| At present,the fire behavior of the concrete slabs was investigated by many researchers,particularly the isolated simply-supported slabs or the continuous slabs subjected to uniform fire,and the traveling fire scenario should be further studied.Therefore,the influence of the heating duration,the time delay,the reinforcement ratio and arrangement on fire behavior of the continuous slabs were investigated.In addition,the ANSYS software was used to predict the temperature and deflection of the tested slabs.Meanwhile,the residual carrying capacities of the concrete continuous slabs were investigated based on the post-fire tests,and the effect of the above factors was analyzed and different theories were used to predict the residual limit carrying capacities of the tested slabs.The main conclusions are as follows:(1)To investigate the mechanical behaviors of different spans subjected to fire in order,fire tests were conducted on three concrete continuous slabs.The influence laws of some parameters,such as the fire subsequences,time interval,reinforcement ratios and reinforcement layout,on the temperature,deflection,corners' reaction forces and failure mode of the continuous slabs,were analyzed.In addition,the limit load-bearing capacity of each span in the continuous slabs were calculated and compared based on six theoretical methods.Experimental results show that the furnace temperature of each span and the temperature of slabs was mainly dependent on the self-furnace temperature.Meanwhile,the fire scenarios and the boundary conditions have important effects on the mid-span deflection trend,crack patterns and failure mechanism of the continuous slabs.The deflection trends in edge spans and middle spans were different.Compared to that of the edge spans,the cracks at the middle span were relatively more,and the integrity failure easily occurred in the middle span.In all,for any fire scenario,increasing reinforcement ratio and using the continuous reinforcement are beneficial to enhance the fire resistant performance of the concrete continuous slabs.(2)Based on the software ANSYS,the temperature and mechanical models were established to analyze the temperature,deformation and mechanical mechanism of the test slabs.Meanwhile,the influence of concrete thermal strain on the slab's fire behavior was investigated.Results show that the predicted temperature was agreement with the test results,but there was large difference between the experimental and predicted results,particularly the middle span.Fire scenario has considerable effect on the development of the stress on the top and bottom surfaces,particularly the middle span.In addition,the final stress pattern of two edge spans in the slab was similar to each other.(3)The carrying capacities of five post-fire slabs and two reference concrete slabs were conducted in this paper,and the cracks on the top and bottom surface and failure modes were observed.In addition,the out-plane(in-plane)deflections,concrete and steel residual strains and corners' restraint were obtained from these tests.The effect of the heating duration,the time delay,reinforcement ratio and arrangement on the residual capacities of the post-fire slabs were studied.Results show that apart from the flexural failure mode,the local or whole punching failure of one span occurred,particularly the serious spalling and many original cracks.Compared to the fire scenarios,the reinforcement ratio and arrangement has more considerable effect on the residual carrying capacities of the fire-damaged slabs.In addition,the yield line theory,Bailey method and punching shear methods were used to predict the residual limit capacities of the fire-damaged slabs based on the mechanical properties of the material after high temperatures.Results show that for the fire-damaged slabs,the minimum value of one slab predicted by the flexural and punching shear failure methods can be used as the residual capacity.There are 96 maps,12 tables and 89 references in this paper. |
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