Starting in the late 1970s with an ad hoc committee, Multiaxial Behaviour of Prestressing Steel, FIP Commission 2 undertook to develop a significant method for testing the susceptibility of prestressing strand under combined transverse and longitudinal loading. It was noted that deviation of strands in the anchorage zone may reduce tensile capacity. The same situation occurs in the case of strands in the deviation zones of saddles.
It was already known that bending tests on wires are a useful method for selecting appropriate production of this prestressing material and that they are accepted requirements in current standards.
A first description of the so-called FIP deflected tensile test was given in FIP Notes 1987/1. This was the result of several years of work under the convenor J. F. P. van Herberghen (Belgium). The aim of the test, also known as the “one-pin test”, is to determine the breaking force of a strand in the deflected (deviated) mode.
Because users and producers of prestressing strand required an accepted method of guaranteeing safety during installation and ensuring adequate manufacturing control, the test has found acceptance in many national standards for prestressing steel and is also proposed in the CEN standard for prestressing strands (prCEN-10138). However, the work of the ad hoc committee (then with a new convenor, B. Creton (France)) had to continue. Test results from different laboratories were not sufficiently reproducible. Therefore, the test needed to be refined in order to develop a new method acceptable to both users and producers.
After the resignation of Mr Creton (1990), Mr G. Hampejs (Austria) guided the Working Group with distinction.
The results of this extensive work, to which seven laboratories contributed through comparative testing, are presented herewith.
This FIP deflected tensile test is a very comprehensive method for improving the quality of prestressing steel and increasing the safety of prestressed structures. It is the second test developed by FIP Commission 2 (besides the corrosion test) in the last decade.
My thanks go to the above-mentioned convenors of the Working Group, and my congratulations to Mr Hampejs.
H. R. Müller
Chairman
Commission 2 – Prestressing Materials & Systems
