تعيين طول موثر شيار در روش شيار زني جهت كنترل پديده ي جداشدگي ورق FRP ازسطح بتن با منظور كردن تعداد لايه ها

چكيده انگليسي :

Determination of Effective Length of Grooves in Grooving Method to Prevent debonding Considering Number of Layer Kamyar Khozaei k khozaei@cv iut ac ir 9 14 2012 Department of Civil Engeenering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Dr D Mostofinejad dmostofi@cc iut ac irAbstractStrengthening and retrofitting of old structures which are being used are important issues and significantlyconsidered from some decades ago There are many aims to strengthening but according to the coderecommendations resist higher design loads correct strength loss due to deterioration correct design orconstruction deficiencies and increase ductility are the main aims The most important problem is thedebonding of FRP from concrete surface Surface preparation is an ordinary method to prevent debondingrecommended by ACI 440 Code In this method substrate of the member must be clear and the weak ordeteriorated layer should be removed by a suitable procedure such as water jet or sanding Wide studies havebeen done all over the world to investigate the failure mechanisms strengthened by this method and thesemechanisms have been categorized into more than 30 groups The most important problem is lack of aconfident method to prevent debonding and yet it threats the strengthened members Grooving is analternative method of surface preparation recently suggested Although this method could improve thebehavior of strengthened members and has controlled debonding phenomenon this method must beoptimized In this paper the effect of different longitudinal patterns of grooves is investigated and threecriteria including ultimate load capacity ductility and failure mechanisms are compared for all groups ofspecimens Also the effect of thickness of CFRP plate is considered To select the appropriate groovingpatterns it is necessary to review the studies on stress distributions along interface and determine theboundary of high stress zones It means that grooves applied on critical areas called high stressed zones andthey omitted from zones in low state of stresses This method has economical profits and can decrease theperiod of construction procedure in addition it could improve the behavior of the members So 26 reinforcedconcrete beams by dimensions of 120x140x1000 millimeters were tested The flexural reinforcement was 0 3of balanced steel ratio and the 4 point load test was applied The specimens were categorized by groovepatterns and thickness of FRP layer The beams were strengthened by 5 grooving patterns First one is lack ofgrooves named EBR method Second includes 100 percentages of groove length Full Grooving thirdincludes 70 percentages of groove length Discontinuous Grooving fourth and fifth includes 50 and 30percentages of groove length respectively concentrated on two ends End Grooving These specimens alsostrengthened with 3 different thicknesses of CFRP plate To compare the ductility of specimens two criteriawere determined The first index is based on energy name energy ductility index and the second one is basedon deflection named deflection ductility index The results show that the specimens strengthened by endgrooving was more suitable in strength and ductility than another groups of specimens and the fibers reachedto their ultimate capacity so ruptured Also specimens strengthened by end grooves with 150mm in length increased ductility while decreased ultimate load It means the end grooving can improve the behavior ofreinforced concrete beams in flexure Key WordsDebonding Surface Preparation Grooving Groove length Patterns FRP thickness

خزاعي، كاميار

تعيين طول موثر شيار در روش شيار زني جهت كنترل پديده ي جداشدگي ورق FRP ازسطح بتن با منظور كردن تعداد لايه ها

آماده سازي سطحي , الگوي طولي شيارها , ضخامت ورق تقويتي