| Summary: | 碩士 === 國立中央大學 === 土木工程學系 === 105 === Knee braced moment resisting frames (KBRF) possess adequate stiffness and ductility, thus are suitable structural forms for earthquake-resistant designs. The performance of KBRF greatly depends on the integrity of the knee braces. When knee braced members buckle under compression, the members may suffer from fracture if the plastic deformation capability is insufficient. This study is focused on the further improvement of multi-story KBRF by adopting high-ductility knee braced members with various brace strength combinations. A series of cyclic loading tests were conducted on the moment resisting frame (MRF) and KBRFs to evaluate the effectiveness of high-ductility knee brace design on the multi-story steel frame constructions. Test results show that the strength of two-story one-bay KBRFs with high-ductility knee braces is 2.32 to 2.57 times of the same-sized MRF, and the energy dissipation is also increased by 4.15 to 4.82 times. The strength of two-story two-bay KBRFs with high-ductility knee braces is 1.78 to 2.05 times of the same-sized MRF, and the energy dissipation is also increased by 2.31 to 2.95 times. It is also found from the comparisons that the improvement in frame performance is higher when the brace strength ratio between the lower and upper stories is higher, provided that the integrity of the beams is sustained. Overall evaluation on the strength, deformation capacity and energy dissipation of the KBRFs validated the effectiveness of the high-ductility knee brace design in the engineering applications.
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