Investigation of Strain Evolutions in Prestressed Reinforced Concrete Beams Based on Nonlinear Finite Element Analyses Considering Concrete Plasticity and Concrete Damaged Plasticity

This study provided an investigation of strain evolutions in bonded and unbonded prestressed reinforced concrete beams via nonlinear finite element analyses considering concrete plasticity and concrete-damaged plasticity. Usually, non-convergence problems often occurred during analyses of prestressed beams due to drastic increase in contact stresses during stress transferring stages and material softening at large deformations. To avoid this issue, material models with gentle softening behaviors can be used. However, authors introduced a method of employing automatic stabilization using damping factor and viscosity parameters to enhance convergencies. Preciseness of models was then verified by test results of ten beams from referenced researches. Furthermore, strains evolution in concrete, rebars, and tendons was investigated. It is noticed that material inelasticity characteristics make the rate of strain activation unique in defining structural performances of beams under loads. However, this concept is not frequently introduced because measuring the strains in experiments was complicated, while most researchers are only interested in load–deflection relationships and conditions at failure stage. This work demonstrates element strains as functions of deflections to show strains activation mechanisms of structural components. The study offered knowledges which can not only enhance material utilization, but also improve the ductility of prestressed beam designs.