DESIGN - Prestressed Concrete Transmission Pole Structures - page 46

VVV
n

=+ (4-8)

c s

where V c is the nominal shear strength provided by the concrete and V s
is the nominal shear strength provided by the shear reinforcement.

Square or Rectangular Prestressed Concrete Poles: For square or
rectangular prestressed concrete members with an effective prestress force
not less than 40% of the tensile strength of the fl exural reinforcement, V c
may be computed as

Vd
M

⎡
⎢

⎛
⎜

⎞
⎟

⎤
⎥

u

V = 0 6 . f ′ + 700 bd

(4-9) c c w

u

but V c need not be less than 2 bd f
w

.
The quantity V u d / M u shall not be greater than 1.0, where M u is the
factored moment occurring simultaneously with V u at the section consid-
ered. The variable d shall be the distance from the extreme compressive
fi ber to the centroid of the prestressing reinforcement, and b w shall be the
width of the web.

nor shall it be greater than 5 bd f
w

′ ′

c c

Circular Prestressed Concrete Poles: For circular prestressed con-
crete members

f

2

+ f f

′ ′ t t pc

V =

(4-10)

c

Q
It

2

where

f t = tensile strength of concrete taken as 4

f c ,

′

f pc = effective compressive stress of concrete due to prestress,

Q = moment of area above centroid,

I = moment of inertia of cross section, and

t = wall thickness.

For the shear strength V s contributed by the steel

Afd
s

vy

(4-11)

V =

s

where A v is the area of the shear reinforcement within a distance s , f y is
the yield strength of the steel, and d is the distance from the compression
force to the centroid of the prestressing steel, or 0.8 times the outside
diameter of the section, whichever is greater.