Simplified Model Of Shear Nonlinearity For High-strength Bolted Joints

High-strength bolted joints are widely used in long-span bridges and industrial and civil steel structures because of their advantages of convenient construction,installation,compactness,fatigue resistance,and ability to withstand dynamic loads.However,the high-strength bolt connection is often subject to damage in the structure,so it is necessary to study the force mechanism,bearing capacity and failure mode of the high-strength bolt connection under the shearing force.In the study of high-strength bolted joints,experimental methods or establishing solid finite element models are often used.The experimental method is costly,time-consuming and labor-intensive,and has many affected factors.The commonly used finite element modeling method of high-strength bolted structures considers the material and the nonlinear behavior of the contact,resulting in high computational cost and long calculation time.It is very difficult to carry out comprehensive and accurate simulation of large and complex bolt groups.Therefore,according to the force characteristics of high-strength bolt connection,a simplified mechanical shear model of high-strength bolted is proposed,and the simplified force-displacement curve is obtained.Combining the simplified model to model the actual structure can effectively simplify the calculation,save time,and ensure the accuracy of the simulation,which has certain value for practical engineering applications.The main research work and conclusions of the paper are as follows:1.The development history,research status and calculation theory of high-strength bolt shear capacity are introduced.Several common mechanical models for simulating high-strength bolted joints are introduced.According to the force characteristics of the high-strength bolt connection,two connected Jenkins units are used to simulate the high-strength bolt shearing process,and the restoring force expression is obtained.2.Use the finite element software to establish a high-strength bolt-connected nonlinear model.The force-displacement curve and the failure form calculated by the model are in good agreement with the classical test results,which proves that the high-strength bolting nonlinear modeling method is accurate and reasonable.3.Through the finite element model,the effects of bolt diameter,core thickness,cover thickness,anti-slip coefficient,bolt and steel plate yield strength on the shear resistance of high-strength bolted joints are studied.Through the parameter analysis,summarize the calculation formula or recommended value of the parameters such as f₁、f₂、X₁、X₂ and X₃.4.Design high-strength bolt connection shear capacity test,the test results show that the eigenvalues are similar to the simplified model calculation results.The force-displacement curve obtained by the experiment agrees well with the curve calculated by the simplified model.It shows that the high-strength bolt shearing simplified model proposed in this paper can describe the whole shearing process of high-strength bolted joints.