中小跨径公路桥梁抗震设计理念

Philosophies on seismic design of highway bridges of small or medium spans

总结汶川地震中不同桥型的性能表现,重点比较简支梁桥与连续梁桥、梁桥和拱桥的受损情况,并基于实际震害经验,提出桥型选择的一些原则;基于抗震计算无法得到结构响应精确值的事实,建议抗震设计中采取"多道设防,分级耗能"的抗震设防理念,重点讲述保险丝式单元的应用,提出桥梁抗震设计的"一可三易(可控、易检、易修、易换)"原则,即"损伤部位及损伤程度可控,损伤部位易检,损伤构件易修,破坏构件易换",基于"多道设防,分级耗能"和"一可三易"原则,建议中小跨径梁桥在破坏性地震作用下,支座作为保险丝式单元优先损坏,桥墩可出现易修复的塑性铰,桩基不能损伤。最后对一个实际工程,阐述孔跨布置的选择理念、桥墩抗剪能力的计算过程及双层抗震挡块的构造措施。研究成果可解决实际桥梁抗震设计工作中的部分问题。

The seismic performances of different types of bridges in the Wenchuan earthquake are summarized, with the comparisons focusing on the damages of simply supported girder bridges and continuous girder bridges, beam bridges and arch bridges, and based on the experiences, several fundamental principles on bridge-type selection are presented. Based on the fact that structural response can not be accurately calculated, the implementation of ＂ multilevel fortification, hierarchical energy-consumption＂ philosophy is recommended, the application of fuse elements is highlighted, and the principle named ＂one-can and three-easy＂ is proposed, which means, in devastating earthquakes, ＂ the injury component and extent of injury can be controlled, the injury position is easy to check, the injury component is easy to repair, the damaged component is easy to change＂, ＂the damage of bearing as a fuse element should be the priority, easily repairable plastic hinges can appear in piers, piles should be intact＂. Finally, a real case is discussed in detail, the span combination, the shear capacity calculation of pier, and double shear keys are studied. The results of present study are expected to be useful for practical problems.