动载下无筋砌体墙的应力场及裂隙分布

为探索动载下建筑物墙体失稳的力学机制,基于弹性力学理论,分析一端刚性固定无筋砌体墙受垂直地震波扰动时的应力场分布规律,得到墙体的应力解析表达式,结果显示应力特征由墙体质点振速、墙体恒载、墙体密度及其几何尺寸等因素共同决定。结合具体算例发现:墙体水平应力、垂直应力与剪应力具有不同的分布特征。水平应力值分别是剪切和垂直应力值的5倍和25倍,为墙体应力场的主控应力,其应力集中区位于刚性固定侧墙体的顶、底角,应力变化梯度为180MPa/m,且随地震强度增加,其应力场进一步向墙体刚性固定侧集中。在此基础上,基于主应力主导墙体裂隙的原则,预测了墙体张开型裂隙的分布位置、长度及角度,获得了墙体最易出现破坏失稳的部位。通过模型计算可为掌握动载下墙体力学行为提供参考。

Stress Field and Fracture Distribution of Unreinforced Masonry Walls under Dynamic Loading

In this study, we explore the mechanism of wall instability in a building under dynamic load. Based on the theory of elastic mechanics, we analyze the stress field distribution of an unreinforced masonry wall with a rigidly fixed end under the disturbance of vertical seismic waves and obtain the analytical expression of the stress. The results show that the stress characteristics are determined by several factors, i.e., the particle velocity, dead load, density, and geometric size of the wall. We found that the horizontal stress values are 5 and 25 orders of magnitude greater than the shear and vertical stress values, respectively. As such, the horizontal stress is the control stress, and the stress concentration area is located at the top and bottom angles of the wall at the rigidly fixed end. The stress change gradient is 180 MPa/m, and the stress field is further concentrated on the rigid fixed side of the wall with increases in the earthquake intensity. Based on the principle that the principal stress leads to wall cracks, we predict the distribution positions, lengths, and angles of open wall fractures, and identify the most vulnerable parts of the wall. The results of this study can provide a reference for further investigation of the mechanical behavior of walls under dynamic load.