Cyclic Performance of GFRP-RC T-Connections with Different Anchorage and Connection Details

Acknowledgments

Notation

A_b

nominal area of an individual FRP bar;

A_c

confined concrete core area of column;

A_f

total area of tensile reinforcement in beam;

A_FH

area of ties for confinement of column in each cross-sectional direction;

A_FH,provided

provided area of horizontal stirrups at connection;

A_FH,required

required area of horizontal stirrups at connection;

A_g

gross area of column section;

A_j

effective joint area parallel to axis of reinforcement-generating shear;

C_c

compressive force developed by concrete in beam section under flexure;

d

effective depth of beam section;

d_b

nominal diameter of FRP bar;

d_cs

the smaller of the distances from closest concrete surface to the center of the bar and the two-thirds of the center-to-center spacing of the bars being developed;

DR

applied drift ratio;

E_f

elastic modulus of FRP bar;

E_i

energy dissipation per cycle;

f_a

anchorage resistance of longitudinal bars of the beam;

f_b

bent portion tensile strength of FRP bar;

f_bf

design tensile stress level in FRP flexural reinforcement of the beam;

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

compressive strength of concrete;

f_f

stress level in tensile reinforcement of the beam;

f_fc

compressive strength of FRP bar;

f_fh

design tensile stress level in FRP transverse reinforcement of the column;

f_fu

ultimate tensile strength of FRP bar;

h

depth of column section;

h_b

depth of beam section;

h_c

cross-sectional dimension of column core;

H_c

vertical distance between the horizontal roller supports on the column;

k_p

peak-to-peak stiffness of hysteresis loop;

k₁

bar location factor;

k₂

concrete density factor;

k₃

bar size factor;

k₄

bar fiber factor;

k₅

bar surface profile factor;

K_c

confinement factor;

L

distance from the loading point to the center of the column;

L_b

length of beam from face of column to center of the loading point;

ℓ_a

anchorage length of the longitudinal FRP bar of the beam;

ℓ_db

development of bent FRP bar in tension;

ℓ_db,provided

provided development of longitudinal bar of the beam;

ℓ_o

greater of depth of the column, one-sixth of clear span of the member and 450 mm;

M_nb

nominal flexural capacity of the beam;

M_nc

nominal flexural capacity of the column;

M_R

column-to-beam flexural strength ratio;

n

number of FRP bars in tension;

P

applied load at the free end of the beam;

P_ci

crack initiation load;

P_e

virtual yield load;

P_f

applied column axial load;

P_max

maximum load achieved by beam during experiment;

P_n

nominal load-carrying capacity of the beam;

P_o

nominal unconfined axial load capacity of column;

P_s

service load;

S

slip of FRP bar;

S₁

slip of FRP bar at maximum bond stress;

S₂

slip of FRP bar at end of effective bond region;

s

spacing of ties;

s₁

spacing of tie legs;

T_f

maximum tensile force developed by tensile reinforcement in beam section under flexure;

V_c

shear force in column;

V_j,max

maximum connection shear developed during the experiment;

V_nf

nominal connection shear capacity;

V_uf

design connection shear force;

Z_b

internal lever arm of beam section;

γ

factor that depends on the level of confinement provided to the joint by adjoining members;

δ

design drift ratio, shall not be less than 0.03;

Δ

beam tip displacement;

Δ_capacity

displacement capacity;

Δ_e

virtual yield displacement;

Δ_u

ultimate yield displacement;

ɛ_b

average strain in longitudinal bar of the beam over the anchorage length;

ɛ_f

strain in longitudinal bar of the beam;

ɛ_f1

strain in longitudinal bar of the beam at the end of anchorage;

ɛ_f2

strain in longitudinal bar of the beam at the face of the column;

ɛ_fu

ultimate strain FRP bar;

µ

displacement ductility;

τ

bond stress for FRP bar;

τ_avg

average bond stress developed in connection during the experiment;

τ_b,max

maximum bond stress;

τ_b,r

residual bond stress;

τ_b,u

average effective bond stress; and

ϕ_f

resistance factor of FRP bar.

References