Residual Shear Capacity of Post-Fire RC Beams under Indirect Loading

Building fire is one of the most frequent disasters. The mechanical properties of concrete and steel will deteriorate to different degrees under fire exposure, thus weakening the bearing capacity of reinforced concrete (RC) members. Therefore, it is of great theoretical and practical significance to carry out research on the bearing capacity of RC members subjected to fire. To study the residual shear capacity of post-fire RC beams under indirect loading, static load tests were carried out on six full-scale RC beams to investigate the development of diagonal cracks and failure modes under an indirect load. Numerical models were established with ABAQUS to study the effect of the shear span-to-depth ratio and stirrup ratio on the residual shear capacity of the tested beams after fire exposure, and the shear capacity calculation method of indirectly loaded beams after high temperature is proposed. The results indicate that although the fire had no obvious affect on the failure mode of the beam under indirect loading, the fire aggravated the failure degree of the beams without additional transverse reinforcement. Moreover, the ultimate bending capacity of beams with additional transverse reinforcement decreased obviously after fire. The residual shear capacity of indirectly-loaded beams subjected to fire decreased compared with the directly-loaded beams due to the variation in the shear span-to-depth ratio and stirrup ratio. The shear capacity theoretical calculation results of the indirectly-loaded beam after high temperature were in good agreement with the tested results, and the average absolute error was 3.88%. Therefore, this calculation method for an indirectly loaded beam with a shear span-to-depth ratio less than 3.0 after fire as proposed in this paper was effective. The findings of this study are expected to provide a reference for the improved fire-resistant design of RC structures under indirect loading.

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