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    Application of Timoshenko Beam-Column Theory in Data Correction for Steel Beam-Column Testing
    (Asce-Amer Soc Civil Engineers, 2020) Chansuk, Piyachai; Özkula, Gülen; Uang, Chia-Ming
    A recent cyclic test program evaluated the performance of steel wide-flange columns under axial loads and lateral drifts; the specimens had either fixed-fixed or fixed-rotating boundary conditions. For both cases, the flexibility of fully restrained moment connections at specimen ends, which varied in degrees based on several factors such as configurations of the bolted connection, end-plate thickness, and magnitude of the applied axial load, was observed to have significant impacts on elastic flexural stiffnesses of the measured responses. Therefore, the measured responses needed to be corrected, accounting for the effects of connection flexibility, before test parameters of interest can be investigated. A data-correction procedure that eliminates the effect of connection flexibility from the measured beam-column responses is developed. The procedure is built upon theoretical knowledge of elastic Timoshenko beam-column behavior. Once the effect of connection flexibility is removed, the corrected test responses become equivalent to the responses of beam-columns with ideal rigid end connections. (C) 2019 American Society of Civil Engineers.
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    Effect of boundary condition on the cyclic response of I-shaped steel columns: Two-story subassemblage versus isolated column tests
    (Wiley, 2022) Chou, Chung-Che; Lai, Yun-Chuan; Xiong, Hou-Chun; Lin, Te-Hung; Uang, Chia-Ming; Mosqueda, Gilberto; McCormick, Jason P.; Özkula, Gülen
    Recent studies on isolated steel columns under combined axial load and cyclic lateral drift showed that the column response is affected by the boundary condition. To consider more realistic boundary conditions of first-story columns in a frame, two-and-a-half story beam-column subassemblages were tested to investigate their behavior under reversed cyclic loading. The subassemblages, composed of a steel column with steel beams at two floor levels, used highly ductile I-shaped sections with web slenderness of either 37 or 49. Two isolated fixed-fixed columns were tested to facilitate a direct comparison with the subassemblage testing. An axial compression force corresponding to 20% of the yield force was applied. Test results showed that the realistic boundary condition at the top end of the first-story column significantly alters the column plastic hinging, moment distribution, and out-of-plane deformation reported previously based on isolated column testing. Plastic hinging of the adjoining beams caused the inflection point of the first-story column to move upward initially, then moved downward when plastic hinging developed at the column base. Out-of-plane deformation observed from isolated columns did not occur in the subassemblage column because hinging did not occur at the top end. Plastic components of the backbone curves for both the subassemblage column and isolated column were very similar; the former delivered a larger story drift angle rotation due to a larger yield rotation, dependent on the elastic lateral stiffness of the column. A closed-form solution that calculates this stiffness for any boundary condition was developed and verified from test results.