Experimental and Numerical Study on Seismic Performance of PEN FRP-Jacketed Circular RC Columns

Acknowledgments

Notation

D′

horizontal distance between the centers of two LVDTs;

d_s

diameter of steel bar;

E₂

stiffness of the second segment of LRS FRP-confined concrete;

$E_2^{\ast }$

stiffness of the third segment of LRS FRP-confined concrete;

E₃

slope of the third segment in the model of Bai et al. (2017b);

E_c

initial tangent modulus of unconfined concrete;

E_frp1

initial elastic modulus of FRP;

E_frp2

second-stage elastic modulus of LRS FRP;

E_s

elastic modulus of steel reinforcement;

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

compressive strength of unconfined concrete;

f_frp

tensile strength of FRP coupon;

f_u

ultimate strength of steel reinforcement;

f_y

yield strength of steel reinforcement;

h_e

equivalent viscous damping (EVD) coefficient;

K

spring stiffness;

l_s

length of steel bar;

l_seg

length of each segment of the test column;

P

load at midspan of the curved beam;

R

column radius;

S_ABCDA

area of the hysteretic loop ABCDA;

S_OAE

area of the triangle OAE;

S_OCF

area of the triangle OCF;

t_frp

nominal thickness of FRP;

V

lateral force of the test column;

$V_i^{-}$

negative peak load in the ith cycle;

$V_i^{+}$

positive peak load in the ith cycle;

V_y

yielding load of the test column;

w

height of the horizontal slice;

ɛ_co

axial strain at peak stress of unconfined concrete;

ɛ_frp

ultimate strain of FRP coupon;

ɛ_frp0

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

ɛ_pl,pseudo

pseudo-plastic strain;

ɛ_pl

plastic strain;

ɛ_t

strain at the transition point of the first parabolic segment and the second linear segment of LRS FRP-confined concrete;

${\epsilon }_t^{\ast }$

strain at the transition point of the second linear segment and the third linear segment of LRS FRP-confined concrete;

ɛ_un,env

envelope unloading strain;

Δ₁

LVDT readings on the push side;

Δ₂

LVDT readings on the pull sides;

ΔC

displacement at midspan of the curved beam;

${\mathrm{\Delta }}_i^{+}$

displacement corresponding to the positive peak load;

${\mathrm{\Delta }}_i^{-}$

displacement corresponding to the negative peak load;

δ_y

yielding displacement of the test column;

ɛ^*

strain at the transition point in the model of Bai et al. (2017b);

ɛ_c

axial strain of FRP-confined concrete;

ɛ_s

strain of steel reinforcement;

ɛ_u

ultimate strain of steel reinforcement;

ɛ_y

yield strain of steel reinforcement;

λ₁

efficiency factor of spring stiffness;

λ₂

efficiency factor of slenderness ratio;

λ₃

efficiency factor of yield strength;

μ

lateral displacement ductility ratio of the test column;

σ^*

stress at the transition point in the model of Bai et al. (2017b);

σ_c

axial stress of FRP-confined concrete;

σ_s

stress of steel reinforcement;

σ_t

stress at the transition point of the first parabolic segment and the second linear segment of LRS FRP-confined concrete;

${\sigma }_t^{\ast }$

stress at the transition point of the second linear segment and the third linear segment of LRS FRP-confined concrete;

σ_un,env

envelope unloading stress; and

ϕ_Δ

average curvature of the column section.

References