INFLUENCE OF ROTATIONAL RESTRAINTS ON FIRE BEHAVIOUR OF RC ELEMENTS

摘要

Although the effects of high temperature on the response of beams and slabs that are subjected to bending have been widelystudied in recent years, a literature review indicates that the fire behaviour of a single member has been the main focus of most of the research projects.Especially for experimental research, due to the limitations of fire test set-up, few fire tests include restrained beams and slabs.However, separate members in anactual reinforced concrete (RC) structure are always experiencing various types of axial and rotational restraints from the adjacentmembers.These restraints may have a significant influence on the flexural behaviour of RC members at elevated temperatures.The existed reseach on the effect of restraints are always assuming that the restraint moment remains constant during fire exposure process which is not as the same with the real conditions.Due to the decrease of the member's stiffness while exposing to fire, the restraint stiffnesses will comparatively increase with heating time.This will lead to an increase in restraint forces and a redistribution of the bending moment along the member.Hence, the investigation for the effect of restraints based on temperature-dependant fire restraint stiffness need further research.In order to have a clear idea of the fire performance of RC beams in real conditions, i.e.continous beams or slabs subjected various rotational restraints, to get a deep insight on the influence of rotationalrestraints on the fire behaviour of RC members, one-way slabswith different rotational restraint conditions are simulated and analyzed in this paper.Based on the analysis and comparison of the simulation results, a parametricstudy onthe effect of rotational restraints on the fire performance of RC membersiscarried out.Finally, some suggestions on how to consider the effects of rotational restraintsin fire resistance design are proposed.