Short-term sustained loading of FRP tendonanchor systems

Abstract

The scope of the paper is to provide a short-term evaluation of some commercially available frp tendon-anchor systems for application in prestressed concrete structures. Ten frp tendon-anchor systems were stressed and subjected to sustained load for a period of three days to determine ease of installation, mechanical performance and anchor seating losses. The frp tendons used aramid, carbon, and glass fibres embedded in epoxy or vinyl ester resin (except for one case). Anchors were of the wedge (or spike) and potted type. A minimum of two tests were conducted for each system at a load level equal to 65% of the manufacturer's specified ultimate tendon strength. Collected data included load, strain, and displacement readings during both initial stressing and three-day sustained load. In most cases, anchorage devices permitted the stressing of the frp tendons at the desired load level. Among wedge-type anchors, plastic and aluminium wedges had questionable performance, whereas steel wedges (in direct contact with the tendon or using a metal sleeve between tendon and wedge) showed good performance. Regardless of wedge material (plastic, aluminium, or steel), grit application to the wedge internal surface was highly beneficial. The spike anchor presented some installation difficulties. Resin potted anchors worked well and were easy to install. For the one case considered (wedge anchor), it was determined that retensioning produces early failure and anchor-zone temperatures between −40 °C and +60 °C have no effect on system performance. Anchor seating losses during short-term use are in general small and could become insignificant depending on the length of the tendon.