1
F2012abn
APPLIED ARCHITECTURAL STRUCTURES:
STRUCTURAL ANALYSIS AND SYSTEMS
ARCH 631
DR. ANNE NICHOLS
FALL 2014
twenty three
masonry construction
Masonry Construction 1Lecture 23
Applied Architectural StructuresARCH 631
lecture
Bright Football Complexwww.tamu.edu
F2010abn
Learning Evaluation
Masonry Construction 2
Lecture 23
Architectural Structures III
ARCH 631
F2009abn
Masonry
• columns
• beams
• arches
• walls
• footings
Masonry Construction 2Lecture 24
Architectural Structures IIIARCH 631
http://www.bluffton.edu
www.archiplanet.org
Masonry Construction 3
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
• solid, grouted, hollow
• unreinforced
• reinforced
• prestressing
Masonry Construction
2
Masonry Construction 4
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Materials
• brick
• concrete masonry units
Masonry Construction 5
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
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
Masonry Construction 6
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Materials
• reinforcement
– deformed bars
– prestressing strand
– development length
– anchorage
– splices
– ties
• steel or composite
Masonry Construction 7
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Materials
• grout
– high slump concrete
– fills voids and fixes rebar
• prisms
– used to test strength, f′m
tmmortar
νmortar > νunit
tb
unit
tmmortar
νmortar > νunit
tb
unit
tmmortar
νmortar > νunit
tb
unit
3
Masonry Construction 8
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Materials
• fire resistance– fire-resistive structural material
– details important to prevent leaks or cracks
– retains strength ifexposure not too long
• mortar and cmu’s dehydrate
• loses 30-60% after that
– no toxic fumes
– cover necessary to protect steel
Masonry Construction 9
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
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 nocontrol joint
Masonry Construction 10
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Walls
– based on empirical requirements for
minimum wall thickness and height
• h/t < 25 (UBC 2105.2 h/t<35)
– wall thicknesses often increased by 4”/story
– bearing walls > 3-5 stories uneconomical,
steel or concrete frames used
– strength design limit states:
• serviceability: deflection
• ultimate: compression & tension
Masonry Construction 11
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
e
Masonry Walls
• compression + bending
h
=
P
Me
P
S
M
A
P+
ab ff −ba ff +
S
M
I
Mcfb ==
A
Pfa =
virtual eccentricity
P
axial stress bending stress
M=Pe
combined
4
Masonry Construction 12
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Walls
• equivalent eccentricity with lateral load
eoP
M V
P
w eoP
V
P
w
e1
P
Me1 =
virtual eccentricity
F2012abn
Masonry Walls
Masonry Construction 14Lecture 23
Applied Architectural StructuresARCH 631
tension normal to bed joints
tension parallel to bed joints
Not allowed in
MSJC code
strong units weak units
F2007abnMasonry Construction 14Lecture 26
Architectural Structures IIIARCH 631
Masonry Beam & Wall Design
• MSJC (ACI, ASCE, TMS)
– limit tensile stress in mortar
– working stress design (ASD)• linear stresses in masonry
• no tension in masonry whenreinforced
• elastic stress in steel < fy• additional compression in walls
– masonry strength = f’m
Masonry Construction 15
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Beam & Wall Design
• reinforcement increases capacity & ductility
5
Masonry Construction 16
Lecture 26
Architectural Structures III
ARCH 631
F2007abn
Masonry Design
BIA Teknote 17 series
grout
unit
t
d n.a.
STRAIN STRESS
As
fm
kd
εs
M
Ts=Asfsfs/n
εm Cm=fmb(kd)/2
jd
bd
A s=ρ
• fs is not the yield stress
• fm is the stress in the masonry
F2012abn
Allowable Masonry Stresses
• tension - unreinforced only
Masonry Construction 18Lecture 23
Applied Architectural StructuresARCH 631
F2012abn
Allowable Masonry Stresses
Masonry Construction 19Lecture 23
Applied Architectural StructuresARCH 631
• flexure
– Fb = 1/3 f’m (unreinforced)
– Fb = 0.45 f’m (reinforced)
• shear, unreinforced masonry
– Fv = ≤ 120 psi
• shear, reinforced masonry
– M/Vd ≤ 0.25: Fv =
– M/Vd ≥ 1.0: Fv=
mf. ′51
mf. ′03
mf. ′02
F2009abn
Allowable Reinforcement Stress
• tension
a) Grade 40 or 50 Fs = 20 ksi
b) Grade 60 Fs = 24 ksi
c) Wire joint Fs = 30 ksi
• *no allowed increase by 1/3 for
combinations with wind & earthquake
– did before 2011 MSJC
Masonry Construction 19Lecture 24
Architectural Structures IIIARCH 631
6
F2007abn
2
kdbffA mss =
Masonry Construction 20
Lecture 26
Architectural Structures III
ARCH 631
Reinforcement, Ms
grout
unit
t
d n.a.
