Connectivity of Components in Hybrid

Structural Systems MRes Urban Sustainability

and Resilience

Student: Jaylina Rana

Supervisors: Dr C.Arya

Dr P.Domone

UCL Department of Civil, Environmental and Geomatic

Engineering, Gower St, London ,WC1E 6BT

Hybrid Concrete Construction ... The New Trend

Current trends in the construction industry show a move towards greater

prefabrication, more efficiency, reduced site activity and safer and faster

construction.

The term ‘Hybrid Concrete Construction’ (HCC) was devised by Goodchild

(1995) to describe the combination of cast in-situ and precast concrete

construction, the word hybrid meaning from two parents.

HCC integrates precast concrete and cast in-situ concrete to take best advantage

of their different inherent qualities which provides:

• Faster construction

• Cost effective construction

• Simple, buildable structures

• Excellent fire performance

• Sustainability benefits associated with high thermal mass

• Exceptional acoustic performance

The Project

This project seeks at analysing and developing the new insulated twin wall

technology structurally.

This form of Hybrid Concrete Construction is greatly dependent on the degree

of composite action taking place and therefore it can sometimes be difficult to

establish this boundary. There is a clear lack of information or standardised

building codes providing design guidance of such systems.

The research is currently analysing the longitudinal shear behaviour of the twin

wall panels. Test specimen will then be tested under single point loading and the

longitudinal shear behaviour observed and measured by strain gauging.

The Ultimate Limit State (flexural strength, shear strength, bearing/anchorage

and, interface shear transfer) and the Serviceability Limit State (cracking,

deflection, differential shrinkage) will be also explored.

How does the Twin Wall work?

Composite action is through the lattice girder which ensures mechanical bond

between the cast in-situ and precast concrete (Elliot, 1996). Each leaf carries the

required wall reinforcement and is obtained from traditional reinforced concrete

wall analysis and design theory for both loadbearing and non-loadbearing walls.

Windows, doors and service openings are designed into the each wall element,

while services can also be accommodated if required.

References Barrett P.S (2003), Hybrid concrete: improved

processes and performance, Structures & Buildings

156 – Issue SB2, Proceedings of the Institution of

Civil Engineers, pp 193-203

Concrete Centre (2005), Hybrid Concrete

Construction – combining precast and in-situ

concrete for better value structural frames, The

Concrete Centre, Surrey

Elliot K (1996), Multi Storey Precast Concrete

Framed Structures, Blackwell Science, UK

Glass, J. and Baiche, B. (2001), “Perceptions of

Hybrid Concrete Construction in the

UK Construction Industry”, Engineering, Construction

and Architecture Management, Vol. 8 No. 1, pp 67-77

Goodchild CH, Glass J (2004), Best practice

Guidance for Hybrid Concrete Construction, The

Concrete Centre, Surrey

Goodchid CH (1995), Hybrid Concrete Construction:

combining structural materials for speed, quality and

economy in buildings, BCA, Crowthorne,

Whittle R, Taylor H (2009), Design of Hybrid

Concrete Buildings- A guide to the design of buildings

combining in-situ and precast concrete, The

Concrete Centre, Surrey

The New Twin Wall

The twin wall system is a fresh, relatively new and effective alternative to

traditional load bearing block work and cast in-situ concrete walls – which have

been used extensively in the UK.

Twin walls are lighter than other single wall systems, easy to manufacture, and

can be erected quickly without the need for formwork whilst providing a high

quality finish.

The three main components of the insulated twin wall are:

• Permanent concrete formwork comprising two 50 to 75mm thick precast

concrete leaves.

• Steel lattice girder to form a core between the plates.

• Polyurethane insulation between the concrete leaves.

‘’One of the main benefits of HCC is

speed. The 2005 London Home Office

Headquarters project constructed

4200m2 in an eleven day cycle, with three

cranes, using insitu concrete for vertical

elements and floor toppings, and precast

beams and slabs’’.

Anne Gate Property plc (2005)

For a structural system that offers…

BUILDABILITY AND SIMPLICITY OF

CONSTRUCTION...

GREATER SPEED AND LESS COST COMPARED TO

OTHER SYSTEMS...

AND ALL THE BENEFITS OF CONCRETE.....

Hybrid Concrete Construction is the right choice!

Concrete Centre (2009)

Left : Propped Twin wall; Right: Cast-in lifter

Source: LOR Design Guide (2010)

TWIN WALL SYSTEM

Advantages

• Precast quality finish for walls and soffits

• No formwork for vertical structure

• Structural connection between wall and slabs is by standard

reinforced concrete detail: inherently robust and, for basements,

‘watertight’

• No permanent sealing at connections between precast units

• Flexible for casting-in items

Disadvantages

• The smaller dimension of the precast units can be a maximum

of 2.8m, so joints in walls and soffits must be dealt with:

expressed or concealed

• Reduced flexibility of layout as there are walls rather than

columns

Proponents of this system claim:

• Twice as fast as in-situ concrete

• Cost neutral compared to in-situ and cheaper than fully precast

PRECAST

CONCRETE

Precast concrete for quality of finish

and speed of erection.

INSITU

CONCRETE

In-situ concrete for flexibility and

economy.

HYBRID CONCRETE

CONSTRUCTION

Hybrid concrete construction for all the

benefits of concrete in the optimum form.

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