负弯矩作用下钢-混组合梁的疲劳试验

介绍了钢-混组合梁在负弯矩作用下的疲劳性能。在两个钢-混组合梁结构上分别进行循环荷载下的疲劳试验,并只局限于初始开裂和稳定开裂。试验结果表明,循环荷载与初始荷载相等时,疲劳试验对梁刚度与裂缝形态的影响有限。然而,当循环荷载与稳定开裂荷载相等时,在初始静态试验时产生了大量的残余应力,造成了破裂,且梁的刚度减小而荷载周期增加。中期的静态试验证实了栓钉与周围混凝土的连接失效,栓钉的承载力随着荷载周期的增加而减小。此外,对经过疲劳测试的样本与未经过疲劳测试的样本进行最终的静态测试发现,循环荷载大于初裂荷载时,疲劳试验会降低梁的刚度及极限承载力。

Fatigue Tests on Straight Steel-Concrete Composite Beams Subjected to Hogging Moment

This paper describes the fatigue behavior of composite steel and concrete beams subjected to negative bending moment. Fatigue tests with repeated load limited to initial cracking and stabilized cracking, were performed on two steel-concrete composite beam substructures respectively. Test results indicated that when the repeated load was equivalent to the initial cracking load, the fatigue test had only limited influence on beam stiffness or crack patterns. However, when the repeated load was equivalent to the stabilized cracking load, a number of residual cracks occurred in the initial static test and the beam became less stiff as the load cycles increase. Failure of the bond between studs and surrounding concrete was confirmed in intermediate static tests; flexural stiffness of studs became smaller as the increase of load cycles. In addition, final static tests were performed on fatigue test specimens and another specimen without fatigue test. The comparison indicated that when the repeated load was larger than the initial cracking load, fatigue test could decrease beam stiffness and its ultimate load carrying capacity.