Experimental study on bending resistance of joints of large-diameter double-layer-reinforced pipe piles

The failure of welded joint of the traditional lateral force pipe piles due to insufficient bending capacity has become a key problem affecting its safety and use. In this study, the full-scale model tests are carried out based on the joints of large-diameter double-layer-reinforced pipe piles, and the influences of reinforcement measures such as optimizing double-reinforced structure, improving reinforcement anchorage mode, improving concrete strength grade, adding steel fiber on the flexural performance, deformation and failure characteristics, crack distribution characteristics of joints of pipe piles are studied. The results show that the ultimate bending moment of joints of a welded pipe pile can not reach the standard value of the whole pile, and the main failure mode is that the upper part of the two ends of the plate is squeezed and deformed, the lower part of the pile is opened in a drum shape, the concrete on the upper edge of the pile hoop is crushed, and the concrete under the pile body is deformed and cracked. The strengthening measures only raise the threshold of cracking moment of joints of two pipe piles to a certain extent, and the bending capacity of joints of pipe piles decreases with the increase of the number of holes in the end plates. Finally, a new type of joint of bending resistant pipe piles is proposed, which adopts the structural form of stiffener joint at the sleeve and end plate, and replaces the steel fiber-reinforced concrete pile body at the pile joint. This kind of joint effectively improves the flexural performance of the joints of pipe piles, and makes the pipe piles have good toughness and ductility.