EXPERIMENTAL RESEARCH ON TORSIONAL PERFORMANCE OF RIGHT-ANGLE COUPLED STEEL PIPE JOINTS

Torsional tests on thirty-three right-angle steel pipe couplers were carried out. The test parameters include fastener tightening torques, fastener turnover frequencies and turnover loading amplitudes, etc. The results showed that with the increase of a fastener tightening torque, the torsional stiffness of steel pipe coupled joints increase, and their increase amplitudes under one failure trial are more evident compared to the turnover tests. The fastener tightening torque has little effect on the torsional stiffness under a higher turnover loading amplitude. The fastener turnover frequency has a greater effect on the joint torsional stiffness. When the couple turnover frequency is 15 times, the torsional stiffness of steel pipe joints reach the maximum, and when the turnover frequency is more than 35 times, the torsional stiffness become a constant. The stiffness of turnover couplers is greater than the stiffness under one failure trial in the tests. Under the greater turnover loading amplitude, the turnover frequency becomes less, and the torsional stiffness decrease more rapidly. Based on the test results, the regression constitutive equation for torsion – rotation relationship is obtained. For the complicated influences on the torsional stiffness of couplers and the problems hard to confirm the turnover frequency and loading amplitude, several effective suggestions on the construction of steel pipe supports with couplers are provided.