上覆土竖向惯性力对浅埋地下框架结构地震损伤#br# 反应影响离心机振动台模型试验研究

已有研究表明不同轴压比下中柱侧向变形能力是影响浅埋框架地铁车站结构抗震性能的关键因素。为了研究由竖向地震作用引起的柱轴压比增高对浅埋地下框架结构的地震损伤反应的影响，采取在结构上覆土中掺入钢砂的方式体现上覆土的竖向惯性力作用，开展地下结构地震破坏离心机振动台模型试验研究。试验结果表明：结构上覆土体掺钢砂的方式对土-结构体系的动力特性、地震作用下地下结构顶、底板水平相对位移反应影响不大；增加上覆土竖向惯性力较大地改变了围岩土体与地下结构的接触压力分布形式，进而改变结构各构件的内力状态，使得框架结构中的关键竖向承力柱的轴压比升高；增加上覆土竖向惯性力导致地下结构框架受力及中柱轴压比增高的后果使得地下框架结构更易发生地震破坏。

Dynamic centrifuge tests for influence of vertical inertia force of overburden soil on earthquake damage response of shallow-buried underground frame structures#br#

Previous researches have showed that the columns under different axial compression ratios performed different lateral deformation capacities, which is the key factor of aseismic performance of the shallow-buried subway frame structures. In this study, dynamic centrifuge model tests on earthquake damage to underground structure are carried out. The model tests aim to shed lights on the effect of the increased axial compression ratio of column, which is induced by the vertical earthquake excitation, on earthquake damage responses of shallow-buried underground frame structures. To simulate the effect of vertical inertia force of overburden soil, the steel grits are mixed into the overburden soil layer. Test results indicate that the way of mixing the steel grits into the overburden soil layer has little influence on dynamic characteristics of soil-structure system and relative horizontal displacement between ceiling slab and bottom slab due to seismic excitation. The increased vertical inertia force of overburden soil significantly changes the contact pressure distribution between underground structure and surrounding soil, and the stress states of structural member are changed accordingly, leading to the increase of axial compression ratio of the key vertical load bearing column in the underground frame structure. Consequently, increasing vertical inertia force of overburden soil effectively increases the stresses of the structural frame and axial compression ratio of middle columns, so that the underground frame structure is more susceptible to seismic damage.