Importance

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Abstract

A composite material, particularly useful for prestressing concrete and in stay cables for cable-stayed bridges and other such uses where strength, corrosion resistance and resistance to fatigue failure are particularly important, comprises high strength wire strand coated and impregnated with an impermeable and strongly adherent epoxy based resin. The impregnated and coated epoxy increases the flexural stiffness of the composite against bending fatigue in the areas of the anchorages in dynamically loaded situations and reduces relative movement and rubbing of the wires of the strand so as to reduce fretting and hence fretting fatigue, the principal mechanism for failure in dynamically loaded strand. Impregnation and coating are effected by passing the fully formed and heated strand through a known electrostatic powder coating line, modified to include a mechanism for temporarily opening successive sections of the strand such that the strand passes into the coater in an opened state, and the strand wires are coated with a fused thermosetting epoxy resin before the strand is permitted to reclose, the resin filling the interstices in the reclosed strand. The strand opening mechanism includes a rotatable template with wire guides for leading the outer spiraled wires temporarily away from the center wire, and can be used in any method where a formed strand or similar member needs to be opened for coating or otherwise surface treating the interior wire surfaces in a continuous process.

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First Claim