Fatigue Experimental Study Of The Concrete Beams Strengthened With Non Sticked Multi-point Anchoring Prestressed FRP

CFRP is more and more applied to structure reinforcement for its good physicaland mechanical performance, nowadays the CFRP reinforced concrete structureresearch mainly focus on the static performance study but the fatigue performance studyis less concerned. Li Tangning et al from ChongQing university had developed the steelcorrugated tooth anchorage prestressed CFRP sheets of anchorage system, which isstable and reliable, economical and practical, simple and rapid reinforcement. In theearly static test research it has been validated that multilayer CFRP sheets can still bereliably anchored in high stress level, and the anchorage failure will not occur until theCFRP sheet break. However, fatigue test research about waveform tooth anchorageprestressed CFRP sheet reinforcement concrete structure is still blank. Therefore,waveform tooth anchorage prestressed CFRP sheet reinforced concrete beam fatigueperformance study is an essential research subject which has important theoreticalsignificance and practical significance.On the basis of the comprehensive consideration of the CFRP sheet reinforcementquantity and prestressed degree, research on fatigue loads concrete beam fatigue life,material strain, horizontal section assumption validation, failure modes, fracturemorphology and deflection, etc are processed through one concrete beam static test and3root concrete beam fatigue test. Test results of the study show that:①Rereinforcement stress amplitude of waveform tooth anchorage prestressedCFRP sheet reinforcement beam is minimum;②Flat section assumption is still correct after applying many fatigue loads;③In the first static load, crack has basically been out together, in the fatigue loadunder the action of repeated, crack keep on expanding, a few new crack wiil also beappeared;④load-deflection curve change into an approximate linear line, and cross sectionchange into elastic after the initial certain fatigue cycle times;⑤Compared with the unreinforced beam, the deflection in the middle of span ofwaveform tooth anchorage prestressed CFRP sheet reinforcement will significantly bedecreased.On the basis of the experimental study, reinforced concrete beam fatigueperformance is discussed theoretically and the test beam of normal section of the fatigue design method is proposed according to the concrete, steel, carbon fiber cloth fatigueperformance and fatigue stress-strain relationship.