基于P-Delta效应的混凝土剪力墙结构地震响应分析

Seismic response analysis of concrete shear wall structure based on P-Delta effect

多高层建筑P-Delta效应是结构在水平荷载作用下产生侧向位移,由于竖向重力荷载的联合作用,结构中产生附加内力和附加变形的一种现象,这种现象称为结构的重力二阶效应,也定义为P-Delta效应。P-Delta效应的根本问题是结构的稳定问题,水平荷载作用下,重力荷载附加弯矩引起结构过大侧移,导致结构失稳,对于多层结构,由于高度较低,影响可能不是很大,对于高层建筑结构,由于高度较高,P-Delta效应凸显,P-Delta效应是影响结构失稳的关键因素。满足刚重比要求,是结构的宏观控制,是否考虑P-Delta效应的影响还要由结构自身的特性和所处的地震场地来决定。P-Delta效应计算属于几何非线性问题。对于建筑结构不论侧向荷载和侧向位移的大小是多少,引起P-Delta效应的竖向重力荷载不变,基于此,ETABS软件建立了一种把P-Delta效应并入基本结构刚度矩阵公式作为几何刚度修正的算法。多层、高层剪力墙结构,抗震弹性分析时,刚重比满足中国规范2010标准,位移验算时需取考虑P-Delta效应和不考虑P-Delta效应两种工况的包络值,强度验算可以不考虑P-Delta效应的影响。

The P-Delta effect of multistory and high-rise buildings is a phenomenon that the structure produces lateral displacement under horizontal load, and additional internal force and additional deformation in the structure due to the combined action of vertical gravity load. This phenomenon is called the second order gravity effect of the structure, and also defined as the P-Delta effect. The fundamental problem of P-Delta effect is the stability of the structure. Under the action of horizontal load, the additional bending moment of gravity load causes excessive lateral displacement of the structure, leading to structural instability. For multi-storey structures, due to the low height, the impact may not be great.For high-rise buildings, due to the high height, the P-Delta effect is prominent, and P-Delta effect is the key factor affecting structural instability. It is the macro control of the structure to meet the requirements of the stiffness weight ratio.Whether the P-Delta effect is considered depends on the characteristics of the structure itself and the seismic site. The calculation of P-Delta effect is a geometric nonlinear problem. For building structures, regardless of the size of lateral load and lateral displacement, the vertical gravity load that causes the P-Delta effect is always constant. Based on this ETABS software, an algorithm is established to incorporate the P-Delta effect into the basic structure stiffness matrix formula as the geometric stiffness correction. For multi-storey and high-rise shear wall structures, when conducting seismic elastic analysis, the ratio of stiffness to weight shall meet the Chinese Code 2010 standard, and the envelope value of two working conditions, including P-Delta effect and not considering P-Delta effect, shall be taken for displacement checking calculation, and the influence of P-Delta effect may not be considered for strength checking calculation.