Effects of freeze-thaw cycling combined with fatigue loading on anchorage of fibre-reinforced polymer sheets bonded to reinforced concrete beams.

摘要

Strengthening reinforced concrete beams with fibre reinforced polymers (FRPs), both in flexure and shear, as well as wrapping reinforced concrete columns with FRPs are repair methods that are becoming more widely accepted and used. Extensive research has been completed around the world, demonstrating that these repair schemes are economical and very effective. Over the past few years, a considerable effort has gone into studying the durability of these FRP retrofit systems under environmental loading such as fatigue cycling and freeze/thaw cycling, especially in Canada due to the cold and harsh climate.; This thesis expands on this research, by studying the combined effect of fatigue cycling and freeze/thaw cycling on the anchorage of FRP to concrete. The results of flexural tests of 45 small-scale beams, reinforced with external FRP sheets and plates, are presented and discussed. Though the results were extremely variable, especially in terms of stresses in the FRP, the results indicate that minor damage to the concrete-FRP bond occurs under combined fatigue and freeze/thaw cycling, resulting in lower ultimate load and strain in the FRP. The results were compared to current design guidelines from CSA, ISIS, and ACI as well as a bond model developed by Chen and Teng. Generally, the current design guidelines were unconservative when predicting the failure load for a bond failure. The bond model, conversely, was found to be both conservative and reasonably accurate in predicting the ultimate stresses in the FRP at failure, though environmental loading was not considered specifically in the model.