Research On Cooperative Working Behavior Of Concrete Beams Strengthened With Multilayer Prestressed CFRP Laminate

Strengthening bridge with CFRP lamina was a new strengthening technique which has been developed in recent years,This technology integrated into the advantages of ordinary pasting CFRP lamina and prestressed strengthening technique that could effectively improve the ultimate bearing capacity of the structure,improve the structure stiffness and the cracking performance of concrete beam,so that results satisfaction of in serviceability limit state.But throughout the research results about prestressed CFRP lamina in the past,mainly about the single prestressed CFRP lamina.For long span bridge or the bottom of the beam width is narrower,and the number of single prestressed CFRP lamina which arrangement would be limited,that likely won't be able to provide the necessary reinforcement prestressed(or the large tonnage of pulling force).Because of this our team for the first time put forward multistory prestressed CFRP lamina reinforcement technology,That means using WSGG anchor clamp multistory CFRP lamina realize multistory CFRP lamina was tensioned,bonding and anchoring at the same time and implementation in the limited space layout more prestressed CFRP lamina for reinforcement,and can provide large tonnage of pretension,meet the actual needs of structure.At present,reinforced concrete structure about the multistory CFRP lamina is a blank field,there is no related research at home and abroad.Multilayer CFRP lamina when in force between the layers of carbon fiber plate if there is a slip or rupture? Do multilayer CFRP lamina and the reinforcing beam coordination work can similar to single CFRP lamina and the original beam joint? Will the pasted multistory CFRP lamina stripping off from the concrete beam? Multistory CFRP lamina flexural reinforcement stress calculation whether suit to plane-section assumption?,etc.About these questions have no related research at home and abroad is also no relevant experimental study.From the perspective of the design and calculation of flexural reinforcement about multistory CFRP lamina,the problem which need to solve is whether the multistory CFRP lamina and reinforced beam can cooperative bearing and whether if their can keep plane-sectionassumption,so base on plane-section assumption to establish the stress model.According to this,it can simplify the calculation about the flexural bearing capacity calculation.Hence,we should do research on multistory CFRP lamina about cooperative bearing through experiment and exploration on the mechanical properties of reinforced structure.In this paper,we have had Three RC T-beams constructed and tested,one of the three as a comparison has no reinforcement,and the others were reinforced by using the prestressed CFRP lamina for three,four layers through the anchorage developed by our team.The pre-tension on the beam in three layers of CFRP lamina way is 350 KN,while it is 450 KN in four layers of CFRP lamina way.Based on the analysis of the test results,following conclusions are obtained:(1)Success of reinforced RC T-beams by using three,four layers greatly improved the cracking load(up 745%)of the structure and yield load(up 100%).This experiment proved multistory CFRP lamina reinforcement technique is feasible and efficient.(2)During the whole loading test,relative slippage or dislocation between the layers of the multistory CFRP lamina is not observed,even after the end of the trial,each layer of CFRP lamina still maintain good bonding.This experiment can confirm the multistory CFRP laminas which are bonded to each other can form a cooperative strss and no slip or rupture in the loading process.(3)During the whole loading test,there are no interface stripping phenomenon between multistory CFRP lamina and concrete.Through the comparison and analysis of pulled steel and multistory CFRP lamina test data,the developments of strain are basically the same.The test basically confirmed that multistory CFRP lamina can work as the original structure pulled steel under the condition of reliable anchorage,in other words,the multistory CFRP lamina can not only have very good collaborative deformation but withstand the stress.The plane-section assumption can basically be satisfied.This paper makes a preliminary exploration on multistory CFRP lamina,so,the study in this dissertation is of important theoretical value and practical significance,It plays an important role in promote the development of the application of CFRP in civil engineering.