冷弯薄壁C形钢-石膏基自流平砂浆组合梁受弯性能试验研究

Experimental study on flexural performance of C-shaped cold-formed thin-walled steel-gypsum based self-leveling mortar composite beam

为研究冷弯薄壁型钢-石膏基自流平砂浆组合梁的受弯性能,对未设置抗剪件、设置钢丝网以及设置Z形抗剪件的3个组合梁足尺模型进行了施工阶段、正常使用阶段和荷载极限阶段的受弯性能试验研究。考察了冷弯薄壁型钢-石膏基自流平砂浆组合梁在不同受力阶段的工作原理和破坏模式。试验结果表明：设置的两种抗剪件对组合梁在施工阶段和正常使用阶段的抗弯刚度影响均较小;组合梁的最终破坏模式为C形冷弯薄壁型钢梁腹板发生严重的剪切变形并伴随扭转屈曲,设置抗剪件可提高组合梁的极限荷载。在试验研究的基础上,将组合梁简化为T形截面,引入考虑组合翼板与C形梁之间相对滑动的滑移模量,提出了部分抗剪连接组合梁的抗弯刚度计算方法,用于计算组合梁的跨中挠度,计算结果与试验结果相近。

In order to investigate the flexural performance of cold-formed thin-walled steel-gypsum based self-leveling mortar composite beams, three full scale specimens were tested under flexural loading, where the construction stage, serviceability limit stage and ultimate load stage were considered. Three different shear connection conditions were considered, namely, no shear connector, with steel mesh, and with Z-shaped shear connectors. The working mechanism and failure mode of the cold-formed thin-walled steel-gypsum based self-leveling mortar composite beams were investigated. The study shows that the two kinds of shear connection have little effect on the flexural stiffness at the construction stage and serviceability limit stage. The failure mode of the composite beams is severe shear deformation at the web of the C shaped cold-formed steel joist with torsional buckling. The ultimate bearing capacity of the composite beams is enhanced by setting shear connections. Based on the experimental results, the composite beam was simplified into a T-shaped section with the slip modulus between the composite slab and C-shaped joist being taken into consideration. A theoretical method for estimating the flexural stiffness of composite beams with partial shear connections was proposed, and the method can be further used to calculate the mid-span deflection of the composite beams. The predictions given by the proposed method are in good agreement with the test results.