Compressive Behavior of Large-Scale PEN and PET FRP–Confined RC Columns with Square Cross Sections

Acknowledgments

Notation

A_g

gross area of the column section with rounded corners;

b

width of the cross section;

C_frp

constant strength value where the second linear curve intersects with the stress axis for the LRS FRP;

D_eq

equivalent diameter in the model of Zhang (2021);

d_e

equivalent diameter in the model of Lam and Teng (2003b);

d_s

steel bar diameter;

E_c

initial tangent modulus of unconfined concrete;

E_frp1

initial elastic modulus of the LRS FRP;

E_frp2

second-stage elastic modulus of the LRS FRP;

E_s

elastic modulus of steel reinforcements;

E_sec

secant modulus at the initial peak point of LRS FRP–confined concrete;

E₂

slope of the linear part of the initial strength–softening branch for LRS FRP–confined concrete;

E₃

slope of the final branch for LRS FRP–confined concrete;

f_c

axial stress of LRS FRP–confined concrete;

f_frp

tensile strength of the LRS FRP;

f_l

confining pressure provided by the FRP jacket;

f_u

ultimate strength of the steel reinforcement;

f_y

yield strength of the steel reinforcement;

$f_c^{\mathrm{\prime }}$

peak stress of the unconfined concrete cylinder;

$f_{co}^{\mathrm{\prime }}$

peak stress of the control RC column;

$f_{c1}^{\mathrm{\prime }}$

initial peak axial stress of LRS FRP–confined concrete;

$f_{cs}^{\mathrm{\prime }}$

axial stress corresponding to the change in slope of the initial strength–softening segment for LRS FRP–confined concrete;

$f_{c2}^{\mathrm{\prime }}$

axial stress corresponding to the end of the initial strength–softening segment for LRS FRP–confined concrete;

$f_{cu,f}^{\mathrm{\prime }}$

final axial stress of LRS FRP–confined concrete;

$f_{cu}^{\mathrm{\prime }}$

ultimate axial stress of LRS FRP–confined concrete;

$f_{cc}^{\mathrm{\prime }}$

maximum axial stress of LRS FRP–confined concrete;

h

length of the cross section;

N_frp

the number of FRP layers;

r

corner radius;

r_c

corner radius ratio;

k_s

shape factor;

k_ɛ

strain reduction factor of the LRS FRP for a noncircular section;

n

coefficient in the model of Pimanmas and Saleem (2019);

K

stiffness ratio.

t_frp

nominal thickness of FRP;

ɛ_c

axial strain of LRS FRP–confined concrete;

${\epsilon }_c^{\mathrm{\prime }}$

axial strain at the peak stress of the unconfined concrete cylinder;

ɛ_co

axial strain at the peak stress of the control RC column;

ɛ_cu

ultimate axial strain of LRS FRP–confined concrete;

ɛ_cu,f

final axial strain of LRS FRP–confined concrete;

ɛ_frp

ultimate strain of the LRS FRP;

ɛ_frp0

strain at which the slopes of two linear portions of the LRS FRP curve intersect;

ɛ_h

hoop strain in the FRP jacket;

ɛ_u

ultimate strain of the steel reinforcement;

ɛ_cs

axial strain corresponding to the change in slope of the initial strength–softening segment for LRS FRP–confined concrete;

ɛ_c1

axial strain corresponding to the initial peak axial stress of LRS FRP–confined concrete;

ɛ_c2

axial strain corresponding to the end of the initial strength–softening segment for LRS FRP–confined concrete;

ɛ_y

yield strain of the steel reinforcement;

ρ_eff

threshold effective confinement stiffness in the model of Zhang (2021);

ρ_f

FRP reinforcement ratio;

ρ_k,eff

effective confinement stiffness ratio;

ρ_sc

longitudinal steel reinforcement ratio;

ρ_ɛ

strain ratio;

κ_a

efficiency factor; and

σ_f

instantaneous tensile stress of the LRS FRP.

References