Page 343 - Design of Reinforced Masonry Structures

COLUMNS 5.63

Also, rQ = 0 as stated above. Therefore, the pertinent Load Combination can be
E
expressed as
U = [0.9 – 0.2 (1.25)]D
= [0.9 – 0.2 (1.25)](20) = 13 kips (smallest value)

Because P is additive to the shear strength of the column, V , the smallest of the above
nm
u
four values of P would be used.
u
P = 13 kips
u
Q = V = 2.0 kips
E
E
r = 1.0 per ASCE-05 Section 12.3.4.1.
M = 1.0 (2) (24) = 48 k-ft
u
The shear span ratio for the column is
( )
M 48 12
u = = 19 37 1 0. > .
Vd v (1 5 19 825. )( . )
u
M
Use u = 10 (MSJC-08 Section 3.3.4.1.2.1)
.
Vd v
u
The nominal shear strength of the column, V , is given by MSJC-08 Eq (3.22)
.
nm
(discussed in Chap. 4, Section 4.10.1):
⎡ ⎛ M ⎞ ⎤
−
⎢
V nm = 41 75. ⎜ u ⎟ ⎥ A n f ′ + 0 25. P u
m
⎣ ⎝ VD ⎠ ⎦
v
u
Using the Load Combination with minimum axial load (P = 13 kips), the shear strength
u
contribution of masonry is
V = [4 – 1.75(1.0)] (369) 2000 + 0.25 (13,000)
nm
= 40,380 lb = 40.38 kips
The shear strength contributed by the shear reinforcement is given by MSJC-08
Eq. (3.23):
y )
V = 05. ( A v fd
ns s v
( )
.
011
.
= 05 ( )(19 825. ) = 8 1. 88kips
60
8
The total nominal shear strength of the column is
V = V + V ns
n
nm
= 40.38 + 8.18 = 48.56 kips