砌体结构沉降角变形限值的试验研究

Experimental Study on the Limit Value of Angular Distortion in Settlement of Masonry Structure

采用集中荷载作用下的悬臂深梁模拟受邻近基坑施工影响下的多层砌体结构的沉降变形,对7个墙段深梁试件进行了单调加载试验,研究砌体结构沉降的角变形限值。试验中测试了试件刚度、剪切变形占总变形的比例、裂缝宽度与主拉应变关系、角变形与主拉应变关系等变化规律。试验结果表明:砌体出现初始斜裂缝时的主拉应变约为0.3‰,砌体开裂后主拉应变的增大主要由斜裂缝宽度的增大造成,主拉应变是度量砌体损伤程度的合适参数;试验过程中试件刚度衰减幅度很大,剪切变形占总变形的比例逐步提高;角变形与主拉应变的比值,在试验初期的实测值高于弹性理论值,而在后期逐步接近或略低于弹性理论值。总体上,在主拉应变为0.3‰~3‰范围内,角变形限值的实测平均值与弹性理论值吻合良好。根据试验结果,提出了弯剪刚度比非线性发展规律的分析方法,分析了现浇圈梁和楼板在控制建筑沉降引起建筑物损坏中所起作用的机理。适当调整主拉应变限值后,角变形限值的弹性理论值可基本适用于各试件的受力变形全过程。

The settlement deformations of muhi-story masonry structures affected by the adjacent pit construction were simulated using the cantilever deep beams under concentrated load. Monotonic loading tests of 7 deep beam specimens of wall segments were carried out to study the limit value of angular distortion of masonry structures. The test results were obtained about the specimen stiffness, the shear deformation proportion of the total deformation, the relation between crack width and principal tensile strain, and the relation between angular distortion and the principal tensile strain. The results showed that, inclined cracks of masonry appeared when the principal tensile strain was about 0.3‰. After cracking, the increase of tensile strain was mainly caused by the increase of inclined crack width. The principal tensile strain was an appropriate parameter for measuring the masonry damage degree. During the test, the specimen stiffness decayed largely, to the shear deformation proportion of the total deformation increased gradually. The ratio of angular distortion and principal tensile strain was higher than the elastic theoretical values at the beginning of the test, but gradually close to or slightly lower than the elastic theoretical value. Overall, when the principal tensile strain was within the range of 0.3‰ -3‰,the average of the measured values of angular distortion was in good agreement with the elastic theoretical values. Based on the experimental results, the analysis method was proposed for the nonlinear development law of the shear-bending stiffness ratio. The mechanism for the cast-in-situ ring beam and floor in the tocontrol the building subsidence damage was also analyzed. By the appropriate adjustment of the limit value of principal tensile strain, the elastic theoretical value of the angular distortion limit can be basically used in the whole process of the specimen deformation.