Study On Equivalent Static Load Method Of Beam Structure Under The Condition Of Chemical Explosion

Explosion shock wave testing has a great risk and many uncertain factors,the test requirement about venue and equipment is high.Now the finite element numerical analysis software is used for simulation,but modeling analysis need researchers who have rich experience in engineering design,and simulation requires high hardware and long time to consume,more and more domestic and foreign scholars began to use the equivalent single degree of freedom theory to analyze the explosion shock wave.In this paper,the equivalent single degree of freedom system theory is studied deeply,and the dynamical coefficient equations are derived by fitting the attenuation load with polynomial curve to simulate the blast wave,and the value of the dynamic coefficient calculated by polynomial curve fitting attenuation load is compared with the value of the dynamic calculated by linear attenuation load.The finite element numerical analysis software LS-DYNA was used to model the reinforced concrete beam,and the influence factors of the ductility ratio about the reinforced concrete beam were studied through the control variable method.Taking the analyzed model as an example,the design equivalent static load is calculated by the equivalent static load method.The main research contents and conclusions of this paper are as follows:(1)In this paper,the dynamic characteristics are analyzed in depth.The establishment of the equivalent single degree of freedom system and the application of the equivalent static load method are expounded,and the law of free vibration of structural members under blast impact load is revealed by the load history curve which is simulated by software.The physical meaning and calculation formula of equivalent coefficient and dynamic coefficient of K_h value are derived by freely supported beam,which natural frequency of vibration are calculated.(2)This paper gives a detailed derivation process and formula through the way of calculating the dynamic coefficient by using polynomial curve fitting attenuation load function,and the results are compared with those obtained by linear attenuation load function with equal impulse,and the feasibility and accuracy of fitting attenuation load with polynomial curve are verified,and the good continuity of the calculated values of dynamic coefficients in early and late states is revealed,and the better continuity of the calculated values of dynamic coefficients in early and late states is revealed.The numerical blind area of dynamic system under high ductility ratio is less than the explosion shock wave with equal impulse linear attenuation load fitting after comparation.The structure with small ductility ratio is majored in the design,and the dynamic coefficient value calculated by using polynomial curve fitting attenuation load is slightly lower than that calculated by using equal impulse linear attenuation load,then the economic value is better.(3)Through the way of modeling and analysis of reinforced concrete beams,it is concluded that the ductility ratio of reinforced concrete beams is not correlated with constraint conditions,but negatively correlated with proportional distance and positively correlated with depth-span ratio.The equivalent static load method is used to calculate the design equivalent static load of the model beam,which verifies the applicability and simplicity of using the equivalent static load method to calculate the blast wave.The results of this study further promote the theoretical study of blast wave.