Seismic Response Study of Buildings with Combined Irregularities

Abstract

Earthquakes are powerful and destructive natural events. The earthquake in Gujarat on January 26th, 2001, highlighted the need to be ready for such disasters. Many lives were lost, mainly because buildings couldn’t withstand the quake. To make buildings more resistant to earthquakes, they should follow specific construction rules based on the seismic history of the area. In the city of Ahmedabad, even well-built structures collapsed like a deck of cards during the earthquake. Research shows that buildings with irregular shapes, like L-shaped plans on corner plots, or with unusual elevations, like large stepbacks in commercial buildings, are more likely to suffer damage during earthquakes. So, it’s vital to carefully analyze structures to ensure they can endure the forces of an earthquake. The seismic performance of structures is a critical aspect in ensuring the resilience and safety of urban infrastructure. This study investigates the dynamic behaviour of reinforced concrete (RC) buildings featuring combined irregularities, seeking to enhance our understanding of their response to seismic forces. The combined irregularities considered in this research encompass vertical mass irregularities, stiffness irregularities, and torsional irregularities, which are often encountered in real-world structures. An experimental evaluation of the dynamic properties of multi-degree-of-freedom (MDOF) building models with various irregularities. Several experimental setups were employed, including regular and irregular MDOF building models, as well as L-shaped structures with setbacks on one and two floors. Utilizing a uniaxial shake table, accelerometers, and a comprehensive data acquisition system, the dynamic responses of these structures were meticulously recorded and analyzed. The primary aim was to determine the natural frequencies, damping coefficients and responses, crucial for understanding the seismic behavior of irregular buildings. This research investigates the seismic behaviour of RC building having combined irregularities. The primary focus of this study is the analysis of static indices as key performance indicators. This research aims to comprehensively understand the impact of irregularities on crucial parameters such as storey displacement, story drift, torsional irregularity ratio, overturning moment, and base shear. The investigation concentrates on two specific irregularities: set-back irregularity (vertical irregularity) and re-entrant corners, (plan irregularity). Three distinct configurations of RC buildings—L, T, and C shapes—are considered, each buildings having different irregularity ratios. The modelling, analysis and design of these buildings are carried out in ETABs Software.