Experimental and theoretical investigations of a new bond-type anchorage system for post-tensioning applications with FRP tendons

Abstract

Fiber reinforced polymer (FRP) composite rods appear very promising to be used as an alternative to steel in prestressed concrete structures and ground anchors, especially for applications exposed to corrosive environments. The objectives of this study are to investigate the bond behavior of FRP rods to grout filled in steel tubes and hence to develop a competent bond-type anchorage system for post-tensioning applications with FRP multirod tendons. The research program includes pullout tests of grouted FRP rods and proving tests of the developed anchorage system for post-tensioning applications. Modeling the bond behavior and predicting the load bearing capacity of bond-type anchorage systems are also involved. Numerous (over 50) pullout tests were conducted and discussed to better understand bond mechanisms and the influence of type of fiber, outer surface, and other significant parameters (i.e., confining stiffness, grout type and curing condition) on bond performance. Modeling of bond-slip behavior of grouted FRP rods is examined to assess its adequacy to reproduce the experimental bond behavior. Based on the monitoring results of strain distribution along the bonded length, the working mechanism of bond-type anchorages for FRP tendons is discussed. A conceptual model for calculating the bond stress at the tendon-grout interface and the tensile capacity of bond-type anchorages for FRP tendons is established. A new bond-type anchorage system has been developed for post-tensioning applications with FRP tendons. Evaluations of the developed anchorage system have been conducted in anchorage models with CFRP mono- and 9- rod tendons under tensile and sustained loading conditions. Furthermore, the developed anchorage system has also been used as an anchor head for post-tensioning of a full-scale FRP anchor model. Primary test results have indicated that the developed bond-type anchorage performs well for post-tensioning applications with FRP tendons. Conclusions and recommendations are made on the design of bond-type anchorages and post-tensioning applications of FRP tendons. Six related papers have been published in referred journals or international conferences, including two papers in the ASCE Journal of Composites for Construction , one in Construction and Building Materials (UK), one in the Canadian Journal of Civil Engineering , and two in the international conferences.