预应力混凝土多梁式梁桥的非线性壳单元模型及极限承载力研究

本文研究了预应力混凝土多梁式梁桥的非线性壳单元计算模型，对多梁式梁桥进行了非线性全过程分析。采用弥散裂缝模式、Ottosen屈服准则和Hinton压碎准则描述混凝土开裂、屈服和压碎非线性性质后，引入实体退化壳单元理论，对混凝土和普通钢筋采用分层壳单元模拟，预应力钢筋采用组合壳单元模拟，并根据位移协调性推求了预应力钢筋对组合壳单元刚度矩阵的贡献，研究了一种非线性组合-分层壳单元计算模型，并编制了相应的三维非线性壳单元计算程序。结合破坏性试验资料可知，非线性计算结果与试验数据吻合良好，并对普通钢筋和预应力钢筋应力发展规律进行研究。研究表明对于预应力混凝土多梁式梁桥这类薄壁结构，采用本文提出的非线性壳单元计算模型来研究其非线性行为是有效的，此单元具有良好的数值稳定性和收敛性。

A Nonlinear Shell Element and Ultimate Loads of Prestressed Concrete Multi-Girder Bridge

For the structure of prestressed concrete multi-girder bridge, a computational model of the nonlinear shell element is deduced and nonlinear whole-course analysis is studied. Respectively based on smearing crack model and Ottosen yielding criterion and Hinton crushing theory, the nonlinear properties of concrete are considered. After the degraded shell element is introduced, steel and concrete are depicted by layered shell element and the prestressed steel is modeled by combined shell element. Then the stiffness matrix of contribution of the prestressed steel to the combined shell element is studied. Then a nonlinear combined-layered shell element is obtained and the analytical procedure is compiled. Through compared with the failure experiment results of a prestressed concrete multi-girder bridge, the calculations are in good agreements with them. The regularities of stress redistribution of prestressed steels and common steels are studied. It shows that it is proper to apply the nonlinear shell element to depict the prestressed concrete multi-girder bridge and the corresponding computational method and procedure for nonlinear whole-course analysis are of satisfying stability and convergence.