高温后型钢混凝土柱抗震性能试验研究

Experimental study on seismic performance of steel reinforced concrete columns after exposure to fire

对5个高温后型钢混凝土柱试件和3个常温下对比柱试件进行低周反复加载试验,研究高温后型钢混凝土柱的承载力和抗震性能。由试验获得了高温后型钢混凝土柱的破坏形态和滞回曲线,分析了剪跨比、轴压比、受火时间对高温后型钢混凝土柱滞回特性、延性、耗能能力、承载力及刚度退化的影响。结果表明:高温后剪跨比为1.5的型钢混凝土柱的破坏形态与常温下基本相同,剪跨比为2.5的型钢混凝土柱的破坏形态则发生明显变化,常温下发生弯曲型破坏的柱在高温后往往发生黏结破坏。与常温下的型钢混凝土柱相比,高温后型钢混凝土柱的滞回曲线更加饱满、骨架曲线的上升段和下降段更为平缓、位移延性系数略有增大、耗能能力更强。高温后型钢混凝土柱的延性、耗能能力与剪跨比、轴压比密切相关。位移延性系数随剪跨比的增大而增大,随轴压比的增大而减小;剪跨比越大,破坏时的等效阻尼比越大。经历高温作用后,型钢混凝土柱的刚度和承载力退化显著,初始刚度退化程度随剪跨比的增大而减小,屈服后刚度和受剪承载力退化程度随剪跨比的增大而加大。提出了火灾高温后型钢混凝土柱受剪承载力计算式,计算结果与试验结果符合较好。

Based on cyclic reversed loading tests of five steel reinforced concrete( SRC) columns after exposure to fire and three comparative specimens at ambient temperature,the shear bearing capacity and seismic performance of SRC columns after exposure to fire were studied. Failure patterns and hysteretis loops were obtained from the tests,and influences of shear-span ratio,axial compression ratio on the hysteretic behavior,ductility,energy dissipation,shear bearing capacity and stiffness degeneration of SRC columns after exposure to fire were analyzed. Test results show that failure patterns of SRC columns after exposure to fire with low shear span ratio( λ = 1. 5) are similar to that at ambient temperatures,while those with high shear-span ratio( λ = 2. 5) are different obviously. Bond failures occur in those SRC columns after exposure to fire while flexure failures mainly occur at ambient temperature. Compared with SRC columns at ambient temperature,SRC columns after exposure to fire have plumper hysteretic loops,more flat skeleton curves,higher ductility coefficient and greater energy dissipation ability. The ductility and energy dissipation ability of SRC columns after exposure to fire are related to shear-span ratio and axial compression closely. Displacement ductility coefficients increase with the increase of shear-span ratio,but decrease with the increase of axial compression ratio.Equivalent damping ratio rises with the increase of shear-span ratio when failures occur. After exposure to fire,the stiffness and shear bearing capacity of SRC columns decline obviously. The degeneration degree of initial stiffness decreases with the increase of shear-span ratios,but the degeneration degree of stiffness and shear bearing capacity after yielding increase with the increase of shear-span ratio. A formula for calculating shear bearing capacity of SRC columns after exposure to fire is presented,and the calculation results are consistent with the experimental results. It can be used to provide the basis for damage assessment of SRC columns after exposure to fire.