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Concrete Spans 1Lecture 25
Foundations Structures
ARCH 331
F2008abn
F^ OUNDATIONS
S
TRUCTURES
:
F^ ORM,
B
EHAVIOR, AND
D
ESIGN
ARCH 331D
R.^
A
NNE
N
ICHOLS
S^ PRING 2009
lecture
twenty five concrete construction:flat spanning systems
Concrete Spans 2Lecture 25
Foundations Structures
ARCH 331
F2008abn
Reinforced Concrete Design •^
economical & common
-^
resist lateral loads
Concrete Spans 3Lecture 25
Foundations Structures
ARCH 331
F2008abn
Reinforced Concrete Design •^
flat plate^ –
5”-10” thick – simple formwork – lower story heights
-^
flat slab^ –
same as plate – 2 ¼”–8” drop panels
Concrete Spans 4Lecture 25
Foundations Structures
ARCH 331
F2008abn
Reinforced Concrete Design •^
beam supported^ –
slab depth ~ L/20 – 8”–60” deep
-^
one-way joists^ –
3”–5” slab – 8”–20” stems – 5”-7” webs
The Architect’s Studio Companion
Concrete Spans 5Lecture 25
Foundations Structures
ARCH 331
F2008abn
Reinforced Concrete Design •^
two-way joist^ –
“waffle slab” – 3”-5” slab – 8”-24” stems – 6”-8” webs
-^
beam supported slab^ –
5”-10” slabs – taller story heights
Concrete Spans 6Lecture 25
Foundations Structures
ARCH 331
F2008abn
Reinforced Concrete Design •^
simplified frame analysis^ –
strips, likecontinuous beams
-^
moments requireflexural reinforcement^ –
top & bottom – both directions of slab – continuous, bent ordiscontinuous
Concrete Spans 7Lecture 25
Foundations Structures
ARCH 331
F2008abn
Reinforced Concrete Design •^
one-way slabs (wide beam design)^ –
approximate analysis for moment & shearcoefficients – two or more spans – ~ same lengths – w
from combosu^
-^
uniform loads with L/D
≤^
l^
is clear span (+M) or average ofn adjacent clear spans (-M)
Concrete Spans 8Lecture 25
Foundations Structures
ARCH 331
F2008abn
Reinforced Concrete Design
Concrete Spans 13Lecture 25
Foundations Structures
ARCH 331
F2008abn
Shear in Concrete •^
at columns with waffle slabs
Concrete Spans 14Lecture 25
Foundations Structures
ARCH 331
F2008abn
Openings in Slabs •^
careful placement of holes
-^
shear strengthreduced
-^
bending &deflection canincrease
Concrete Spans 15Lecture 25
Foundations Structures
ARCH 331
F2008abn
General Beam Design •^
f’c
& f
neededy^
-^
usually size just b & h^ –
even inches typical (forms) – similar joist to beam depth – b:h of 1:1.5-1:2.5 – b
w^
& b
for Tf^
–^
to fit reinforcement + stirrups
-^
slab design, t^ –
deflection control & shear
2
bh
S
Concrete Spans 16Lecture 25
Foundations Structures
ARCH 331
F2008abn
General Beam Design (cont’d) •^
custom design:^ –
longitudinal steel – shear reinforcement – detailing
Concrete Spans 17Lecture 25
Foundations Structures
ARCH 331
F2008abn
Space “Frame” Behavior •^
handle uniformly distributed loads well
-^
bending moment^ –
tension &compression“couple” withdepth – member sizescan vary,but difficult
Concrete Spans 18Lecture 25
Foundations Structures
ARCH 331
F2008abn
Space “Frame” Behavior •^
shear at columns
-^
support conditions still important^ –
point supports not optimal
-^
fabrication/construction can dominatedesign
Concrete Spans 19Lecture 25
Foundations Structures
ARCH 331
F2008abn
Folded Plates •^
increased bending stiffness with folding
-^
lateral buckling avoided
Concrete Spans 20Lecture 25
Foundations Structures
ARCH 331
F2008abn
Folded Plates •^
common for roofs
-^
edges needstiffening
