4446

4196

كارشناسي ارشد

سازه

اصفهان: دانشگاه صنعتي اصفهان، دانشكده عمران

1387

دوازده،109،{II}ص:مصور،جدول،نمودار

ص.ع به: فارسي وانگليسي

داوود مستوفي نژاد، مجتبي ازهري

23/1/1388

فرهنگ فرحبد،كياچهر بهفرنيا

1396/09/11

كتابنامه

مهندسي عمران

ID4196

به فارسي وانگليسي: قابل رؤيت درنسخه ديجيتال

Abstract Retrofitting concrete structures with fiber reinforced polymer FRP has today grown tobe a widely used method throughout most parts of the world Nevertheless whenstrengthening a structure with external FRP it is often not possible to make full use of theFRP By prestressing a higher utilization of the FRP material is made possible The current thesis is dedicated to investigation of changes in strength ductility andserviceability of RC beams strengthened with prestressed NSM CFRP strips Five fullscale simply supported beams were cast and tested at Isfahan University of Technology including one reference non strengthened specimen and four strengthened specimenswith NSM CFRP strips over their full length Among strengthened specimens one was notprestressed and three other ones were imposed by three levels of prestressing force whichmade initial strain of 5 20 and 30 percent of nominal ultimate strain in CFRP strips Allbeams were reinforced by internal tensile steel reinforcement of 0 5 b b is the tensilebalanced reinforcement ratio and tested with three point loading system The experimental results indicated that the load carrying capacity of strengthened beamscompared to that of control beam had an increase of 10 percent in non prestressedspecimen while it was 11 5 to 15 percent in prestressed ones The tests showed a largeincrease in the crack and steel yielding load The prestressing level had a direct influenceon both of these parameters the prestressed strengthened specimens showed the crackingload 17 to 45 percent and the yielding load 5 5 to 9 percent higher than those of controlbeam Together with higher crack loads the cracks also were smaller in both width anddepth and propagated in more limited area The non prestressed strengthened beamshowed almost the same behavior in cracking and yielding as non strengthened one Itshould be mentioned that the prestressed beams lost a part of their ductility at failure which is because a part of the possible strain in the strips was used during prestressing resulting in failure at smaller deflections As a part of this study an analytical evaluation was developed for the estimation offlexural behavior and ultimate load carrying capacity in strengthened specimens using M diagram and concepts of prestressed concrete Comparing experimental data withanalytical results showed that this developed method was just helpful to understand thebehavior of strengthened beams in elastic region

داوود مستوفي نژاد، مجتبي ازهري

فرهنگ فرحبد،كياچهر بهفرنيا