Connections and Joints for Buildings and Bridges of Fibre Reinforced Polymer

Lead Research Organisation: University of Warwick
Department Name: Sch of Engineering


For economic impact and sustainable construction the aim of this project is to conduct a programme of underpinning applied research on connections and joints that shall lead to the safe and reliable design of new-build structures of Fibre Reinforced Polymers (FRPs). Work packages one to three are for studies of conventional bolted connections for frames executed of pultruded FRP shapes that shall be fit for purpose when subjected to actions over the working life. Characterisation will therefore be required for both short and long-term (creep) loadings, which for building structures will be static. In work package one a comprehensive series of targeted physical tests will be conducted to characterise pin-bearing strengths; one objective being to find a test method that can be a standard for the determination of this key strength property. New test results will allow us to understand how this material design property changes with: the bolt diameter to material thickness ratio; the clearance hole size (including tolerance for hole drilling); the position of the pin relative to the centreline of the hole; the presence of bolt thread; hot/wet environmental conditioning. The physical tests in the second package will be to understand the behaviour of plate-to-plate bolted connections, corresponding to both those found in practice and permitted in universal design standards, such as in preparation. Specific questions to be addressed shall include the following. What is the strength reduction factor for the single-lap plate-to-plate configuration? What is the open hole stress concentration factor for by-pass load? What is the distribution of force between bolts in a multi-row connection? Can we have a design formula for the staggered bolt arrangement? By how much does viscoelasticity affect how the load is transferred between components and the connection fails? Many aspects of this structural engineering research are novel, and in work package three there are to be new studies for stiffnesses and strengths of bracing joints with eccentrically loaded members, and for frame joints subjected to tension action (for disproportionate collapse). For serviceability and ultimate designs, additional novel tests will be completed for the determination of the moment-rotation curves of beam-to-column, splice and column-to-base connections. The programme of research is planned to address the many gaps in knowledge that impede the opportunities for engineers to specify these eco-friendly, durable building components in projects for refurbishment and/or sustainable construction. The results will be evaluated and findings will be used to revise and/or modify the design guidance, which, in a code of practice, shall encourage wealth creation and innovation. Conventional bolted connection details for buildings are not always suitable for bridge engineering as the latter need to be slip (and fatigue) resistant. The fourth work package will be for a study to find and characterise a new method of connection that will give a structural performance (slip resistant) similar to what riveting offered the Victorian/Edwardian engineers in their execution of steel structures. The results of this study could, after follow-on development research, give us a transformative step-change leading to the execution of longer span structures with FRP components. Dissemination of the results and findings from an evaluation of the test series will have a major impact on structural engineering research and will assist a growing industry by way of the preparation of recognised design rules, such as to be found in the new-build parts to the future structural Eurocode for fibre reinforced polymer materials. Design standardisation for the structural material of FRP will provide the confidence for wealth creation and future innovation towards buildings and bridges that have an overall performance to satisfy the drivers for sustainability and a Green Economy.

Planned Impact

Addressed now is who will benefit from this research, how will they benefit and how we shall ensure they benefit from this research? The research and the deliverables have been planned to have very positive impacts and benefits to both the academic community (see the Academic Beneficiaries section) and the commercial private sector that are, or will be, working with fibre reinforced polymer materials for life extension and new-build applications in structural engineering . The PI is well known (see Previous Track Record) to all parties that will immediately want to take advantage of the new results, and it is no coincidence that planned oral presentations are to be given to a number of them (CEN/TC250, IABSE, NGCC, IStructE, etc.). The Warwick team will use the an e-depository to store all the salient test results and supplementary technical information; this will include photographs of every failed specimen in work packages 1 to 3. This archival source will be maintained by the PI with free external access. This form of communication is not new to the PI who provides a R&D literature database, via The usual dissemination channels of journal and conference papers and conference, workshop and professional institution presentations will be used to educate others to the opportunities they can gain from this research. In the short-term the principal beneficiaries are to be the external supporters from the Bridge Division of Mott MacDonald and the fabricators of FRP structures at Access Design and Engineering. They shall receive results as they appear and will integrate them into their practices. A successful outcome in work package four would activate the writing of a follow-on collaborative EPSRC proposal for research leading to the exploitation of the novel connection method to innovative infrastructural structures. The Startlink TSB project (second generation family of FRP shapes for low cost housing) could benefit from the early results. In the medium term, three to five years, main beneficiaries will be code writers and code maintenance groups (ASCE and Italy). Given that committee CEN/TC250 has approved the need to the prepare a FRP Eurocode [A16] the outputs will be directly of use (essential) to the new build clauses with design rules for bolted connections. It is expected that this project can, in five plus years, improve the economic competitiveness of European in the same way existing structural Eurocodes will do. With the dissemination of research founded on the need for 'useful' results to prepare design rules, many UK companies and their clients (e.g. Network Rail, Highways Agency, County Councils) will have greater confidence to specify FRPs, and this will delivery what the public want. It is recognised that publication of design standards [A1, A16, A17] will help structural engineers and architects to use pultruded FRP shapes and systems in building and transportation designs. Other applications of FRP, such as the refurbishment of 'older' residential properties for reduced energy needs, will benefit from us having a deeper and broader understanding on the strength and stiffness of mechanical fastened connections. It is anticipated that there will be a transfer of technology to parties interested in engineering large FRP structures, such as towers to support wind turbines, antennae, etc. This will generate the wealth creation to be the driver for innovation, and by reducing the use of carbon in new build and retrofit will help to provide the long-term benefit of achieving a sustainable built environment (good for enhancing quality of life and health) . It can further be expected that the PGRS will receive training in research that will open career opportunities to work with professional on FRP projects, most likely in the context of a design consultant. Additional issues towards this impact summary are to be found in the Impact Plan.
Description We have developed an extensive and comprehensive data base for the resistances of steel bolted connections and joints for construction FRP materials that scope the key variables to be found in practice (and associated with an LRFD design guidance to be given in a forthcoming American design standard). This North American standard is still to be made ready to be published (in 2019?) by the American Society of Civil Engineers. Outcomes from this project are being used to inform the drafting of clauses for the structural design of FRP structures with bolted connections that has the potential to be in an FRP Eurocode standard (work with CEN TC/250 Working Group 4).

