You can view the sequence of our work as a flowchart.


Yifan Li (Research student)
Mitigation of Fire-Induced Spalling of Concrete using Recycled Tyre Fibres
This project is an investigation of the fire spalling mechanism of concrete and its mitigation using recycled tyre fibres. Under extreme circumstances, such as rapid heating, concrete can spall explosively. The propensity to fire spalling is higher for High-Performance Concrete (HPC) than for normal concrete, mainly due to its low permeability. Effective spalling mitigation measures include the use of small quantities of micro-polymer fibres, such as polypropylene (PP). To improve the sustainability of this mitigation method, The project uses Recycled Tyre Polymer Fibres (RTPF) and Recycled Tyre Steel Fibres (RTSF) as novel substitutes for manufactured PP fibres.

The main objectives are to:

  • Assess the effectiveness of RTPF and RTSF in mitigating fire-induced spalling,
  • Improve the cleaning, separation, integration methods of raw recycled fibres,
  • Determine optimum fibre dosage and optimise concrete mix design for RTPF and RTSF concrete,
  • Understand better the mechanism of fire-induced spalling and develop predictive models for fire spalling.

The project involves experimental work, investigating the fire spalling behaviour of concrete subject to various fire intensities, loading conditions, moisture contents, etc. The project also aims to develop a simplified model which can guide civil engineering practitioners to correctly predict the propensity of concrete to spall under fire conditions. The model will be developed and validated based on experimental results from macro-scale fire spalling tests and micro-scale neutron scanning tests.


Spalled specimen

Fire spalling test arrangement


Yu Liu (Research student, funded by EPSRC & China Scholarship Council)
Ductile Connections to Improve Structural Robustness in Fire
Connection failures observed in the collapse of the World Trade Centre and some of the Cardington full-scale fire tests have indicated that connections are more vulnerable in fire conditions than conventional assumptions in prescriptive codes indicate. To maintain structural integrity and prevent progressive collapse, connections are particularly important as the key components tying structural members together. However, current commonly-used connection types lack the axial ductility required to accommodate compressive deformation due to thermal expansion of long-span beams in the early stages of a fire, leading to large compressive forces being applied to surrounding structural members. They are also incapable of allowing tensile deformation of beam-ends at high temperatures, in order to reduce the catenary forces in beams to levels that can be resisted.

In order to improve the performance of connections, and therefore to enhance the robustness of entire structures against fire, a novel ductile connection is proposed. This novel connection consists of two identical parts, each of which can be manufactured by deforming a steel plate, and takes the form of a fin-plate which is bolted to the beam web, an end-plate which is bolted to either the column web or flange, with a semi-cylindrical section between the fin-plate and end-plate. The function of the semi-cylindrical section is the key to providing the additional axial push-pull ductility which is necessary in fire, by allowing the fin-plate to move towards and away from the end-plate. Analytical models of this ductile connection, based on plastic theory, have been developed and tested against Abaqus simulations and experiments, and the component-based model of the novel connection, which will be implemented into the fire engineering software Vulcan, has also been proposed.

Fabio Figueiredo (Research associate)
euse of tyre fibres for fire-spalling-proof concrete (IGNIS)
Reuse of Tyre Fibres for Fire-Spalling-Proof Concrete (IGNIS) is a research project funded by H2020 through the Marie Slodovska Curie Programme. Fire-induced explosive spalling (violent peeling-off of concrete surface) is a major drawback of modern high-performance and high-strength concrete. Tunnels and buildings have been seen to experience catastrophic failure due to fire spalling of concrete, leading to huge economic costs and potential loss of life. Recent EU directives and legislation require adequate addressing of the spalling problem in any new project and all major existing road tunnels need to be upgraded. However, fire spalling still remains one of the least well understood aspects of concrete behaviour and the need to fill this knowledge gap has significantly increased, due to the increasing demand of infrastructure and materials that are sensitive to spalling. Therefore, the research community has set fire spalling as a research priority; a RILEM Technical Committee (TC256-SPF) has been dedicated to this topic.

