PSI - Issue 70

Maheshwar Bose et al. / Procedia Structural Integrity 70 (2025) 137–144

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1. Introduction Earthquake poses a significant threat to structures, particularly in seismically active regions. Since India is located at high seismic zone over the globe as the Indian and Eurasian plate is flowing underneath. The past Earthquake such as Nepal (2015), Sikkim (2011), Kashmir (2005), and Uttar kasha (1990) caused serious loss of life and damage of structure Dutta SC et al. (2015). Reinforced Concrete buildings often experience severe damage due to inadequate lateral strength and stiffness. This issue becomes more pronounced in Irregular shape buildings such as L-shape, H shape structures etc. These irregular buildings like Vertical irregularities and plan irregularities or both exhibits stiffness irregularity, mass irregularity, Torsional irregularity effects and uneven force distribution under seismic loads. To enhance the seismic performance of such buildings, steel bracing systems has been used to stabiles laterally tallest building structures Masood et al. (2019). Irregularity in the structure bring on stress in the beams, slabs and columns. Retrofitting of these structure is the method to resist the earthquake load and here the bracing systems are introduced. This paper includes the braces like X-type, V-type and Eccentric. These are nothing but the shape of the placement of steels bracings to the structures. First two are as same as the name mentioned, the Eccentric bracing is used in the model which is provided in shape of inverted V shape having a central gap of 1-meter. These Braces are highly effective when placed on Re-entrant corners which mostly occurs in the irregular shape buildings. As per IS 1893(part 1) if the projection of building is more than 15% of the overall plan dimension in that direction, it is known as Re entrant corners. Many researchers studied the effect of using the steel braces in multi-story building. Some brief review based on previous study on effect of using the braces as retrofitting structures on the seismic behavior is presented. Mohammad et al. (2017) studied the vertical irregularity of the structure and the effect during the earthquake analyzed in ETABs software. To conduct the THA and RSM Amer Hassan and Shilpa Pal (2018) studied the influence of soil condition beneath the base isolation. Ar Khaloo and M. Mahdi Mahseni (2008) had worked on nonlinear seismic behavior of RC frame with RC braces Mithesh Surana et al. (2020) observed the seismic vulnerability of the hillside building of the Indian Himalayas region. Chopra A.K & Goel R.K (2004) studied the pushover analysis methodology for irregular structures and estimated the seismic demand of asymmetrical buildings. Generally the torsional effect in the structures is due to the eccentricity induced between the center of mass and center of rigidity in the asymmetric plan buildings. M.A Youssef et al (2006) had worked on the efficiency of using the RC frames is experimentally evaluated and adopted the design the braced frame including the connections between the brace members and the concrete frame. J.P Desai et al. (2004) had worked on the two-bay, six story frame designed by limit state method subjected to artificial earthquake. Some researchers such as S.S. Trezcan, C. Alhan [2001] Omzen et al. (2014), Ali Kocak et al. (2015) were focused on the study of the torsional effect of the shear wall buildings. A.Rahimi et al. [2018] studied the effect of X brace type steel brace in the 2D RC Frame to understand the braced and unbraced performance of the structure. A. Hemmati et al. (2020) studied the experimental analysis of the rehabilitation of the RC frame by using the concentric and eccentric bracings and observed that the absorbed energy capacity of rehabilitate frames with the eccentric and concentric bracings increased about 1.98 and 1.68 times of the concrete frame.

Nomenclature RSM Response Spectrum Analysis THA Time History Analysis FF/NF Far Field/ Near Field ISD Inter Story Drift

1.1. Objective The primary objective of this research are as follows:

• To analyze an unsymmetrical G + 5 L-shaped RC Building with and without steel bracing and location of braces. • To evaluate and compare the effectiveness of different bracing configurations (X-type, V-type and Eccentric type) and determine most efficient bracing system that enhances the seismic resilience.