Modeling and analysis of precast concrete beam based on unified theory of concrete

Abstract

A reinforced concrete structure may be subjected to four basic types of actions: bending, axial load, shear and torsion. All of these actions can, for the analyzed and designed by a single unified theory based on the three fundamental principles of mechanics of materials: namely, the stress equilibrium condition, the strain compatibility condition, and the constitutive laws of concrete and steel. Because the compatibility condition is taken into account, this theory can be used to reliably predict the strength of a structure, as well as its load–deformation behavior. Concrete and steel bar are idealized as uniform and continuity materials, smeared (average) stress-strain relations of concrete and steel bars should be used. The smeared stress-strain relationships of concrete for precast concrete beam have been proposed in soften compression curve and stiffening tensile curve. This study proposes a smeared stress-strain relationship of steel bars embedded in concrete. Also a Belarbi’s model is proposed, the analytical approaches are stated. Using the smeared stress-strain relationship of concrete and steel bars for model of precast beam. In this study, the pre-cast concrete beam has been modelled and analyzed when subjected to two point loads at one third spans from each support, using Finite Element Analysis tool, popularly called ABAQUS software. The modelled and analyzed precast beam cross-section having size 120mm×80mm with 2 numbers of 12 mm diameter bars as bottom reinforcement,12mm diameter bars as top reinforcement and 6 mm diameter at 150 mm c/c as shear reinforcement. The behaviour of the analyzed precast beam has been observed in terms of the flexural cracking, crack pattern, failure load, bucking failure of the stirrups, and maximum deflection. Based on the analysis carried out on the pre-cast beams using ABAQUS Software, it is found that results are more sensitive to mesh size, compressive strength, dilation angle, viscosity parameter, and static load. The model is validated using different experiment results for pre-cast beam elements presented in the literature. Comparison is made between the experimental results and finite element analyses with respect to initial crack formation and the ultimate load capacity of precast beams. The results indicate a good agreement with load vs. deflection curve and observed crack patterns.