S2013abn Masonry Construction 1 Architectural Structures
lecture
twenty eight
masonry construction:
beams & columns
www.tamu.edu
A
RCHITECTURAL
S
TRUCTURES
:
F
ORM,
B
EHAVIOR, AND
D
ESIGN
A
RCH 331
HÜDAVERDİ TOZAN
• Masonry Standards Joint Committee
– ACI, ASCE, TMS
– ASD (+empirical)
• linear-elastic stresses
– LRFD added in 2002
– referenced by IBC
– unreinforced allows tension in
flexure
– reinforced - all tension in steel
– walls are also in compression
S2013abn Masonry Construction 4 Architectural Structures
Masonry Beam & Wall Design
• reinforcement increases capacity &
ductility
Masonry Design
BIA Teknote 17 series
grout
unit
t
d
n.a.
STRAIN
STRESS
A
s
f
m
kd
s
M
T
s
=A
s
f
s
f
s
/n
m
C
m
=f
m
b(kd)/2
jd
bd
A
s
• f
s
is not the yield stress
S2013abn Masonry Construction 6 Architectural Structures
Masonry Materials
• units
– stone, brick, concrete block, clay tile
www.GlenGerybrick.com
Masonry Materials
• mortar
– water,
masonry cement,
sand, lime
– types:
• M
higher strength – 2500 psi (ave.)
• S
medium high strength – 1800 psi
• N
medium strength – 750 psi
• O
medium low strength – 350 psi
• K
low strength – 75 psi
W
R
A
O
National Concrete Masonry AssociationS2013abn Masonry Construction 8 Architectural Structures
Masonry Materials
• rebar
• grout
– fills voids and fixes rebar
• prisms
– used to test strength,
f
m
• fire resistant
Ryan-Briggs Associates
Masonry Materials
• moisture resistance
– weathering index
for brick
– bond and detailing
– expansion or
shrinking from water
• provide control joints
• parapets, corners,
long walls
parapet with no
control joint
S2013abn Masonry Construction 10 Architectural Structures
Allowable Masonry Stresses
Masonry Walls
tension normal to bed joints
tension parallel to bed joints
Not allowed in
MSJC code
strong units
weak units
S2013abn Masonry Construction 12 Architectural Structures
Allowable Masonry Stresses
• flexure
– F
b
= 1/3 f’
m
(unreinforced)
– F
b
= 0.45 f’
m
(reinforced)
• shear, unreinforced masonry
– F
v
=
120 psi
• shear, reinforced masonry
– M/Vd
0.25:
F
v
=
– M/Vd
0.25:
F
v
=
m
f
.
5
1
m
f
.
0
3
m
f
.
0
2
Allowable Reinforcement Stress
• tension
a) Grade 40 or 50 F
s
= 20 ksi
b) Grade 60
F
s
= 32 ksi
c) Wire joint
F
s
= 30 ksi
• *no allowed increase by 1/3 for
combinations with wind & earthquake
S2013abn
MSJC: F
s
= 20 ksi, 24 ksi or 30 ksi by type
Masonry Construction 14 Architectural Structures III
Reinforcement, M
s
grout
unit
t
d
n.a.
A
s
T
s
=A
s
f
s
C
m
=f
m
b(kd)/2
jd
F=0:
M about C
m
:
kd
2
kd
b
f
f
A
s
s
m
if f
s
=F
s
(allowable) the moment capacity is limited by the steel
s
2
s
s
s
A
f
jd
ρbd
jf
M
Reinforcement, M
m
grout
unit
t
d
n.a.
A
s
T
s
=A
s
f
s
C
m
=f
m
b(kd)/2
jd
F=0:
jk
bd
f
5
.
0
jd
2
kd
b
f
M
m
m
m
2
kd
MSJC F
b
=0.33f’
m
2
kd
b
f
f
A
s
s
m
if f
s
=F
s
(allowable) the moment capacity is limited by the steel
S2013abn Masonry Construction 16 Architectural Structures
Masonry Lintels
• distributed load
Strategy for RM Flexural Design
• to size section and find reinforcement
– find
b
knowing f’
m
and f
y
– size section for some
<
b
• get k, j
•
• get b & d in nice units
– size reinforcement (bar size & #):
– check design:
s
jF
M
bd
2
needs to be sized
for shear also
jd
F
M
A
s
s
b
b
s
s
s
F
jk
bd
.
M
f
M
jd
F
A
M
2
5
0
S2013abn Masonry Construction 18 Architectural Structures
Ultimate Strength Design
• LRFD
• like reinforced concrete
• useful when beam shear is high
• improved inelastic
model
– ex. earthquake loads
T
1
c
0.80
f’
m
C
2
c
1
Masonry Columns and Pilasters
S2013abn Masonry Construction 20 Architectural Structures
Masonry Columns and Pilasters
• considered a column when
b/t<3 and h/t>4
• b is width of “wall”
• t is thickness of “wall”
• slender is
– 8” one side
– h/t
25
• needs ties
Masonry Columns
– allowable axial load
h/r
99
h/r > 99
h = effective length
r = radius of gyration
A
n
= effective area of masonry
A
st
= effective area of column reinforcement
F
s
= allowable compressive stress in column reinforcement
2
140
1
65
0
25
0
r
h
F
A
.
A
f
.
P
a
m
n
s t
s
7 0
2
6 5
0
2 5
0
h
r
F
A
.
A
f
.
P
a
m
n
s t
s
S2013abn Masonry Construction 22 Architectural Structures
Masonry Walls (unreinforced)
– allowable axial stresses
h/r
99 h/r > 99
2
140
1
25
.
0
r
h
f
F
a
m
2
70
25
.
0
h
r
f
F
a
m
0
.
1
b
b
a
a
F
f
F
f
Design
• masonry columns and walls
– h/r < 99
– h/r > 99
2
140
1
25
.
0
r
h
f
F
a
m
2
70
25
.
0
h
r
f
F
a
m
m
b
f
F
0
.
3 3
and
t
a
b
f
F
f
(unreinforced)
S2013abn Masonry Construction 24 Architectural Structures
Design
• masonry columns and walls - loading
– wind loading
– eccentric axial load
– “virtual” eccentricity, e
1
h
P
e
w
e
o
P
M
V
P
w
P
e
o
w
V
P
e
1
P
M
e
1
virtual eccentricity
Design
• masonry columns and walls – with rebar
– wall reinforcement usually at center and ineffective
in compression
b
b
a
f
F
f
provided
f
a
F
a
grout
unit
t
d
n.a.
BENDING STRESS
A
sf
mM
T
s=A
sf
sf
s/n
C
m=f
mb(kd)/2
jd
f
a=
P/A
AXIAL STRESS
F
P
C
m
T
s
for equilibrium:
S2013abn Masonry Construction 26 Architectural Structures
Design Steps Knowing Loads
1. assume limiting stress
•
buckling, axial stress,
combined stress
2. solve for r, A or S
3. pick trial section
4. analyze stresses
5. section ok?
Final Exam Material
• my list:
– systems
• components & levels
• design considerations
– equilibrium -
F &
M
• supports, trusses, cables, beams, pinned frames,
rigid frames
– materials
S2013abn Masonry Construction 28 Architectural Structures
