Elastic-Viscoplastic Dynamic Constitutive Model Of Concrete And Application In Finite Element Analysis

Concrete structures are often subjected to dynamic loads such as earthquake, impact and blast. Rate sensibility and damage mechanism of concrete materials subjected dynamic loads need to be settled urgently for many large engineering projects such as high dams, nuclear power stations, highways and military works. As a sub-topic of "The study of dynamic property and dynamic damage mechanism of concrete" .supported by the academician fund of Hohai university, this paper deeply studied dynamic constitutive model and damage theory of concrete.The main work done in this paper is as follows: (1) Based on the viscoplastic theory of Perzyna and considering the influence of strain rate on initial Young's modulus of concrete, elastic-viscoplastic dynamic constitutive model for concrete under uniaxial loading was formulated. (2)Based on the equivalence assumption of strain and using crack closing effect coefficient to reflect the difference between damage in tension and damage in compression of concrete, the elastic-viscoplastic damage dynamic constitutive model for concrete under uniaxial loading was presented. Through comparing the stress-strain curve obtained from test with that from the constitutive model in uniaxial tension and compression of concrete under different loading rates, the constitutive model was verified; (3) Through applying the viscoplastic theory of Perzyna to the dynamic stress analysis of concrete in plain stress state, considering the influence of strain rate on initial Young's modulus of concrete, using the yield criterion of Drucker-Prager , the elastic-viscoplastic dynamic constitutive model for concrete in plain stress state was derived.; (4) The test of third-point flexural-tensile beams was done in static loading and impact loading; (5) Applying the elastic-viscoplastic dynamic constitutive model for concrete in plain stress state to the finite element program in plain state, the dynamic finite element program in plain state was worked out considering the change of initial Young's modulus of concrete. Using the program, the test of third-point flexural-tensile beams under static loading and impact loading was simulated numerically.The above studies indicate: (1) There are mainly two influencing factors on dynamic response of concrete-the strengthening effect of strain rate and the weakening effect of damage; (2) The viscoplastic theory of Perzyna can be applied to characterize the dynamic behavior of concrete. The elastic-viscoplastic damage dynamic constitutive model for concrete under uniaxial loading presented in the paper is reasonable. The elastic-viscoplastic dynamic constitutive model considering thechange of initial Young's modulus for concrete in plain stress state is also reasonable. (3) The study on the test of third-point flexural-tensile beams in static and dynamic loading indicates that with the loading rate increasing, the initial Young's modulus of concrete increases by 8.5% and the ultimate flexural-tensile strength increases by 21.7%. (4) The dynamic finite element program formulated in the paper can simulate the flexural-tensile property of the third-point flexural-tensile beams under static loading and impact loading. All above research findings are benefited for future reasearches.