This research aims to develop a better understanding of the complex mechanism behind fire spalling as well as a novel sustainable spalling-mitigation solution by using waste fibres recovered from end-of-life tyres. The fire spalling risk will be investigated through high-temperature slab tests. The test data will be used to develop a predictive numerical model. If successful, this will enable manufactured polymer fibres, currently used to prevent fire-induced spalling, to be replaced with a reused product of equal or better performance, thereby providing a possible annual reduction of 0.5 million tonnes of CO2 in an EU market worth about £50 million per annum.


Asif Hussain Shah (Research associate)
Sustainable fire-spalling-resistant concrete (SusFire)
Fire-induced spalling of concrete experienced by constructed facilities such as tunnels, buildings and bridges has been shown to cause catastrophic failure, and to lead to huge economic costs and potential loss of life. However, despite the consequences, fire-induced spalling remains one of the least well understood aspects of concrete behaviour. This project is funded by EPSRC aiming at developing an improved understanding of fire-induced spalling of modern high-performance concrete, and finding a sustainable spalling-mitigation solution by using fibres recovered from end-of-life tyres. To achieve this, four key objectives will be focused on:

  • Developing a better understanding of fire-induced spalling and the spalling-mitigation mechanism of polymer fibres;
  • Exploring the potential of tyre fibres for preventing fire-induced spalling of high-performance concrete;
  • Contributing to the standardisation of fire-spalling characterisation testing;
  • Building a high-quality database for future research.
Ian Burgess
Development of a kinematically consistent approach to tensile membrane action in composite floor slabs in fire

It is widely recognized that composite floor slabs experiencing large displacement develop a central zone of hydrostatic membrane tension, surrounded and equilibrated by a ring of membrane compression around the periphery. This mechanism, known as tensile membrane action, can greatly enhance the load-bearing capacity of a slab compared with that defined by yield line analysis. This is a very useful effect in cases where large deflections can be accepted, particularly in fire-resistance design of composite slabs, since the strength enhancement permits some beams to be left unprotected. Studies of TMA in the 1960s led to the development of several methods to define slab load capacity under large displacement. The method due to Hayes has become the most widely accepted, and was adopted in developing the BRE method for fire-safe design of composite floors. Based on observations from the Cardington fire tests and on assumptions concerning yield line patterns and membrane stresses, it calculates the load-carrying enhancement of a slab as a function of its deflection. It also postulates a deflection limit at which the maximum acceptable strain in the rebar is reached. On close examination, however, several hypotheses, such as the assumed failure mechanisms, seem illogical.

A new simplified method, which re-examines the mechanics of tensile membrane action in weakly-reinforced thin slabs at high deflections, based on the principles of large-deflection plastic yield-line analysis, has been launched at Sheffield in the past few years. The initial applications of this approach have addressed plain flat slabs, both isolated and continuous. Starting with the optimal yield-line pattern, the method relates a slab’s load capacity to its deflection, allowing for the effects of change of shape of the concrete stress blocks and progressive fracture of the reinforcing mesh. These have been compared with the existing procedure, showing very different behaviour in many cases. The application of tensile membrane action in structural fire engineering is usually for slabs designed as arrays of parallel composite beams, with wide concrete upper flanges connected to downstand steel beam sections by shear studs. The strength of the steel reduces with temperature, and since the applied load intensity is constant the analysis now needs to calculate the steel temperatures at which a yield-line mechanism is created and at which the panel loses stability. The new method has been extended to analyse composite slabs with unprotected steel beams at high temperatures. It monitors small-deflection yield-line patterns, of which the optimum continuously changes as the strength of the steel sections degrades. When the optimal mechanism’s load capacity degrades to the applied load the mechanism for large-deflection enhancement is established. Tensile membrane action can then allow further growth in steel temperature until a maximum is reached. Since integrity failure is also important in fire-resistant design, it is notable that the method provides the internal forces needed to calculate the maximum mean tensile stress in the concrete cross-section. In this project the new kinematically consistent method will be developed to take into account the different mechanisms through which a rectangular composite slab can fail and its different modes of failure. It needs to predict where the reinforcement fractures, and at which temperatures and deflections. The intended outcome is to develop a mechanically justifiable design procedure for performance-based fire-resistant design of composite slab panels.