预应力混凝土箱梁桥偏载系数的数值分析与试验

Numerical Analysis and Experimental Study on Eccentric Load Coefficient of Prestressed Concrete Box Girder

基于薄壁箱梁约束扭转的广义位移概念、板梁框架法原理,以约束扭转微分方程、畸变微分方程齐次解为单元插值函数,运用能量变分原理,以递推矩阵法推导箱梁约束扭转单元、箱梁畸变单元刚度矩阵,考虑了悬臂板、箱梁顶板变厚度的影响.用Fortran语言编写了箱梁弯曲、约束扭转与畸变单元的计算程序.基于原型桥制造了1∶4大比例的预应力混凝土连续箱梁模型,开展了偏心荷载作用下的受力特性试验研究.试验实测偏载系数与程序计算结果一致,同时计算了5座预应力混凝土箱梁桥的偏载系数.试验研究和数值分析表明:目前设计工程师所使用剪应力偏载系数严重偏小,在设计阶段留下腹板主拉应力超限甚至开裂的隐患.

A new element based on the plate girder-frame method and the Umansky Second Theory was proposed to analyze the effect of torsion and distortion of thin box-girder bridge.Different from previous literatures,homogeneous solutions of differential equation of restrained torsion and distortion were used to build the shape function of the new element,in order to enhance the accuracy of calculation.Further more,the influence of cantilever plate and thickness of top plate on the geometrical properties of cross-section was considered.A large-scale model was built,which was in 1∶4 geometrical scale of a real prestressed concrete continuous box-girder bridge,and the experimental study on the mechanical characteristics under eccentric load was carried out.The comparison of the large-scale model test and numerical simulation results shows that the proposed element is reliable.Finally,the eccentric load effects of five real bridges are calculated by the proposed method,and the results show that the shear strain eccentric load coefficient currently being adopted in design is serious,and there is a big security risk.