Assessment of FRP–Concrete Interfacial Debonding with Coupled Mixed-Mode Cohesive Zone Model

Acknowledgments

Notation

a–c

variables in the calculation of Δ_m;

c₀

cohesion in the Mohr–Coulomb strength criterion;

d, e

variables in the calculation of k;

D

damage index that describes the damage evolution in mixed-mode conditions;

f_t

tensile strength of the concrete;

G_I

energy release rate in the normal direction;

G_Ic

pure mode I fracture energy;

G_II

energy release rate in the tangential direction;

G_IIc

pure Mode II fracture energy;

K_n

initial stiffness of the cohesive relation in the normal direction;

K_t

initial stiffness of the cohesive relationship in the tangential direction;

k

damage evolution parameter;

L_e

effective bond length of the interface;

l_b

bond length of the FRP plate;

P_max

peak peel load;

P_peel

peeling load at steady state;

P_shear

peak load in pure Mode II load condition;

s

slip of the interface;

s_m

slip in the interface that corresponds to the ultimate strength;

$s_m^0$

tangential relative displacement at the onset of interfacial softening;

s₀

upper limit slip of the linear branch of the cohesive relation in the tangential direction;

t_f

thickness of the FRP plate;

w

opening of the interface;

w_m

opening in the interface that corresponds to the ultimate strength;

$w_m^0$

normal relative displacement at the onset of interfacial softening;

α

descending slope of the normal cohesive relation characteristic parameter;

β

descending slope of the tangential cohesive relation characteristic parameter;

γ

mode–mixity ratio;

Δ

effective relative displacement under mixed-mode conditions;

Δ_m

effective relative displacement that corresponds to the damage initiation;

Δ_u

effective relative displacement that corresponds to the failure state;

ζ

power exponent in PL criterion;

η

power exponent in BK criterion;

θ

peel angle;

τ

shear stress at the interface in the tangential direction;

τ_m

shear strength of the cohesive relationship under pure Mode II condition;

${\tau }_m^0$

instantaneous tangential strength under mixed-mode condition;

σ

stress at the interface in the normal direction;

σ_m

traction strength of the cohesive relation under pure Mode I condition;

${\sigma }_m^0$

instantaneous normal strength under mixed-mode condition; and

φ

internal friction angle in the Mohr–Coulomb strength criterion.

References