Development of a Reliability Framework for the Use of Advanced Nonlinear Finite Elements in the Design of Concrete Structures

Abstract

This paper proposes a methodology that uses advanced nonlinear finite-element analysis for determining a global resistance factor for the design of reinforced concrete structures. It introduces a new reliability approach that takes into account the uncertainties of the material properties and the performance of the concrete model used in the calculations. In the proposed approach, the global resistance factor is computed following a procedure in which the coefficient of variation of the calculated resistance is estimated using Rosenblueth’s point-estimate method. The robustness and simplicity of the method are demonstrated through validation examples. It is seen that good approximations of the resistance factor can be achieved for the case of normal or quasi-normal distributions of the resistance. Estimation of the coefficient of variation of the prediction error is then performed for a given reinforced concrete element and a nonlinear finite-element package. The accuracy of the selected software is considered through its ability to predict the behavior of a set of benchmarks selected for the target design structure, going from the material level to the structural level. The suggested methodology is well suited for structural engineers having access to nonlinear deterministic finite-element packages with concrete models. It proposes a reliability format that focuses on the variability on the resistance side while using the concept of critical load paths on the load side, which is compatible with the philosophy of the existing design codes.