Study On Equivalent Damping Ratio Of Concrete-Filled Steel Tube Members

Due to its outstanding strength,good plastic toughness,and good seismic performance,concrete-filled steel tube structures have been widely used in various fields.So far,the understanding of damping of a single material at home and abroad is relatively consistent,but the concrete-filled steel tube is composed of two completely different materials.The equivalent damping ratio will be affected by many factors such as the relative proportions of the two materials.In practical projects,structural engineers often use the suggested values in the specification for calculations.When the actual damping ratio is greater than the recommended value,the structural reliability is improved,but the economic efficiency is poor,on the contrary,it is risky and may seriously threaten the safety of life.Therefore,whether or not the damping ratio can be accurately calculated and its variation rule will be directly affected will have a direct impact on the reliability of structural dynamic response analysis in practical projects.In this paper,the equivalent damping ratio of concrete-filled steel tube members is studied by using finite element numerical simulation method,mainly around the following points:Firstly,take the concrete-filled steel tube members in an engineering project as an example,and use the finite element analysis software ADINA and MSC.NASTRAN respectively to calculate and compare the calculation results of the two,and verify the feasibility of the numerical simulation method used by ADINA;Then take the different damping ratio values to calculate the response spectrum and the equivalent wind load,and compare and analyze the calculated results to illustrate the influence of the damping ratio on the structural dynamic response analysis.Secondly,the factors affecting the equivalent damping ratio of concrete-filled steel tube members are studied.This article analyzes two aspects that affect the equivalent damping ratio of six factors one by one——the analysis of influence rule,the analysis of influence mechanism.Among them,the ratio of diameter to thickness,length of calculation and ratio of axial compression have significant influence on the equivalent damping ratio of concrete-filled steel tube members.The strength grade of core concrete and interfa ce bond slip performance have certain influence on the equivalent damping ratio of concrete-filled steel tube members.However,considering regularity of using high-strength concrete,feasibility and convenience in practical engineering applications,its influence is negligible;the cross-sectional form and aspect ratio have little effect on the equivalent damping ratio of concrete-filled steel tube members and can be neglected.Finally,the rule of the equivalent damping ratio of concrete-filled steel tube members with the calculated length and axial compression ratio are studied.Further,a parametric analysis was performed on the ratio of diameter to thickness(or section size),calculated length,and axial compression ratio.On this basis,an equivalent expression of the equivalent damping ratio is fitted to each diameter-to-thickness ratio(or section specification).In order to facilitate the practical application,the parameterization analysis results of the equivalent damping ratio are organized into two tables,The seamless steel pipes are sorted according to the section specifications,and the remaining sections are sorted by diameter ratio.The research results in this paper can provide references for the equivalent damping ratio of concrete-filled steel tube members in practical engineering.