Research On Constitutive Relationship Of Steel Material Under Elevated Temperature And High Strain Rate And Explosion Resisting Performance Target

In recent years,the terrorist attacks in the world is increasingly rampant,and the number of attacks is increasing,which caused public panic and great social negative effect.With the development of technology and the accelerated process of urbanization,the explosion happened in industry,chemical industry,civil and commercial buildings is becoming more and more frequent.It brings great loss to people's daily life and life safety.With the development of the country,the steel structure building is more and more popular.The test and application of high temperature and high strain rate constitutive relation of steel has become a hot research topic in the present research.There is not a set of structural code of domestic explosion protection.So as a basis for explosion protection code,it is imperative to establish a set of Chinese explosion protection criterion suitable to China's national conditions.By considering the properties of steel after impact loading,the constitutive model was modified,and through the experimental data and the constitutive relation formula fitting method to verify the reliability of the modified model,and through the analysis of domestic and foreign bombing,thinking of making reference China seismic code,the blast precautionary classification standard and explosion protection criterion suitable to China's national conditions are developed in this paper.The main research contents are as follows:(1)Applying the Split-Hopkinson Pressure Bar(SHPB)testing technique,the impact experiment under high temperature(25?,350?,450?,750?)and high stain rates(2300s-1,3200s"1)of the Q345 steel were carried out.The stress-strain curves are described in detail.(2)By considering the Adiabatic heating effect and the viscous properties of the metal when the steel is subjected to impact load at high temperature,the constitutive relation of steel has been modified in this paper.(3)The fitting function of Origin software was used to fit the modified Johnson-cook model and the experimental data.The fitting effect is very good,it is proved that the modified Johnson-cook model can be well applied to the research in this area.(4)In the research of the blast precautionary goal of building structure,classification of explosive strength has been established based on statistical analysis of building structure explosion events with the concept of scaled-distance.(5)Different types of building structures are divided into different levels of risk refer to the Building structure importance classification method in the Standard for classification of seismic protection of building constructions(GB50223-2008)and Unified standard for reliability design of engineering structures(GB50153-2008)(6)Comprehensive explosion risk level and explosive strength level,which target of explosion protection should be meet for different structure has been determined in this paper.