PSI - Issue 71

Nisha Thakur et al. / Procedia Structural Integrity 71 (2025) 233–240

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members and strengthening of existing members Desai et al.(1988).

1.1.1. Retrofit Method using addition of new structural member: In this method, there are two approaches for retrofitting. Conventional methods of retrofitting are used in seismic resistance building to reduce the effect of design or construction Ghaffarzadeh et al.(2006). In this method, we used a) shear walls, installing additional walls within the building which helps to better distribute the forces caused by an earthquake by making the structure more stable, b) infill walls, typically made of masonry or concrete and placed between structural components like columns and beams, can significantly improve the seismic performance of RC structures by providing additional stiffness and strength, and c) steel braces to structure. Adding steel braces to the building frame strengthens it, helping it to resist the side-to-side forces of an earthquake Badoux and Jirsa (1990). In a non-conventional method, base isolators and the inclusion of other techniques are most popularly used Ferraioli et al. (2006). By providing base isolators, between the foundation and the building structure, the building moves apart from the ground, reducing the impact of seismic activity. The use of this technique reduces the horizontal seismic forces in buildings Maheri and Sahebi (1997). 1.1.2. Retrofit Method for strengthening of existing members: This method is generally more expensive than the global retrofit technique. The most frequently employed technique in local retrofitting is jacketing, which involves adding a layer of concrete and steel around existing columns to enhance their strength and flexibility Kano and Imanpour (2018) . During jacketing, materials such as steel reinforcement, concrete, or fiber-reinforced polymer are used to encase the reinforced concrete columns, beam joints, and foundations KG et al.(2010). By wrapping building components with a durable and flexible material like FRP, their capacity to endure movement and stress is improved significantly. 1.2. Steel Bracing Systems: A steel bracing system strengthens the building against sideways forces, such as those caused by wind or earthquakes, by adding steel braces to its structure. These braces which can be arranged in diagonal, X, K, and V shapes, connect various structural parts to offer extra support and stability Maheri, M. R. (2005). They distribute lateral loads throughout the structure, reducing the stress on individual components and preventing failures. By enhancing lateral stiffness, steel braces control deformation and movements during seismic or wind effects, improving the building's overall stability and integrity Bureau of Indian Standards (2002) . Often used to retrofit existing buildings, steel bracing systems offer a cost-effective way to enhance seismic performance with minimal changes to the original design, and they can be installed relatively easily with little disruption. 1.3. Categories of Steel Bracing Systems: Based on the connection of steel braces with structural elements, the steel bracing systems can be divided into two categories i.e. concentric and eccentric bracing systems. a) Concentric Steel Bracing System: The concentric steel bracing system shown in Fig.1, involves diagonal braces that intersect at a central point forming patterns like X or V shape Ravikumar and Kalyanaraman (2005). The configuration efficiently transfers the lateral forces to the structure’s core or perimeter, providing strong support and stability. It simplifies structural analysis and design due to its straightforward load paths, though it can limit usable floor space and may not be suitable for all architectural layouts. b) Eccentric Steel Bracing Systems: Eccentric steel bracing as shown in Fig. 2, features diagonal braces connected at different points along the structural members, creating an offset in force transfer. This system allows for greater design flexibility and accommodates architectural features but requires more complex analysis due to the moments and additional stresses it introduces Kevadkar and Kodag (2013). While it can adapt to various designs, the non-central load paths make it more challenging to analyze and design compared to concentric systems.