多年冻土区桥梁抗震研究进展

本项研究从冻土场地效应、冻土对桥梁地震响应的影响、冻土与桥梁结构相互作用3个方面总结了冻土区桥梁抗震的多年研究现状,旨在推动多年冻土区桥梁抗震理论的发展.结果表明:冻土场地地震效应显著,目前多年冻土区桥梁抗震设计中未充分考虑冻土场地效应的影响,且缺乏相应的抗震规范依据.大量数值分析结果显示,季节与多年冻土层均对桥梁地震响应产生显著影响,而目前多年冻土区桥梁结构-冻土体系的耗能机制及破坏特征的研究不充分,仍需大量震害调查和试验研究.对于多年冻土区桥梁工程广泛采用的桩基础形式,冻土层的存在使得地震作用下桩-冻土相互作用机理复杂化,桩-冻土相互作用理论计算模型有待完善.桥梁抗震分析中未充分考虑冻土水热效应的影响(冻土随温度和含水量等水热特性变化引起的力学性能的改变).上述问题都是今后多年冻土区桥梁抗震研究需重点关注的方向.

Research advance on seismic performance of bridges in permafrost regions

This study summarizes the domestic research status of bridge seismic resistance in permafrost area from three aspects: effect of permafrost site, effect of permafrost on bridge seismic response, interaction between permafrost and bridge structure. Results show that frozen soils have significant effect on response within the seismic site in permafrost regions. Existing seismic design of bridges is performed without taking the response within the permafrost site into account, and there are no provisions in current seismic codes. Larger numbers of numerical studies show that both seasonally frozen soil and permafrost have significantly effects on seismic responses of bridges in cold regions. However, the present researches on energy dissipation mechanism and failure characteristics of bridge structure-frozen soil system in permafrost regions under earthquakes are still insufficiently clear so far. For the bridges with pile foundation widely used in permafrost regions, the pile-frozen soil interaction mechanism becomes more complicated due to the frozen soils, therefore, the existing predictive model of pile-frozen soil interaction should be improved. Without the improvement, the influence of the hydrothermal effect caused by frozen soils (changes of the hydrothermal properties such as temperature and water content may lead to the change of mechanical properties of the frozen soils), will not been fully taken into account in seismic analyses of bridges. All of above problems should be the focus of seismic research of bridges in permafrost area in the future.