Unified Ultimate Axial Strain Model for Large Rupture Strain FRP–Confined Concrete Based on Energy Approach

Data Availability Statement

Acknowledgments

Notation

b

width of specimen (mm);

D

diameter of circular column (mm);

E_c

elastic modulus of unconfined concrete (GPa);

E_frp0

initial elastic modulus of LRS FRP (GPa);

E_frp1

second-stage elastic modulus of LRS FRP (GPa);

E_l

confinement stiffness ratio;

E₁

first slope of LRS FRP–confined concrete (E₁ = E_c);

E₂

second slope of LRS FRP–confined concrete (MPa);

E₃

third slope of LRS FRP–confined concrete (MPa);

f_co

unconfined concrete strength (MPa);

f_cu

ultimate strength of LRS FRP–confined concrete (MPa);

f_cuo

strength corresponding to ultimate strain of unconfined concrete (MPa);

f_frp

ultimate rupture strength for LRS FRP sheet (MPa);

f_frp0

tensile stress of LRS FRP at transition strain ɛ_frp0 (MPa);

f_l

maximum confining pressure provided by FRP jacket (MPa);

f_m

axial stress at postpeak transition strain ɛ_m (MPa);

f₃₀

strength of Grade 30 concrete (f₃₀ = 30 MPa);

H

height of column (mm);

h

length of rectangular section (mm);

k_frp

FRP volume rate;

k_ɛ

strain reduction factor;

r

corner radius (mm);

t

thickness of FRP (mm);

U_ad

additional energy absorption of concrete due to increased internal resistance of concrete caused by confinement (J);

U_c

total strain energy capacity of LRS FRP–confined concrete (J);

U_cf

additional energy absorption capacity of LRS FRP–confined concrete (J);

U_co

strain energy capacity of unconfined concrete (J);

U_frp

total work done by FRP jacket (J);

U₀

equivalent LRS FRP energy absorption capacity (J);

U₁

energy of unconfined concrete with strain from 0 to ɛ_cuo (J);

U₂

energy difference between confined concrete and unconfined concrete (J);

U₃

residual strain energy for unconfined concrete (J);

U₄

residual strain energy absorption capacity for LRS FRP–confined concrete after LRS FRP rupture (J);

V_column

volume of concrete column (mm³);

V_frp

volume of FRP jacket (mm³);

ɛ_c

axial strain of concrete;

ɛ_co

axial strain corresponding to peak strength for unconfined concrete;

ɛ_cu

ultimate strain of LRS FRP–confined concrete;

ɛ_cuo

ultimate strain of unconfined concrete (ɛ_cuo = 1.75ɛ_co);

ɛ_f,rup

rupture strain of LRS FRP jacket;

ɛ_frp

tensile rupture strain of LRS FRP sheet;

ɛ_frp0

coupon test tensile strain of FRP at transition point;

ɛ_m

axial strain at postpeak transition point of LRS FRP–confined concrete;

λ

energy absorption factor;

σ_c

axial stress of LRS FRP–confined concrete (MPa); and

σ_co

axial stresses for unconfined concrete.

References