中国规范钢筋混凝土抗震墙延性和位移角的量化研究

Quantitative research of ductility and drift in Chinese code for reinforced concrete earthquake- resistant walls

分析了中国、美国、新西兰规范三种不同钢筋混凝土剪力墙约束箍筋设计方法的内在机理,讨论了三国规范存在的问题。结果表明,中国规范仅按照轴压比判断是否加约束箍筋的设计方法不合理,使同一抗震等级剪力墙的位移和延性指标不平衡。美国和新西兰规范是基于位移和延性的设计方法,但其没有考虑剪力墙钢筋拉断的受拉破坏,导致混凝土高度很小时高估了位移和延性能力,而实际位移和延性不能满足要求。提出了基于修正后的美新规范位移角和延性计算方法,评估了现行中国规范不同的抗震等级、烈度下剪力墙具有的位移和延性能力。按照中国规范设计剪跨比为4的剪力墙在抗震等级为一级(9度)、一级(6、7、8度)、二三级时,延性指标平均值分别能达到5.1、3.6和2.6,位移角指标能达到1/81、1/129和1/175。

The theories of confining stirrup design methods for reinforced concrete （RC） walls in Chinese code GB 50011-2010, American code ACI 318-11 and New Zealand code NZS 3101：2006 are analyzed. The problems of three design methods are discussed. The drift capacity and ductility of RC walls designed according to GB 50011- 2010 in different seismic design levels are evaluated. Results show that Chinese design method, in which the confi- ning stirrup requirement is only dependent on axial load ratio, is unreasonable, which would make the drift capacity and ductility of RC walls different. ACI and NZS methods are displacement-based and ductility-based, respective- ly. However, they both do not consider the failure mode of bar fracture and overestimate the drift capacity and duc- tility in some cases. For walls with aspect ratio 4 designed in accordance with Seismic Grade I （ Intensity 9 ）, Grade I （Intensity 6, 7 or 8）, and Grade II or III of GB 50011-2010, the ductility can be 5.1,3.6 and 2.6, respective- ly and the drift can be 1/81, 1/129 and 1/175, respectively.