冷弯U形组合梁长期受力性能研究

Study on Long-term Mechanical Behavior of Cold-formed U-shaped Composite Beams

为评估冷弯U形组合梁的长期受力性能,建立U形组合梁三维有限元模型,在子程序中开发混凝土的徐变与收缩时变本构及焊钉连接件的抗剪刚度时变本构,研究恒载、徐变及收缩作用对组合梁长期效应的影响.结果表明,混凝土徐变与收缩10年,组合梁在自重作用下的跨中挠度终值较初期增加约75%,跨中挠度终值由恒载、收缩及徐变三种作用组成的比例分别为50.2%,37.2%,12.6%.组合梁端部的焊钉剪力大小增加约1倍,梁端处焊钉的承剪安全储备削弱.组合梁跨中截面的中性轴高度终值较初期降低26.3%,U形钢梁屈曲失效的可能性增大.工程设计宜考虑混凝土的时变作用对冷弯U形组合梁的预拱度设置、界面焊钉连接件的承剪安全性及冷弯U形钢梁长期稳定性的影响.

In order to evaluate the long-term mechanical behavior of cold-formed U-shaped composite beams,a three-dimensional finite element model of the U-shaped composite beam was established.The creep and shrinkage constitutive equations of concrete and the time-varying shear stiffness of headed studs were developed in subroutines,the effects of dead load,creep and shrinkage on the long-term effects of cold-formed U-shaped composite beams were studied.The results reveal that after 10 years of creep and shrinkage,the final mid-span deflection of the composite beam increased by about 75%under self-weight compared with the initial value,the final mid-span deflection is composed of 50.2%,37.2%and 12.6%by dead load,creep and shrinkage,respectively.The shear force of headed studs at beam ends are almost twice than the initial results,which reduces the safety margin of headed studs.The neutral axis height of the mid-span section of the composite beam is reduced by 26.3%,which increases the possibility of buckling failure of U-shaped steel beams.In engineering designs,the influence of time-dependent effects of concrete on the pre-camber setting of cold-formed U-shaped composite beams,the shear safety of headed studs at the steel-concrete interface and the long-term stability of cold-formed U-shaped steel beams should be considered.