等效线性化方法在基于位移抗震设计中的应用

为了比较割线刚度法和两维搜索法2种等效线性化方法在基于位移抗震设计中的应用,对比阐述上述2种等效方法确定等效参数的基本原理和基于位移抗震设计的步骤,同时推导分析2种方法应用下结构基底剪力设计值的差别,并通过钢筋混凝土框架结构的设计算例考察其对结构抗震设计的影响.结果表明,应用2种等效方法得到的基底剪力比值只与结构的非线性滞回模型和延性系数有关；在延性系数为3.0的情况下,按割线刚度法设计得到的基底剪力将被放大20%左右,从而使通常的结构抗震设计趋于保守.

Comparison of different equivalent linearization approaches applied to displacement-based seismic design methodology

Displacement-based seismic design adopts equivalent linearization approach to estimate the maximum inelastic displacement of the structural system. The appropriate equivalent natural period and effective damping are the key points to insure a reliable displacement estimation of the approach. Application comparison of two different equivalent linearization approaches, secant-stiffness approach and 2D searching approach, was mainly carried out in the study when they were applied to displacement-based seismic design methodology. The basic principle of two equivalent approaches and the detailed procedure of displacement-based seismic design methodology were introduced and the design base shear forces were deduced and compared when the two different equivalent approaches were adopted. The influence of two approaches on the seismic design of structures was investigated through a reinforced concrete frame structure design example. Research results indicate that the ratio of design base shear forces that obtained through the two different equivalent linearization approaches is only decided by the structural nonlinear hysteretic model and the ductility coefficient. For the general design case that the ductility coefficient equal to 3.0, the base shear force is amplified by 20% or so when the secant-stiffness approach adopted, and thus the structural seismic design tends to be conservative when compared with the 2D searching approach.