Finite element crack width computations with a thermo-hygro-mechanical-hydration model for concrete structures

Abstract

The paper presents an overview of a finite element approach for the analysis of the thermo-hygro-mechanical-hydration behaviour of concrete structures. The thermo-hygro component considers the mass balance equation of moisture as well as the enthalpy balance equation, and uses two primary variables, namely the capillary pressure and temperature. Heat of hydration is simulated using the approach of Schindler and Folliard. The basic mechanical model simulates directional cracking, rough crack closure and crushing using a plastic-damage-contact approach. Hydration dependency is introduced into the mechanical constitutive model. The material data from the Concrack benchmark are considered with the model. This includes data on adiabatic temperature changes during curing, changing elastic properties during curing, shrinkage and creep. The model, as implemented in the finite element program LUSAS, is used to analyse the Concrack benchmark beam RL1. Particular attention is paid to crack openings and the difference between predicted crack openings from analyses with and without time-dependent effects. It is concluded that ignoring time-dependent effects can result in a significant underestimate of crack openings in the working load range.

Keywords:

• concrete
• plasticity
• damage
• hydration
• shrinkage
• creep
• cracking