| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 101 === This thesis mainly focused on studying the pre-fire and post-fire cyclic behaviors of fire-resistant (FR) grade steel SN490C-FR, earthquake- resistant grade steel SN490B, the two corresponding electroslag welding (ESW) materials and the two corresponding flux-cored arc welding (FCAW) materials. Five temperature treatment cases, including non-heat treatment, air-cooling after reaching 800ºC for 1 hour, water-cooling after reaching 800ºC for 1 hour, air-cooling after reaching 900ºC for 1 hour, and water-cooling after reaching 900ºC for 1 hour, were utilized to simulate the possible changes of each material after fire. Each material with a temperature treatment was manufactured into two round-bar specimens for constant-strain cyclic loading test and increased-strain cyclic loading test respectively. The test data were used to derive the strain hardening parameters for each material under cyclic loading. The test results showed that both of the two steels exhibited the cyclic hardening behavior, and all of the weld materials exhibited the cyclic softening behavior for non-heat treatment case. All the steels and weld materials demonstrated the cyclic hardening behavior for the case of air-cooling after reaching 900ºC for 1 hour, and demonstrated the cyclic softening behavior for the case of water-cooling after reaching 900ºC for 1 hour. In this study, the pre-fire and post-fire strain hardening parameters of each material were substituted into the finite-element numerical models to simulate the same cyclic test for verification. The numerical simulation results showed that the pre-fire and post-fire stress-strain hysteresis loops simulated from the developed finite-element numerical models for the considered six steels and weld materials agreed well with the experimental test results.
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