Optimization approaches for robust and durable reinforced concrete and fibre concrete structures under consideration of scale bridging polymorphic uncertainty modelling
A continuation of the topic is currently taking place in the second project phase.
The objective of this project is the development of computational reliability and optimization methods for the lifetime oriented design of reinforced and steel fibre concrete structures, which allow to follow the influence of uncertain, i.e. non-deterministic describable design parameters and uncertain time variant structural actions on the structural state throughout its life. Thereby, interactions between loading induced damage and environmentally induced deterioration processes are considered by multiscale models in conjunction with physically sound durability models, see Figure 1. The structural reliability is computed by multifield simulations under consideration of polymorphic uncertain data (stochastic parameters, intervals and fuzzy numbers as well as generalized uncertainty models).
Multiscale modelling strategy to follow time variant uncertainties through various spatial scales
For the numerical structural design, optimization approaches with polymorphic uncertain data are developed, with the structural robustness and durability as the objectives, considering accepted probabilistic serviceability and safety measures and aspired lifetimes as constraints. The design parameters and respective critical components of the structure (“hot spots”) are determined from sensitivity analysis. For solving the resulting optimization problems considering uncertainties of the loading and of deterioration processes, respectively, the original structural model will be substituted by highly efficient surrogate models. In addition, a concept for numerical accelerated life testing is developed.
Selected scientific questions addressed in the first phase of the project include:
- How do uncertainties connected with design parameters at the lower (material) scale (e.g. concrete composition, fibre distribution, steel-concrete bond properties), propagate through the scales and affect the concrete durability and, as a consequence, the structural reliability?
- How does the reinforcement technology (fibres vs. conventional reinforcement) affect the robustness of the structure? How could hybrid approaches further improve robustness?
- How do construction related tolerances and human induced imprecisions affect the structural reliability and lifetime?
Essential project findings
- sub-modelling strategy for the simulation and analysis of crack pattern in reinforced concrete structures
- uncertain bond behaviour has a main influence on the crack behaviour
- load displacement curve is not significantly influenced by the bond behaviour
- reduction of the computational effort during optimization by space subdiving method and multilevel surrogate modelling strategy
- intervall radii have a main influence on the optimization results
- small variations of the stochastic parameters can have a huge influence on the limit state function and the objective function
