Porosity Effects on the Composite Girder by Rheological Dynamics and FEM

A theoretical model for porous viscoelastoplastic (VEP) materials in the dry state is investigated in this research study. The model is based on the principles of conservation of mass and energy using the rheological dynamic theory (RDT). The model provides expressions for the creep coefficient, Poisson's ratio, modulus of elasticity, damage variable, and strength as a function of porosity and/or void volume fraction (VVF). The reliability of the proposed model was analyzed by comparing numerical results with experimental ones on hardened concrete. A numerical model was created and analyzed in the commercial software Abaqus and validated by comparison with experimental data obtained by geodetic measurements on a composite wood-lightweight concrete girder. The deflections and stresses of the beam resulting from the influence of concrete creep and porosity were analyzed at the initial moment of time and after 6 years. The results showed that the RDT provided a reliable model for estimating parameters after exposure to long-term loads.