Cyclic Testing of Scaled Three-Story Special Concentrically Braced Frame with Strongback

• Main Authors: Tsai, I-Jung, 蔡易融
• Other Authors: Chen, Chui-Hsin
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/ygr7z2

碩士 === 國立交通大學 === 土木工程系所 === 103 === The typical damage modes of Special Concentrically Braced Frame (SCBF) are overall and local buckling of the braces. It is common that the damage concentrates at certain floor(s) instead of spreading over all floors. Once the damage occurs, the soft story mechanism will result in the failure of the whole system. In this study, we use an extra structure, strongback, to redistribute the nonlinear deformation of SCBF and activate more structural members to dissipate energy and thus avoid damage concentration and improve the seismic performance of SCBF. We tested one-third-scaled, three-story, double-story X SCBF specimens with static cyclic loading procedure. Three testd specimens are S73, S42 and S0, which represent different combinations of stiffness and strength factors α and β for strongbacks. Specimens S73 and S42 are the specimens with strongbacks and S0 is the specimen without strongback. Qualitatively, we can expect that different properties of strongback have different impacts on the drift concentration of SCBF. To quantify the trends, we conduct the tests and observe that the speciem with the stiffest and strongest strongback (S73) is more capable of redistributing its nonlinear deformation. Test results show that the deformation distribution of Specimen S73 is more uniform and more brace members in three stories perform nonlinearly. Comparing Drift Concentration Factor (DCF), which is the ratio of the maximum dirft ratio to the averge drift ratio, we can observe 30% and 10% improvement in Specimen S73 and S42, respecitively. This improvement increases the nonlinear demand of the third-story braces ad reduce that of the first-story braces where the demand used to be excessive. Therefore, postpone the rupture of the first-story braces and enhance the ductility of the whole SCBF system.