Jointing Principles for Combination of Concrete Elements Produced by Different Additive Manufacturing Processes
Utilizing the additive manufacturing (AM), (particle-bed processes, extrusion and shotcrete), facilitates resource-efficient segmental concrete construction. In which joints' performances and their production methods play a crucial role, affecting analysing and assembling approaches. Three different types of connection in such a structure are feasible, including dry joints, adhesive joints and mortar joints. Due to various issues such as the necessity of formwork, scaffolding and curing, dry joints are broadly preferred. Utilizing particle-bed printing method or post-processing technics in other printing methods develops an automated construction approach, for producing printed-precast segmental constructions. Thus, this project, through experimental and numerical analyses, investigates the correlation between the joints' production methods and the joints' load-bearing capacities, regarding different AM materials. Accordingly, C05 gains fundamental experiences for further development and application of resource-efficient AM components in construction.
DFG – German Research Foundation within CRC / TRR 277 - C 05
Project Aims/ Working program
This project aims to investigate the execution process and load-bearing capacity of the joints, to adaptively, be utilized in the construction of post-tensioned segmental beams and shells. In this study, four types of concrete-printing technics and materials, produced with two loading types, evaluate the compressive and shear resistance. In the first step, the research is pursued by finding the optimal geometries of two profiles, preparing the clamping system and initial evaluation of the CNC process. It will be followed by production and compressive tests of the profiles, applied to the concrete specimens prepared by different printing technics (AM). Subsequently, the performance of these profiles and materials against the shear load will be investigated. Furthermore, the monolithic elements, the flat connections, and printed layers' angles should also be analyzed and compared. Ultimately, based on the studies, a large scale segmental girder beam will be produced. The result of this experimental test will be used in developing the analytical approach of a post-tensioned segmental girder.
In 2017, by extrusion technics, the first post-tensioned segmental pedestrian bridge was constructed. In this construction mortar joints were used, in comparison to cast in place bridges could save time and cost, coming from unnecessarily falsework and installation process. CNC technique can assist in the execution of the high accuracy geometries, which should be investigated based on tests; since no explicit regulations for the dimensional accuracy of dry joined components are in the normative rules provided. Studies on the dry joints' load-bearing capacity and investigations on their performance as segmental components were widely carried out, in which conventional concrete and production method were used. Based on these studies, an analytical approach for determining the load-bearing capacity of normal strength dry joints was proposed.
Besides testing machine and FE software, this study enjoys the robot-based CNC process for evaluating the resistances of different profiles and materials [Fig 2]. Hereof, the CAD software along with the CNC simulation software, produce the G-codes, which can be sent to the robot to determine the moving directions, angles of the arm, type of milling tools, etc. of the robot. For the CNC simulation, the raw material and clamping systems dimensions, along with coordinates, should be measured and introduced to the CNC software. During, the milling process a wide range of the parameters, should be respected to reduce the tolerances, smoothness and probability of causing damages.