Abstract
The development of fiber-reinforced composites (FRP) began about 60 years ago. At the beginning of this period the first body parts for the Corvette were produced from FRP. The fi rst glider was constructed of fi berglass-reinforced plastic at the University
of Stuttgart. Between 1956 and 1970, approximately 70 different plastic types of houses had been developed. Some of the unique plastic houses, like the Monsanto House, Futuro, Rondo, etc., are still regarded as examples of developments during this period.
Despite the enormous public response these houses disappeared back in the 70s. This was due in part to the building design and building physics problems and in part to the lack of an appropriate architectural implementation.
In the last two decades, the use of CFRP composites as a reinforcement for concrete members has emerged as one of the most exciting and promising technologies in materials / structural engineering. They have risen in importance due to their ideal
material properties, namely light weight, fl exibility on site and interesting areas of application. They are used primarily for the rehabilitation and strengthening of support structures and present here a performance alternative to conventional steel plates.
Due to the high price of CFRP-Strips their application today is mostly found in buildings, where their strength is highly utilized and the strips are needed in small quantities, e.g. for the strengthening and rehabilitation of reinforced concrete structures.
The CFRP-Strip is glued to the concrete structure with an epoxy resin mortar. In this case, about 12% of its tensile force can be utilized. Due to the high cost of carbon fi ber material, this significant restriction reduces the effi ciency of this process.
In the meantime, new developments and research focus on direct gluing of pre-stressed CFRP-Strips on reinforced concrete constructions in order to improve their stability. The applied prestress increases the degree of utilization for the CFRP-Strip, while at the same time the pre-stressed CFRP-Strips need to anchor their force locally into the concrete. This is not easy due to the sensitivity of the carbon fi bers to transverse loads. The development of CFRP-Strip anchorage is presently under investigation in many research institutions and universities.
This strip could also be used for external prestressing of bridges or for slabs building structures. Because of the fl at and broad cross section of a CFRP-Strip, the lateral strain at the bearing saddle and the end anchorages is smaller than that induced by circular tension members, and this may be of advantage. At present, knowledge of the deviated CFRP-Strips is still missing: How does load bearing capacity change, if the CFRP-Strip is deviated on a saddle and stressed?
The aim of this work is to gain an initial understanding of diverted FRP strips to evaluate their suitability as external tendons. For this purpose, the work is divided into two main parts.
Part 1: Static tests on deviated CFRP-Strips The fi rst part consists of a series of experiments to determine the load bearing capacity, strain responses up to failure and the failure mode of CFRP-Strips at different deviation saddle geometries.
Part 2: Experiments with a relative movement to the Deviation saddle
A very important effect was not being captured by the Experiments in part 1, namely the movement of the strip on the deviation saddle during the prestressing process. Furthermore, the deformation of the strip which occurs under loading can infl uence the fracture load. In order to capture this effect, experiments with relative strip
movement to deviation saddle were carried out according to the ETAG 013, Annex B5.1.
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