Study On Dynamic Response And Damage Of Steel Beams With Web Openings Of I-shaped Cross-section Subjected To Impact Loads

The steel beam with web openings of I-section is a conventional form of steel structure widely used in various industrial and civil buildings.In engineering practice,this structure is often subjected to impact loads,which may cause dynamic responses and damage to the structure,thereby posing a threat to personnel safety and normal use of the building.A comprehensive understanding of its dynamic response characteristics and the development of damage assessment methods can improve its safety in practical engineering applications.In this paper,drop hammer impact tests were conducted on the steel beam with web openings of I-section,and the dynamic responses and damage under impact loads were studied using the finite element software ABAQUS.The main work carried out is as follows:（1）Conducted drop-weight impact tests and dynamic response analysis on steel beams with hexagonal and circular web openings.The average peak impact force of the hexagonal web opening beams was 88.10%of that of the circular web opening beams.During the platform stage of the impact force,the average platform value of the hexagonal web opening beams was 89.92%of that of the circular web opening beams.As the impact energy increased,the maximum displacement of both types of beams increased;as the spacing between openings increased,the maximum displacement decreased;as the opening height increased,the maximum displacement increased.The circular web opening beams exhibited stronger energy absorption capacity and produced a maximum displacement of approximately 86.49%of that of the hexagonal web opening beams.The displacement response decreased as the distance from the impact area increased.The hexagonal web opening beams deformed more severely and had a larger reduction in opening projection area than the circular web opening beams.As the impact energy increased,the energy absorbed by the beams gradually increased.Reducing the spacing between openings and increasing the opening height increased the energy absorption and energy absorption ratio of the beams.The circular web opening beams exhibited stronger energy absorption capacity,with an average energy absorption ratio of 57.63%,1.11 times that of hexagonal web opening beams.（2）A finite element model of a steel beam with web openings of I-section was established using the ABAQUS software to analyze internal forces and dynamic response parameters.The numerical simulation accurately reflected the deformation mode of the beam’s web under the impact of a falling hammer,and predicted peak impact force,impact plateau value,and maximum displacement.The axial force distribution gradually changes from non-uniform to uniform,the shear force gradually transfers towards both ends of the beam,and the bending moment presents a symmetrical distribution along the length of the beam with the maximum moment occurring at the mid-span.The stress distribution of the web shows different characteristics at different time points during the impact process.The finite element parameter analysis showed that the increase of impact velocity will lead to the increase of maximum deflection,maximum shear force,and maximum bending moment of the beam.As the impact mass increases,the maximum deflection increases.The ratio of the spacing between the openings and the height of the beam（S/H）has a small effect on the beam deflection curve between 1.083 and 1.75,while the ratio of the opening height to the beam height（D/H）has an impact on the local deflection as it increases from 0.5 to0.7.Fixed-end boundary conditions can reduce deflection and the time required to dissipate impact energy,but may cause larger bending moments,affecting the safety of the beam-column joint.（3）Exploring the buckling and damage classification of steel beam with web openings of I-section under impact loads,dividing the damage into assessment levels,and establishing a damage evaluation criterion.The severity of damage is proportional to the impact energy and is influenced by the distance and height of the openings.Hexagonal perforations and acute angle openings are prone to stress concentration and cracking,whereas circular openings have a more uniform stress distribution and are less likely to crack.When steel beams with web openings of I-section are subjected to impact loads,different damage classifications may occur,including upper flange depression and bulging deformation,buckling and twisting deformation of web-plates between the openings,compression and twisting deformation of the perforations,cracking and damage,and lower flange bending deformation.The damage assessment level is determined by using the beam-end rotation angle and equivalent plastic strain,and the damage degree is classified into four levels:slight damage S₁（θ<2°,PEEQ is 0.0099～0.0647）,moderate damage S₂（2°≤θ<4°,PEEQ is0.0647～0.1067）,severe damage S₃（4°≤θ<6°,PEEQ is 0.1067～0.1873）,and destructive failure S₄（θ≥6°,PEEQ is≥0.1873）.By using numerical simulation,a damage evaluation curve has been established to determine the degree of damage to the component,providing an important reference for structural safety assessment.