Analysis of the seismic behavior and comparison of the behavior factor of steel structures braced with centered and eccentric bars

Purpose The study of structures subjected to seismic action is important in countries with high seismicity. However, observation of the damage caused to these structures shows that they absorb much greater forces. The explanation lies largely in the energy dissipation mechanism. In particular, the structure’s overall behavior coefficient is “q”. The purpose of this study is to provide a method for evaluating the behavior factor and the comparison between two types of bracing of metal structures. Design/methodology/approach The aim is to provide a method for evaluating the overall behavior coefficient of structures braced with a centered bar system and an eccentric bar system and to carry out a comparative study between them. The work was carried out on three structures. The authors then estimated an average value for the “q” coefficient and a plastic hinge formation sequence was presented for each type. Findings As a result, the breaking of all structures is achieved by plasticization of the bars for centered bar bracing and by the formation of plastic hinges in the seismic eccentricity sections and then in the beams for eccentric bracing. The mean values of the behavior factors for centered and eccentric bar bracing are of the order of 3.5 and 2.5, respectively. The study showed that we are within the range recommended by Eurocode-8 in accordance with an average level of ductility. Originality/value The comparison between the types of bracing studied and the portal frame type shows that eccentric bar bracing is intermediate to the other two. This confirms the reliability of the study and is more dissipative than centered bar bracing.