Experimental Behavior of UHPC Shear Walls with Hybrid Reinforcement of CFRP and Steel Bars under Lateral Cyclic Load

Acknowledgments

Notation

A

cross-sectional area of the specimen;

A_sv

cross-sectional area of the shear reinforcement;

A_sw

total cross-sectional area of the steel bars;

a_s

distance from centroid point of the outermost tensile reinforcement to the tensile edge of the shear wall;

b

width of the shear wall;

d

diameter of the reinforcement bars;

E_c

elastic modulus of UHPC;

E_f

elastic modulus of the CFRP bars;

E_s

elastic modulus of the steel bars;

E_sc

secant modulus of UHPC corresponding to peak stress;

E_u

energy consumption at the ultimate drift ratio of the specimen;

F

lateral force applied at the top of the specimen;

F_cr

cracking force of the specimen;

+F_j

maximum lateral force in the positive direction of the jth loading level;

−F_j

maximum lateral force in the negative direction of the jth loading level;

$F_j^1$

maximum lateral force on the first loading cycle of the jth loading level;

$F_j^3$

maximum lateral force on the third loading cycle of the jth loading level;

F_m

maximum lateral force of the specimen;

F_u

ultimate lateral force of the specimen;

F_y

yielding force of the specimen;

f_c

compressive strength of UHPC;

f_cm

mean value of tested axial compressive strength of the UHPC;

f_cd

design value of axial compressive strength of the UHPC;

f_cu

compressive strength of standard 100-mm UHPC cubes;

f_ftu

tensile strength of the CFRP bars;

f_lf

confinement pressure induced by steel fibers;

f_ls

confinement pressure induced by stirrups;

f_t0

initial cracking strength of the UHPC under uniaxial tension;

f_tu

tensile strength of the UHPC under uniaxial tension;

f_u

tensile strength of the steel bars;

f_y

yield strength of the steel bars;

f_yv

yielding strength of the shear reinforcement;

H

height of the specimen;

h

height of the cross section of the shear wall;

h₀

effective height of the cross section of the shear wall;

K_j

secant stiffness of the specimen in the jth loading level;

k

coefficient in calculating the height of compressive zone;

M

moment at the bottom of the specimen;

N

design value of the axial load applied on the specimen;

N_t

test value of the axial load applied on the specimen;

n

design axial-load ratio of the shear wall;

n_t

test axial-load ratio of the shear-wall specimen;

S_(ABC+CDA)

area surrounded by one hysteresis loop, as shown in Fig. 15;

S_(OBE+ODF)

total area of triangle OBE and ODF, as shown in Fig. 15;

s

space of the shear reinforcement;

x_c

depth of the compressive zone;

z

distance from the compressive side of the shear wall to the location of the CFRP bar;

α₁

ratio of average stress of equivalent rectangular stress block to axial compressive strength of UHPC;

β₁

factor of compressive height of equivalent rectangular stress block;

β_v

influence coefficient of steel fiber on the shear capacity of the UHPC compressive members;

γ

self-centering coefficient of the specimen;

γ₁

relative height of the tensile zone corresponding to the ascent segment of the tensile stress distribution;

γ₂

relative height of the tensile zone corresponding to the invariant segment of the tensile stress distribution;

γ_F

partial safety factor for dead load;

γ_j

strength-degradation coefficient of the specimen in the jth loading level;

γ_m

partial safety factor for compressive strength of the UHPC;

γ_n

coefficient between design and test axial-load ratio of UHPC shear wall;

Δ_cr

cracking displacement of the specimen;

+Δ_j

maximum lateral displacement in the positive direction of the jth loading level;

−Δ_j

maximum lateral displacement in the negative direction of the jth loading level;

Δ_m

maximum lateral displacement of the specimen;

Δ_rm

maximum lateral displacement in the same hysteretic loop of Δ_r;

Δ_r

residual displacement in the hysteretic loop;

Δ_u

ultimate displacement of the specimen;

Δ_y

yielding displacement of the specimen;

δ

lateral displacement at the top of the specimen;

δ_y

yielding displacement of the specimen;

δ_u

ultimate displacement of the specimen;

ɛ_c

compressive strain of UHPC;

ɛ_c0

compressive strain of UHPC corresponding to peak compressive stress;

ɛ_ct0

tensile strain of UHPC corresponding to peak tensile stress;

ɛ_ctu

ultimate tensile strain of UHPC;

ɛ_cu

ultimate compressive strain of UHPC;

ɛ_f

tensile strain in CFRP bars;

λ_f

characteristic parameter of steel fibers;

μ

length coefficient in calculating the critical buckling force of the shear walls;

ξ_c

relative height of the compressive zone;

ρ_s

vertical reinforcement ratio of the UHPC shear wall;

σ_c

compressive stress of UHPC; and

ω

ratio of the height of the steel strip to the effective height of the cross section.

References