受火后叠合板组合梁受力性能试验研究

EXPERIMENTAL STUDY ON THE MECHANICAL BEHAVIOR OF COMPOSITE BEAMS WITH SUPERPOSED SLABS AFTER FIRE

为研究受火后叠合板组合梁的受力性能,分别对五个火灾后叠合板组合梁和一个常温下叠合板组合梁进行静力加载试验,研究了后浇层厚度、栓钉间距、预制底板在钢梁上翼缘的搁置长度、预制底板接缝形式、是否受火等因素对叠合板组合梁的破坏形态、承载能力和抗弯刚度的影响。结果表明:火灾后整体式叠合板组合梁的极限承载力较分离式叠合板组合梁提高9%;后浇层厚度和栓钉间距是影响火灾后整体式叠合板组合梁初始抗弯刚度的主要因素;火灾前后整体式叠合板组合梁在荷载作用下均发生受弯破坏,且破坏形态基本相同,但经历火灾高温作用后,整体式叠合板组合梁出现裂缝的时间提前,其抗弯承载力和延性均有不同程度的降低,本次试验中火灾后整体式叠合板组合梁在荷载作用下的抗弯承载力和延性较常温下分别降低23.3%和55.4%;分离式叠合板组合梁中预制底板接缝的存在,破坏了预制底板的连续性,造成试件发生粘结破坏,但在远离接缝处,叠合板的协同工作性能良好;提出火灾后叠合板组合梁剩余承载力和抗弯刚度的计算方法,该方法具有良好的精度。

In order to study the performance of composite beams with superposed slabs after fire,five composite beams with superposed slabs after exposure to fire and one composite beams with superposed slabs at room temperature were statically tested.Influence of factors such as the thickness of post cast slab,the stud spacing,the overlapping length of the precast slab on the upper flange of the steel beam,the joint form of precast slabs and exposure to fire or not on failure mode,bearing capacity and initial flexural stiffness of composite beams with superposed slabs were tested.The results indicate that the ultimate bearing capacity of integral composite beams with superposed plates are 9%higher than that of separated composite beams with laminated slabs after fire.The thickness of post-casting layer and the spacing of stud are the main factors influencing the initial flexural stiffness of integral composite beams with superposed plates after fire.Before and after the fire,the integral composite beams with superposed plates are subjected to bending failure under the action of load,and the failure modes are basically the same.However,after the action of fire with high temperature,the cracking of integral composite beams with superposed plates occurs earlier,and the flexural capacity and ductility decrease to different degrees,In this test,the flexural capacity and ductility of integral composite beams with superposed plates after fire under load are reduced by 23.3%and 55.4%,respectively,compared with those under normal temperature.The existence of the joint of precast base plate in the separated composite beams with laminated slabs damages the continuity of the precast base plate and causes the bond failure of the specimen.However,the cooperative performance of the superposed slabs is good at the place far away from the joint.The proposed calculation method for the residual strength and flexural rigidity of composite beams after fire has high accuracy.