尼泊尔自建RC框架结构的抗震能力分析

Seismic Performance of Owner-Built RC Frame Structures in Nepal

2015年8.1级尼泊尔郭尔喀地震对尼泊尔北部民居造成了较大的破坏.与采用砖木、砖石、土坯结构等结构形式的传统民居相比,当地常见的含砌体填充墙的自建钢筋混凝土(RC)框架结构的震害相对较轻.通过静力弹塑性分析方法,从抗侧承载力、延性和抗震能力指数等方面,对比了这一结构体系和按照我国抗震规范设计的约束砌体结构的抗震能力.针对不同层数结构的分析结果表明,在结构整体布置、层数和用钢量大致相同的条件下,与我国不同设防水平下的约束砌体结构相比,尼泊尔自建RC框架结构均表现出更好的延性性能,但其综合抗震能力随着楼层数的增加而显著降低.对3、4层的结构,其抗震能力甚至高于按我国8度设防的要求设计建造的约束砌体结构,但对5、6层的结构,其抗震能力则远远低于后者.

The 2015 Ms8.1 Gorkha earthquake in Nepal caused severe damage to local dwellings in Northern Nepal.Compared with brick-wood buildings,stone masonry,or adobe structures,owner-built reinforced concrete(RC)frame structures with masonry infills,which are commonly seen in both urban and rural areas in Nepal,sustained less severe damage.The seismic capacity of typical RC frame structures with masonry infills,which are representative of the local practice in Nepal,was compared with that of confined masonry structures conforming to the Chinese seismic design practice.The comparison was made in terms of lateral strength,ductility,and a previously proposed seismic capacity index through nonlinear static analysis.The analysis results on buildings with different numbers of stories show that the owner-built RC frames with masonry infills in Nepal exhibit higher ductility when the structural layout and amount of reinforcement are similar.However,their seismic capacity decreases significantly as the number of stories increases.For three and four-story buildings,owner-built RC frames exhibit higher seismic capacity compared with confined masonry structures in Intensity 8 regions in China,but exhibit much lower seismic capacity than the latter when the building is five stories or more.