Effect of Infill Vertical Irregularity on Seismic Demands of RC Buildings

Use of brick masonry infill panels is a common practice in construction of reinforced concrete structures. Generally, infill panels are considered as non-structural elements and their effect is not contributed in analysis and design. During an earthquake, the interaction between infill panels and surrounding frames would alter the dynamic properties of the main resisting system. Dynamic properties of infilled reinforced concrete frames depend on a number of variables such as distribution of infill panels in the plan of the building, distribution of infill panels over the height of the structure, the material properties of the infill, and the ratio of infill to frame stiffness. Nevertheless, the Iranian Code of Practice for Seismic Resistant Design of Buildings, Standard No. 2800 (IS2800), ignores the effects of distribution of infill panels over the height of the structure, and recommends a reduction of 20 percent in the calculated fundamental period of infilled reinforced concrete frames. According to this recommendation, the base shear should be estimated upon the modified fundamental period. This paper deals with the influence of mass and mass-stiffness irregularities due to the presence of infill panels over the height of eleven ten-story reinforced concrete planar frame. This effect is to be considered in estimating the vertical distribution of the story shears and story-drift demands over the height of the structure. It was found that infill panel considerably decreases story-drift demands and increases the story shear forces in the infilled and vicinity stories

کلیدواژه ها:

base shear ، vertical distribution ، vertical irregularity ، story-drift demand ، stiffness-mass irregularity ، masonry infilled RC frames ، spectral dynamic analysis ، equivalent static analysis