Experimental investigation of topology-optimized reinforced concrete beams with varying volume Fractions

Abstract

Researchers have developed algorithms for topology optimization of concrete and reinforced concrete designs. However, concrete is a complex composite material and there is still a lack of validation of fabricated topology-optimized designs of concrete structures. It hinders the progress of incorporating topology-optimized structural components in the civil engineering industry. This work aims to address the issue stated above by experimentally evaluating deep reinforced concrete beams with strut-and-tie models (STMs) designed with the Hybrid Truss-Continuum Topology Optimization Algorithm [5]. The algorithm is chosen to alleviate the need for post-processing as it incorporates the discrete nature of the steel reinforcement in the design problem which allows continuous force flow within the concrete phase of the design. The hybridity, therefore, originates from a truss element ground structure design in the density-based continuum topology optimization framework. The resultant optimized truss elements represent the tensile load path whereas the optimized continuum structure indicates the compressive load path. When using STM to design reinforced concrete beams, there will be underutilized areas within the concrete phase where minimal force is predicted to be present. In this work, we experimentally investigate the consequences of removing material in these regions. The used algorithm [5] is adjusted to enable control of the volume fraction of both the reinforcing and the concrete phase. A preliminary relationship between the reduction in strength of the reinforced concrete beams and the extracted volume of the underutilized areas is explored. The design domain is a 2D prismatic deep reinforced concrete beam with dimensions 3 feet by 9 inches by 2 inches. The tested beams are simply supported with a single point load at mid-span. Using the same steel volume, concrete volume fractions of 75%, 85%, 90%, 95%, and 100% are presented and experimentally tested.