往复荷载作用下开洞砖塔子结构受力性能研究

Research on mechanical properties of sub-structure of brick masonry pagoda with holes under hysteretic load

结构开洞对砖石古塔的抗震能力影响显著,为研究不同开洞形式砌体古塔的抗震性能,以玄奘塔中部楼层为原型结构,设计制作了3种洞口开设方式的子结构模型,对其进行低周反复加载试验。观察了模型结构的破坏现象,得到了模型顶点水平荷载-位移滞回曲线与骨架曲线,对比分析了采用不同开洞方式时,模型结构的滞回特性、刚度退化以及耗能能力等。建立子结构有限元模型进行分析,将分析结果与试验结果进行对比。结果表明,在塔体结构平面尺寸相同的条件下,开洞口方式对结构的刚度、承载力及延性的影响显著;单面开洞、双面开洞及四面开洞时结构的破坏模式不同,但均为洞口顶部首先开裂,并与其他墙体内所产生的剪切裂缝将塔体分割为不同形状的破坏单元,改变了荷载原有的传递方式,从而影响结构的破坏模式;有限元分析与试验所得极限水平荷载相差均在15%以内,有限元模型能够较为准确地模拟开洞古塔子结构的受力性能。研究结果可为砖石古塔的抗震性能评估提供依据。

The opening of the ancient masonry tower structure has a significant impact on its seismic performance. In order to study the seismic performance of the ancient masonry towers with different opening forms, using the middle floor of Xuanzang Tower as the prototype structure, three sub-structure models of various opening methods were designed and fabricated. The test specimens were subject to low cycle reversed cyclic loading. The failure phenomenon of the model structure was observed, and the hysteresis curves and the skeletons curve were obtained. The hysteresis characteristics, stiffness degradation, and energy consumption capacity of the structure were compared and analyzed when different opening methods were used. A finite element model was established for analysis, and the calculation results were compared to the test results. The results show that when the tower structure has the same planar size, the opening method has a significant influence on the stiffness, ultimate capacity, and ductility of the structure. The failure mode of the structure is different for various opening schemes, including single-sided opening, double-sided opening and the case when the hole is opened on all sides. For all opening schemes, when the specimen is loaded, the top of the hole first ruptures and the shear cracks generate and segment the walls of the tower into different parts, thereby changing the original load transfer mechanism and affect the failure mode of the structure. The difference of ultimate load from the finite element and the test is within 15%, and the finite element method model can simulate the mechanical performance of the ancient tower substructure with accuracy. The research outcome can serve as reference for seismic properties assessment of masonry pagodas.