Tensile behavior of parallel threaded couplers for reinforcements by natural cooling after elevated temperatures

Parallel threaded couplers (PTC) are increasingly being applied to prefabricated concrete (PC) structures owing to their excellent structural performance. To evaluate the effect of high temperatures on the tensile behavior of PTC, the specimens were cooled to natural temperature after the fire (400 degrees C, 500 degrees C, and 700 degrees C), and monotonic and cyclic tests were carried out on PTC with two thread angles (60 degrees and 75 degrees). After the test, the failure mode, ultimate bearing capacity, load-displacement curve, and ductility of PTC were investigated. The results show that the failure mode of PTC is steel bar necking, and the ultimate load of PTC after the fire are reduced by 6.7 %, 7.3 %, and 11.1 % under the monotonic test, the connection performance of mechanical splices is excellent. Besides, the finite element model was established to simulate the mechanical properties of PTC. The load-displacement curves and the constraint effect of the sleeve obtained by the finite element simulation corresponded well with the tests. Based on this agreement, a parametric study was carried out to investigate the effect of the thread pitch and thread angle on the ultimate bearing capacity and ductility of PTC, and the constraint effect of the sleeve on the thread head was further investigated by the finite element parametric analysis.