强震下多跨斜交简支梁桥桥面旋转机理研究

摘要

为分析强震下多跨斜交简支梁桥梁体出现较大转角的原因及斜度、宽跨比对桥面转角的影响,以某装配式预应力混凝土箱梁桥为背景,利用OpenSees软件建立多跨(两跨和三跨)斜交简支梁桥动力计算模型,采用时程分析法研究斜度、宽跨比和碰撞作用对桥面旋转的影响.结果表明:强震下两跨斜交简支梁桥桥面出现较大转角主要是由结构偏心效应造成的;考虑相邻梁间单边纵向碰撞后,当与斜度、宽跨比有关的参数η＜1时,碰撞力矩会抑制两跨桥面的旋转;当η＞1时,碰撞力矩会加剧其中一跨而抑制另一跨桥面的旋转.强震下三跨斜交简支梁桥中跨桥面的旋转主要由邻梁间纵向碰撞作用引起,斜度小于45°时,仅考虑梁体单边纵向碰撞,中跨桥面最大转角随η的增大而增大;考虑梁体双边纵向碰撞,中跨桥面最大转角随η的增大呈先增大后减小的趋势.%To analyze the causes of the great rotation angles occurring on the skewed multispan simply-supported girder bridges under the strong earthquake and the influences of the skew degrees and width-to-span ratios on the rotation angles of the decks of the bridges,an assembly prestressed concrete box girder bridge was taken as the example,the software OpenSees was used to establish the dynamic calculation models for the bridges (respectively with two spans and three spans) and the time-history analysis method was used to study the influences of the skew degrees,width-to-span ratios and pounding action on the rotation of the decks.The results of the study indicate that the occurrence of the great rotation angle on the deck of the skewed two-span simplysupported girder bridge under the strong earthquake is mainly caused by the eccentric effect of the structure.When the unilateral longitudinal pounding between the adjacent decks is considered and the parameter related to the skew degrees and width-to-span ratios η＜1,the moment produced by the pounding will restrain the rotation of each deck of the two-span bridge.When the η＞1,the moment will intensify the rotation of one of the decks and will restrain that of the other.The rotation of the deck of the central span of the skewed three-span simply-supported girder bridge under the strong earthquake is mainly caused by the longitudinal pounding among the adjacent decks.When skew degree is less than 45°,if the unilateral longitudinal pounding of the decks is considered only,the maximum rotation angle of the deck of the central span increases with the increase of the ηand if the bilateral longitudinal pounding is considered,the maximum rotation angle of the deck exhibits the tendency of increasing first and decreasing then with the increase of the η.