Analytical Fragility Function for Seismic Damage Evaluation of Unreinforced Masonry Buildings in High Seismic Zone

摘要

The paper describes the evaluation of seismic capacity of the unreinforced masonry building in the high seismic zone by an analytical procedure, based on nonlinear static approach. In this procedure, each wall plane is modeled as some vertical strip walls separated by the openings and is characterized by two primary components such as vertical component pier and horizontal component spandrel. These walls are analysed considering the capacity of pier in conjunction with the coupling effect between pier and spandrel. However, capacity of spandrel is not considered in this case. The shear capacity of the wall is calculated based on lower bound theorem of plasticity without considering the tensile strength of masonry. Capacity curves of the walls are determined by three parameters as shear capacity, yield displacement and ultimate displacement at zero stiffness approaching a bilinear approximation and these capacity curves of the walls in a certain orthogonal direction are superposed to obtain capacity curve of the building in that direction. The smaller capacity of the building in the prevalent direction is then compared with seismic demand and a capacity-demand relationship is found and damages are introduced in this capacity-demand relationship to obtain vulnerability function. The vulnerability function of the representative masonry building models are used to construct fragility function of the building group and this fragility function shows the expected damage of the building group as a function of spectral displacement.