Numerical Modeling of the Stress-Strain State of a Prestressed Physically Nonlinear Reinforced Concrete Shell

Abstract

Objective . This work is devoted to a quantitative assessment of the effect of internal prestressing of reinforcement on the stress-strain state and load-bearing capacity of a thick-walled cylindrical shell. Method . The study is carried out through a computational experiment using the finite element method in an axisymmetric formulation. The physical nonlinearity of concrete is described by the Sargin diagram, the parameters of which are verified according to Eurocode 2 data. Result . An iterative algorithm based on the method of variable elasticity has been developed for correcting the secant modulus of concrete deformations. The reinforcement is modeled discretely, and the prestressing effect is specified as initial stresses in the reinforcement elements. The modeling results showed that for a cylinder made of B40 concrete with a reinforcement percentage of 3.11%, failure under internal pressure is of a deformation nature and is associated with reaching ultimate tensile strains in the concrete, rather than with the exhaustion of compressive strength. The ultimate internal pressure for a non-stressed structure is 0.55 MPa. A hoop prestressing threshold of 265 MPa has been determined. Exceeding this threshold causes unacceptable tensile stresses in concrete even before the initial operational phase. It has been shown that the optimal hoop prestressing level of 250 MPa allows for doubling the ultimate internal pressure to 1.1 MPa. Conclusion . The developed numerical model and calculation algorithm enable predicting the behavior of reinforced concrete structures, taking into account the actual properties of materials and process factors. The obtained results demonstrate the high effectiveness of prestressing for thick-walled cylinders and highlight the need to control not only the strength but also the deformation criteria of concrete failure.