柱底位移影响下的某RC框架结构安全性分析及破坏机制研究

Safety analysis and failure mechanism study of a RC frame structure affected by column bottom drift

原有建筑邻近基坑的开挖可能会对其地基变形造成影响,甚至会使上部结构受力变形发生较大变化,影响结构的安全。为了研究邻近基坑开挖引起的柱底位移对框架结构安全性的影响及破坏机制,以某RC框架结构为研究对象,利用LS-DYNA软件进行了结构在正常荷载和多倍荷载下角柱柱底位移逐步增大情况下的结构响应分析。结果表明:在正常荷载下,角柱底部发生较大位移均不会导致案例结构出现大面积的结构破坏,仅会出现局部构件破坏;在多倍荷载下,柱底向不同方向位移时,极限位移大致与荷载放大系数呈反比,结构最终破坏程度大致随荷载放大系数的增加而增加;柱子受力为大偏压情况下,柱底位移更容易引发结构破坏,若上部荷载增大使其由大偏压转为小偏压,则结构的抗倒塌能力在一定程度上反而会增加。

Excavation of adjacent foundation pit of the original building may affect the deformation of its foundation, and even can cause great changes in the stress and deformation of the superstructure, which affects the safety of the structure.To study the influence of the column bottom drifts caused by excavation of adjacent foundation pit on safety and failure mechanism of frame structures, responses of a RC frame structure are studied under normal loads and multiple loads with gradually increasing bottom drifts of corner column using LS-DYNA software. Results show that: under normal loads,large bottom drifts of corner column do not lead to large-scale damage of the RC frame, and only partial component failure occurs;under multiple loads and with column bottom drifts in different directions, the ultimate drifts are roughly inversely proportional to the load amplification factor, and the structure final damage levels increase with the increasing of the load amplification factor;when the column is under large eccentric compression load, column bottom drifts are more likely to cause structural failure, and the collapse resistance increases to a certain extent with the increasing upper load which changes the column load state to compression with small eccentricity.