Performance of x and inverted v bracing systems in controlling progressive collapse of reinforced concrete buildings

Abstract

Progressive collapse can lead to partial or total failure of structures under extreme events such as explosions or earthquakes. While brace systems effectively enhance lateral stiffness, their use in reinforced concrete (RC) buildings is limited due to detailing challenges at connection points. This study evaluates the influence of X and inverted V bracing systems on the progressive collapse behavior of RC buildings and investigates the effectiveness of optimally placed X-bracing configurations under multiple column removal scenarios. Three groups of 9-, 12-, and 15-story RC buildings, designed per the Turkish Building Earthquake Code (TBEC2018), were modeled using the Applied Element Method (AEM) in the ELS software. The first group included unbraced reference models. The second group comprised 54 fully braced models using X and inverted V configurations, subjected to three distinct column removal scenarios. The third group included 27 models with X bracing placed only in selected bays to determine optimal configurations for collapse prevention. Nonlinear dynamic analysis of 84 models revealed that both the reference buildings and those with inverted V bracing experienced progressive collapse, with maximum top displacements reaching over 65 cm. In contrast, fully braced X systems effectively prevented collapse, reducing displacements to below 10 cm. Optimized Xbracing layouts, applied to only 30-50 % of the bays, achieved comparable performance while reducing material usage and detailing complexity. This study demonstrates the superiority of RC X-bracing in enhancing progressive collapse resistance and provides practical recommendations for optimal placement in reinforced concrete (RC) buildings.