An Investigation on the bhavior of composite beams in negative bending moment zone which was strengthened with CFRP strips and bonding with epoxy

Key words : Composite beams, negative bending, epoxy resin, carbodur strips In the state of reinforced concrte slab's and steel profiles working together in negative bending moment zone of composite beam, how the changing size and clearence of lapped joints which were made by Sika Carbodur Strips (Carbon Fibre Reinforced Polymer Strips - CFRP ), affects the bearing capacity and behaviour of composite beam is being invastigated and how it prevent or doesn't prevent the separation of concrete slab from steel profile, as a result of deformation under negative bending in composite beam is being investigated. In this experimental study, the beam consists of a ready-mixed reinforced concrete slab which has 3000x800x100 mm size and steel profile ( I 120 profile ) onthe reinforced concrete slab. When the composite beam is prepared an epoxy resin is used to supply the connection between ready-mixed reinforced slab and steel profile.Calculated steel bars put in to the ready- mixed reinforced concrete slab in order to prevent the tensile which cannot prevented by the concrete. Additionally, in negative bending moment zone, the CFRP strips (Sika Carbodur ) whose size and clearence differ and which increase the bearing capacity of composite beam, are used. Detailed information are given about characteristic values of concrete, steel profile, epoxy resin and CFRP strips which is used when the composite beam is prepared. As a result of this experimental study, theoretical and experimental results are being compared, in situations of the CFRP strips being used or not being used in negative bending moment zone of composite beams which were bonded with epoxy. The purposes of experimental research are first to be informed about CFRP strips and epoxy resin that each was a new strengthening material in building trade and secondly to be informed about behaviour of composite beams in negative bending moment zone according to changing size and clearence of CFRP strips and epoxy resins and suggestions are made.