Effectiveness of shear key on torsional resistance of precast beam: An experimental and numerical investigations

The present study evaluates the behaviour of wet precast beam-to-beam connection under pure torsion through experimental and numerical studies. A wet connection is provided at the central region of the precast beam. Two precast beam elements are connected by welding the overlapped portion of reinforcement bars projecting from each beam element. Furthermore, inward and outward shear keys are provided within the connection region to examine the efficacy of shear keys on the torsional resistance of the precast beam. Also, the behaviour of precast beams with and without shear keys is compared with monolithic beams. Experiments are conducted using a loading frame, designed and fabricated to create a pure torsion effect on the beam specimen under the application of monotonic vertical load. The response of test specimens is evaluated through various parameters such as torque and corresponding twist at different phases of loading, torsional ductility index, crack formation and failure propagation. Experimental studies show that shear keys provided within the connection region effectively contribute to force transfer and enhance torsional resistance of the precast beam by 16 %-24 % as compared to monolithic beam and precast beam without the shear key. A numerical analysis of the precast beam is carried out, and the behaviour of test specimens obtained from experimental studies is compared. The damage pattern and torque-twist behaviour obtained from numerical studies adequately simulate the response of test specimens observed during the experimental study.