先简支后连续预应力箱梁施工阶段受力与变形分析

Stress and Deformation Analysis of Simply-Supported-to-Continuous Prestressed Beam Bridge During the Construction Stage

先简支后连续结构既有简支桥梁的施工简便,又有连续桥梁的刚度大、行车舒适等优势,因此在各等级公路中广泛使用。为研究该类桥梁在施工过程中梁体的受力和变形的情况,本文以国道312线K1955+160处张城堡大桥为例,运用MIDAS/CIVIL有限元软件,建立不同施工阶段梁体的有限元模型,分析在不同施工阶段梁体的受力与变形。结果表明:正预应力张拉完后最大负弯矩出现在梁体正弯矩预应力钢束弯起点位置;其次由于反拱作用使得梁体跨中与台座离开,主要靠梁体两端支撑于台座上,只有竖向约束,梁体处于不稳定状态;在负弯矩区预应力张拉前,支点截面会出现拉应力;由双支座向单支座转换的过程中,梁体受力发生重新分布。

The Simply-Supported-to-Continuous structure was widely used in highway construction,because it has the advantages of convenient construction of simple-supported bridges,and large stiffness of continuous bridges.In order to research the stress and deformation of this kind of bridge,we take Zhang Cheng Pu Bridge at K1955+160 on 312 national highway as an example.The finite element models of beam bridge at different construction stages are established to analyze the stress and deformation of beams at different construction stages,by using general finite element software named MIDAS/CIVIL.The results showed that the maximum negative moment appears at the bending point of prestressed steel beam after the positive prestress tension is completed.Secondly,due to the reversed arch effect,the middle span of the beam body and the platform are separated,and the beam body is mainly supported by beam end.Due to vertical constraints,the beam body is in an unstable state.There will be tensile stress in the fulcrum section,before prestressed tension in negative bending moment zone.The force of the beam body is redistributed,during the transformation from simply-supported to continuous support.