Ductile Concrete Columns Enabled by Multilayer Basalt TRM Shells: Confinement Mechanism and Modeling

Acknowledgments

Notation

A_m, A_co, and A_sh

the cross-sectional areas of the shell mortar, core, and shell, respectively (mm²);

d

diameter of the concrete core (mm);

E_c

secant modulus of the concrete core (MPa);

E_c0

elastic modulus of unconfined concrete (MPa);

E_f

elastic modulus of basalt textile (MPa);

E_m

elastic modulus of mortar (MPa);

E_sh,V and E_sh,L

compressive and tensile elastic moduli of the shell material in axial and lateral directions, respectively (MPa);

f_c0

compressive strength of unconfined concrete (MPa);

f_cc

compressive strength of confined concrete (MPa);

$f_{ce}^{\ast },f_{cc}^{\ast },\mathrm{and}{f}_{cr}^{\ast }$

elastic limit, peak axial and residual stresses of actively confined concrete (MPa);

f_l

lateral confining pressure (MPa);

f_lu

nominal maximum confining pressure by assuming lateral strain as ɛ_fu (MPa);

G_fc

compressive fracture energy of concrete (MPa × mm);

K

initial stiffness of the columns (MPa/mm);

l_c

characteristic length of the specimen in the loading direction, namely, specimen height (mm);

n

number of textile layers (dimensionless);

P₀

elastic limit point;

r and E_s

parameters determining the shapes of stress–strain curves of actively confined concrete in ascending stage;

t

thickness of the confinement shell (mm);

t_f

nominal equivalent thickness of basalt textile in the weft direction (mm);

u_u

ultimate secant Poisson’s ratio of confined concrete (dimensionless);

V_f and V_m

volume fractions of textile and matrix in the specific direction (dimensionless);

Δ and β

parameters to determine the secant Poisson’s ratio of confined concrete, u_c;

α

parameter determining the shapes of stress–strain curves of actively confined concrete in descending stage (dimensionless);

ɛ_c0

axial strain corresponding to unconfined concrete compressive strength f_c0 (dimensionless);

ɛ_cc

ultimate axial strain of confined concrete (dimensionless);

ɛ_cc,test and ɛ_cc,pred

testing and predicted ultimate axial strain of confined concrete (dimensionless);

${\epsilon }_{ce}^{\ast }\mathrm{and}{\epsilon }_{cc}^{\ast }$

elastic limit strain and axial strain at peak axial stress, $f_{cc}^{\ast }$ (dimensionless);

ɛ_co,h

hoop strain of the concrete core (dimensionless);

ɛ_co,Lu

ultimate lateral strain of the concrete core (dimensionless);

ɛ_co,V and ɛ_co,L

axial strain and lateral strain of the concrete core (dimensionless);

ɛ_fu

maximum tensile strain of basalt textile (dimensionless);

ɛ_sh,V and ɛ_sh,L

axial strain and lateral strain of the confinement shell (dimensionless);

ɛ_textile,L

lateral strain of textile (dimensionless);

μ_c and μ_sh

secant Poisson’s ratios of the concrete core and shell, respectively (dimensionless), and the latter one taken as μ_m0;

μ_c0

Poisson’s ratio of unconfined concrete (dimensionless);

μ_m0

Poisson’s ratio of mortar (dimensionless);

ρ_k

confinement stiffness ratio (dimensionless);

σ_m, σ_co,V, and σ_sh,V

axial stresses of shell mortar, core, and shell, respectively (MPa);

σ_nc

the nominal axial stress of the thick-shell confined system (MPa);

σ_sh,L

lateral tension stress of confinement shell (MPa); and

σ_u

tensile strength of basalt textile (MPa)

References