Furthermore, our experimentally based research has given confidence for the slip and fatigue resistant method of connection that involves taking a conventional steel bolted connection and removing the clearance voiding by injecting in a polymer resin that hardens. An open-access paper published in Structures in 2016 has raised interest from an industry project using resin injected bolted connections.
Exploitation Route The test results from the series of tests in work packages 1 to 3 for the resistances of steel bolted connections for FRP shapes are going to be used by others (with myself) to inform the preparation of design procedures. With effective calibration the design formulae will be developed for introduction in recognised codes of practice. The UK government (BIS) is keen to support work that publishes design guidance to support client and other stakeholders aspirations to execute bridges of FRP materials,

The specific (preliminary) and very promising test results from work package 4 towards having knowledge on the performance of resin injected bolted connections for FRP material has the potential to be a practical method of joining in bridge engineering. No other method of connection can offer the same (outstanding) level of slip and fatigue resistance that has been achieved because of this work.
Sectors Construction

Description To date the (extensive series of) test results for the resistances of bolted connections and joints of (pultruded) fibre reinforced polymer shapes has been used to inform: an American standards committee (with ASCE) preparing new standard Load and Resistance Factor Design (LRFD) of Pultruded Fiber-Reinforced Polymer (FRP) Structures (publication date could be 2017?); academics on what we know and where additional testing is needed to address gaps in knowledge towards the community preparing reliable (safety critical) design guidelines for general civil engineering practice. Our promising test results on the performance of using resin injected bolts for a slip and fatigue resistant method of connection have given professional engineers the information to considered using this approach in FRP bridge engineering. When Chapter 8 on Connections in the EU publication given below was in preparation between 2012-15 the knowledge and understanding gained from the results of this EPSRC project was used to inform the writing of the design guidance. Two of the 16 references with Chapter 8 are from dissemination of the EPSRC programme of testing. L. Ascione, J-F. Caron, P. Godonou, K. van IJselmuijden, J. Knippers, T. Mottram, M. Oppe, M. Gantriis Sorensen, J. Taby, L. Tromp. Editors: L. Ascione, E. Gutierrez, S. Dimova, A. Pinto, S. Denton. 'Prospect for New Guidance in the Design of FRP,' Support to the implementation and further development of the Eurocodes, JRC Science and Policy Report JRC99714, EUR 27666 EN, European Union, Luxembourg, 2016, p 171. ISBN 978-92-79-54225-1 doi:10.2788/22306 (PDF) We have provenance that WSP/Parsons Brinkerhoff have used our results (in a Structures journal paper) on resin injected bolts when deciding how to join together two halves of a FRP composite bridge that will be assembled on a public site neat to the National Composites Centre in Bristol.
First Year Of Impact 2012
Sector Construction
Impact Types Economic

Description Technology transfer for the application of resin injected bolted connection for a carbon fibre reinforced polymer footbridge in Bristol,UK 
Organisation WSP Group plc
Country United Kingdom 
Sector Private 
PI Contribution WSP (Bristol) knew that I have led research [1] that is showing how promising the connection method of resin injected bolting can be for having fatigue and slip resistant joints in fibre reinforced polymer structures. I therefore provided professional services in terms of technology transfer from research into practice, by way of conversations/emails during November 2017. Reference 1. B. Zafari, J. Qureshi, J. T. Mottram and R. Rusev, 'Static and fatigue performance of resin injected bolts for a slip and fatigue resistant connection in FRP bridge engineering,' Structures, 7, (2016), 71-84. ISSN: 2352-0124 DOI:
Collaborator Contribution Structural Engineers with the consultants WSP, in Bristol, are designers for a new innovative footbridge fabricated of carbon fibre reinforced polymer. The bridge will be moulded in two sections and joined together at the middle. One method for providing joints that are fit for purpose is to have the detailing with resin injected bolts. Our research (paper 1 above) and my expertise is being use by these partners to finalise their engineered solution for how to join the two sections of the bridge structure on site.
Impact Not yet available.
Start Year 2017