Confinement Characteristics of GFRP-RC Circular Columns under Simulated Earthquake Loading: A Numerical Study

Acknowledgments

Notation

A_c

cross-sectional area of column core;

A_g

gross cross-sectional area of the column;

A_sh

required area of confinement reinforcement;

c_ts

tension stiffening factor;

D

column diameter;

d_s

nominal cross-sectional diameter of the hoop;

E_c

elastic modulus of concrete in compression;

E_EXP

experimental total energy dissipation;

E_FEM

total energy dissipation estimated by FEM;

E_f

elastic modulus of FRP reinforcement in tension;

f_c′

specified concrete compressive strength;

f_Fh

design stress level in FRP confinement reinforcement;

f_Fu

ultimate strength of the GFRP reinforcement;

f_t-cr

tensile stress at the crack location;

f_t′

tensile strength of concrete;

G_F

specific fracture energy of concrete;

h_c

cross-sectional dimension of column core;

K_EXP

experimental initial stiffness;

K_FEM

initial stiffness estimated by FEM;

K_P

proposed coefficient that denotes the synergistic effect of axial load level and the concrete strength;

K_n

normal shear crack stiffness of cracked concrete;

K_s

proposed coefficient combining the effects of spiral pitch and concrete compressive strength;

K_t

tangential shear crack stiffness of cracked concrete;

k_c

confinement efficiency coefficient;

L

column shear span;

P

axial load applied to the column;

P_o

nominal unconfined axial capacity of the column;

$r_c^{\lim }$

reduction factor of compressive strength;

S_F

shear factor coefficient of concrete;

s

spiral pitch;

w_d

critical compressive displacement of concrete;

V_EXP

experimental lateral load capacity in pushing direction;

V_FEM

lateral load capacity in pushing direction as estimated by FEM;

V′_EXP

experimental lateral load capacity in pulling direction;

V′_FEM

lateral load capacity in pulling direction as estimated by FEM;

w_cr

crack width;

β

multiplier for the specific flow direction;

Δ

lateral displacement at the column tip;

δ

design drift ratio;

δ_CSA

failure drift estimated as per CSA S806-12 (CSA 2017);

δ_EXP

experimental failure drift;

δ_FEM

failure drift estimated by FEM;

δ_I

failure drift estimated using Model I [Eq. (6)];

δ_II

failure drift estimated using Model II [Eqs. (9) or (10), as appropriate];

ɛ_cp

plastic strain at compressive strength;

ɛ_zz

plastic strain of concrete in the longitudinal direction of the column;

µ

Poisson's ratio;

ρ

specific material weight;

ρ_f

GFRP longitudinal reinforcement ratio; and

ϕ_f

material resistance factor for FRP reinforcement, taken equal to unity.

References