Effect of Sulfate Attack on Reinforced Concrete Columns Confined with CFRP Sheets under Axial Compression

Acknowledgments

Notation

A_c

cross-sectional area of concrete, mm²;

A_e

effective cross-sectional area of concrete, mm²;

A_g

cross-sectional area of columns, mm²;

A_st

cross-sectional area of longitudinal reinforcements, mm²;

C_tlc

experimental factor accounting for immersion time in sulfate solution, the number of FRP layers, and properties of concrete;

D

equivalent diameter of rectangular section, mm;

EA₀

axial initial stiffness, kN/mm;

E_adhesive

elastic modulus of adhesive, GPa;

E_f

elastic modulus of CFRP sheets, GPa;

E_s

elastic modulus of steel, GPa;

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

compressive strength of confined concrete, MPa;

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

compressive strength of unconfined concrete cylinders, MPa;

f_c,cube

compressive strength of unconfined concrete cubes, MPa;

f_adhesive,u

tensile strength of adhesive, MPa;

f_ffu

ultimate strength of CFRP sheets, MPa;

f_l

lateral confinement stress, MPa;

f_sp,cube

spliting tensile strength of concrete from concrete cubes, MPa;

f_u

ultimate strength of longitudinal reinforcements, MPa;

f_uw

ultimate strength of stirrups, MPa;

f_y

yield strength of longitudinal reinforcements, MPa;

f_yw

yield strength of stirrups, MPa;

IEP_CFRP

sulfate prevention efficiency index;

k₁

confinement calibration factor for confined concrete = 3.3 (Lam and Teng 2003);

k_s1

shape factor;

M_y

index for concrete strength;

n

number of CFRP layers;

P_core

contribution of concrete core to the axial load–carrying capacity, kN;

P_FRP

contribution of CFRP to the axial load–carrying capacity, kN;

P_u

failure load, kN;

P_u,0

failure load of unconfined columns, kN;

P_u,60

failure load of columns in Group B, kN;

P_{u,Lam-Teng,pred}

predicted load-carrying capacity of the columns using Lam and Teng’s (2003) model, kN;

P_u,mode,pred

predicted load-carrying capacity of the columns using the proposed model, kN;

P_u,exp

experimental load-carrying capacity of the columns, kN;

P_y

yielding load, kN;

R_c

radius of rounded corners, mm;

t

number of wet–dry cycles;

t_f

nominal thickness of CFRP sheets, mm;

x

group index, = C (150 cycles) or = D (210 cycles);

δ_y

axial displacement at yielding load, mm;

δ_hu

lateral displacement at the failure load, mm;

δ_vu

axial displacement at the failure load, mm;

ɛ_cu

ultimate compressive strain of concrete, ‰;

ɛ_f

CFRP strain, ‰;

ɛ_fu

rupture strain of CFRP sheets, ‰;

ɛ_j

Nominal rupture strain of CFRP sheets, ‰;

ɛ_st

longitudinal-reinforcement strain, ‰;

ɛ_stu

longitudinal-reinforcement strain at the failure load, ‰;

ɛ_sw

stirrup strain, ‰;

ɛ_swu

stirrup strain at the failure load, ‰; and

ρ_sc

longitudinal-reinforcement ratio.

References