大跨径预应力混凝土箱梁的剪切变形分析

Analysis on Shearing Deformation of Long-span Prestressed Concrete Box Girders

为分析剪切变形对预应力混凝土箱梁挠度的影响,依据经典Timoshenko梁理论,参照已建大跨预应力混凝土箱梁的截面尺寸,简化选取等截面悬臂箱梁为分析对象建立了空间有限元模型.按不考虑剪切变形和考虑剪切变形两种情况计算了箱梁的挠度,分析了剪切变形的影响随箱梁高跨比的变化,并讨论了传统观点中的考虑剪切变形的高跨比门槛值在大跨径预应力混凝土箱梁挠度计算中的适用性.然后,建立了虎门大桥辅航道桥的施工阶段分析模型,模拟箱梁的实际悬臂施工过程,分析了剪切变形对箱梁挠度的影响规律,计算并探讨了箱梁的长期徐变挠度,进而推算了箱梁的剪切徐变挠度.分析结果表明,剪切徐变是造成箱梁持续下挠的原因之一.

In order to analyze effects due to shearing deformation on deflection in prestressed concrete box girders,based on Classical Timoshenko Beam Theory,and referring to the typical cross-section of an existing prestressed concrete box girder,a FE model for a cantilever box girder with a simplified constant cross-section was developed.The girder＇s deflections were calculated respectively by considering its shearing deformation or not.The influence of shearing deformation caused by the height-span ratio of girder was analyzed.The discussion was implemented on the applicability of the traditional threshold value of height-span ratio,which was used to decide whether the shear deformation need to be considered in the calculation of deflection of large-span prestressed concrete box girders.Then,a FE model was used to simulate the Assistant Shipping Channel Bridge of Humen Bridge during cantilever construction.The influence on the deflection of the box girder,caused by its shearing deformation,was analyzed,and the long-term creep deflection was also calculated with some essential discussions.Thus,a shear creep deflection of prestressed box girder was deduced.The results presented that the shear creep deflection is one of the reasons resulting in consecutive deflection of long-span box girders.