DETERMINATION OF LATERAL CAPACITY OF TWO-STORY X-BRACED FRAMES CONSIDERING HYSTERESIS BEHAVIOU OF CONNECTIONS

Special concentrically braced frames (SCBF) are stiff, strong and economical lateral load resisting systems which can sustain large inelastic deformation if properly detailed. The failures observed during recent earthquakes, such as bracing failures or deterioration of different types of connections, make it necessary to investigate these structural resisting systems more accurately. The main objective of this paper is to determine seismic lateral capacity of special concentrically two-story x-braced frame systems for responses in roof drift, interstory drift, base shear, frame fracture-index and failure contribution of each story in overall deterioration using nonlinear static cyclic analysis in OpenSEES software. Therefore, in this study, in order to have a thorough investigation of frame regularity, eight SCBFs were designed based on AISC seismic provision to represent different values for response reduction factor, R with identical plans and elevations. For performing analysis, recommended FEMA461 loading history was applied. In addition to modeling hysteresis behavior of gusset plate connections, shear tab connections were also considered. Therefore, for validating of this, a three-story one-bay tested in NCREE in Taiwan was particularly used. To identify the bracing fracture developements, the maximum strain range has been monitored. Due to the lack of the fracture expression implementation in the OpenSEES framework based on maximum strain range limit, fracture material model was imported in the program with the ability of being open-source in OpenSEES. Moreover, for validation of hysteresis behaviour of brace failure beyond brace fracture, a one-story one-bay tested in University of Washington was used.

کلیدواژه ها:

SCBFs ، Capacity ، Connections ، Fracture ، Nonlinear Static Analysis