Stress-based design of reinforced concrete structures

Project data

Short description

The objective of the project is to develop a novel design concept for steel-reinforced concrete structures that is stress-based while accounting for the nonlinear behavior of the composite material. The hypothesis is that the proposed approach will lead to more economical design results than elastic stress-based concepts. Design concepts based on internal forces are already more efficient than purely elastic approaches and will therefore serve as a reference in validation benchmarks. The intended field of application comprises very deep beam-, plate-, and shell-like structures as well as structures with general three-dimensional geometries for which design based on internal forces is not applicable. The first phase of the project will initially focus on problems involving biaxial load transfer, such as deep beams.

The fundamental methodological idea of the project, which is being conducted jointly with the Institute of Structural Analysis and Dynamics (IBB) at the University of Stuttgart, is to generate the required amount of reinforcement using an FE program developed by the IBB in an iterative growth process. As part of a feasibility study, the concept of automated reinforcement growth based on materially nonlinear analyses has already been successfully implemented and demonstrated prototypically for a simple tension member.

The iterative analyses of the reinforced concrete structure account for the materially nonlinear behavior of concrete and steel as well as their nonlinear interaction. In addition to axial forces, the reinforcement elements will also be capable of transmitting bending moments, particularly to represent dowel action, which is important for the economical design of shear reinforcement. To model the mechanical interaction between concrete and steel in the cracked state while accounting for the bending stiffness of the reinforcement, an appropriate bedding model transverse to the bar axis needs to be derived based on findings from experimental investigations. In addition to questions concerning the mechanical and numerical modeling required for the structural analyses, a concept for reinforcement generation, including appropriate criteria, rules, and their algorithmic implementation, must be developed. Finally, the overall concept will undergo systematic numerical and experimental validation.