PSI - Issue 70

Vivek Kumar C et al. / Procedia Structural Integrity 70 (2025) 97–104

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1. Introduction Modern approaches to designing earthquake-resistant steel structures focus on ensuring that structural elements can endure significant yielding and plastic deformation while maintaining their strength during major seismic activities. Steel moment-resisting frames have become popular structural systems in regions prone to earthquakes. Nevertheless, in certain cases, these structures have not performed as anticipated, leading to considerable economic losses even from earthquakes of lower intensity than the design level. The forces arise from the structure's resistance to displacement, despite ground movement. In seismically active regions, a key challenge is ensuring a building's lateral stability due to substantial deflections from earthquake-induced forces, generating significant internal stress Haamidh et.al (2020), Marcu et.al (2021). Every building has a finite displacement capacity. To mitigate this, engineers implement bracing systems designed Nassani et.al (2017), Neethu (2021), to undergo plastic deformation prior to failure, categorized into eccentric, concentric, and knee-braced types. Reinforced concrete multistory structures are prone to excessive deformation, requiring specialized mitigation techniques Shen et.al (2022), Shirpour et.al (2023). Concentrically Braced Frames (CBFs) resist lateral loads through a vertical concentric truss system, with member axes aligning at joints Yeom (2015), Yassin(2023), Ganesh (2022). Concentrically X-braced steel frames are favored for countering lateral seismic forces and limiting drift Chen (2019), Zhao (2011), Krishnasamy (2024), Ravikumar (2023). A seismic performance evaluation was conducted by (Brian Cagua et.al, 2023), examining the nonlinear behavior of 27 structural typologies under monotonic loads and focused on steel moment frames with 4, 8, and 12 stories, as well as structures incorporating various bracing configurations such as chevron brace, multistory X brace, and eccentrically braced frames (Cagua et al., 2023), Lopez et.al (2023). Neeraj Kumar investigation demonstrated that pre-engineered building structures utilizing tapered sections which adhere to Indian Standards IS 800-2007, integrate both PEB tapered sections and standard hot rolled sections (Kumar & Grover, 2022). (Bohara et al., 2021) (Khanal & Chaulagain, 2020) employed ETABS software to perform response spectrum analysis on L shaped reinforced concrete buildings, examining structures with and without steel bracings at various frame locations. Two novel quasi-X bracing systems were proposed by (Shirpour & Fanaie, 2023) Acosta et.al (2024), Alvarado et.al (2023) to enhance the ductility and seismic performance factors (SPFs) of moment-resisting frames that incorporate concentrically braced frames (CBFs) and tackle its shortcomings.

Fig. 1. Different types of Bracing System (Abazar Asghari, 2021)

While X-bracing is common in steel-framed buildings, research is lacking in its optimal placement in multi-story structures. Studies mainly compare frames with and without bracing, observing how X-bracing location at building cores, corners, or alternating floors affects seismic performance. Effects on inter-story drift, base shear, natural period, lateral displacement, and mode shape remain unexplored. This gap challenges engineers working on mid- to high-rise buildings, where balancing architectural needs with seismic safety is complex. Limited empirical validation exists for bracing layouts under dynamic loading, and bracing-architecture interactions are understudied, forcing designers to use traditional methods. Nomenclature CBF Concentrically Braced Frames CSB Crescent Shaped Bracing EN European Nation Standards EQx Earthquake loads at X direction EQy Earthquake loads at Y direction IS Indian Standards IVBF Inverted V-Braced Frames FEA Finite Element Analysis PEB Pre-Engineered Building RCC Reinforced Cement Concrete SPF Seismic Performance Factor SCBF Special Concentrically Braced Frames SFRS Seismic Force Resisting System SSI Soil-structure interaction VBF V Braced Frames XBF X Braced Frames