No abstract

The building industry, and especially the concrete industry, consumes a considerable proportion of the natural resources extracted from the lithosphere and is responsible for a large part of the solid waste generated worldwide. Unfortunately, this fact has not yet generated a movement to counter the trend; rather, a huge increase in the use of concrete in new structures can be observed. It is imperative to counteract this development by optimally exploiting the material properties of concrete in order to improve its efficiency. One strategy being pursued at the University of Natural Resources and Life Sciences, Vienna and TU Wien is to reduce the amount of concrete and reinforcement in structures by using high‐performance materials such as carbon‐fibre‐reinforced polymers (CFRP) in ultra‐high‐performance concrete (UHPC) members. This permits a crucial reduction in the self‐weight and allows for the design of very lightweight precast concrete elements. The authors' goal is to use CFRP rods as bending reinforcement and a combination of flat and preformed CFRP textiles as shear and structural reinforcement. In the first part of this paper, the research approach is introduced and a comprehensive overview of the state of the art of UHPC and CFRP reinforcement is given. The second part contains a description of the conceptual design of some structural members (one floor element and two T‐beams), starting with the development of a suitable UHPC mixture. Furthermore, preliminary uniaxial tensile tests of textile‐reinforced UHPC strips are described and evaluated. In the final part of this paper, the authors present parameter studies for different reinforcement types, values, additional prestressing of the rod reinforcement and the first prototypes. They are used to give an estimation of the feasibility, the load‐bearing and deflection behavior of the proposed building components.

Textilbewehrung ist ein innovativer Werkstoff, der es ermöglicht, leichte, filigrane Bauwerke auch im Betonbau umzusetzen. Der Werkstoff besteht aus Multifilamentrovingen, die nach heutigem Stand der Technik mit einer Tränkung aus Reaktionsharzen oder wässrigen Dispersionen versehen werden, um die Verbundeigenschaften zu verbessern. Untersuchungen, die am Institut für Tragkonstruktionen der TU Wien durchgeführt wurden, haben gezeigt, dass bei hohen Beanspruchungen vor allem epoxidharzgetränkte Textilien zum Abspalten der Betondeckung neigen. In diesem Zusammenhang wurden weiterführende Untersuchungen vorgenommen. In dieser Veröffentlichung wird versucht, die unterschiedlichen Einflussparameter auf eine beginnende Spaltrissbildung zu identifizieren und zu quantifizieren. Dazu sind Verbunduntersuchungen an Rovingen durchgeführt worden, an denen die einzelnen Einflussparameter separiert wurden. Es konnte gezeigt werden, dass vor allem die Querschnittsgeometrie und die Längsform der Rovinge eine entscheidende Rolle auf das Verbundverhalten und die Entstehung von Spaltrissen hat, wohingegen der Knotenwiderstand von untergeordneter Bedeutung ist. Aufbauend auf diesen Untersuchungen können Überlegungen zur Modifizierung von bisher am Markt erhältlichen Textilien vorgenommen werden, um eine Neigung zur Spaltrissbildung zu verringern.

No abstract

The production of the formwork and falsework for shells built using conventional construction methods requires considerable input. As is known, labour costs in industrialized countries have increased over recent decades in comparison to the costs for construction materials. Consequently, the practical application of shells has decreased and the aforementioned building technique has hardly been employed in the last 30 years. Recently, architects and engineers started to integrate free-form concrete surfaces in their building designs once again. State-of-theart design software and industrial engineering methods save costs and provide the technologies for building shells in an economic way. One example of an impressive posttensioned shell structure measuring 93 × 52 m was built in Chiasso, Switzerland [7]. The formwork, shown in Fig