Structures Strengthened with Bonded Composites (Woodhead Publishing Series in Civil and Structural Engineering)

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Structures Strengthened With Bonded Composites
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Contents
Preface
Symbols
1 Fundamental behavior of fiber-reinforced polymers and their bonding technique
	1.1 Fiber-reinforced polymer constituents
		1.1.1 General
		1.1.2 Fibers
		1.1.3 Matrix materials
	1.2 Characteristics of fiber-reinforced polymer composites
		1.2.1 Basic mechanical properties and behavior
			1.2.1.1 Tensile test method
			1.2.1.2 Tensile properties of fiber-reinforced polymer composites
		1.2.2 Property enhancement by hybridization
			1.2.2.1 Concept
			1.2.2.2 Effect
			1.2.2.3 Design method
		1.2.3 Temperature-dependent behavior
			1.2.3.1 High-temperature performance
			1.2.3.2 Low-temperature performance
			1.2.3.3 Performance under freezing and thawing cycles
		1.2.4 Time-dependent behavior
			1.2.4.1 Fatigue behavior
			1.2.4.2 Creep behavior
		1.2.5 Durability behavior
			1.2.5.1 Fiber degradation
			1.2.5.2 Matrix degradation
			1.2.5.3 Fiber-reinforced polymer Composites degradation
			1.2.5.4 Degradation mechanism of fibers and composites
			1.2.5.5 Enhancement of corrosion resistance
		1.2.6 Impact behavior
			1.2.6.1 Damage appearance and mechanism
			1.2.6.2 Comparison of impact resistance for FRP
	1.3 Fiber-reinforced polymer bonding technique for the concrete and steel structures
		1.3.1 Installation procedure
		1.3.2 Strengthening strategy
	References
2 Bond characteristics and debonding mechanism of FRP–concrete interface
	2.1 Interfacial fractures and debonding modes
	2.2 Stress transfer and fracture propagation of FRP–concrete joints
		2.2.1 Fundamental formulas
		2.2.2 Pull–push joint
			2.2.2.1 Model I: linear interface shear stress–slip relationship with an abrupt decrease in stress
			2.2.2.2 Model II: τ–δ relationship with linearly ascending and descending branches
			2.2.2.3 Model III: τ–δ relationship with only linearly descending branch
			2.2.2.4 Model IV: τ–δ relationship with only exponential softening branch
			2.2.2.5 Effective stress transfer (bond) length le
			2.2.2.6 Debonding propagation of FRP–concrete joints
		2.2.3 Pull–pull joint
	2.3 Short-term behavior of FRP–concrete interface
		2.3.1 Experimental methods and observations
		2.3.2 Factors influencing FRP–concrete interface
			2.3.2.1 Influence of FRP thickness
			2.3.2.2 Influence of FRP elastic modulus
			2.3.2.3 Influence of width of FRP laminates
			2.3.2.4 Influence of concrete strength
			2.3.2.5 Influence of FRP effective bond length
			2.3.2.6 Influence of width of concrete prism
		2.3.3 Numerical study of bond behavior of FRP–concrete interface
			2.3.3.1 Experimental observation
			2.3.3.2 Mode II fracture model (macrorepresentation)
			2.3.3.3 Mode I fracture model (microrepresentation in concrete)
			2.3.3.4 Mixed mode fracture and calibration of GfI and GfII
		2.3.4 Prediction of bond strength of FRP–concrete interface
	2.4 Long-term behavior of FRP–concrete interface
		2.4.1 Fatigue performance of FRP–concrete interface
			2.4.1.1 Observed fatigue-induced failure modes
			2.4.1.2 Fatigue damage accumulation
			2.4.1.3 Crack propagation
			2.4.1.4 Pre and post fatigue performance of FRP–concrete interfaces
			2.4.1.5 Fatigue life of FRP–concrete interfaces and evaluation of code provisions
		2.4.2 Creep performance of FRP–concrete interface
			2.4.2.1 Pull-out test for double-shear specimens
			2.4.2.2 Beam strengthened with prestressed FRP sheet
		2.4.3 Modeling of time-dependent performance of FRP concrete interfaces
			2.4.3.1 Finite element hybrid viscoelastic model of FRP–concrete interface
				2.4.3.1.1 Before debonding initiation
				2.4.3.1.2 After debonding initiation
			2.4.3.2 Determination of parameters of the viscoelastic model
