钢-混组合梁的火灾试验及剩余承载力

Fire experiment and residual strength of steel-concrete composite girders

完成了3根试验梁的火灾试验,测试了钢-混组合梁受火时的温度场、挠度变形和裂缝分布情况,并对受火后的3根试验梁分别展开静载试验,实测了其剩余承载力和破坏形态.基于高温后混凝土强度表达式和温度场分布函数,推导出高温后的混凝土受压区高度计算公式.结果表明,恒载作用下,3根试验梁的竖向挠度随受火时间的增长而明显增加.简支T梁和箱梁的顶板混凝土未见明显裂缝,连续箱梁负弯矩区的顶板混凝土出现数条横向贯通裂缝,裂缝宽度随构件受火时间的增长而增大.箱梁的混凝土顶板温度上升较慢,其耐火性能优于T梁.所提的剩余承载力计算方法具有良好的精度.

The fire experiments of three test beams were accomplished. The temperature field,the deflection deformation and the cracking distribution of the steel-concrete composite girders exposed to fire were tested. And the residual strengths and the failure modes of these three test beams under static loads were measured. The calculation formula of the compressive zone depth of concrete after fire was deduced based on the strength expression of concrete after fire and the temperature distribution function. The results indicate that the vertical deflections of the three test beams under dead loads in fire increase as the time goes on. The simple supported T-beam and the box girder have no obvious crack at the top of concrete. But as for the continuous box girder,several cut through cracks are observed at the top of concrete in the hogging moment area and the widths of these cracks increase as the time goes on. The temperature at the top of the box girder rises slowly,resulting in better fire resistance compared with the T-girder. The proposed calculation method for the residual strength has high accuracy.