Connections for textile reinforced concrete structures: Fid-Bau Portal

Connections for textile reinforced concrete structures

Feldmann, Markus / Pak, Daniel / Geßler, Achim / Schleser, Markus

Overhead presentation. To allow for an extensive expansion of the application field for pre-fabricated parts of textile reinforced concrete in structural tasks, the design of connections between individual elements of an entire structure is of decisive importance. Particularly with regard to the set-up and assembling of lightweight framework structures the following joining techniques of thin textile-reinforced specimens have been investigated within the DFG-funded 'Collaborative Research Centre 532', an interdisciplinary collaboration of 11 research institutes at RWTH Aachen University: - detachable, punctiform joints with bolts, - permanent, plane adhesive joints, - detachable hybrid joints with bolts and inserted jackets. Parametric studies running tensile tests have been carried out with the primary objective to determine strength parameters of the different types of joints. Concerning the structural design of the connection it has to be assured that the ultimate resistance of the whole structure is not reduced. Joints with bolts reach up to 90 % of the tensile load bearing capacity of the gross cross-sections, if the edge distance between bolt and edge of the specimen is sufficiently large enough and some jacket is fitted into the borehole. For glued joints with adhesive systems on polyurethane base the full load bearing capacity of the gross cross-sections can be reached, provided there is sufficiently large adherent surface. Unfortunately they show comparatively large deformations. That disadvantage can be avoided through the application of high-strength adhesive systems on epoxy resin base. However, due to the occurrence of tension peaks, such adhesives do not quite reach the load bearing capacity of the gross crosssection. Hybrid joints combine the advantages of an easy assembly and disassembly on the one hand, and the two-dimensional transmission of force on the other hand. This joining geometry involves so-called 'collar jackets' which are inserted into the holes. The collar flange surfaces are bonded to the concrete surfaces by rigid epoxy resin adhesives. Due to the bonded collar surfaces the full tensile load bearing capacity of the gross cross-section can be reached: The tension stresses concentrated in the region next to the hole, perpendicular to the direction of load, are reduced by the collar of the jacket, since the jacket attracts these stresses and distributes them two-dimensionally in a homogenous way via the high-modulus adhesive to a larger area of concrete.