Research On Dynamic Behavior Of Impacted Steel Arch In High Temperature Environment

With the rapid development of modern architecture,arch steel structure is widely used in practical engineering,and the design theory and academic research of arch steel structure are also constantly developing.In addition to withstanding the general design loads during the design life of a public building,it should also have the ability to resist accidental loads.After the"9·11 incident",many scholars have conducted in-depth research on the fire and impact load resistance of steel structures,but the relevant theoretical research mainly focuses on beams,columns and frame structures,while steel arches,as load-bearing elements of buildings,also need to conduct the necessary fire and impact resistance analysis.This paper mainly conducts numerical analysis on the dynamic behavior of steel arch under impact load and high temperature environment.The main research contents are as follows:（1）First,select reasonable thermal parameters of the material under high temperature environment,and material constitutive under normal temperature and dynamic environment.Subsequently,the steel arch structure was analyzed by the ABAQUS finite element software to determine the appropriate element type and number of meshes,and a correct and reasonable finite element numerical analysis model was established.Finally,the finite element comparison is carried out based on the theoretical results in the existing similar research documents to verify the feasibility of the numerical simulation method in this thesis and the correctness of the finite element calculation model.（2）The nonlinear finite element software ABAQUS is used to numerically analyze the dynamic response and flexural-torsional buckling of the impacted steel arch under high temperature environment.By introducing geometric initial defects and using quasi-static loading to obtain the critical load of steel arch structure under flexural-torsional buckling at room temperature;again determine the critical temperature of steel arch structure flexural-torsional buckling under different static load ratios;finally consider the influence of geometric initial defects,According to the critical load and critical temperature,the steel arch structure under different static load ratios is heated up.When the temperature rises to a certain value,an impact load is applied to the structure,so as to complete the analysis of the combined effect of temperature and impact load on the entire structure.About ABAQUS The thermal-mechanical analysis and implicit-display joint analysis process of the middle structure can provide thought and method for other scholars to carry out related research.（3）Exploring the relationship between different static load ratioη,temperature T and the critical speed v_crwhen steel arch buckling occurs based on finite element,discussing the main factors that affect steel arch buckling in different temperature ranges,and obtain:At20℃≤T≤100℃,the static load ratio plays a major role;at 100℃≤T≤400℃time,the static load ratio and temperature work together;at 400℃≤T≤700℃,temperature plays a major role.Secondly,the dynamic response analysis of the fixed-supported steel arches at both ends under different static load ratios,temperatures and impact speeds is carried out,and the arch deflection,impact time history curve and structural deformation cloud diagram are obtained.As the temperature rises or the impact speed increases,the structure As the deflection increases,the impact force increases and decreases;then the relationship between the temperature T,impact velocity_Gv,peak deflectionw_{ma x}or peak impact forceF_max is analyzed to obtain the main factors affecting the changes in the three relationships;finally according to different temperatures The impact force time history curve of the lower steel arch,the deflection time history curve and the velocity change of the impact object,define three dimensionless quantities,namely the dimensionless impact forceF/F_{ma x},the dimensionless deflectionw/w_{ma x} and the dimensionless speedv/v_{ma x},to describe the dynamic response of the steel arch,and The response process is divided into four stages,namely,the sudden increase stage,the rebound stage,the descending stage,and the unloading stage,and each stage is described in detail.（4）Investigate the five aspects of static load ratio,impact mass-speed,friction coefficient between impact object and steel arch contact surface,structural modification slenderness ratio,and restraint conditions at the arch foot,and explore its impact on fire steel arch The impact response and the influence of bending torsional buckling,as well as the ability of the steel arch to resist impact.The following conclusions are obtained:whenη=0.1～0.2 acts,it mainly affects the out-of-plane deformation of the steel arch under impact load;whenη=0.3～0.6 acts,it mainly affects the torsional deformation of the steel arch under impact load.Large mass and low-speed impact are more likely to induce out-of-plane bending and torsion buckling of steel arches.Friction has an important influence on the deformation of the impacted steel arch.When friction is not considered,it is easy to cause out-of-plane deformation of the steel arch.The friction coefficient between the impact object and the contact surface of the steel arch needs to be considered in the analysis.As the modified slenderness ratio increases,the load-bearing capacity of the steel arch decreases,and the ability to resist impact also decreases.Out-of-plane restraint is more unfavorable to the dynamic behavior of steel arches,and releasing in-plane rotation restraint is beneficial to improve the ability of steel arches to resist impact in high-temperature environments.（5）Finally,the CONWEP method is introduced,the applicability conditions of the method to circular arches are discussed,and the blast analysis of an arch wall in an engineering example based on the CONWEP method is carried out to obtain the incident wave pressure time curve and the damage state of the arch wall under different explosive loads.