PC多梁式梁的横向受力非线性分析

Nonlinear analysis on mechanical performance of PC multi-girder structures under lateral loading

为研究破坏全过程中预应力钢筋应力变化、主梁和横隔板裂缝发展及其对荷载横向受力分布的影响,建立PC多梁式梁的计算模型,利用弥散裂缝模型等来描述混凝土的材料非线性性能,根据PC多梁式梁的结构受力机理和受力特点,设计了中载加载和偏载加载工况,并对横向受力性能指标进行相应的计算分析和综合评价.研究表明:建立的PC多梁式梁力学计算模型是正确的,主梁和横隔板开裂顺序与荷载布置方式有关,中载作用下横隔板先于主梁开裂,偏载作用下主梁先于横隔板开裂;横隔板开裂削弱整体横向联系,使主梁协同受力性能减弱,荷载横向分布趋于不利变化;预应力钢筋应力在结构处于弹性阶段增长缓慢,其后应力迅速发展直至屈服.

A computational model is studied to analyze the mechanical performance of PC multi-girder structure,which includes the propagation of cracks within the beam and diaphragm,the cracking pattern,the distribution of transverse loads and the stress redistribution in the prestressed steels.In the study,the nonlinearity of concrete material is described by using smeared crack model and other corresponding criteria.According to the mechanical characteristics of PC multi-girder structure,two typical loadcases defined as symmetric loadcase and offset loadcase are designed and then the lateral mechanical performances are analyzed and clarified in detail.Numerical results testify that the computational model is correct and the occurrence of cracks is closely related with the disposal of the acted loads.When subjected to symmetric loads,the PC multi-girder structure firstly produces cracks in its diaphragm and then in its beam;under offset loads,the crack appears earlier in the beam than in the diaphragm.Cracks in the diaphragm weaken the transverse connections between the beams,which leads to unfavorable change of the transverse loads distribution.The stress in the prestressed bar increases slowly in the elastic stage and then fast until the yielding stress is reached.