Assessment of Punching Shear Design Models for FRP-RC Slab–Column Connections

Acknowledgments

Notation

A_Fv

area of FRP shear reinforcement;

A_s

area of single shear stud or vertical stems of corrugate bars, stirrups, and spirals;

a

maximum aggregate size;

b_o

perimeter of the critical section for shear;

b_o,0.5d

perimeter of the critical section for shear located at 0.5d from the column face;

b_x

critical section dimension in the x-direction;

b_y

critical section dimension in the y-direction;

b₁

width of the critical section in the direction of unbalanced moment;

b₂

width of the critical section perpendicular to b₁;

C

column width;

d

average depth of the slab;

d_b

stirrup diameter;

E_F

modulus of elasticity of FRP reinforcement;

E_Fv

modulus of elasticity of FRP shear reinforcement;

E_S

modulus of elasticity of steel reinforcement;

e

distance from the centroid of the critical section to the point where shear stress is being calculated;

e_x

load eccentricity in the x-direction;

e_y

load eccentricity in the y-direction;

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

specified compressive strength of concrete;

f_Fv

allowable stress in FRP stirrups;

f_fbend

ultimate strength of the bent portion of FRP stirrups;

f_pcd

factor to account for concrete strength;

f_uv

ultimate strength of straight portion of FRP stirrups;

h

slab thickness;

I_cr

cracked moment of inertia per unit width of the slab;

I_g

gross moment of inertia per unit width of the slab;

J_c

property of the critical shear section analogous to the polar moment of inertia;

k

ratio of neutral axis depth of the cracked section to depth of reinforcement;

L₁

slab dimension perpendicular to unbalanced moment;

L₂

slab dimension parallel to unbalanced moment;

M/V

moment-to-shear ratio;

M_cr

cracking moment per unit width of the slab;

M_f

factored unbalanced moment transferred between the slab and the column;

M_n

ultimate moment per unit width of the slab;

M_p

equivalent plastic moment capacity for FRP-RC slabs;

N

factor to account for the effect of slab restraining;

n

number of vertical stems of shear reinforcement in a peripheral row around column;

n_F

ratio between the modulus of elasticity for FRP to the modulus of elasticity for concrete;

r_b

stirrup bend radius;

s

spacing of FRP shear reinforcement measured perpendicular to the critical section;

u

perimeter of the loaded area;

V_c

punching shear strength provided by concrete;

V_exp

experimental capacity of test connection;

V_f

total factored shear force transferred between the slab and the column;

V_g

gravity shear force transferred between the slab and the column;

v_c

shear stress resistance provided by concrete;

v_c,inner

shear stress resistance provided by concrete at the inner critical section;

v_c,outer

shear stress resistance provided by concrete at the outer critical section;

v_exp

experimental shear stress resistance;

v_exp,0.5d

experimental shear stress resistance at the critical section located at a distance of 0.5d;

v_exp,1.5d

experimental shear stress resistance at the critical section located at a distance of 1.5d;

v_f

factored shear stress on the critical section;

v_n

nominal shear stress resistance;

v_pred

predicted shear stress resistance;

v_s

shear stress resistance provided by shear reinforcement;

v_sF

shear stress resistance provided by FRP shear reinforcement;

α

load eccentricity factor;

α_s

dimensionless coefficient to account for the location of slab–column connections;

β_c

ratio of the long side to the short side of the column;

β_d

size effect factor;

β_p

reinforcement axial stiffness factor;

β_r

factor to account for the column perimeter-to-slab depth ratio;

γ_b

factor of safety generally taken as 1.3;

γ_v

fraction of unbalanced moment transferred by eccentricity of shear;

δ

interstory drift ratio;

ɛ_Fv

allowable strain in FRP shear reinforcement;

λ

factor to account for concrete density;

ρ_F

longitudinal FRP reinforcement ratio;

ϕ

strength reduction factor;

ϕ_F

resistance factor for FRP shear reinforcement; and

ϕ_c

resistance factor for concrete.

References