Bridging cracks in concrete structures with composite materials : experimental study and modeling Mickaël MULLER, Evelyne TOUSSAINT and Michel GREDIAC Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP Specimen preparation Optical device EXPERIMENTAL RESULTS Reinforced concrete Pre-cracked strengthened reinforced concrete NUMERICAL RESULTS PRESENT MODEL CONCLUSION Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION INTRODUCTION The usual life of concrete structures lies between 50 and 120 years Pathologies Longevity shortened To keep the structures in service Composite reinforcement New service conditions Environment effects, ... Local effects like cracks and microcracks due to tensile effects Optical method that allows the determination of displacement fields Numerical results Present Model Experimental results Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION EXPERIMENTAL SETUP Different specimens under tension are studied Reinforced concrete Pre-cracked strengthened reinforced concrete Specimen preparation The width of the crack is measured with an optical method Displacement measurement Experimental setup Optical device Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Specimen preparation Section 80mm x 80mm 4 steel bars f = 6mm fc28 = 35MPa ft28 = 3.2MPa 500mm Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Specimen preparation Carbon epoxy unidirectional composite plates (SIKA Carbodur S812) Section 1.2mm x 80mm Strength = 2800MPa Adhesive thickness 1mm 340mm Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Optical device Measurement of the vertical displacement field with a suitable non-contact optical method,based on image correlation (P. Vacher) Zwick tensile/compressive machine Tensile speed loading = 0.4µm/s 3 cycles for each specimen Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION EXPERIMENTAL RESULTS Vertical displacement field at a load of 40 kN Two cracks are visible with a width of about 100 µm y axis x axis Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION EXPERIMENTAL RESULTS Vertical displacement field Vertical displacement at x = l/2 The resolution is about 5 µm The objective is to detect the cracks and to measure the width of the crack and the crack spacing Different specimens under tension are studied Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Reinforced concrete Displacement field at the center of the concrete specimen at a load of 5 kN No crack Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Reinforced concrete Displacement field at the center of the concrete specimen crack at a load of 5 kN and 40 kN Two cracks of about 100 µm width Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Reinforced concrete Evolution of the width of the crack at the middle of the specimen RC without composites First cycle increase First cycle decrease The measure was performed only every 5kN The crack appears at about 20 kN The crack appears suddendly Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Reinforced concrete Evolution of the width of the crack at the middle of the specimen RC without composites First cycle increase First cycle decrease Second cycle increase Second cycle decrease The crack grows at the beginning The width of the crack is the same The width of the crack does not close up Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Pre-cracked strengthened reinforced concrete Evolution of the width of the crack at the middle of the specimen RC without composites First cycle increase First cycle decrease Precracked RC with composites Peeling off Before peeling off After peeling off After reinforcement the width of the crack is smaller After the appariton of the peeling off, the width of the crack grows suddently Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Pre-cracked strengthened reinforced concrete Evolution of the width of the crack Unbridged crack at 35 kN Bridged crack at 35 kN The influence of the composite is more important near the reinforcement Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION NUMERICAL RESULTS Numerical model carried out CAST3M The aim of the numerical model is to predict the crack’s width of : reinforced concrete specimen strengthened reinforced concrete specimen Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Presentation Just one quarter is modelisated Steel bar diameter 6 mm assimilates to a parallepipede with a side of 5 mm Length of the sample 120 mm (72 elements) Width and height of the sample 40 mm (24 elements) Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Presentation a = 0 : all concrete-steel elements are tied together a  0 : along the distance a, concrete-steel elements are free a Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Results Evolution of the width of the crack at the middle of the specimen RC without composites First cycle FE simulation a = 0 The FE simulation with a=0 is not suitable Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Results Evolution of the width of the crack at the middle of the specimen RC without composites First cycle FE simulation a = 0 a = 30 mm The FE simulation with a=30mm gives a good approximation of the width of the crack Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Results Evolution of the width of the crack at the middle of the specimen Precracked RC with composites FE simulation a = 0 The FE simulation with a=0 gives a good approximation of the width of the crack Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Results Evolution of the width of the crack at the middle of the specimen Precracked RC with composites FE simulation a = 0 a = 30 mm The variation of a does not influence the result The composite introduces a new mechanism, which has an influence on the steel-concrete join Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION PRESENT MODEL The objective of the present model is to propose a simplified expression with a good approximation of the crack’s width of a repaired concrete sample Based on the Jaccoud’s model (1987) wm = 2.x.lr.eS2 lr : crack spacing x = 0.35 coefficient eS2 : effective strain in the reinforcement Present model (PM) wm = 2.a.x.lr.eS2* a : correcting factor eS2* : takes into account the composite Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Results Evolution of the width of the crack at the middle of the specimen Precracked RC with composites Linear curve The pink curve is the linear evolution of the crack’s width before peeling off Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Results Evolution of the width of the crack at the middle of the specimen Precracked RC with composites Linear curve Present model The present model (gray curve) is calibrated on the linear curve and is obtained with a = 0.67 Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION Results Evolution of the width of the crack at the middle of the specimen FE diameter 6 PM diameter 6 FE diameter 8 PM diameter 8 FE diameter 10 PM diameter 10 The present model based on Jaccoud’s modeling gives good prediction results compared with numerical results Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION CONCLUSION The crack’s width increases at fairly linear rate as the loading increases Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION CONCLUSION The crack’s width increases at fairly linear rate as the loading increases After bonding the composites, the width of the crack is smaller at the same load, and the influence of the composite is greater near the reinforcement Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION CONCLUSION The crack’s width increases at fairly linear rate as the loading increases After bonding the composites, the width of the crack is smaller at the same load, and the influence of the composite is greater near the reinforcement The numerical modeling gives good results in comparison to the experimental ones Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION CONCLUSION The crack’s width increases at fairly linear rate as the loading increases After bonding the composites, the width of the crack is smaller at the same load, and the influence of the composite is greater near the reinforcement The numerical modeling gives good results in comparison to the experimental ones A new analytical modeling is proposed on the base of Jaccoud’s model and gives good prediction results compared with numerical results Comptest - Composites Testing and Model Identification

Comptest - Composites Testing and Model Identification INTRODUCTION EXPERIMENTAL SETUP EXPERIMENTAL RESULTS NUMERICAL RESULTS PRESENT MODEL CONCLUSION CONCLUSION The crack’s width increases at fairly linear rate as the loading increases After bonding the composites, the width of the crack is smaller at the same load, and the influence of the composite is greater near the reinforcement The numerical modeling gives good results in comparison to the experimental ones A new analytical modeling is proposed on the base of Jaccoud’s model and gives good prediction results compared with numerical results These first results have to be confirmed with additional tests Comptest - Composites Testing and Model Identification

Bridging cracks in concrete structures with composite materials : experimental study and modeling Mickaël MULLER, Evelyne TOUSSAINT, and Michel GREDIAC Comptest - Composites Testing and Model Identification