Bond behaviour of FRP bars in concrete.

摘要

This thesis investigates the bond behaviour of Fibre Reinforced Polymer (FRP)udreinforcing bars in concrete elements both analytically and experimentally.udTwo series of experiments were conducted. In the first series, more than 100udcube specimens were tested in direct pullout. The mode of bond failure of FRP bars inudthe pullout tests was found in most cases to differ substantially from that of deformedudsteel bars. Within this series the parameters that influence bond development wereudexamined. The bond strengths developed by CFRP and GFRP bars appear to be veryudsimilar, and just below what is expected from deformed steel bars.udIn the second series of experiments, nine beams were tested in four-pointudbending to examine the bond splitting behaviour of FRP single anchorages and splices.udCFRP bars develop higher bond splitting strength than respective GFRP bars, whichudcontradicts the findings of pullout tests. The lower elastic modulus of GFRP bars isudthought to play an important role to their lower bond splitting strength. For this reason,udthe suitability of the cube tests for measuring the bond strength ofFRP bars for practicaludpurposes is questioned. Spliced bars appear to develop similar bond splitting strength toudsingle bar anchorages. The distribution of bond stresses along the anchorage length andudthe effect of flexural cracks on the bond development were also examined. The thesisudalso discuss other parameters that influence bond splitting such as transverseudreinforcement, concrete cover, and support action.udAn analytical study was conducted to enhance further the understanding of theudbond behaviour of FRP bars. Both the pullout and beam tests were modelled by usingudFE packages. Non-linear springs describing the bond behaviour of short embedmentudlengths were chosen and used for predicting the behaviour of longer embedments. Theudinfluence of flexural cracking was also considered in the case of beams. The analyticaludresults showed a good correlation with the respective experimental.udFinally, some important issues regarding the design of anchorage lengths forudFRP reinforcing bars were addressed and a method of working towards the formulationudof design recommendations is suggested.