As
Ts=Asfs
Cm=fmb(kd)/2
jd
kd
MSJC: Fs = 20 ksi, 24 ksi or 30 ksi by type
ΣF=0:
ΣM about Cm:
if fs=Fs (allowable) the moment capacity is limited by the steel
s2
sss jfρbdjdfAM ==
F2007abnMasonry Construction 20Lecture 26
Architectural Structures IIIARCH 631
Reinforcement, Mm
grout
unit
t
d n.a.
AsTs=Asfs
Cm=fmb(kd)/2
jd
kd
ΣF=0:
jkbdf5.0jd2
kdbfM 2
mmm ==
MSJC Fb =0.33f’m
2
kdbffA mss =
if fs=Fs (allowable) the moment capacity is limited by the steel
ΣM about Ts:
F2007abnMasonry Construction 21Lecture 26
Architectural Structures IIIARCH 631
Masonry Lintels
• distributed load
– triangular or trapezoidal
Masonry Construction 22Lecture 26
Architectural Structures IIIARCH 631
F2007abn
Strategy for RM Flexural Design
• to size section and find reinforcement
– find ρb knowing f’m and fy– size section for some ρ < ρb
• get k, j
•
• get b & d in nice units
– size reinforcement (bar size & #):
– check design:
sjF
Mbd
ρ=2 needs to be sized
for shear also
jdF
MA
s
s =
bb
sss
Fjkbd.
Mf
MjdFAM
<=
>=
250
7
F2009abn
Ultimate Strength Design
• LRFD
• like reinforced concrete
• useful when beam shear is high
• improved inelastic model
– ex. earthquake loads
Masonry Construction 23Lecture 24
Architectural Structures IIIARCH 631
T
β1c
0.80f’m
C2
c1β
Masonry Construction 23Lecture 26
Architectural Structures IIIARCH 631
F2007abn
Masonry Walls
– one-way or two-way bending
– usually use hollow units (< 75% solid)
– reinforcement grouted
• into cells if hollow units
• between wythes if solid
– reinforcement usually at center
– reinforcement in compression ineffective
– avoid stirrups
– desirable in seismic zones
Masonry Construction 24Lecture 26
Architectural Structures IIIARCH 631
F2007abn
Masonry Walls
• axial force-moment
interaction diagram1≤+
b
b
a
a
F
f
F
f
F2012abn
Masonry Shear Walls
• bearing, bending, and shear
– compression increases resistance
unreinforced reinforced
– unreinforced stress limit 1.5 ≤ 120 psi
Masonry Construction 28Lecture 23
Applied Architectural StructuresARCH 631
v
nvn
v FA
Vor
bI
VQf ≤=
mf ′
8
F2012abn
Masonry Shear Walls
• (and beams)
– reinforcement strength included:
– where
– stress limit depends on ratio of bending
moment to overturning moment: M/Vd
– spacing limits Masonry Construction 29Lecture 23
Applied Architectural StructuresARCH 631
n
mvmA
P.f
Vd
M..F 25075104
2
1+
′
−=
=
sA
dFA.F
nv
svvs 50
Fv = Fvm + Fvs
F2007abnMasonry Construction 26
Lecture 26
Architectural Structures III
ARCH 631
Masonry Shear Walls
• model as deep cantilever beam
– flexure reinforcement
– shear stirrups
d
Masonry Construction 26Lecture 26
Architectural Structures IIIARCH 631
F2007abn
Masonry Columns and Pilasters
• must be reinforced
Masonry Construction 27Lecture 26
Architectural Structures IIIARCH 631
F2007abn
Masonry Columns and Pilasters
• considered a column when b/t<3 and h/t>4
• slender is
– 8” one side
– h/t ≤ 25
• needs ties
• eccentricity
– 10% of side dimension required
– interaction diagrams like r/c
9
Masonry Construction 28Lecture 26
Architectural Structures IIIARCH 631
F2007abn
Masonry Columns
– allowable axial load
h/r ≤ 99
h/r > 99
h = effective length
r = radius of gyration
An = effective area of masonry
Ast = effective area of column reinforcement
Fs = allowable compressive stress in column reinforcement
[ ]
−+′=
2
1401650250
r
hFA.Af.P sstnma
[ ]2
70650250
+′=
h
rFA.Af.P sstnma
(unreinforced Ast = 0)
F2009abn
Masonry Pilasters, Arches
• column in wall
– increase bearing area and stiffness
Masonry Construction 31Lecture 24
Architectural Structures IIIARCH 631
www.tamu.edu
Masonry Construction 30Lecture 26
Architectural Structures IIIARCH 631
F2007abn
Construction Supervision
• proper placement of allreinforcement
• prism construction
– masonry
– mortar
• hot/cold weatherprotection