桥面板徐变对大跨径钢混组合梁桥力学性能的影响

Creep effect of concrete slab on mechanical properties of long-span steel-concrete composite bridge

为探讨混凝土桥面板收缩徐变效应对大跨径钢混组合梁桥的影响,以沁河特大桥的钢混组合梁桥为工程背景,采用Midas Civil软件建立了有限元模型,研究了桥面板徐变效应下钢混组合梁桥成桥10年的应力和挠度变化,并分别探讨了时间历程、预制板龄期和相对湿度等因素对钢混组合梁桥徐变效应的影响。结果表明:混凝土桥面板徐变效应使得钢梁上缘压应力增大、下缘拉应力减小;徐变应力在次边跨最大、中跨较小、边跨最小;徐变挠度在边跨最大、中跨较小、次边跨最小;混凝土桥面板徐变效应对钢混组合梁桥的影响随时间增加而减弱,对挠度影响最大是在成桥第1年,对应力影响最大是在成桥前3年;预制板龄期和相对湿度的增加可降低徐变效应对组合梁的影响,成桥10年时龄期为28 d的中跨徐变挠度是龄期180 d的中跨徐变挠度的1.33倍,相对湿度为62%的中跨徐变挠度是相对湿度为79%的中跨徐变挠度的1.21倍。

In order to explore the effect of shrinkage and creep of concrete slab on long-span steel-concrete composite bridge,this paper takes the steel-concrete composite bridge of Qinhe River Bridge as the engineering background and uses a finite element model established with Midas Civil software to study the change of stress and deflection of steel-concrete composite bridge in 10 years under the creep effect of concrete slab,and discussed the influence factors such as time history,age of prefabricated slab and relative humidity on the creep effect of steel-concrete composite bridge respectively.The results show that the creep effect of the concrete slab increases the compressive stress on the upper edge and decreases the tensile stress on the lower edge of the steel beam.The creep stress is the highest at the secondary span,the smaller at the middle span and the lowest at the edge span.The creep deflection is the maximumt at the edge span,the smaller at the middle span and the minimum at the secondary edge span.The creep effect of concrete slab decreases with the increase of time.The maximum effect on deflection is 1 year after the completion of bridge,and the maximum effect on stress is 3 years after the completion of bridge.The increase of age and relative humidity of prefabricated panels can reduce the influence of creep effect on composite beams.The mid-span creep deflection of the bridge at 28 days of age is 1.33 times that of the bridge at 180 days of age,and the mid-span creep deflection of the bridge at 62% relative humidity is 1.21 times that of the bridge at 79% relative humidity.