Integration of manufacturing and structural design of 3D concrete printed bridges

Abstract

3D concrete printing (3DCP) is a new, innovative construction method in which concrete structures are produced layer-by-layer using a 3D printer. A printed concrete structure, can be self-supporting, which means no formwork is required anymore, increasing the freedom of form, while decreasing construction cost and material use. However, the engineer designing 3DCP structures is challenged, because the construction process is completely different than from designing conventional concrete structures. The fresh concrete structure must be stiff and stable enough to resist the increasing self-weight of the subsequent layers and the material properties can become anisotropic due to a limited bond-strength between two layers. The objective of this research is to integrate the manufacturing process into the structural design of a simply supported 3DCP cyclist bridge, to provide guidelines for designers and for future research. Using a parametric research model, the performance and feasibility of the design can be assessed as a function of 22 parameters describing the bridge geometry, material properties (fresh and hardened) and printing process parameters. The model is built in Grasshopper and Python by using analytical formulations only. The use of FE software is omitted to make the model as fast as possible. Like this, a global sensitivity analysis based on thousands of parameter combinations could be conducted, revealing the most important parameters for determining the design's performance and feasibility, as well as the absolute effect of specific parameters. These results were used in an optimisation run, seeking the most cost-efficient and sustainable design. The research shows that integrating the manufacturing process into the structural design of 3DCP objects yields more optimal designs and the analytical model that has been developed has proven to be a useful tool for research and design.