OPTIMIZING REINFORCEMENT LAYOUT IN CONCRETE DESIGN CONSIDERING CONSTRUCTABILITY

摘要

Structural topology optimization is increasingly being used to remove the guesswork in identifying natural force flow paths for reinforced concrete and prestressed concrete, particularly for complex 3D design domains. Tension and compressive forces that follow the principle stress trajectories, i.e., ties and struts, are automatically identified with topology optimization using a formulation that minimizes strain energy, or equivalently that minimize crack widths. While a useful alternative to trial-and-error process of generating strut-and-tie models (STM), the approach falls short of design objectives as it neglects constructability and rebar detailing, which is often the governing cost. This paper uses a new advancement in topology optimization for addressing constructability issues by considering both material and construction costs. By assigning different construction costs for each tension tie (rebar or prestressing), the placement of steel can be controlled to a large extent by the designer, thus it is capable of generating practical designs that also perform well in service. A hybrid truss-continuum FE model with bilinear orthotropic material properties is used to generate the optimized strut-and-tie models that can be used directly for design and detailing. Results demonstrate that the designer gains the ability to explore tradeoffs between material and labor cost while maintaining reinforcement layouts that ensure structural integrity at service and ultimate limit states.