ارزيابي الگوهاي مختلف تقويت در اتصال تير قوي-ستون ضعيف با استفاده از كامپوزيت هاي FRP

چكيده انگليسي :

Seismic evaluation of reinforced concrete strong beam weak column joints strengthened by different configuration of CFRP composites Elaheh Ilia Elaheh Ilia@cv iut ac ir September 18 2019 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 IranDavood Mostofinejad dmostofi@cc iut ac irMojtaba Azhari mojtaba@cc iut ac irFarhad Behnamfar farhad@cc iut ac ir Professor Department of Civil Engineering Isfahan University of Technology Isfahan Iran Department Graduate Program Coordinator Associate Professor Department of Civil Engineering IsfahanUniversity of Technology Isfahan Iran AbstractBeam column assemblies of many existing reinforced concrete RC buildings are typically designed and builtbefore the development of the current seismic codes that may permanently fail in non ductile behaviors includingcolumn flexural hinging or joint shear failure mode during ground motions The current research therefore wasconducted to evaluate the efficiency of newly proposed rehabilitation schemes in retrofitting of deficient RCbeam column connections using fiber reinforced polymers FRPs To do so ten half scale exterior beam columnjoints were constructed and tested under constant axial and reversal cyclic lateral loadings These joints weredesigned with strong beam weak column theory and insufficient transverse reinforcement in the joint region Thetest specimens consisted of one control and nine specimens retrofitted with FRP composites used in differentconfiguration Longitudinal or transverse CFRP sheets were used to improve the seismic performance of theretrofitted columns while either an L shaped pattern of FRP sheets or CFRP anchor fans as a new anchoragetechnique were employed to anchor the longitudinal FRP sheets at the beam column interface Moreover transverse sheets were utilized via the innovative corner strip batten technique to confine the column of the jointspecimen The joint panel of the rehabilitated specimens was retrofitted with X shaped CFRP strips Further insome specimens the parts of the beam near the joint core were also strengthened to shift plastic deformationsaway from the joint area The externally bonded reinforcement on grooves EBROG method was used in allstrengthening patterns to eliminate surface debonding of CFRP sheets The test results revealed that the adoptedstrengthening schemes successfully prevented the brittle failure of the specimens and were able to provide a moreductile mechanism by relocating the plastic hinge away from the weak column and the joint zone toward the beam Furthermore a significant enhancement was observed for specimens in terms of their strength ductility and energydissipation up to 80 139 144 respectively Additionally the EBROG technique together with the CFRPfans at the interface of the beam column joints eliminated any debonding or slipping of the longitudinal CFRPs In the analytical section the behavior of joint specimens were first verified in the ABAQUS software whichshowed very good agreement with test results After that case studies were done on both control and strengthenedspecimens by changing some parameters including the ratio of beam longitudinal reinforcement the amount ofcolumn axial load and the volume of FRP used Based on the obtained results increasing both the ratio of beamlongitudinal reinforcement and the column axial load increased the initial stiffness of lateral load displacementcurves Also the maximum lateral strength of the joint is completely affected by its mode of failure and canincreased by up to 56 2 in ductile modes KeywordsRC beam column joint Fiber reinforced polymer FRP Strong beam weak column Shear deficiency EBROG FRP anchor fan Plastic hinge relocation Cyclic loading IntroductionBeam column connections are the most critical regions in reinforced concrete RC buildings that play a mainrole in the overall stability of the structure during an earthquake However in many existing RC frame structures

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ارزيابي الگوهاي مختلف تقويت در اتصال تير قوي-ستون ضعيف با استفاده از كامپوزيت هاي FRP

اتصال تير قوي- ستون ضعيف , كامپوزيت‌هاي FRP , تقويت خمشي , تقويت برشي , روش شيار زني EBROG , مهار بادبزني FRP