Research On Mechanical Properties Of Joints Of Assembled Semi-rigid Frame

In recent years,prefabricated buildings have been greatly promoted and developed in our country.The beam-column connection of the fabricated frame structure has two methods: dry connection and wet connection.For the low-rise prefabricated concrete frame structure,this paper proposes a dry connection method using angle steel connection.Dry connection can greatly shorten the construction period and reduce environmental pollution,but the prefabricated frame nodes are often semi-rigid.This kind of joint exhibits nonlinear mechanical properties under earthquake action.Therefore,it is necessary to study the mechanical properties of prefabricated semi-rigid frame joints connected by top and bottom angles.The factors affecting the rotational stiffness of the assembled semi-rigid frame joints connected by the top and bottom angles mainly include the beam height,the thickness of the angle steel,and the distance from the back of the top angle cross limb to the center of the high-strength bolt hole at the column end.Based on these three factors,this paper uses a combination of experiment and numerical simulation to study the rotational stiffness of the top and bottom angle steel connection nodes,and calculate the internal force of the semi-rigid frame.The specific content is as follows:(1)Use the ABAQUS finite element software to establish the frame node model of the top and bottom angle steel connections,determine the material constitutive relationship of the angle steel according to the test results in the literature,and apply the test load in the literature to obtain the bending moment-rotation curve of the node.The numerical analysis results are compared with the experimental and theoretical derivation results to verify the feasibility of the numerical analysis method.(2)Using the validated numerical analysis method,establish 9 groups of frame node models connected by top and bottom angle steels,apply reciprocating load by means of displacement control,and obtain the bending moment-corner skeleton curve of the nodes.The basis for dividing the elastic stage and the plastic stage of the joint is determined on the skeleton curve,and the calculation formula for the rotational stiffness of the elastic stage and the plastic stage is proposed,and the influence of various factors on the rotational stiffness of the joint in the elastic stage and the plastic stage is analyzed.(3)Taking the semi-rigid element as a basic unit of structural mechanics,the calculation formula for the bending moment of the member element under different loads is deduced.The internal force analysis of a frame structure connected by top and bottom angle steels of one-to-two-story and two-spans was carried out,and compared with the internal force analysis results of the cast-in-place frame,it was found that the rotation stiffness of the joints had a significant influence on the internal force distribution of the structure.By changing the thickness of the angle steel and the cross-leg of the top angle steel The distance from the back of the limb to the center of the high-strength bolt hole at the column end can be used to adjust the internal force distribution of the fabricated frame structure.