Time Depending Thermo Mechanical Bond Behavior of Epoxy Bonded Pre-Stressed FRP-Reinforcement

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Title: Time Depending Thermo Mechanical Bond Behavior of Epoxy Bonded Pre-Stressed FRP-Reinforcement

Author(s): K. Borchert and K. Zilch

Publication: Special Publication

Volume: 230

Issue:

Appears on pages(s): 671-684

Keywords: CFRP reinforcement; creep; epoxy resin; long-termbehavior; pre-stressing; SLS; strengthening; sustained load;temperature

Date: 10/1/2005

Abstract:
The development of different pre-stressed epoxy bonded CFRP-reinforcement systems for retrofitting RC-structures continues. In addition torequirements concerning the ultimate limit state (ULS) pre-stressed systems couldsatisfy demands in regard to the serviceability state (SLS) like crack limitation orfatigue. In comparison with the well known material behavior of concrete undersustained loading epoxy resins show material properties more sensitive to thermaleffects, for example loss of strength or creep deformations. In experimental tests theinfluence of permanent load and temperature is examined. The pure epoxy resinadhesive was evaluated in lab-shear tests and the structural behavior of the system inthe form of epoxy bonded pre-stressed near surface mounted CFRP-strips. Theexperiments reveal a significant influence of the epoxy resin adhesive behavior on thelong-term structural behavior in service. To evaluate the effects with regard to designsrelevant problems as long-term development of transfer lengths of pre-stressedreinforcement or of the slip between reinforcement and concrete under varying loadand thermal conditions results of a simulation model are presented.