生土砌块墙体地震失效机理试验研究

Test study on seismic failure mechanism of raw soil block walls

为研究生土砌块墙体的地震失效机理,对基于典型尺寸的实体墙、带门洞墙,以及带窗洞墙等3类墙体1∶2.5缩尺模型试件进行了低周往复水平加载试验,获取了墙体从开裂到倒塌的失效全过程损伤演变规律以及滞回曲线、骨架曲线、延性系数等抗震性能指标,建立了抗剪承载力计算公式,并在相关文献统计数据的基础上探讨了生土砌块墙体的抗震性能评估指标量化取值。研究表明:典型尺寸的生土砌块墙体在地震作用下发生剪切破坏,最终以墙体“X”型主裂缝交汇处砌体被压碎,两侧三角型区域砌体脱落标志着墙体倒塌失效;生土砌块墙体承载能力、变形能力、耗能能力及延性系数均随开洞率增大而降低;采用基于剪摩理论的生土砌块墙体抗剪承载力计算公式可获得与试验误差较小的结果;依据我国现行《建筑抗震设计规范》中抗震性能设计目标划分,给出了无约束生土砌块墙体基本完好、轻微破坏、中等破坏、严重破坏、墙体倒塌5个性能水准的层间位移角上限建议值,分别为1/2 000、1/350、1/180、1/100。

Here, to study seismic failure mechanism of raw soil block walls, low cycle reciprocating horizontal loading tests were conducted for 1∶2.5 scale model specimens of 3 types walls of solid walls, walls with door openings and walls with window openings based on typical sizes to obtain damage evolution laws of the whole failure process of walls from cracking to collapse as well as aseismic performance indexes, such as, hysteretic curve, skeleton curve and ductility coefficient, and establish the calculation formula of shear-bearing capacity. On the basis of relevant literature and statistical data, quantitative value ranges of aseismic performance evaluation indexes of raw soil block wall were explored. The results showed that shear failures of typical size raw soil block walls occur under the action of earthquake, and finally masonries are crushed at intersections of “X” type main cracks of walls, and falling off of masonries in triangular areas on both sides marks collapse and failure of walls;load-bearing capacity, deformation capacity, energy dissipation capacity and ductility coefficient of raw soil block walls decrease with increase in opening rate;the calculation formula of shear-bearing capacity of raw soil block walls based on the shear-friction theory can obtain the results with smaller error compared with test data;according to the classification of aseismic performance design objectives in the current code for aseismic design of buildings in China, recommended upper limit values of interlayer displacement angles for unconstrained raw soil block walls’ 5 performance levels of basically intact, slightly damaged, moderately damaged, severely damaged and collapsed are given, they are 1/2 000, 1/350, 1/180, 1/100 respectively.