单缝桥梁在温度作用下的结构受力计算

Study on temperature effects of single expansion joint bridge

桥台处伸缩缝问题是长期困扰工程界的难题,它会带来跳车、桥梁局部损坏、伸缩缝装置经常更换等各种问题。为有效解决这一问题,提出了一种适用于大中型桥梁的新型结构体系——单伸缩缝桥梁(单缝桥)。在考虑接线路面裂缝开展的情况下,建立了温度作用下单缝桥的简化计算模型,推导了单缝桥受力、变形的理论公式,用Fortran90编制程序,进行计算。以一座总长280 m的单缝梁桥为例,温度降低20℃时,接线路面钢筋最大应力为148 MPa,最大裂缝宽度为0.185 mm,符合规范要求;台后结构对主梁产生的附加应力仅为0.105 MPa,影响很小。通过对影响单缝桥性能的因素:支座类型、配筋率、接线路面长度、摩擦系数、土体刚度、桥长、温差等进行分析,绘制图表,得到以下主要结论:温降时,接线路面受拉,混凝土开裂,是较不利的状况;30 m长的接线路面可以满足结构受力和变形的需要;选择摩擦系数较小的支座和减少接线路面与垫层的摩擦力可以减少结构内力,在接线路面与垫层间推荐加铺土工格栅。

There are some problems of easy damage and arduous maintenance in the expansion joints at abutment,and a new type of single expansion joint bridge（SEJB） is herein proposed to deal with them.To investigate the mechanical characteristics of SEJB under temperature load,simplified calculation model is proposed in this paper.Considering the distribution and development rule of cracks in approach pavement,theoretical formulas for internal force and deformation were derived,and calculation programs were compiled.For example,under the effect of temperature drop of 20 ℃,the maximum steel stress was 148 MPa,and the maximum crack width was 0.185 mm for a 280 m-length SEJB,which met the requirement of criterion;the additional stress of beam was 0.105 MPa,which could be ignored.Moreover,taking the different temperatures into account,parameter analysis was performed.The results show that the 30 m-length pavement can well meet the needs for use.Internal force is reduced by using bearing and cushion materials with low surface friction coefficient,and a biaxial geogrids is recommended.