Earticle

Among various styles of the mixed building structures in domestic construction field, the mixed building structures of upper wall-lower frame system are composed of upper shear walls, lower beam-column frames and transfer girder connecting both structures. This mixed building structure usually shows irregularity of stiffness, weight and geometrics. Regarding the mixed building structures of upper wall-lower frame system, four models with different sizes of transfer girder were chosen to investigate the response characteristics of pushover analysis of structures. Following is the pushover analysis results. 1) As the dimension of transfer girder increases, the upper structure shows independent behavior features due to transfer girder and the increase of stiffness. Although trivial, we identified separate system behaviors between upper structure and lower structure. 2) If the transfer girder is dimensioned with depth of 1/10(m) of upper story height and width of 1/3 depth, it is safe but may be considered as an excessive schemes.

Most structures are expected deform nonlinear and inelastic behavior when subjected to strong ground motion. Nonlinear time history analysis(NTHA) is the most rigorous procedure to compute seismic performance in the various inelastic analysis methods. But nonlinear analysis procedures necessitate more reliable and practical tools for predicting seismic behavior of structures. Some building codes propose the capacity spectrum method. This method is the concept of an equivalent linear system, wherein a linear system having reduced stiffness and increased damping is used to estimate the response of the nonlinear system. This procedure are conceptually simple, but the iterative procedure is time-consuming and may sometimes lead to no solution or multiple solutions. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for mixed building structure.