Performance-based quantitative evaluation of RC building frames with vertical mass Irregularities

Non-uniform distribution of mass in high-rise buildings constitutes a structural irregularity in elevation through which the behavior of these edifices during major earthquakes suffers severe structural damage due to the concentration of nonlinear strains, notably between adjacent stories and hence, can lead to changes in structural and material characteristics over the height of the building. The choice of the degree and location of the vertical mass irregularity is then of great importance in evaluating the seismic performance of such structures. The current study focus on the seismic performance of typical RC buildings designed considering effects of irregular mass distribution, by means of displacement-based adaptive pushover analysis. For this purpose, a ten-story regular frame structure is selected and modified by incorporating vertical mass irregularity to estimate and quantify essential parameters response such as base shear forces-roof displacement, inter-story drift and story-shear distribution. Regarding the results, it was found that the mass irregularity is somehow risky and conservative and that the irregular structure cannot meet the requirements of the earthquake-resistant design and must be constructed in such a way as to minimize the seismic effects.