Studies On The Constitutive Relation For Nonlinear Viscoelastic Concrete With Damage

Concrete is the composite multiphase material made up of stones and ossified cement grout. There are many micro-cracks between the stones and the ossified cement grout. Under load, the number of the micro-cracks increases; the micro-cracks expand and eventually become macro-cracks, which result in the failure of the structure. The continuous damage in concrete is recognized by researchers. Concrete is also a time-dependant material. Creep is one of its time-dependent properties. The constitutive relation is very important for the computational mechanics. There are not many research jobs on the concrete nonlinear viscoelastic relations, and the damage is not considered in many jobs. With the development of the computer skill, to develop concrete nonlinear viscoelastic constitutive relation is not only reasonable but also realistic. In this paper, using the elasticity recovery correspondence principle and the nonlinear viscoelastic continuum thermodynamics, we utilize the irreversible thermodynamics to get the nonlinear viscoelastic relations with damage.In the end, we use the constitutive relations with damage and these without damage to analyze the uni-axial concrete compression experiment under different constant strain-rates, so it is validated by mechanical simulation. We find that when the strain-rate is low, we should use the constitutive relations with damage to predict; when the strain-rate is high, we should use the constitutive relations without damage to predict. The elastic recovery correspondence principle can be applied to analyze the concrete, which makes a new research method for the concrete nonlinear viscoelastic problem.