Seismic Performance Of Buckling Restrained Braced Steel Frames Considering Connection

The rapid increase of using Buckling Restrained Braced Frames (BRBFs)around the world motivates researchers for further investigation and development ofthe system. Previous, studies of BRBF showed that there are two main requirementsto reach the desired mechanical behavior of buckling restrained braced frames(BRBF) under seismic loadings. This behavior could be represented by sufficientinelastic (plastic) deformation and ductility capability of core plate member.1) Thefirst requirement is to prevent global buckling of BRB; and2) the secondrequirement is to prevent out-of-plane buckling of gusset plates. This study focuseson the second main requirement through presenting finite element analysis results ofseveral proposed gusset plates and two joint sections for connecting core platemember with gusset plate. Further, study the impact of proposed gusset plates andjoint sections on behavior of steel frames. The proposed gusset plates have differentshapes and dimensions while the proposed joint sections are distinguish withconventional connection in transferring loads between gusset plate and BRB. Theobjective of the study is to conduct a parametric study of connection section of BRBwith Frame. The study of global buckling of BRB is not included in this research,by assuming the core plate is resisted from buckling by sufficient flexural rigidity ofrestrainer. Therefore, BRB is resisted by designing very strong restrainer with aratio of the Euler buckling load to the yield strength, Pe/Py is10times greater thanrequired limit by AISC (Pe/Py>=1.5). The pushover analysis that performed in thisstudy is followed the method that discussed in AISC-2010Seismic Provisionmanual. Therefore, the proposed connection of buckling restrained braced steelframe required to sustain cyclic loadings start with elastic drift up to two times ofdesign drift. The analysis results showed that the proposed connections sufficientlysustain all the axial force from BRB without under going out-of-plane buckling orlosing the stable hysteretic response of the BRB. This result obtained by decreasingthe rotation of the BRB ends through the proposed joint section, the analysis resultsalso showed that gusset shapes with big or small ratio of vertical length tohorizontal length can badly affect the frame while those with equal dimensions has much better effect on frame specially on the column which is identical with thetheory of strong column weak beam.