Structural performance analysis and numerical modeling of 3D-printed formwork systems

Abstract

The construction sector is frequently considered accountable for low productivity and is perceived as a sluggish adopter of new technology. It has been noted that the construction industry, in contrast to other sectors like the manufacturing industry, has not been able to take advantage, on a large scale, of the cutting-edge technologies in the last decade and has not shown any significant improvement in project delivery. Digital Concrete (DC) construction encompasses a broad range of digital technologies that can be implemented in the design and construction of concrete structures. 3D-printing of concrete is one of the facets of DC construction which involves layer-by-layer extrusion of concrete. The intended structure is therefore fragmented into the printing of several layers.

Owing to the nature of this method, i.e., laying filaments layer over layer to build a 3D shape, the behavior of printed concrete components varies significantly from those cast using conventional methods. The feasibility of printing concrete has been well-researched in recent years. One of the primary challenges identified in the 3D printing of concrete is the lack of methodologies to incorporate reinforcement. Engineered composites such as Engineered Cementitious Composites (ECC), Strain Hardening Cementitious Composites (SHCC), offer several advantages, few of which are enhanced tensile strain capacity, ductility, and durability by limiting shrinkage-induced cracking. These are significant limitations of traditional concrete. ECC/SHCC materials when used in the context of 3D-concrete printing can significantly optimize the structural performance of printed structures. Owing to these unique characteristics, these materials could potentially eliminate this significant limitation and make this technology more suitable for industrial applications. The potential benefits of composite materials in the context of 3D printing have been the subject of several studies, but there has not been sufficient research done on the numerical modeling of 3D-printed structures. To close this gap, the present research uses the Finite Element (FE) method to investigate the flexural and tensile performance of 3D-printed structures. The commercial FE software ABAQUS was used to establish various numerical models and tests to simulate the flexural and tensile behavior of the printed structures. Further, several researchers in the past have emphasized the use of 3D-concrete printing for the production of permanent formwork. This strategy allows several advantages, from complex geometries with sufficient load-bearing capacities to structural performance enhancement of the component. This application of the technology, despite the lack of standard code and design guidelines for the structural application of 3D-concrete printing, allows it to be incorporated in load-bearing components in commercial large-scale infrastructures. In this study, an experimental investigation on the bending performance of a small-scale beam with 3D-printed permanent formwork is carried out in order to ascertain the optimum thickness of the bottom-most section (which is subjected to the highest bending stresses) for best bending performance. Further, a numerical model corresponding to the experiment is also developed following the validated modeling strategies discussed in the earlier sections of this thesis to demonstrate the potential of the FE method for the analysis of complex systems.