Carbon Fiber-Reinforced Polymer Composites (CFRPs) have been used as tensile members for 25 years in prestressed concrete pilot applications, and recently as hangers in network arch railway bridges. Despite their widely accepted advantages with respect to prestressing steel, they are still not state of the art in pretensioning and post-tensioning tendons, nor in bridge hangers or cables. Some of their first commercial applications in pretensioning precast high strength concrete members where in the years 2000-2005, when CFRP tendons were used for power line and lighting poles and for prestressing façade beams. Empa, The Swiss Federal Laboratories for Materials Science and Technology, introduced novel applications of CFRP reinforcements for structures in the 1990s such as the externally bonded and/or prestressed flexural and shear reinforcement of reinforced concrete and steel structures, CFRP parallel-wire post-tensioning cables for bridge girders and CFRP pre-tensioning of precast high performance concrete. In the last decade one focus of Empa's CFRP research in collaboration with its spinoff Carbo-Link was on novel pin-loaded looped straps as durable hangers for arch bridges. Nowadays, highly loaded tensile elements made of CFRP are well established e.g. in the sailing industry and for crawler cranes, where they are used to replace corrodible and comparatively heavy steel rigging systems.

For the use of unidirectional CFRP strap hangers in the Stuttgart network arch bridge, and in a subsequent German railway bridge project, a single type approval by the responsible authorities was requested and obtained. This involved comprehensive testing programs performed at Empa in 2017-2020. However, design considerations limited the design strength of the CFRP strap hangers due to the limited amount of fatigue and tensile tests data available.

This PhD project aims to explore the strength and durability limits of modern unidirectional Carbon Fiber Reinforced Polymer (CFRP) tendons for bridge engineering applications. The ultimate aim of the project is to formulate new design recommendations to better use the full mechanical potential of CFRP tendons for prestressing and cable applications in different civil engineering environments.