This paper presents an experimental investigation of digitally manufactured, reinforced concrete beams designed with topology optimization. The backbone of the current work is a hybrid mesh topology optimization algorithm that automatically generates strut-and-tie layouts. The resulting designs have tensile truss elements describing the reinforcing phase and compressive continuum force flow elements that illustrates how the concrete is carrying load. The aim of this work is to investigate the effect of removing a percentage of the non-load carrying concrete phase. A beam is designed with a standard, by-hand approach and the same steel amount is used in to generate a topology-optimized design. This work considers three beam designs; (i) the standard, (ii) a topology-optimized beam with a prismatic section (i.e. 100% concrete), and (iii) the topology-optimized steel layout in a beam with a reduced concrete volume (herein 75%). An alternative reinforcement method is used in which steel plates are cut by waterjet. To improve the bond quality between concrete and reinforcement, corrugations and anchors are added to the steel layouts. However, as opposed to previous experimental tests conducted by the authors, a poor bond quality is achieved, leading to premature failures of all test specimens. Due to the lack of proper bonding, comparison can only be made in the early elastic range. Here, a significant trend is that the by-hand and the topology-optimized specimens with 75% concrete exhibit near identical behaviors.
With the rise of interest in digital fabrication of reinforced concrete structures, a great number of structural concrete designs that depart from standard prismatic shapes are being suggested. This has prompted an exploration of steel reinforcement strategies that are alternative to the classical deformed or “ribbed” rebars. One such is to cut internal reinforcement from steel plates using a waterjet cutting machine. Advantages of automated waterjet cutting steel reinforcement include high precision and accuracy, and minimal expense for increasing the complexity of (2D) reinforcement layouts. However, it is not known how the application of ribbing patterns along the cut edge of reinforcing bars affects the steel–concrete bond. This work conducts experimental pullout tests of waterjet-cut steel plate reinforcement with three different ribbing patterns and compares the bond strength with equivalent classic rebars. Two of the tested geometries averaged within 90–91% of the pull-out force of conventional rebar, demonstrating viability of this alternative reinforcement method.
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