预应力混凝土箱梁桥施工过程剪力滞试验

Experimental Study of Shear Lag Effect in the Construction of Prestressed Concrete Box Girder Bridge

国内外箱梁剪力滞研究多按结构一次成型进行分析,无法准确模拟自平衡施工过程所产生的累计效应.依托某连续梁桥的实桥测试,同步采集施工过程中的应变数据,分析研究预应力混凝土箱梁桥自平衡施工过程中的剪力滞特性.通过测试荷载作用前后的应变增量,归纳出累计剪力滞规律,并与块体有限元模型计算结果进行对比.总结出若干规律：梁段累计剪力滞系数随着长高比或长宽比的增大而逐渐减小并趋于稳定,其中自重和挂篮前移会增大剪力滞效应,预加力则减小剪力滞效应;剪力滞系数按结构一次成型计算平均小于考虑施工阶段的20%-30%,这一点在箱梁施工阶段分析时必须重视.

The study at home and abroad about the shear lag of box girder conducted by the one-step forming structure analysis. And it wasn＇t able to accurately simulate the cumulative effect which self-balancing construction generated. Relying on a real continuous beam bridge test,synchronously collected strain date in the construction process,and the shear lag characteristics were analyzed which in the self-balancing construction of prestressed concrete box girder bridge. By testing strain increment before and after load application, the cumulative shear lag law was generalized,and the results were compared with the block finite element model.The following summarizes were as follow. Cumulative shear lag of beam gradually decreases with the increase of the ratio of length to width or length to height and tends to stable. Among them,the weight and hanging basket forward will increase shear lag effect and pre-energizing reduce it. The shear lag coefficient which considers the one-step forming structure is average of less 20% - 30% than which considers the construction. This point must pay attention in the analysis of box girder in construction stage.