Study On The Constitutive Relation Of Reinforcing Bar Under Dynamic Action

The constitutive relation of steel bars is an important performance parameter in construction engineering materials.Previous studies have shown that the constitutive relation of steel bars depends on the bonding method,chemical composition,crystal structure,etc.on the material itself.As we all know,in the steel structure stability theory,under axial force,if considering the influence of deformation,the axial compression(pull)stiffness of the component will become smaller(larger),and the change of the stiffness of the component will result from the change of the rigidity and cross-section form of the component material.Therefore,the constitutive relation is related to the load.However,there is no clear quantitative relationship between the constitutive relation and the load at this stage.In addition,during the earthquake,taking into account the destructive strain amplitude frequency in the earthquake is about 2 ~ 3Hz,the duration is about 30 s or less,the steel bars are subjected to high strain and low cycle fatigue load.Therefore,when the earthquake occurs,the reinforcement is mainly subjected to the destruction of alternating stress,which is not the same as the damage of the steel bar under static load.In the field of mechanics,mechanics and aerospace,a large number of studies have shown that steel bars are strain rate sensitive materials.At high strain rates,as the strain rate increases,the yield strength and ultimate strength of the steel bar will increase accordingly,so the steel bar is a highly strained movement under seismic action.However,the stress-strain curve of building steel bars under earthquake has not yet attracted wide attention.There are no relevant articles on dynamic mechanical performance in the current seismic design code for building structures.Based on this,in this paper,under the consideration of the force and deformation of the steel bar,based on the stability theory deduced by the axial force of the steel bar,the relational expression of the load of the steel bar is obtained.By comparing the principle of the shaking table test with the stress principle of the reinforced asphaltasbestos isolation layer,the normal state-of-use equation of the asbestos-isolation layer of the reinforced asphalt is obtained,and the vertical reinforcement of the reinforced asphalt-isolated layer is obtained by using the original shaking table test of the present and the echelon.The data of strength,displacement and shock absorption coefficient were found to be highly consistent with the theoretical and experimental results,verifying the correctness of the equation.Using MATLAB to analyze the reliability of the equation,it can meet the requirements of the seismic isolation structure of the "Unified Standard for Structural Reliability of Building Structures",and use the PDS module in ANSYS to analyze the sensitivity of this equation,and get the design parameters of the steel bars to normal.Using the influence of the limit state equation,the applicable range of the vertical bar diameter and height in the reinforced concrete bitumen isolation layer was further obtained.By simplifying the interaction of the vertical rebar in the reinforced concrete asphalt isolation layer into the in-plane stability problem of the ideal axial compression rod on the elastic foundation,the ultimate bearing capacity considering the vertical rebar under the asphalt grease is deduced.Through the shaking table test of the isolation layer with bitumen grease and no bituminous grease,the acceleration and displacement of different test models were compared,and then the natural vibration period and damping ratio were compared and analyzed,and the results were obtained in the reinforced concrete bituminous isolation layer.Asphalt ointment has the following effects: it can reduce the acceleration response;it can control the displacement;it can provide the lateral support of the vertical stressed steel bars in the reinforced asphalt anti-seismic layer,so as to improve the critical bearing capacity of the vertical reinforcement;it can protect the vertical Stress-reinforced steel does not rust and enhance the durability of the reinforced asphalt insulation layer.By simulating a seismic shaking table test,the dynamic mechanical properties of steel bars under earthquakes are investigated.The static mechanical properties of steel bars are obtained by testing the steel bars of the same batch on a universal testing machine.The dynamic and static elastic moduli are compared and the test results are obtained.It shows that the dynamic elastic modulus is not fixed and the constitutive relation of the steel bar under earthquake is influenced by two aspects: the load and the strain rate of the steel bar.