| Summary: | 碩士 === 國立暨南國際大學 === 土木工程學系 === 101 === This thesis describes the experiment of five hollow reinforced concrete (RC) beam specimens subjected to pure torsion, and compares the test results with .
Previous torsion tests of concrete beams often used metal components to clamp the concrete beam specimen while exerting a twisting torque. This type of apparatus could have gaps and slips between the clamping metal components and the concrete specimen, introducing errors into the small deformation measurement. This study used a monolithic transverse RC beam to convey a twisting torque without gaps to the twist end of the longitudinal test beam, and constructed a monolithic RC block at the fixed end. Pre-tensioning forces were used to fasten the RC blocks of the specimens to the underlying steel seat and to the strong floor, thus producing a slippage-free mechanism for the fixed end. The test apparatus also incorporated devices to eliminate any constraints on the longitudinal elongation of the test beams. Seven quantities were experimentally determined for each of the specimens through continuous measurement, using various measuring lengths.
The test results show that the test apparatus is rather efficient in determining small twists, and that the initial branches of the obtained torque-twist curves exhibit a high degree of linearity. The results also demonstrate that a measuring length should be long enough to incorporate the entire failure region, but should not be too long as too much length can cause the twist angles to be underestimated. Furthermore, the experimental values of the shear flow zone thickness reduce drastically around the cracking and remain relatively constant after cracking. The obtained elongation-twist curves are smooth when the measuring length covers the entire failure region, but otherwise have abrupt turns due to drastic losses of measured twist angles. The experimental torque-twist curves of specimens D075a and C065a agree reasonably well with the analytical curves.
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