Nonlinear Analyses for the Design of Safety–Critical Concrete Structures

Nonlinear finite element analysis provides deep insight into the real structural performance and behavior. This contrasts with the traditional design approach, where typically elastic beam theory is applied. The nonlinear models consider the complex three-dimensional state of stress and simulate real material behavior, including crushing of concrete in compression, cracking in tension or yielding of the steel reinforcement as well as long-term rheological phenomena. Design guidelines and suitable safety formats for nonlinear analysis are becoming available in the new design codes such as the latest fib Model Code 2020 and the new generation of Eurocodes. An important aspect is the consistent treatment of model uncertainties. The safety formats considering model uncertainty will be briefly presented in the paper. Two case studies from the engineering practice will be presented demonstrating the feasibility and advantages of nonlinear analysis in the design and assessment of concrete bridges.