			2.4.3.3 Evaluation of the hybrid viscoelastic model based on the experimental results
				2.4.3.3.1 Sustained loading
				2.4.3.3.2 Fatigue loading
			2.4.3.4 Comparison between creep and fatigue performance of FRP–concrete interfaces
	2.5 Durability of FRP–concrete interface
		2.5.1 Temperature effect
		2.5.2 Combined effect of freeze–thaw cycling and sustained load
			2.5.2.1 Experimental program
			2.5.2.2 Test results
			2.5.2.3 Discussion of the coupled effects
		2.5.3 Moisture effect
			2.5.3.1 Effect of moisture at the time of FRP installation (construction moisture)
			2.5.3.2 Effect of moisture during service life (WD) cycles
	2.6 Enhanced FRP bonding system
		2.6.1 Fiber anchorage system
			2.6.1.1 FRP sheet anchorage method
			2.6.1.2 Fiber anchors
		2.6.2 Hybrid-bonded FRP system
			2.6.2.1 Mechanism of HB-FRP
			2.6.2.2 Experimental tests
			2.6.2.3 Bond models
	References
3 Fiber-reinforced polymer-strengthened tensile members
	3.1 Experimental investigations of FRP-strengthened tensile members
		3.1.1 Experimental observation
		3.1.2 Debonding mechanism
	3.2 Fracture energy approach for analyzing tensile properties of FRP-strengthened tensile members
		3.2.1 Energy balance and strain formulation in reinforced concrete members
		3.2.2 Debonding fracture energy
		3.2.3 Calculation of stress in reinforced concrete members
		3.2.4 Comparison of analytical/experimental results
	3.3 Modeling of tension stiffening effect
		3.3.1 Yoshizawa–Wu model
		3.3.2 Experimental studies
		3.3.3 Numerical studies
			3.3.3.1 Outline of analysis
			3.3.3.2 Modeling of bond deterioration of steel bars
			3.3.3.3 Modeling of bond deterioration in fiber-reinforced polymer sheets
			3.3.3.4 Modeling of bond deterioration owing to decrease in crack spacing
		3.3.4 Comparison of analytical and experimental studies
			3.3.4.1 Load–average strain relationship
			3.3.4.2 Average bond stress in steel and continuous fiber sheets
			3.3.4.3 Tension stiffening effect
	3.4 Formulation of crack spacing
		3.4.1 Wu–Yoshizawa model
		3.4.2 Sato’s model for crack spacing estimation
		3.4.3 Peeling propagation at cracked region
	References
	Further reading
4 Flexural strengthening of structures
	4.1 Introduction
	4.2 Flexural strengthening methods for structural members
	4.3 Effect of flexural strengthening on the performance of structural members
		4.3.1 Strengthening effect under monotonic load
			4.3.1.1 Failure modes
			4.3.1.2 Experimental observations
		4.3.2 Strengthening effect under fatigue load
			4.3.2.1 Failure mode under fatigue loading
			4.3.2.2 Experimental observations
			4.3.2.3 Influence factors of the fatigue behavior of FRP-strengthened RC beams
	4.4 Bonding and debonding mechanisms in FRP-strengthened RC members
		4.4.1 Flexural crack-induced debonding in FRP-strengthened RC beams
		4.4.2 Shear crack-induced debonding failure in FRP-strengthened RC beams
		4.4.3 Strengthening effects due to different interfacial behavior
	4.5 Design of flexural strengthening
		4.5.1 Design flexural load-carrying capacity
		4.5.2 Existing models for the prediction of IC debonding failure
		4.5.3 Reliability-based approach for flexural design of IC debonding failure
		4.5.4 Flexural design recommendations under fatigue loads
	4.6 Performance enhancements for FRP flexural strengthening
		4.6.1 Active strengthening with prestressed fiber sheets
			4.6.1.1 Anchorage treatment methods and prestressing system
			4.6.1.2 PBO prestressing upgrading technique
			4.6.1.3 Strengthening effect
		4.6.2 Strengthening with hybrid fibers
	4.7 Special field applications
		4.7.1 Strengthening of concrete tunnel lining
		4.7.2 Fatigue strengthening of concrete bridge deck
		4.7.3 Retrofit of columns with longitudinal reinforcement cut-offs
			4.7.3.1 Experimental verification
	References
	Further reading
5 Shear and torsional strengthening of structures
	5.1 Introduction
	5.2 Why shear and torsion strengthening?
	5.3 What is shear and torsion strengthening with FRP?
