From Jointing Systems to Light-Weight Structures: Hybrid, dry-fit beam, surface and spatial structures made of UHPFRC

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As part of the ongoing SPP1542 the applicants are working on the subproject: development of novel jointing systems for geometrically complex surfaces and beam elements made of UHPC. Focus of the investigation is the development of dry fit jointing systems for thin UHPFRC components for the transmission of compression, bending and shear forces. The main approach is to achieve a high mechanical efficiency through increased precision and geometric complexity in the jointing area. Besides precise fitting the components are axially prestressed by integrated tendon elements. The novel jointing systems are being developed for the following UHPFRC components: Axial loaded and dry fit thin walled pipes for the transmission of compressive forces, bending stiffness node elements of thin walled tubes for guiding forces in beam structures, as well as line shaped dry fit jointing systems for accurate assemble of segmented shell components. The objectives identified in the first funding are reached by the end of the first research-period. The results so far have been published several times. The aim of the subsequent application is now to transfer the previously developed new jointing principles for UHPFRC components into powerful light weight beam, surface and spatial structures. The goal is to increase the load bearing capacity of structural components and systems by intelligent coupling of individual modular beam and shell elements into hybrid, cooperating supporting elements and systems. By combining dry fit rods associated with shear resistant, flat or curved surface elements a variety of relevant building structure types can be realized mainly from the bending load bearing structures towards optimized shells. The preconditions of the first project phase remain valid: Using UHPFRC to improve tension resistance and post cracking behaviour, dry fit jointing and efficient material utilization through prestressing. Since in this research project not all possible combinations of beams and shells in their geometric diversity can be investigated, exemplified three relevant construction practice cases from the possible support element combinations for the research program are selected: combination of beam and shell elements into a uniaxial prestressed girder element, combination of beam and shell elements into an orthogonal biaxial prestressed surface structure and combination of beam and shell elements into curved spatial structures. Depending on the geometric constraints the resulting hybrid structural systems and elements in three dimensional space can work as beams and surfaces as mainly bending loaded component or function as membrane structure.