decking plate girders 1 lecture 21 arch 631 standard...
TRANSCRIPT
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APPLIED ARCHITECTURAL STRUCTURES:
STRUCTURAL ANALYSIS AND SYSTEMS ARCH 631
DR. ANNE NICHOLS
SPRING 2018
twenty one
steel construction
and designSteel Construction 1
Lecture 21
Applied Architectural Structures
ARCH 631
lecture
http://nisee.berkeley.edu/godden
F2009abn
Steel
• cast iron – wrought iron - steel
• cables
• columns
• beams
• trusses
• frames
Steel Construction 2
Lecture 21
Architectural Structures III
ARCH 631
http://nisee.berkeley.edu/godden
Steel Construction 3
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Construction
• standard rolled shapes
• open web joists
• plate girders
• decking
F2012abn
Steel Construction
• welding
• bolts
Steel Construction 4
Lecture 21
Applied Architectural Structures
ARCH 631
AISC Education
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2
Steel Construction 5
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Construction
• fire proofing
– cementicious spray
– encasement in gypsum
– intumescent – expands
with heat
– sprinkler system
Steel Construction 6
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Materials
• high strength to
weight ratio
• ductile
• beam size
often limited by
deflection
• column size
limited by
slenderness
F2007abnSteel Construction 7
Lecture 20
Architectural Structures III
ARCH 631
Steel Beams
• types
– manufactured shapes
castellated
http://nisee.berkeley.edu/godden
Steel Construction 8
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beams
• types
– wide flange
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3
Steel Construction 9
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beams
• types
– open web joists
(manufactured
trusses)
Steel Construction 10
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beams
• types (more)
– plate girder
– decking
F2009abn
Steel Beams
Steel Construction 11
Lecture 21
Architectural Structures III
ARCH 631
http://nisee.berkeley.edu/godden
Steel Construction 12
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beams
• lateral stability - bracing
• local buckling - stiffen
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4
Steel Construction 13
Lecture 20
Architectural Structures III
ARCH 631
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Local Buckling
• steel I beams
• flange
– buckle in
direction of
smaller radius
of gyration
• web
– force
– “crippling”
Steel Construction 14
Lecture 20
Architectural Structures III
ARCH 631
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Local Buckling
• flange
• web
Steel Construction 15
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Shear in Web
• panels in plate girders or webs with large shear
• buckling in compression direction
• add stiffeners
Steel Construction 16
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beams
• end conditions
• a) away from
connection - full
section effective
• b) high shear –
only web
effective
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5
Steel Construction 17
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beams
• end conditions
• c) bolt holes –
less material
• d) local web
buckling
Steel Construction 18
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beams
• bearing
– provide
adequate
area
– prevent
local yield
of flange
and web
Steel Construction 19
Lecture 20
Architectural Structures III
ARCH 631
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Steel Beams
• connections
– welds
– bolts
Steel Construction 20
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Design – Open Web Joists
• SJI: www.steeljoist.com
• Vulcraft: www.vulcraft.com
– K Series (Standard)
• 8-30” deep, spans 8-50 ft
– LH Series (Long span)
• 18-48” deep, spans 25-96 ft
– DLH (Deep Long Spans)
• 52-72” deep, spans 89-144 ft
– SLH (Long spans with high strength steel)
• pitched top chord
• 80-120” deep, spans 111-240 ft
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Steel Construction 21
Lecture 20
Architectural Structures III
ARCH 631
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Steel Design – Open Web Joists
load for live load
deflection limit in RED
total in BLACK
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load for live load deflection
limit (L/360) in RED
total in BLACK
Steel Design – Open Web Joists
Steel Construction 22
Lecture 21
Applied Architectural Structures
ARCH 631
Steel Construction 22
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Steel Beam Design
• American Institute of Steel Construction
– steel grades
• ASTM A36 – carbon
– plates, angles
– Fy = 36 ksi & Fu = 58 ksi
• ASTM A572 – high strength low-alloy
– some beams
– Fy = 60 ksi & Fu = 75 ksi
• ASTM A992 – for building framing
– most beams
– Fy = 50 ksi & Fu = 65 ksi
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Steel Beam Design
• AISC: 14th ed.
