改进直接基于位移的钢筋混凝土框架结构抗震设计研究

Improved direct displacement-based seismic design procedure

直接基于位移法进行抗震设计时,最初结构的刚度和承载力均是未知的,设计中需假定预期设计结构的振型模式和由此得到的结构侧向地震力分布,这样的设计结果会产生一定的偏差。针对此问题,提出了改进直接基于位移的抗震设计方法,即首先初步设计结构,根据初设结构的振型模式等效单自由度体系,结合目标位移反向设计结构刚度,将设计结构的刚度与初设结构刚度比较,进行调整设计,最后进行承载力设计。程序中为减少迭代次数,定义了结构竖向刚度调整系数,用以简化结构弹性刚度的确定过程,从而实现设计结构在相应地震设防水准下满足预期位移的控制要求。最后通过算例证明了该方法具有一定的准确性。

The traditionary direct displacement-based seismic design depends on supposing the elastic mode and corresponding lateral force distribution of structure,in which the supposition is liable to cause some deviations.So,an improved direct displacement-based seismic design procedure for structures is presented.In the procedure,by means of conceptual design,the modes and corresponding equivalent SDOF systems are obtained,and the lateral equivalent stiffness of structure can be designed on the basis of the displacement objective and the equivalent SDOF system.Finally,the structural stiffness is adjusted to make the weak places of the structure meet the limited displacement objective under the specified level of seismic intensity.The implementing procedures of this method are introduced in details,in which the adjustment coefficient is defined to reduce the iterative design.With the analysis of an example,it is shown that the procedure developed in this paper may be used as a simple and effective seismic design method for multi-storey structures.