Research on Seismic Performance and Rotational Stiffness of Dry Connections Between Prefabricated RC Columns and Steel Beams

The prefabricated steel-concrete composite structure is a type of prefabricated structure with broad application prospect, there is a kind of semi-rigid joint among the joints of prefabricated concrete columns and steel beams, and the rotational stiffness and seismic performance of the semi-rigid joint are closely related to the structure of the joint. In order to study the seismic performance and rotational stiffness of the dry connection joint between the precast concrete column and the steel beam, a full-scale component with a semi-rigid connection joint beween the precast concrete column and steel beam was designed and subjected to quasi-static loading tests. The yield characteristics of the steel joint module, the joint core area reinforcing steel, and the longitudinal rebars of the precast column were analyzed in the connection joint, as well as the bearing capacity, hysteretic behavior, and failure mechanism of the connection joint’s seismic performance indicators and rotational stiffness. The key components in the connection joint were simulated by using the ABAQUS finite element software, and the concrete damage plastic model was used to simulate the concrete failure process. The uniaxial compression and tension constitutive models of concrete were adopted from the model provided in the Code for Design of Concrete Structures (GB/T 50010—2010), and the constitutive model of steel rebars was adopted from the ABAQUS user-defined material subroutine package PQ-Fiber developed by Tsinghua University, which used the uniaxial elastic-plastic hysteretic constitutive model of steel rebars (USteel02). The key components include the thickness of the side plates of steel joints module, the diameter of the tie rods, the thickness of the stiffeners on the corbels, the thickness of the vertical plate on the corbels, the thickness of the horizontal plate on the corbels, and the diameter of the high-strength bolts for connection. The research showed that the failure modes of the connection joint were beam hinge mechanism failure, concrete crushing of the slab, and yielding of the steel joint module side plates and internal tie rods. The existence of the steel joint module ensured the stiffness and bearing capacity of the beam-column node zone, which could meet the requirements of "strong joints" in seismic design. The displacement angle between adjacent storeys exceeded 2% when the connection joint showed obvious damage, and the bearing capacity had not yet decreased. When the displacement angle exceeded 2.75%, the steel joint module side plates experienced tensile outward bulging at the corresponding location, and the tie rods yielded, but no obvious damage was found in the steel corbels or the welds. The hysteretic curve of the specimen was in the shape of a spindle, the skeleton curve experienced a long strengthening section, and the bearing capacity decreased slowly. The bending moment-angle curve of the beam ends indicated that the joint had the characteristics of a semi-rigid joint, and the positive and negative rotation stiffnesses were not consistent, with the negative rotation stiffness being six times greater than the positive rotation stiffness. The components that had a significant impact on the rotational stiffness of the connected joints were the thickness of the steel module side plates, the diameter of the tension rods, and the thickness of the vertical plate on the corbels. The thickness of the side plates and the diameter of the tension rods had a significant impact on the positive rotational stiffness, while the thickness of the vertical plate and the stiffeners could effectively improve the negative rotational stiffness, but their thickness had little effect on the positive rotational stiffness.