Concrete Columns Reinforced with GFRP and BFRP Bars under Concentric and Eccentric Loads: Experimental Testing and Analytical Investigation

Acknowledgments

Notation

A_c

area of confined concrete core measured to the outside diameter of the spiral/tie;

A_f

cross-sectional area of FRP bars;

A_g

column's cross-sectional area;

A_st

cross-sectional area of steel bars;

a

depth of the concrete block in compression;

e

load eccentricity value (mm);

e/h

load eccentricity-to-width ratio;

E_f

tensile modulus of elasticity of FRP bars;

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

concrete compressive strength;

f_fu

tensile strength of FRP bars;

f_y

yield strength of steel bars;

h

column's dimension (equal to 180 mm for all columns);

L_e

effective column length;

M_u

bending moment corresponding to ultimate load P_u;

P_bars

force carried by the longitudinal bars;

P_exp

column's axial capacity measured experimentally;

P_norm

normalized axial load;

P_pred

column's axial capacity predicted by design equations;

P_u

column's ultimate capacity;

r

radius of gyration of the column's cross section;

y_c

distance from the centroid of the concrete compression block to the centroid of the column section;

y_fc

distance from the centroid of compression reinforcement to the centroid of thecolumn section;

y_ft

distance from the centroid of tensile reinforcement to the centroid of the column section;

α₁

column's capacity reduction factor;

Δ

measured midheight lateral displacement of the column at the peak load;

δ₁

axial displacement corresponding to a load of 85% of the peak load in the descending branch of the load–displacement curve;

δ₂

axial displacement obtained by extending the linear portion of the load–displacement curve to intersect with a horizontal line corresponding to the peak load;

ɛ_bar

measured strain in the longitudinal bars at the peak load;

ɛ_c

concrete strain at peak stress;

ɛ_fc

strain in the FRP bars in compression;

ɛ_ft

strain in the FRP bars in tension; and

ρ

column's longitudinal reinforcement ratio.

References