DESIGN OF MASONRY
COLUMNS
UNIVERSITY OF WISCONSIN STOUT
COLLEGE OF SCIENCE, TECHNOLOGY, ENGINEERING, AND MATHEMATICS
LECTURE XXI
Dr. Jason E. Charalambides
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Nomenclature
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Dimensional Limitations of
Columns

Limitations are imposed on column
dimensions in MSJ C Secs. 1.6,
2.1.6.1, and 2.1.6.2 to prevent
lateral instability. As shown, the
minimum nominal column width is
limited to 8 in.

The ratio of the distance between
lateral supports and least nominal
width must not exceed 25. The
minimum nominal column depth is
limited to 8 in, and the maximum
depth must not exceed three times
the nominal width.
Column Reinforcement
Requirements

Axial Limitations are imposed on
column longitudinal reinforcement in
MSJC Sec. 2.1.6.4. As shown in Fig,
reinforcement must comply with the
following requirements.

Longitudinal reinforcement is limited
to a maximum of 4% of the net
column area of cross section to
reduce congestion in the column.

To prevent brittle failure, the area of
longitudinal reinforcement must not
be less than a minimum of 0.25% of
the _net column area of cross
section.
Column Reinforcement
Requirements

At least four longitudinal reinforcing
bars must be provided, one in each
corner of the column.

Lateral ties, for the confinement of
longitudinal reinforcement in a
column, are specified by MSJC Sec.
2.1.6.5. As shown in Fig, lateral ties
must comply with the following
requirements.
Column Reinforcement
Requirements

Lateral ties for the confinement of
longitudinal reinforcement must not be
less than 1/4 in diameter.

Lateral ties must be placed at a spacing
not exceeding the lesser of 16
longitudinal bar diameters, 48 lateral tie
diameters, or the least cross-sectional
dimension of the column.

Lateral ties must be arranged such that
every corner and alternative longitudinal
bar will have support provided by the
corner of a lateral tie, and no bar will be
farther than 6 in clear on each side from
a supported bar.
Column Reinforcement
Requirements

Lateral ties must be located not more
than one half lateral tie spacing above
the top of the footing or slab in any story,
and must be placed not more than onehalf lateral tie spacing below the
horizontal reinforcement in the beam or
slab reinforcement above.

Where beams or brackets frame into a
column from four directions, lateral ties
may be terminated not more than 3 in
below the lowest reinforcement in the
shallowest beam or bracket.
BASIC EQUATIONS


UnThe allowable axial
compressive strength of an
axially loaded reinforced
masonry column, is given
by MSJC Sec. 2.3.3.2.1.
For columns having a ratio
of effective height to radius
of gyration not greater than
99, the allowable axial
strength is:
For columns having a ratio
of effective height to radius
of gyration greater than 99,
the allowable axial load is:

1

2
Note: h refers to actual height as written. Let's use our known lu notation in the exercise.
abpfdk=lc=j^plkov=`lirjk
Determine the design axial strength of the column and the required
spacing and size of lateral ties. Neglect effects of potential
eccentricity.
fy := 60ksi
f'm := 3ksi
Fs := fy ⋅ 0.4
2
h := 15.625in b := 15.625in As := 0.8in
l u := 15ft
2
2
An := b = 244.141 in
Solution:
ρ :=
As
= 0.003
An
According to MSJC 1.14.1.2. Vertical reinforcement in columns shall
not be less than 0.0025*An nor exceed 0.04*An. The minimum
number of bars is 4.
b⋅ h
3
4
In :=
= 4967.05 in
12
r :=
lu
r
In
An
Using #3 lateral ties, #4 verticals, all grade 60 within a
16" CMU column.
= 4.511 in
= 39.906
  l  2
u
Pa := ( .25⋅ f'm⋅ An + .65⋅ As⋅ Fs) ⋅ 1 − 
 = 179.694 kip
  140 ⋅ r  
d long := .5in d lat := .375in
min( b , h ) = 15.625 in
s := min16d long , 48d lat , ( min( b , h ) ) = 8 in


Bar Designation
Number
3
4
5
6
7
8
9
10
11
14
18
Weight per
foot (lbf)
0.376
0.668
1.043
1.502
2.044
2.670
3.400
4.318
5.304
7.650
13.600
Diameter db
0.375
0.500
0.625
0.750
0.875
1.000
1.128
1.270
1.410
1.693
2.257
Area As
0.11
0.20
0.31
0.44
0.60
0.79
1.00
1.27
1.56
2.25
4.00
Perimeter
1.178
1.571
1.963
2.356
2.749
3.142
3.544
3.990
4.430
5.319
7.091
Reading
Reading:



Required: This set of slides!
Recommended: This set of slides!!!
ASSIGNMENT

Assignment is impossible due to time
limitations
Assignments will be received at th