– combined ASD & LRFD
in one volume in 2005
Steel Construction 24
Lecture 21
Applied Architectural Structures
ARCH 631
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Su2011abn
• ASD
– bending (braced) = 1.67
– bending (unbraced*) = 1.67
– shear = 1.5 or 1.67
– shear (bolts & welds) = 2.00
– shear (welds) = 2.00
* flanges in compression can buckle
Ra ≤Rn
Unified Steel Design
Steel Construction 25
Lecture 21
Applied Architectural Structures
ARCH 631
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Unified Steel Design
• braced vs.
unbraced
Steel Construction 26
Lecture 21
Applied Architectural Structures
ARCH 631
Su2011abn
LRFD Steel Beam Design
• limit state is yielding all across section
• outside elastic range
• load factors & resistance factors
Steel Construction 27
Lecture 21
Architectural Structures III
ARCH 631
E
1
fy = 50ksi
001724.0y
f
Steel Construction 27
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Load Types
• D = dead load
• L = live load
• Lr = live roof load
• W = wind load
• S = snow load
• E = earthquake load
• R = rainwater load or ice water load
• T = effect of material & temperature
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LRFD Load Combinations
Steel Construction 29
Lecture 21
Applied Architectural Structures
ARCH 631
ASCE-7
(2010)
• 1.4D
• 1.2D + 1.6L + 0.5(Lr or S or R)
• 1.2D + 1.6(Lr or S or R) + (L or 0.5W)
• 1.2D + 1.0W + L + 0.5(Lr or S or R)
• 1.2D + 1.0E + L + 0.2S
• 0.9D + 1.0W
• 0.9D + 1.0E• F has same factor as D in 1-5 and 7
• H adds with 1.6 and resists with 0.9 (permanent)
Steel Construction 29
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Pure Flexure
Mu - maximum moment
b - resistance factor for bending = 0.9
Mn - nominal moment (ultimate capacity)
Fy - yield strength of the steel
Z - plastic section modulus*
ZFMMR ynbuii 9.0
Steel Construction 30
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Internal Moments - at yield
yyy fbh
fc
IM
6
2
• material hasn’t failed
y
2
y
2
f3
bc2f
6
c2b
Steel Construction 31
Lecture 20
Architectural Structures III
ARCH 631
F2007abn
Internal Moments - ALL at yield
• all parts reach yield
• plastic hinge forms
• ultimate moment
• Atension = Acompression
yyp MfbcM 232
E
1
y = 50ksi
y = 0.001724
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F2007abnSteel Construction 32
Lecture 20
Architectural Structures III
ARCH 631
n.a. of Section at Plastic Hinge
• cannot guarantee at
centroid
• fy·A1= fy·A2• moment found from
yield stress times
moment area
1.
p y y i in a
M f A d f A d
Steel Construction 33
Lecture 20
Architectural Structures III
ARCH 631
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Plastic Hinge Development
Steel Construction 34
Lecture 20
Architectural Structures III
ARCH 631
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Plastic Hinge Examples
• stability can be effected
Steel Construction 35
Lecture 20
Architectural Structures III
ARCH 631
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Plastic Section Modulus
• shape factor, k
= 3/2 for a rectangle
1.1 for an I
• plastic modulus, Z
y
p
M
Mk
y
p
f
MZ
SZk
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F2007abnSteel Construction 36
Lecture 20
Architectural Structures III
ARCH 631
Shear
Vu - maximum shear
v - resistance factor for shear = 1.0
Vn - nominal shear
Fyw - yield strength of the steel in the web
Aw - area of the web = twd
iRi = Vu ≤ vVn = 1.0(0.6FywAw)
Su2011abn
Flexure Design
• limit states for beam failure
1. yielding
2. lateral-torsional buckling*
3. flange local buckling
4. web local buckling
• minimum Mn governs
Steel Construction 38
Lecture 21
Architectural Structures III
ARCH 631
1.76y
p y
FL r
E
i i u b nR M M
Su2011abn
Compact Sections
• plastic moment can form before any
buckling
• criteria
–
– and
Steel Construction 39
Lecture 21
Architectural Structures III
ARCH 631
0.382
f
f y
b E
t F
3.76c
w y
h E
t F
Su2011abn
Cb = modification factor
Mmax - |max moment|, unbraced segment
MA - |moment|, 1/4 point
MB = |moment|, center point
MC = |moment|, 3/4 point
Lateral Torsional Buckling
Steel Construction 40
Lecture 21
Architectural Structures III
ARCH 631
pbn MCM moment based onlateral buckling
CBAmax
maxb
MMMM.
