Study On Hysteretic Behavior Of Steel Structure T-stub Under Cyclic Loading

High-strength bolt connection is the most common connection method for steel structures.It is widely used because of its simple structure,easy disassembly and low technical requirements.In the design and analysis of steel structures,joints are usually simplified as hinged or rigid joints,but studies have shown that high-strength bolted connections are actually semi-rigid connections with certain rotational stiffness.At present,the component method is the most commonly used method to study the semi-rigid rotation characteristics of joints.Among them,the T-stub is one of the most important mechanical components in the component method,and its mechanical properties directly affect the rotational performance of the entire joint.In order to accurately represent the semi-rigid rotation characteristics of joints under cyclic loading,it is of great significance to study the hysteretic behavior of T-stub and establish a theoretical model to describe its nonlinear mechanical behavior.Based on the four-parameter Iwan model,this paper proposes a constitutive model that conforms to the hysteretic behavior characteristics of T-stubs,carries out numerical simulation calculation and theoretical derivation research work.The main research work and conclusions are as follows :(1)Aiming at 23 groups of steel structure T-stubs,considering the influence of web thickness,end plate thickness,bolt end distance,bolt diameter and flange plate width,the numerical simulation of cyclic loading is carried out to study the hysteretic performance of T-stubs under cyclic loading.The initial stiffness,residual stiffness,full yield load,amplitude load and energy dissipation capacity of each specimen were analyzed.The change process of stress distribution characteristics of T-stub under cyclic loading is summarized.The results show that the flange thickness and bolt diameter have a great influence on the mechanical properties of T-stub,but the stress distribution of T-stub under cyclic loading is basically the same.(2)Based on the variation characteristics of stress distribution of T-stub under cyclic loading,considering the residual stiffness after yielding,a constitutive model is proposed.The unloading equation,reverse loading equation and analytical expression of energy dissipation of constitutive model in local yield stage and complete yield stage are derived.The correlation between the parameters of the constitutive model and the geometric parameters of the T-stub is analyzed,and a parameter identification method of the constitutive model based on the geometric parameters of the T-stub is proposed.The results show that the hysteresis curve of the T-stub obtained by the mechanical model is in good agreement with the experimental curve.(3)According to the stiffness equation of the T-stub,the mechanical model of the T-stub part is discretized by the stiffness-based arithmetic series discretization method.The influence of different discrete element numbers on the accuracy of simulation calculation is discussed.The results show that more accurate simulation results can be obtained by using three discrete Jenkins elements.