| Summary: | 碩士 === 國立暨南國際大學 === 土木工程學系 === 101 === Abstract
This thesis describes the tests of four full-size hollow reinforced concrete (RC) beams
subjected to pure torsion. The designed width and depth of the beam specimen is 50 cm ×
75 cm or 71.1 cm. The length of the beam testing zone is 3.5 m; the longitudinal length of
entire specimen is 5.76 m. The designed compressive strengths of concrete are 45, 70, 100
MPa, and the wall thicknesses of the hollow cross section are 12 cm, 8.5 cm, 15.5 cm, and
8.7 cm.
Most previous torsion tests of RC beams emphasized large (ultimate) torque and large
twist angle, and the deviation in small-twist measurement were appreciable. Since the
SMMT theory can now analyze the ranges before and after cracking and the cracking
torque and twist can provide linear torsional stiffness for the members, this study aimed at
developing a new test setup and method that can achieve precise small-twist measurement.
Most previous torsion tests of RC beams used steel members to clamp the RC specimen
and exert the applied torque. Such setups, however, often had inevitable gaps and slips
between the clamping steel members and the RC specimens, introducing significant errors
for small twist measurement. To overcome this handicap, this experiment uses a
monolithic transverse RC beam to convey the applied torque at the twisting end of the
IV
specimen, and designs a monolithic RC block at the fixed end. The RC block of a
specimen is also fastened to the underneath steel seat and strong floor using prestressed
steel rods. To effectively transmit the applied torque, a novel curved device is used
between the upper and lower unit of the twisting end, and a new force transmission setting
is added to the force delivering members linked to the actuator. The torque, twist angle,
shear flow zone thickness, steel and concrete surface strains, and longitudinal elongation of
the specimens are continuously measured and recorded in the tests. This thesis describes
the test specimens construction, test equipments, measurement facilities, installation and
test procedure, and presents the experimental results of four specimens.
Keywords: reinforced concrete, hollow section, torsion, experiment, beam, torque, twist
angle
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