Department of Architecture and Civil Engineering

Fibre Reinforced Polymer (FRP) Stay In Place (SIP) participating formwork for new construction

At a glance

Funding body: BRE Trust studentship
Principal investigator: Antony Darby
Co-investigator: Tim Ibell
Researcher: Xian Gai
Dates: 2007-2010


The proposed research focuses upon FRP SIP participating formwork for use in bridge deck and floor slab construction.

Whilst a few experimental studies have investigated the participating behaviour between FRP form-work and concrete there are still many important issues which remain unexplored. It is essential that these aspects be addressed if efficient and cost effective use of FRP SIP formwork is to be realised.

These aspects include:

  • shape optimisation
  • bond mechanisms
  • bond failure behaviour
  • serviceability performance
  • ultimate limit state behaviour
  • long-term durability for environmentally exposed structures.

It is by the intelligent, rational and innovative use of these materials, that lightweight but, at the same time, strong and durable construction systems may be achieved. This will benefit both construction (rapid construction using minimal plant and temporary works) and long-term maintenance. It is for these reasons that, investigating how FRP SIP formwork can be made to contribute to the overall structural behaviour will provide designers and contractors with a great technological advantage.

The proposed study aims to address the key issues associated with such systems. The project will look at optimisation of the shape of such formwork, using geometry to provide the required structural stiffness, both during and following construction, and using a novel bone growth analogy to optimise strength development in the FRP for the complete structural system.

Use of voids in the formwork will be considered to prevent needless use of concrete in the tension zone of the structure. Use of different fibres (glass, aramid and/or carbon) within the FRP composite section will be examined in order to achieve desired structural and durability properties.

The investigation will also look at the most appropriate method of achieving bond between the concrete and the FRP (by surface treatments, embedded mechanical anchors or chemical bonding) and thermographic NDE (non-destructive evaluation) techniques will be developed to examine this bond by imaging the delaminations which may form during mechanical loading (static, fatigue and creep). This will allow the development of rational theoretical models of this type of bond.

Such investigations will be carried out in the context of providing acceptable serviceability performance and ultimate limit state performance, as well as long-term durability.

The project will initially involve a series of small scale tests aimed at investigating particular aspects of design along side numerical form finding of the FRP followed by large scale testing (long term, short term and fatigue loading) of overall structural systems (one- and two-way spanning slabs) developed out these small scale tests, in order to establish overall behaviour to failure. Novel thermographic imaging will be used as part of the process.

The results of the tests and modelling will be used to provide design guidance and develop design tools for the use of FRP SIP formwork.