Published Paper Details:

Soft-story construction is frequently used in high-rise or multi-story buildings due to architectural considerations that produce story height differences. These give the building structures irregularities in stiffness, which lessens the stiffness of the lateral load-resisting system. A sudden decrease in stiffness concentrates more stress at the stiffness-reduced story columns, making the columns incapable of providing sufficient resistance during an earthquake. Given the aforementioned considerations, the impact of soft stories on the building's seismic performance must be taken into account while evaluating and designing the structural building frames. This study's primary goal is to use numerical models based on finite element principles to investigate the seismic performance of stiffness irregular buildings caused by a large story height difference on RC structures. G+10 and G+20 are the basis case structures for these two regular buildings, while instances representing irregular structures are defined by altering the base case's vertical distribution stiffness. By extending the base case's ground and second floors' height by 200%, the stiffness irregularity is produced. Consequently, ETABS 2021.2.1 (CSI ETABS 2022, Integrated Building Design Software, Computers and Structures Inc. Berkeley) is used to study and design various model scenarios of RC buildings. According to the new Ethiopian Buildings Code Standards (ES EN: 2015), the suggested building model examples were analyzed and designed using the traditional design methodology. The numerical model on SeismoStruct is then based on the design outputs of the primary structural elements [SeismoSoft, 2016]. The response in terms of basic periods, base shear-top displacement, interstory drift, lateral displacements, and fragility curve at various performance levels is obtained by pushover and nonlinear dynamic studies. As the number of soft stories and the number of stories or building height increase, the effect of stiffness irregularity on the fundamental period becomes more significant. In all cases, the story drifts demands increase in the soft story and decrease in most other stories, and the drift of most floors is greater than the low able drift according to the seismic base shear for stiffness regular buildings are greater than the stiffness irregular ones. Lastly, the probability of failure for each limit state capacities of stiffness irregular building models is greater than stiffness regular buildings models in all cases.