汶川地震中底层框架砖房震害特点及分析

Lessons from the Performance of Masonry Structure with Ground RC Frame during Wenchuan Earthquake

底层框架砖房是一种混合结构形式,底部一层全部或部分采用钢筋混凝土框架承重,上部多层采用砖墙承重,在我国城镇地区应用非常广泛,通常具有"上刚下柔"的结构特性。512汶川地震中不同烈度地区均有大量该类建筑严重破坏甚至倒塌,也有部分位于极震区的底框砖房表现出很好的抗震性能。地震发生后,四川大学组织了考察队,对地震灾区建筑物的震害情况进行了广泛深入的科学调查。在介绍和总结了汶川地震中底框砖房的表现——底层过大的水平侧移、过渡层严重破坏或完全坍塌、底层严重破坏或房屋完全倒塌、上部砌体整体发生侧移、以及设计和施工质量良好的底层抗震墙砖房"大震不倒"的基础上,得出以下结论和建议:在抗震设防地区应禁止使用部分底框砖房,地震中过渡层的实际受力情况与设计所采用的受力状态有明显的区别,规范应考虑砌体和钢筋混凝土材料的不同力学性质来制定上下层刚度比要求,明确对过渡层的延性和强度要求,明确该类结构抗震概念设计的具体措施。

An 8.0 magnitude earthquake attacked the northwestern margin of the Sichuan Basin on May 12, 2008. A large number of buildings suffered damage to different degree in the epicenter regions. Sichuan University reconnaissance team investigated the performance of residential masonry structure buildings with ground R. C. frame for commercial purpose following the Earthquake. This kind of structure style is widely taken in the epicenter area. Many of them suffered severe damage or even collapsed totally, however, some of them had perfect performance during the Earthquake. Many structural deficiencies and mistakes were highlighted, which including excessive horizontal displacement in the ground, more severe damaged transition tayer （the first masonry structure layer）, ground with farraginous structure, and poor construction quality. Finally, lateral stiffness ratio of the second to ground story in masonry buildings with RC frame structure at the bottom will be optimized following difference of materials between the ground floor and the upper floors. The strength and the ductility of transition layer, as well as shear walls in the ground floor, are crucial to keep the building standing during large earthquake.