Dynamic Constitutive Model Of Steel Fiber Reinforced Concrete And Its Finite Element Method

Steel fiber reinforced concrete (SFRC) is a kind of new-type concrete, it is in the ordinary concrete adding to the confusion of steel fiber distribution after form a multiphase composite materials. The existence of the steel fiber can effectively block micro cracks of concrete expanded, remarkably raised the concrete of matrix tenacity, ductility and impact resistance properties. The mixed distribution of SFRC steel fiber increased the complexity of such concretes, so it is a kind of extremely complex performance material for which the research of mechanical properties is not yet perfect. The steel fiber's geometric dimensioning and volume factor play an important role in SFRC's physical and mechanical properties, thus the research to SFRC's basic mechanical properties and constitutive theory under the dynamic loads still seem eager for urgent.On the base of quasi-static tests and SHPB impact compression test research to SFRC, this paper mainly established two kinds of dynamic constitutive model, which were embedded in the finite element analyse software followly. Then, the calculation of SFRC structure under dynamic loads can be performed. The works specific include the following:1. The impact of compression test and quasi-static tests of SFRC are tested. Through analysis of experiment data, the stress-strain curve of SFRC at different concrete strength, steel fiber content and strain rates were obtained.2. Based on HJC constitutive model for concrete, through analyzing strain rate effect of SFRC and steel fiber's strengthening and toughening effect, an improved HJC constitutive model for SFRC was proposed. The new constitutive model was improved at the yield surface equation and the damage evolution equation, in order to make the steel fiber can reflect the enhancement, toughening role. Numerical examples show, the improved HJC constitutive model for SFRC under impact loadin in this paper is reasonable and effective.3. Using the improved BP neural network combined with genetic algorithm, the neural network constitutive model for SFRC was established. The network use test datas as the training sample, the current strain increment, the strain rate, and the time step of strain, stress and strain rate as inputs, the current stress increment as output. Numerical examples show that the neural network implicit dynamic constitutive model is also reasonable.4. The neural network finite element method of steel fiber reinforced concrete structure under dynamic loads was studied.5. The second development for large explicit finite element software ABAQUS was applied. Through material user subroutine interface VUMAT, the programe code was compiled and then, the dynamic finite element method for SFRC was established. The numerical examples validated that the implementation process is correct and effective.6. By use of two dynamic constitutive models for SFRC established in this paper, the penetration of SFRC target under high and low speed impact was the simulated. The destruction result was obtained respectively, and then the two constitutive model's characteristics and applicability were discussed.