Study On The Dynamic Response Of Steel Beam And Ⅰ-shaped Column Under The Presence Of Pre-loading

The steel structure has the advantages of uniform material,good plastic toughness,high reliability,easy mechanized manufacturing and convenient construction and installation.With the wide application of steel structure in the field of construction engineering in China,its stability and safety have also received extensive attention.Steel beams and steel columns are the main components of steel structures.They may cause large deformation or collapse when subjected to dynamic loads,which may cause the building to lose its bearing capacity.While the steel structure is subjected to dynamic loads,it is often subjected to normal design loads such as dead weight and floor live loads.However,the dynamic response of steel structures in service has been rarely studied.Therefore,the research on the impact dynamic response of steel beams and steel columns under pre-loading has a very clear engineering background.In this paper,the dynamic response and collapse behavior of steel beams and I-shaped steel columns subjected to concentrated impact loads under pre-loading are studied by means of experiments and numerical simulations.Its main content is reflected in the following three aspects:(1)The impact test of the clamped beam under different pre-loading was carried out by using the self-developed bending moment loading device.Based on the comparison between the transient response recorded by the high-speed camera and the final deformation of the test piece,the lateral impact dynamic behavior of the specimen under different bending moment types was studied.Experimental studies have shown that the dynamic response of steel beam structures is strongly dependent on the type of initial kinetic energy and pre-added bending moments.The mid-span displacement of the specimen changes with the type of bending moment.(2)Based on the general finite element program ABAQUS,the numerical simulation of the dynamic response of the clamped beam under the pre-added bending moment is carried out.The transfering resuces technique is applied to realize the numerical analysis process of the first impact after loading,and the correctness of the numerical simulation is verified by comparison with the experimental data.The variation law of bending moment in each section along the beam span under different working conditions is analyzed.Combined with the characteristics of plastic energy dissipation,the variation and movement law of plastic hinge in the deformation process of the specimen are discussed.Numerical simulations show that when the specimen with fixed negative bending moment is subjected to impact,the displacement of the impact point is the largest,and the plastic deformation at the impact point is the main energy dissipation mode;when the positive bending moment is pre-added,Large plastic rotation occurs at the fixed end,and the root rotation is the main energy-consuming form.When the equivalent bending moment is pre-added,the impact point is zero and the displacement point is the same as the pre-loaded clamped beam.Close,but different degrees of plastic rotation occur at the left and right fixed ends,and the deformation and energy consumption between the left and right spans of the clamped beam will no longer be symmetrical.(3)Based on the general finite element program ABAQUS,the impact response and collapse behavior of the I-shaped steel column under axial force and pre-added bending moment are simulated.The numerical simulation results show that under the same axial force condition,the critical speed of collapse of the specimen with negative bending moment is slightly lower than that of other specimens,that is,the negative load applied to the steel column reduces its stability;The critical speed of collapse to the bending moment specimen is slightly higher than that of other specimens,that is,the application of a forward load to the steel column improves the crashworthiness.Under the same bending moment,with the increase of axial force,the critical velocity of the specimen decreases obviously.The axial force is the main factor affecting the crashworthiness and stability of the steel column.The bending moment is the secondary of the critical collapse speed.In this paper,by means of experimental and numerical simulation methods,the response mechanism and collapse behavior of steel beam and steel column structure under pre-loading are analyzed,which provides a technology for understanding the impact dynamic behavior of steel beam and steel column structure under service environment.Support and lay the foundation for optimizing design and theoretical evaluation of such structural forms.