Abstract.In

In this paper, the authors present experimental observations and results of full scale standard fire tests as well as thermo-mechanical sequentially coupled finite element simulations on partition walls. A procedure for carrying out numerical simulation of the coupled-thermo-mechanical behaviour is proposed. The numerical models presented for predicting behaviour during fires were calibrated and verified by full scale fire testing.The test wall was constructed using steel C-section studs with gypsum boards fixed on both sides. The wall cavity was filled with Rockwool insulation. The partition wall was tested during exposure to the standard fire test. The thermo-mechanical behaviour of the wall was found to be heavily coupled and influenced by the physical and chemical changes in all constituents of the wall during exposure to fire.The sequentially coupled mechanical response simulation included geometric and material non-linearity as a function of temperature. In spite of the complexity of the fire effects and the strongly coupled thermomechanical behaviour, the results of the computational model practically agree with the full scale experimental results. The numerical prediction of the maximum thermal bowing of the wall was found to be very similar to the maximum values measured during the fire test. This has practical implications for assessing the integrity such wall assemblies during exposure to elevated temperatures. The proposed procedure can be used by fire structural engineers and fire testing laboratories as a tool to assist technical assessment exercises. In addition, the proposed procedure can be used during the developmental and modification stages of building components to optimise performance during fire.

This paper describes a laboratory investigation into the adoption of the stiffness damage test to assess fire-damaged concrete structures. Laboratory-prepared concrete cores (75 mm diameter, 175 mm long) were fired under different heating regimes and their uniaxial compression stress-strain response at low stress level was determined. The area of hysteresis of the load-unload loops and other characteristics of the response such as the degree of concavity, the loading chord modulus, the unloading modulus and the residual plastic strain provide a quantitative measure of the extent of structural damage caused by thermal exposure. Fire-damaged specimens were also monitored by measuring the ultrasonic pulse velocity. The microstructure of the damaged specimens was studied using scanning electron microscopy (SEM) and X-ray diffraction. 320°C marked the onset of significant modification in the characteristics of the stress-strain response loops, with a sudden increase in the damage index (area of hysteresis loops). The ultrasonic pulse velocity in the fired concrete showed similar variation with temperature to that of the elastic properties. At temperatures higher than 320°C, SEM photographs showed significant cracks in the cement paste, especially in the interfacial zone.