Behavior of Steel Braced Frame Structures by using Pushover and Response Spectrum Analysis

Bracing systems are one of the efficient methods used for buildings to resist lateral loads. Steel structures need to be strong and at the same time have adequate ductility against various loading conditions. The objective of this study was to investigate the behavior of the steel concentric and eccentric braced frames by using pushover and response spectrum analysis. Diagonal-shape, inverted chevron (Λ-shape) are the types concentric braced systems and diagonal and inverted chevron (Λ-shape) are the types of and eccentric bracing systems considered for the study, respectively. 4- and 12-story high buildings, H and square plan shape with 5x5 symmetric number of bays were used to design with relevant Eurocodes and carry out performance analysis. Pushover analysis results show that the collapsed plastic hinges mainly occurred in the buildings with eccentric diagonal bracing systems with low target displacements. Response spectrum analysis results show that buildings with diagonal concentric bracing systems achieved the lowest story displacement and furthermore it was the only braced system that met the displacement criteria. Comparing the results of story drift majority of the investigated cases with diagonal braced frame achieved the lowest drift value, except for 4-stroy H plan. The economical comparison between the selected braced frames has been done by comparing the weight of structure for all analyzed conditions. It was found that eccentric inverted chevron (Λ-shape) achieved the lowest structural weight. Comparing only the base shear for the pushover and response spectrum analysis it was found that the former had higher base shear than the latter in both x- and y-directions for all conditions, except for 4-story square plan, when response spectrum analysis achieved larger base shear than the pushover analysis.