	5.4 Failure modes of shear strengthened beams
	5.5 Fundamental mechanism for FRP retrofitting
		5.5.1 Side bonded and U-jacket techniques
		5.5.2 Complete wrapping technique
	5.6 Experimental investigation of parameters influencing shear capacities
	5.7 Numerical investigation of parameters influencing shear capacities
		5.7.1 Material modeling and properties
			5.7.1.1 Concrete
			5.7.1.2 Steel reinforcement and steel plates
			5.7.1.3 FRP composites
		5.7.2 Parametric study of shear capacity
			5.7.2.1 Modeling RC beam
			5.7.2.2 Influence of the beam width
			5.7.2.3 Influence of FRP thickness
			5.7.2.4 Influence of concrete strength
			5.7.2.5 Influence of height of FRP sheet
			5.7.2.6 Influence of beam depth
			5.7.2.7 Influence of shear span–depth ratio
			5.7.2.8 Influence of type of wrapping scheme
			5.7.2.9 Influence of elastic modulus of FRP configuration
	5.8 Shear strength models
		5.8.1 Models based on experimental observations
		5.8.2 The models for design codes
	5.9 Numerical-based model for prediction of shear capacity
		5.9.1 Prediction model
		5.9.2 Comparison with the existing experimental results
		5.9.3 Comparison with available models
	5.10 Failure modes of torsional strengthened beams
		5.10.1 Complete wrapping strips and sheets
		5.10.2 U-Jacket sheets and strips
		5.10.3 Combined torsion and shear
		5.10.4 Combined torsion and bending
	5.11 Resistance mechanism of FRP torsional strengthening
	5.12 Evaluation of torsional strength of FRP-strengthened elements
		5.12.1 Available models
			5.12.1.1 FRP effective stress ff
		5.12.2 Design codes
	References
	Further reading
6 FRP strengthening of concrete columns
	6.1 Performance of under-designed existing structures
		6.1.1 Columns with shear deficiency
		6.1.2 Columns with lap-splice deficiency
		6.1.3 Columns with flexural deficiency
	6.2 Provisions of current seismic design codes
	6.3 Strengthening of RC columns
	6.4 FRP as external reinforcement for existing RC columns
		6.4.1 Methods used in FRP strengthening/upgrading of existing structures
		6.4.2 Concrete confinement mechanism and objectives
		6.4.3 Parameters affecting behavior of FRP-confined concrete
			6.4.3.1 Concrete cross-section
			6.4.3.2 Scale size of test specimens
			6.4.3.3 Grade of unconfined concrete
			6.4.3.4 Fiber direction
			6.4.3.5 Lateral rigidity (stiffness) and confinement ratio
			6.4.3.6 Bonding condition between FRP and concrete
			6.4.3.7 Existence of internal steel stirrups
			6.4.3.8 Loading condition [(concentric, eccentric), (monotonic and cyclic), (static, dynamic)]
			6.4.3.9 Predamaged level of the unconfined concrete
	6.5 Modeling of stress–strain behavior of FRP-confined concrete
		Direct application of steel-based confinement models
		Design-oriented models for FRP-confined concrete
		Finite element models with plasticity approach
		6.5.1 Stress–strain models of FRP-confined circular columns
			6.5.1.1 Design-oriented models
				Models of group A (ascending slope of second branch)
				Models of group B (descending slope of second branch)
				Models of group C (descending or ascending slope of second branch)
				Models of group D (ultimate stress/strain)
			6.5.1.2 Analysis-oriented models
		6.5.2 Stress–strain models of FRP-confined rectangular columns
			6.5.2.1 Design-oriented models
			6.5.2.2 Analysis-oriented models
		6.5.3 Plasticity approach for modeling circular/rectangular FRP-confined concrete
	6.6 Ductility enhancement
		6.6.1 Rei nforced concrete columns confined with FRP
		6.6.2 Large-scale-reinforced concrete building confined with FRP
	6.7 Durability of FRP-confined concrete columns
		6.7.1 Laboratory evaluations for durability of FRP-confined columns
			6.7.1.1 FRP-confined plain concrete
			6.7.1.2 FRP-confined reinforced concrete columns
		6.7.2 Short-term field study on durability of RC bridges (3 years investigation)
		6.7.3 Long-term field study on durability of RC bridge columns (15 years investigation)
