Experiment And Numerical Simulation Analysis Of Steel Beam- Column Impacted By Dropping Harmmer

In recent years, steel structure has been used increasingly in civil engineering due to its widely recognized advantages,which promotes the development of relevant design theory and academic research to a certain extent.Specially,study on the resistance of steel structures under explosion and impact load is becoming a hot spot. Within the design life, in addition to the conventional design load, steel stuctures also bear accidental explosion or impact load sometimes, so they must have the appropriate resistance. The dynamic response under impact load of steel beams and columns, which are the main load-bearing members, is the first problem to be solved. At the same time,it can also provides the basis for further design.This article mainly studys the dynamic response of I-shaped cross-section beam-columns under impact load, including impact experiment, finite element simulation and the equivalent single degree of freedom model analysis.In the experiment, we use a cylindrical helical compression spring to apply the axial load, record the deformation process and strain of the member using high-speed cameras and dynamic signal acquisition system. Experimental results show that:when subjected to lateral midpoint impact effect, simply supported beam-column members appear not only bending deformation in the plane but also bending and torsional deformation out of the plane; and the local buckling of web is the reason of bending and torsion deformation; the bending deformation in the plane and torsional deformation out of the plane will increase as the increasing impact velocity and axial load, but a specific range of impact velocity and axial load will decrease torsional deformation out of the plane; changes in axial force relate to the axial deformation and the stiffness of the spring, which indicates that using less rigid compression spring to apply an axial load is suitable.Using the software ANSYS/LS-DYNA, simulation about the experiment has been made. By the comparison of deforming process,the final displacement and strain data, we find out that both finite element analysis and experiment results have a good match, showing that it is feasible to study bending and torsional buckling using the finite element numerical simulation method. On this basis, further analysis of the contact surface friction, axial force, drop hammer mass, impact velocity, boundary conditions, etc. on the influence of bending and torsion deformation has been made as well as the verification about the single degree of freedom model.Using finite element software to study the dynamic response can provide accurate analysis results, but its operation process is complex and requires higher theoretical level. While the use of single degree of freedom model which is commonly used in dynamics is just the opposite.In this article, the order of plastic hinges formed in the hyperstatic member is determined by ultimate load theory. Then according to mechanics of materials, deformation curves in various deformation stages are received. Combined with Hamilton’s principle and other dynamics theory, differential equations of motion and its coefficient expressions about beam-column members with rotational constraint boundary conditions are deduced. The linear acceleration method is used to get numerical calculations of the equation of motion. In order to reasonably considering the strain rate effect, we assume that plastic hinges have fixed length distribution and then calculate plastic strain and strain rate according to angle turned of plastic hinge. Ultimately, the results of single degree of freedom model and finite element simulation are compared, to verify the applicability of equivalent single degree of freedom model of the beam-column members and the proposed method in this paper.