PSI - Issue 70

Abhishek Badalia et al. / Procedia Structural Integrity 70 (2025) 121–128

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chosen based on financial factors. As part of proactive disaster mitigation, there has been a greater sense of urgency in recent years to reinforce the weaker buildings and determine what adjustments could be made to an existing structure to enhance its structural performance in the event of an earthquake.Retrofitting is often a more viable solution than replacing seismically deficient buildings, as it addresses both economic concerns and the urgent need for shelter. 3.1 Steel as brace material Steel is a popular material for bracing systems due to its superior strength in both tension and compression. Because of its dual capabilities, it can effectively withstand lateral loads. The ductility of steel is essential, particularly in areas where seismic activity is common (Castro et al., 2018). Over the past two decades, multiple reports have demonstrated the use of steel bracing in RC frames. When utilized as an external plan, steel bracing offers significant non-structural advantages over alternative methods. It is possible to install the bracing system quickly and with little interference with operations. It is also possible to reduce the amount of space lost and the expense of remodelling (Marc Badoux and Jirsa, 1991). 3.2 Effects of adding steel braces in MRF One of the best ways to increase lateral stiffness and lessen inter-story drift among retrofitting methods is to employ steel braces (Babu et al., 2017). Because of the ease of application and ability to withstand lateral stress, bracing is frequently utilized. Various bracing configurations are used based on structural specifications. Despite numerous advantages, there are possibilities of some serious undesirable impacts of using braces of specific types; therefore, a thorough evaluation of existing structural frames' behavior is vital to land up on a feasible retrofit solution using braces. The guidelines outlined in IS 15988: 2013 must be followed when upgrading RC frames with steel braces in India. To improve energy dissipation and avoid brittle failure, this involves making sure that the reinforcement detailing is ductile following IS 13920: 2016 provisions. Stiffness compatibility should be taken into consideration in the retrofitting design to prevent torsional abnormalities or unanticipated failure mechanisms from being introduced by additional bracing elements (Boru and Aydin, 2022). Additionally, when integrating steel bracing with pre-existing RC parts, material compatibility is crucial, necessitating appropriate anchorage and connection detailing. Usually, the braces are joined by bolted or welded joints following IS 800: 2007 structural steel design criteria. Furthermore, to handle the extra forces brought on by the bracing system, weak structural components, particularly columns and joints may need to be strengthened. The danger of structural failure can be decreased, and total resilience is increased by properly evaluating and modifying RC frames to withstand seismic stresses (Faella et al., 2014). 4. Seismic Evaluation and Retrofitting To evaluate the seismic susceptibility of reinforced concrete (RC) structures and ascertain whether retrofitting is necessary, seismic evaluation is an essential procedure. There are two phases to the evaluation: preliminary and detailed evaluation. To find possible flaws such as structural abnormalities, load route discontinuities, weak or soft stories, and insufficient detailing, the preliminary inspection is a quick visual review. It entails basic computations using historical seismic performance data and building geometry. The extensive evaluation, which includes a thorough structural study utilizing techniques such as equivalent static analysis, response spectrum analysis, time history analysis, or pushover analysis, is the next step if the structure is determined to be possibly vulnerable. Material characteristics, section strengths, and overall stability are considered when comparing the structural capability to the demand imposed by seismic forces. This assessment adheres to IS 1893:2016 and IS 15988:2013 requirements, guaranteeing a thorough comprehension of the structure's reaction to seismic pressures. 5. Literature Review Past studies said that steel bracings, especially X-bracing, provide a cost-effective and efficient way to retrofit existing buildings for seismic resistance. They improve lateral stiffness, reduce lateral displacements, and distribute