Research on Calculation Method of Characteristic Torque of Prestressed UHPC-RC I-Shaped Composite Beam

The prestressed UHPC-RC I-shaped composite beam is a common new type of beam structure at present, and there is relatively little research on the torsional calculation method for this type of structure. This article first defines the mechanical concept of characteristic torque based on the structural characteristics and different stage stress states of prestressed UHPC-RC I-shaped composite beams. Considering the initial pre stress, UHPC tensile strength, and concrete tensile and compressive stress states, theoretical formulas for initial cracking torque, cracking torque, and ultimate torque are derived based on elastic theory, plastic theory, and variable angle spatial truss theory, respectively; Subsequently, taking a 25m prestressed UHPC-RC I-shaped composite beam as an example, the accuracy of the theoretical formula in this paper was verified through finite element calculation results, where the theoretical value of the ultimate torque differed only 2.3% from the finite element calculation value. Finally, a parametric analysis of the characteristic torque of the beam was conducted, and the results of this study showed that the initial cracking torque value of the section was not affected by the initial pre stress and UHPC tensile strength, provided that the main tensile stress of the bottom concrete did not exceed the limit; Increasing the initial prestressing stress of the section or enhancing the tensile strength of UHPC can enhance the cracking torque and ultimate torque of the section. Considering the initial prestressing stress and UHPC tensile strength, the ultimate torque of the section can be increased by 57.9% and 94.1%, respectively. If the influence of the tensile and compressive stress states of concrete is neglected in the calculation, the values of the initial cracking torque and cracking torque of the section will be overestimated by 8.6% and 13.3%, respectively.