装配式钢筋混凝土叠合梁抗火性能研究OA北大核心CSTPCD

To study the influence of interface between new and old concrete due to twice pouring on the fire resistance of prefabricate concrete composite beams(PCCBs),fire tests on three PCCBs and two reinforced concrete beams(RCBs)were conducted,especially to investigate the influence of load ratios on the fire resistance of PCCBs.The fire performance was compared between PCCBs and RCBs comprehensively.The temperature field data across the beam depth and vertical deflections were collected during the tests,and test phenomenon and typical failure patterns were recorded.It is shown that the maximum vertical deflection of both the PCCBs and RCBs under fire reaches 1/20 of the span-length,and no collapse is detected eventually.15 minutes before the furnace is shut down,a fast deflection speed is observed,showing an unstable working condition of beams.At the same load level,the PCCBs have a subequal duration of fire resistance with RCBs.After tests,a horizontal disjointed crack is observed and a certain concrete spalling is detected in the vicinity of inter-plate joints under the flange of slabs.For the PCCB with a load ratio of 0.3,the duration of fire resistance is 149 minutes.By contrast,the duration of fire resistance of the PCCBs with load ratio of 0.5 and 0.7 is reduced by 24.8％and 41.6％,respectively,which shows the impact of load ratio is significant.A calculation procedure was programed and verified to evaluate the duration of fire resistance of both PCCBs and RCBs based on the bending moment-curvature relationship.