURAL PRECAST ASSOCIATION 60 Charles Street, Leicester LE1 1FB. Tel: 0116 253 6161. Fax: 0116 251 4568

                                     P A G E    S I X

								
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