| Summary: | 碩士 === 國立暨南國際大學 === 土木工程學系 === 93 === This research aims at developing a new analytical model for torsion, the Softened Membrane Model for Torsion (SMMT). Comparison of the analytical results of the SMMT with those of Rotating-Angle Softened Truss Model for Torsion (RAT) and experimental data for 71 tested specimens is conducted to examine the feasibility of the SMMT. It is found that the Hsu/Zhu ratio and the steel stress ratio in the Softened Membrane model theory need to be modified in the SMMT due to the strain gradient effect in the concrete of torsional beams. Modification of the two parameters is proposed.
The effect of tensile constitutive relationship of concrete is also studied in this thesis. Two such constitutive relationships, namely the Vecchio and Collins model (1986) and the Belarbi and Hsu model (1994) are evaluated. It is found the analytical results of the SMMT utilizing these two constitutive relationships do not well agree with the experimental data. Therefore, a new tensile constitutive relationship is proposed. The new tensile constitutive is a simple modification of the Belarbi and Hsu model (1994). Incorporating the tensile constitutive relationship, the SMMT is capable of predicting overall torque-twist response, including the cracking torque and twist.
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