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Towards Unified Bond Modelling for the Structural Behaviour of GFRP-RC Kypros Pilakoutas Harsha Sooriyaararachchi Maurizio Guadagnini Centre for Cement and Concrete Department of Civil and Structural Engineering, University of Sheffield, Sheffield, United Kingdom. GFRP-RC in Construction.
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Towards Unified Bond Modelling for the Structural Behaviour of GFRP-RC Kypros Pilakoutas Harsha Sooriyaararachchi Maurizio Guadagnini Centre for Cement and Concrete Department of Civil and Structural Engineering, University of Sheffield, Sheffield, United Kingdom
GFRP-RC in Construction GFRP bars Use of GFRP for bridge deck construction (Franklin county bridge Virginia) Stiffness of GFRP compared to Steel
Outline • Hierarchy of bond modelling • Macro level Modelling • Meso level modelling • Average bond stress slip relation • Formulation of bond modelling using strain distribution • Local bond stress-slip-strain relation t-s-e
Hierarchy of bond Modelling Steel reinforcement FRP reinforcement Macro-level modelling
Hierarchy of bond Modelling Steel reinforcement FRP reinforcement Macro-level modelling Meso-level modelling
Hierarchy of bond Modelling Steel reinforcement FRP reinforcement Macro-level modelling Meso-level modelling Micro-level modelling
RC response Bare bar response Tension stiffening effect Macro Level Bond Modelling Tension stiffening of concrete is defined as: the ability of concrete to carry tension between cracks and provide extra stiffness for RC in tension.
Strain Softening Behaviour Concrete Average stress strain behaviour of concrete Test results bar stress Vs overall strain
Typical Test Results Stage III Post Cracking Stage II Crack Propagation Stage I Pre Cracking Strain of the composite specimen at Average Stress Strain of the bar at crack Response of composite section Bare bar response Average Strain Tension Stiffening Behaviour Reinforced concrete in tension
3rd 1st crack 2nd Strain Distribution while Cracking Stage I Stage II Internally strain gauged bar
Post cracking slip and strain Stage III
Strain and bond between cracks Typical strain and bond stress distribution between cracks
Meso Level Bond Modelling Direct tension test Pullout test Magnified images showing bond failure
50% (a) (d) (b) (c) Average Bond Stress Vs. Slip Comparison of average bond stress slip behaviour for the two test in almost identical circumstances
Stress Conditions During Testing Direct tension test Pull out test
Strain Strain Distance along the embedment length Distance between cracks Bond Stress based on strain distribution
100 150 175 125 25 0 50 75 100 125 150 25 0 50 75 Local Bond Stress Slip Relationship
t-s-e x
t-s-e Relation for BOND Scal= Slip at peak bond stress at calibrated strain ecal= Referred strain for calibration
Local Bond Stresses in Pull-out 5D Grade 45 Grade 90
Local Bond Stresses in Pull-out 10D Grade 45 Grade 90
Comparisons of results Local bond behaviour in pull out test 19/45/10D
Conclusions • Different levels of bond modelling • Testing conditions affect bond behaviour • Bond stress profile changes with increasing load • Is Average bond stress slip relationship useful? • t-s-eapproach proposed • More work to be done