M.C
34352
512
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Beam Design Charts
Steel Construction 41
Lecture 21
Architectural Structures III
ARCH 631
F2007abnSteel Construction 40
Lecture 20
Architectural Structures III
ARCH 631
Deflection Limits
• based on service condition
• no “impairment” to serviceability
• avoid ponding
• L/360 due to live load for beams &
girders supporting plaster (service)
F2009abn
Steel Arches and Frames
• solid sections
or open web
Steel Construction 41
Lecture 21
Architectural Structures III
ARCH 631
http://nisee.berkeley.edu/godden
Steel Construction 42
Lecture 20
Architectural Structures III
ARCH 631
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Steel Shell and Cable Structures
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Steel Construction 43
Lecture 20
Architectural Structures III
ARCH 631
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Approximate Depths
Su2011abn
Unified Column Design
• limit states for failure
1. yielding
2. buckling
Fe – elastic buckling stress (Euler)
Steel Construction 46
Lecture 21
Architectural Structures III
ARCH 631
ncu PP gcrnc AFP. 900
ye
y
F.ForF
E.
r
KL440714
ye
y
F.ForF
E.
r
KL440714
na
PP
Su2011abn
Unified Column Design
• Pn = FcrAg– for
– for
– where
Steel Construction 47
Lecture 21
Architectural Structures III
ARCH 631
yF
E.
r
KL714 y
F
F
cr F.Fe
y
6580
ecr F.F 8770
22
rKL
EFe
yF
E.
r
KL714
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Procedure for Analysis
1. calculate KL/r• biggest of KL/r with respect to x axes and y axis
2. find Fcr from appropriate equation• tables are available
3. compute Pn = FcrAg• or find fc = Pa/A or Pu/A
4. is Pa Pn/ or Pu Pn?• yes: ok
• no: insufficient capacity and no good
Steel Construction 48
Lecture 21
Architectural Structures III
ARCH 631
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1. guess a size (pick a section)
2. calculate KL/r• biggest of KL/r with respect to x axes and y axis
3. find Fcr from appropriate equations• or find a table
4. compute Pn = FcrAg• or find fc = Pa/A or Pu/A
Procedure for Design
Steel Construction 49
Lecture 21
Architectural Structures III
ARCH 631
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Procedure for Design (cont’d)
5. is Pa Pn/ or Pu Pn?• yes: ok
• no: pick a bigger section and go back to step 2.
6. check design efficiency
• percentage of stress =
• if between 90-100%: good
• if < 90%: pick a smaller section and
go back to step 2.
Steel Construction 50
Lecture 21
Architectural Structures III
ARCH 631
%P
P
c
r 100
Su2011abn
Column Tables
Steel Construction 51
Lecture 21
Architectural Structures III
ARCH 631
Su2011abn
Beam-Column Design
• moment magnification (P-)
Cm – modification factor for end conditions
= 0.6 – 0.4(M1/M2) or
0.85 restrained, 1.00 unrestrained
Pe1 – Euler buckling strength
Steel Construction 52
Lecture 21
Architectural Structures III
ARCH 631
factoredmaxu MBM 1 )PP(
CB
eu
m
1
11
22
1
rKl
EAPe
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Beam-Column Design
• LRFD (Unified) Steel
– for
– for
Pr is required, Pc is capacity
c - resistance factor for compression = 0.9
b - resistance factor for bending = 0.9
Steel Construction 53
Lecture 21
Architectural Structures III
ARCH 631
019
8.
M
M
M
M
P
P
nyb
uy
nxb
ux
nc
u
:.P
P
c
r 20
012
.M
M
M
M
P
P
nyb
uy
nxb
ux
nc
u
:.P
P
c
r 20
Steel Construction 57
Lecture 20
Architectural Structures III
ARCH 631
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Construction Supervision
• proper grade material
– high strength bolts
• quality welds
• proper bolted
conditions (ex. sc)
• fabrication and erection
of steel frame
connection details