Chris Burgoyne
Department of Engineering, University of Cambridge, UK
Test have been carried out on two
beams prestressed with parallel-lay aramid ropes (Parafil) to demonstrate the
feasibility of producing structural elements in this way. This paper summarises
the tests that been carried out, and the results that were obtained. Full
details of the tests are given elsewhere. The tests were carried out by the
author and his co-workers Dr. J. J. Chambers and Dr. G. B. Guimaraes at
imperial college in London.
The work was sponsored by Linear Composites Ltd.
Parafil ropes contain a core of
parallel filaments of yarn within a thermoplastic sheath. A variety of core
yarns can be used; in the case of the Type G Parafil, the yarn used is a stiff
polyaramid yarn. The combination of high yarn strength (2760 N/mm2)
and stiffness (126 kN/mm2) makes this version of the rope suitable
for structural applications, particularly prestressing tendons for concrete.
Figure 1 shows the short term
stress-strain curve for 60 Tonne nominal breaking load (NBL) tendon, as used in
these test. The response is essentially linear, with slight stiffening once the
load exceeds about 50% of the NBL. This stiffening is also observed in the
response of the fibres themselves and is not due to the rope construction.
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