Experimental Study on Flexural Behavior of Joint in Negative Moment Area at Pier Top of Hot Rolled-shape Steel-UHPC Composite Continuous Beam

Regarding the lower price and better fatigue resistance of hot-rolled steel (HRSS), it was combined with ultra-high performance concrete (UHPC) to construct the HRSS-UHPC composite beam that could be prefabricated with a wide width and lifted in a lightweight manner. To further improve the stiffness of the composite beam, improve driving comfort, and reduce the cost of operation and maintenance, the structure, crack resistance, and bending capacity of cast-in-place joints were investigated in the negative moment area at the pier top of the beam, which was continuous after simple support. Based on the development of a joint construction in the negative moment area at the pier top without construction site erection of the formwork, the overall calculation of the 4 X 30 m HRSS-UHPC composite continuous bridge was performed using MIDAS/Civil software. To investigate the flexural behavior of the joints in the negative moment area at the pier top of the HRSS-UHPC composite beam, two 1:2 scaled-down models were examined in the three-point flexural test. The results show that the damage mode of the two specimens of the HRSS-UHPC composite beam is a typical bending failure, multiple main cracks appeared on the top surface of the UHPC in the mid-span area. The outermost tensile longitudinal reinforcement in the mid-span area was pulled off. The crack resistance of the joints in the negative moment area at the pier top of the HRSS-UHPC composite beam met the engineering requirements, the restriction ability of reinforcement on the development of cracks was stronger than that of steel plate bars, and the reinforcement was conducive to enhancing the ductility. The anti-cracking effect of the groove interface was better than that of the flat interface. Based on elastoplasticity, the method of calculating the bending capacity of the joints in the negative moment area at the pier top of the HRSS-UHPC composite beam was proposed. According to the proposed theoretical formula for the ultimate flexural capacity of the joint in the negative moment area at the pier top of the composite beam, the calculated value was within 3% relative error with the test value. In engineering applications, use of the structural form of the groove interface, as well as dense reinforcement of joints in the negative moment area at the pier top are recommended. © 2023 Xi'an Highway University. All rights reserved.