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Fiber reinforced polymer (FRP) rods are used for pre-stressing and reinforcing in civil engineering applications. Damage in FRP rods can lead to sudden brittle failure, therefore, a reliable method that provides indicators of damage progression and potential failure in FRP rods is highly desirable. Acoustic emission (AE) signal analysis has been used for damage detection and monitoring of FRP materials. In this study, a new AE event detection algorithm, utilizing the root mean square envelope of AE signal, is applied to AE data to isolate each AE event separately, even when AE events are nearly coincident. A fuzzy c-means (FCM) clustering algorithm is used to classify these isolated AE events into 3 clusters. Scanning electron microscopy images of FRP rod cross-sections also show 3 types of damage. The hypothesis in this study is that each cluster represents a damage mechanism. The number of events in each cluster is monitored versus the percent of the ultimate load. The ratio of the number of AE events in one of the FCM clusters to the number of AE events in another FCM cluster was useful for providing an indication of when the stress levels have reached the point where the loads may cause the FRP rod to fail. The results of applying this parameter to four FRP rods show a significant slope change (factor of 10) in this ratio at around 40% and 60% of the ultimate load for glass FRP rods and carbon FRP rods, respectively. This method may prove useful in damage progression and failure prediction of the FRP rods in prefabricated structures where pre-stressed FRP is used and in field monitoring of FRP materials.

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An experimental program was undertaken at The University of Manitoba to test timber stringers strengthened with glass fibre reinforced polymer (GFRP) bars. Various strengthening schemes were investigated as a means of increasing the load carrying capacity of timber stringers in shear and flexure. The shear strengthening was achieved by inserting GFRP dowels in the centre of the cross section along the length of the stringers. The flexural strengthening used the concept of near-surface-mounted GFRP bars. Fifty beams were tested to evaluate the performance of the various strengthening schemes. The behaviour of the beams is described in terms of mode of failure, mechanical properties, and load-deflection behaviour. This study found that strengthening timber stringers with GFRP reinforcement increased the ultimate strength of the stringers and reduced its variability. It is believed that the shear and flexural GFRP reinforcements act as a truss member within the timber beam and bridge the local defects and discontinuities of the timber.Résumé : Un programme expérimental a été entrepris à l'Université du Manitoba pour tester des longerons de bois d'oeuvre renforcés avec des barres en polymères renforcées de fibres de verre (« glass fibre reinforced polymer : GFRP »). Divers scénarios de renforcement ont été étudiés afin d'accroître la capacité portante des longerons en bois d'oeuvre en cisaillement et flexion. Le renforcement au cisaillement a été accompli en insérant des goujons en GFRP au centre de la coupe transversale dans l'axe de la longueur des longerons. Le renforcement en flexion a utilisé le concept de barres de GFRP montées près de la surface. Cinquante poutres ont été soumises à des essais pour évaluer le rendement des divers scénarios de renforcement. Le comportement des poutres est décrit en termes de mode de défail-lance, de propriétés mécaniques et de comportement en flexion sous charge. L'étude a montré que le renforcement des longerons en bois d'oeuvre avec renforcement en GFRP augmentait la résistance à la rupture des longerons tout en ré-duisant sa variabilité. Nous croyons que le renforcement GFRP en cisaillement et en flexion agit comme membre d'armature dans la poutre en bois d'oeuvre et fait le lien entre les discontinuités et les défauts locaux dans le bois d'oeuvre.