简支梁桥位移与内力动力系数差异研究

Study on Differences between Displacement and Internal Force Dynamic Impact Factor of Simply-Supported Bridges

动力系数是桥梁结构设计和检定中一个基本而关键的参数,其可以用位移放大系数来表示,也可以用内力(弯矩、剪力)放大系数来表示,而在桥梁的设计、检定工作中,并未注意到它们量值之间的区别。文中理论探讨了移动荷载列过桥模型的位移、内力放大系数的异同,以及不同动力系数沿简支梁桥跨长的变化规律,为区分制定桥梁动力系数的合理表达形式提供理论依据。并计算分析了车桥耦合模型与移动荷载列过桥模型的桥梁动力系数计算值的差异,结果表明应用移动荷载列模型计算简支梁桥动力系数可以得到安全可靠的结果,即可应用该模型解析解分析动力系数的主要影响因素。

Dynamic impact factor is a fundamental and key parameter in bridge design and rating. It can be expressed by a displacement magnification factor, or a force （including bending moment and shear force ） magnification factor. The value difference between these magnification factors has never been noticed in prac- tice. By an analytical approach, the similarities and differences of displacement and force magnification factor were studied, and the variation law of impact factor along bridge span was identified, which provided theoretical foundation for the establishment of different reasonable formula for impactfaetors of bridges. Impact factors were calculated using coupled vehicle-bridge interaction model and uncoupled model simulating the train as a series of non-vibrant constant moving loads. The differences are analyzed and the rationality of studies on dynamic impact factor using uncoupled vehicle-bridge model was discussed. It was found that studies on dynamic impact factor using uncoupled vehicle-bridge model is reliable and safe. Then non-dimensional key parameters of impact factor can be obtained by uncoupled model.