集中荷载下钢木组合梁试验研究及有限元分析

Experimental and numerical investigation of steel-timber composite beams under concentrated load

【目的】用钢材替代工字型木梁的腹板部分以解决纯木梁腹板易剪切破坏、抗弯刚度低的问题,有助于减小构件尺寸,增加其在大跨度建筑中的应用。【方法】在H型钢上下翼缘各覆一层木材并使用螺栓连接制备组合梁。对11根组合梁开展三点弯曲试验,研究螺栓间距、剪跨比对组合梁破坏模式、刚度和承载力的影响。通过4个推出试验研究钢木界面滑移对组合梁性能的影响。【结果】钢木组合梁的抗弯刚度比相同截面尺寸的矩形木梁提高了201%;H型钢在集中荷载作用下易发生上翼缘的局部屈曲,剪跨比为2时,试件出现脆性破坏特征,破坏始于上层木材,随着剪跨比增大,试件由脆性破坏转变为延性破坏,木材最先破坏位置由上层木材转变为下层木材;剪跨比增大时,组合梁抗弯刚度减小,延性系数增大,峰值荷载下降了15%以上;螺栓间距增大时,组合梁抗弯刚度增大,延性系数减小,峰值荷载上升了15%以上。考虑钢木界面滑移的屈服承载力和跨中挠度的计算公式具有较高的准确性,所得计算值与试验值误差基本在10%以内;由材性试验获取材性参数,在此基础上使用ABAQUS软件建立考虑钢木界面滑移的有限元模型,模拟结果较为准确,组合梁抗弯刚度和屈服荷载的模拟值与试验值误差基本在10%以内。【结论】钢材用作腹板部分可以显著提高梁的抗弯刚度,并防止腹板剪切破坏;考虑界面滑移后,组合梁抗弯性能的理论计算和有限元模拟结果均较为准确。

[Objective]Replacing the web of I-shaped timber beam with steel can solve the problems of web shear failure and low bending stiffness of bare timber beam.This helps to reduce the component size and increase its application in large-span buildings.[Method]The steel-timber composite(STC)beam was prepared by connecting two timber slabs on the H-shaped steel flanges with bolts.The influence of different bolt spacing and shear-span ratio on the structural behavior(failure modes,stiffness and load capacity)of STC beams were studied.Three-point bending tests were carried out on 11 STC beams.Four push-out tests were carried out to investigate steel-timber interface slip.[Result]The bending stiffness of the STC beams was 201%higher than that of the rectangular timber beam with the same section size.The steel upper flange was prone to buckle by concentrate load.Increasing the shear-span ratio,the failure converts from brittle to ductile,the initial failure transforms from top timber slab to bottom.Increasing the shear-span ratio or decreasing the bolt spacing,the bending stiffness was declined,the ductility coefficient was improved and the peak load decreased by more than 15%.The formulations of yield load and mid-span deflection considering interface slip between steel and timber were proposed,the error of most specimens was less than 10%between calculated and experimental results.In addition,referencing material properties and push-out test,the finite element models of STC beams were established.The errors between simulated and experimental values of bending stiffness and yield load were basically within 10%.[Conclusion]Steel used as the web can significantly improve the bending stiffness of beams and prevent shear failure of webs.Considering the interface slip,the theoretical calculation and simulation results of flexural performance of STC beams are accurate.