		6.7.4 Axial force assessment of FRP-confined columns based on durability
			6.7.4.1 Concrete axial compressive strength after exposure to freeze–thaw cycles
			6.7.4.2 FRP-confined RC column compressive strength under various environmental conditions
		6.7.5 Design specifications and recommendations
	6.8 Design methods of FRP jacket for deficient RC columns
		6.8.1 Ductility design method by Seible et al. (1997)
			6.8.1.1 Shear
			6.8.1.2 Flexural hinge confinement
			6.8.1.3 Lap-splice clamping
		6.8.2 Ductility design method by Monti et al. (2001)
			6.8.2.1 Ductility upgrading of piers in seismic regions
			6.8.2.2 Design procedure for designing an FRP jacket for circular columns
		6.8.3 Ductility design method by Tastani and Pantazopoulou (2006)
			6.8.3.1 Strength assessment of FRP rehabilitated RC members
				Shear strength calculations
				Ideal flexural capacity calculations
				Anchorage/lap-splice strength calculations
				Resistance to longitudinal bar buckling in FRP-wrapped RC elements
				Deformation capacity assessment for FRP-encased members
		6.8.4 Ductility design method by Japan society of civil engineers (Japan Society of Civil Engineers JSCE, 2001)
	6.9 Numerical simulation of columns under axial and lateral loads
	6.10 Evaluation of design-oriented models in simulating RC columns retrofitted with FRP jackets under axial and lateral loa...
	6.11 Recoverability of FRP-retrofitted columns
		6.11.1 Residual deformations as a seismic performance index
		6.11.2 Postyield stiffness as a seismic performance index
		6.11.3 Idealized load–deformation model of FRP-RC damage-controllable structures
		6.11.4 Enhancing recoverability and controllability of deficient RC columns using of FRP confinement as a retrofitting tech...
			6.11.4.1 Postyield performance of FRP-confined rectangular and circular columns
		6.1.4.2 Residual inclination and limit states of FRP-confined RC columns
	References
7 Reinforcing spalling resistance of concrete structures with bonded fiber–reinforced polymer composites
	7.1 Introduction
	7.2 Spalling resistance of beams with fiber-reinforced polymer sheets
		7.2.1 Experimental study on peeling and spalling resistance of unidirectional fiber–reinforced polymer sheets
			7.2.1.1 Failure modes
			7.2.1.2 Load–deflection relationships
			7.2.1.3 Parameters affecting spalling resistance
				Effect of different continuous fibers
				Effect of different adhesives
				Effect of surface treatment and concrete strength
		7.2.2 Theoretical evaluation for spalling resistance of beams with fiber-reinforced polymer sheets
	7.3 Spalling resistance of structures with bidirectional fiber–reinforced polymer sheets
		7.3.1 Experimental studies
			7.3.1.1 Small-scale specimens
				Parameters affecting spalling resistance
					Effect of fiber-reinforced polymer sheet layers and direction
					Effect of concrete strength
					Effect of adhesives
					Effect of fiber types
			7.3.1.2 Large-scale specimens
				Parameters affecting spalling resistance
					Effect of bond length
					Effect of plate constraint
					Effect of hole diameter
					Effect of fiber type
			7.3.2 Analytical studies
			7.3.2.1 One-layer fiber-reinforced polymer sheet
			7.3.2.2 Two layers of fiber-reinforced polymer sheet
		7.3.3 Theoretical results
	7.4 Experimental study on arched beams
	7.5 Spalling prevention design method
		7.5.1 Basic assumption of the design
		7.5.2 Design method
		7.5.3 Unit spalling strength (spo) and spalling angle (θ)
			7.5.3.1 Spalling model and spalling resistance
			7.5.3.2 Relationship between the weight of the spalling chunk and the elongation of the fiber sheet
			7.5.3.3 Unit spalling strength
			7.5.3.4 Plotting monogram
		7.5.4 Reduction factor of curvature
	7.6 Selection of method to prevent spalling
	7.7 Conclusions
	References
	Further reading
Index
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