Extending the design space of concrete structures using stay-in-place flexible formworks with integrated textile reinforcement

Abstract

The ability to create almost any shape makes structural concrete one of the most versatile construction materials, with a high potential for material-lean structural design, such as vaulted shells or ribbed slabs. However, conventional formwork technologies to build such structures are associated with time- and cost-intensive fabrication procedures due to the laborious erection of the scaffolding and the complex reinforcement layout. A potential approach for more efficient construction of concrete structures with complex geometries is the KnitCrete technology developed at ETH Zurich, which is a stay-in-place flexible formwork system that makes use of weft-knitted textiles and can be activated as reinforcement by using technical textile materials, which typically exhibit high tensile strength and are not affected by corrosion, allowing the design of slender elements since no minimum concrete cover is required. Thereby, the proper design of connection details is crucial to ensure the stress transfer between the concrete and the textile. However, textile reinforcement materials display a brittle failure behaviour. This study addresses the implications of brittle material behaviour on the global structural response and how textile reinforcement integrated in stay-in-place formworks may be applied in the design of concrete structures. The combination of brittle and ductile materials and the exploitation of the complex load-bearing behaviour of doubly curved shell structures are two strategies to induce an adequate post-cracking response that ensures compliance with design principles known from conventional reinforced concrete despite using brittle reinforcement materials.