ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load...
Transcript of ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load...
![Page 1: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/1.jpg)
1
AISC
LRFD and ASD
Source: GT
STRUDL Users GroupLas Vegas, Nevada, 2005
Hamid Zand
![Page 2: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/2.jpg)
2
AISC ASD and LRFD
•
AISC =
American Institute of SteelConstruction
•
ASD =
Allowable Stress DesignAISC Ninth Edition
•
LRFD
=
Load and Resistance Factor DesignAISC Third Edition
![Page 3: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/3.jpg)
3
ASD and LRFD Major Differences
•
Load
Combinations and load factors•
ASD results are based on the stresses and LRFD results are based on the forces and moments capacity
•
Cb
computation
![Page 4: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/4.jpg)
4
ASD Load Combinations
•
1.0D
+ 1.0L•
0.75D
+ 0.75L
+ 0.75W
•
0.75D
+ 0.75L
+ 0.75E
D
=
dead loadL
=
live loadW
=
wind loadE
=
earthquake load
![Page 5: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/5.jpg)
5
LRFD Load Combinations
•
1.4D•
1.2D
+ 1.6L
•
1.2D
+ 1.6W + 0.5L•
1.2D
±
1.0E
+ 0.5L
•
0.9D
±
(1.6W or 1.0E)
D
=
dead loadL
=
live loadW
=
wind loadE
=
earthquake load
![Page 6: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/6.jpg)
6
Deflection Load Combinations for ASD and LRFD
•
1.0D
+ 1.0L•
1.0D
+ 1.0L
+ 1.0W
•
1.0D
+ 1.0L
+ 1.0E
D
=
dead loadL
=
live loadW
=
wind loadE
=
earthquake load
![Page 7: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/7.jpg)
7
Forces and Stresses
•
ASD =
actual stress values are compared to the AISCallowable stress values
•
LRFD
=
actual forces and momentsare compared to the AISClimiting forces and momentscapacity
![Page 8: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/8.jpg)
8
Slenderness Ratio
•
CompressionKL/r
≤
200
•
TensionL/r
≤
300
![Page 9: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/9.jpg)
9
Tension Members
•
Check L/r
ratio•
Check Tensile Strength based on the cross-
section’s Gross Area•
Check Tensile Strength based on the cross-
section’s Net Area
![Page 10: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/10.jpg)
10
Tension Members
ASDft
= FX/Ag
≤
Ft
Gross Area
ft
= FX/Ae
≤
Ft
Net Area
LRFD
Pu
= FX
≤
ϕt Pn
= ϕt Ag Fy
ϕt
= 0.9 for Gross Area
Pu
= FX
≤
ϕt Pn
= ϕt Ae
Fu
ϕt
= 0.75 for Net Area
![Page 11: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/11.jpg)
11
Tension Members
ASD (ASD Section D1)
Gross Area Ft
= 0.6Fy
Net Area
Ft
= 0.5Fu
LRFD (LRFD Section D1)
Gross Area ϕt Pn
= ϕt Fy
Ag
ϕt
= 0.9Net Area
ϕt Pn
= ϕt Fu Ae
ϕt
= 0.75
![Page 12: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/12.jpg)
12
Compare ASD to LRFD
ASD
1.0D
+ 1.0LLRFD
1.2D
+ 1.6L
0.6Fy
(ASD)
×
(1.5)
= 0.9Fy
(LRFD)
0.5Fu
(ASD)
×
(1.5)
= 0.75Fu
(LRFD)
ASD ×
(1.5)
= LRFD
![Page 13: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/13.jpg)
13
Tension Members
X
Y
Z
FIXED JOINT
-400.
o
![Page 14: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/14.jpg)
14
Tension Members•
Member is 15 feet long
•
Fixed at the top of the member and free at the bottom•
Loadings are:
•
Self weight•
400 kips tension force at the free end
•
Load combinations based on the ASD and LRFD codes
•
Steel grade is A992•
Design based on the ASD and LRFD codes
![Page 15: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/15.jpg)
15
Tension Members
ASD
W18x46
Actual/Allowable Ratio = 0.989
LRFD
W10x49
Actual/Limiting Ratio = 0.989
![Page 16: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/16.jpg)
16
Tension Members
ASDW18x46
Area = 13.5 in.2
FX = 400.688 kips
Ratio = 0.989
LRFDW10x49
Area = 14.4 in.2
FX = 640.881 kips
Ratio = 0.989
![Page 17: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/17.jpg)
17
Tension MembersLoad Factor difference between LRFD and ASD
640.881 / 400.688 = 1.599Equation Factor difference between LRFD and ASD
LRFD = (1.5) ×
ASD
Estimate required cross-sectional area for LRFD
LRFD W10x49 Area = 14.4 in.2
Area for LRFD 135 640881400 688
1015
0 9890 989
14 395. ..
.
...
.
![Page 18: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/18.jpg)
18
Tension MembersCode Check based on the ASD9 and using W10x49
FX = 400.734 kips
Ratio = 0.928
Load Factor difference between LRFD and ASD640.881 / 400.734 = 1.599
LRFD W10x49
Ratio = 0.989
LRFD Ratio computed from ASD 0 928 640881400 734
1015
0 989. ..
.
..
![Page 19: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/19.jpg)
19
Tension MembersASD
Example # 1Live Load = 400 kips
W18x46
Actual/Allowable Ratio = 0.989LRFD
Example # 1Live Load = 400 kips
W10x49
Actual/Limiting Ratio = 0.989Example # 2
Dead Load = 200 kipsLive Load = 200 kips
W14x43
Actual/Limiting Ratio = 0.989Code check W14x43 based on the ASD9
W14x43
Actual/Allowable Ratio = 1.06
![Page 20: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/20.jpg)
20
Compression Members
•
Check KL/r
ratio•
Compute Flexural-Torsional Buckling and Equivalent (KL/r)e
•
Find Maximum of KL/r
and (KL/r)e
•
Compute Qs
and Qa
based on the b/t
and h/tw
ratios•
Based on the KL/r
ratio, compute allowable
stress in ASD or limiting force in LRFD
![Page 21: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/21.jpg)
21
Compression Members
ASD
fa
= FX/Ag
≤
Fa
LRFD
Pu
= FX
≤
ϕc Pn
= ϕc Ag FcrWhere
ϕc
= 0.85
![Page 22: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/22.jpg)
22
Limiting Width-Thickness Ratios for Compression Elements
ASD
b/t
=
h/tw
=
LRFD
b/t
=
h/tw
=
95 / Fy
056. /E Fy
253 / Fy
149. /E Fy
![Page 23: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/23.jpg)
23
Limiting Width-Thickness Ratios for Compression Elements
Assume E
= 29000 ksiASD
b/t
=
h/tw
=
LRFD
b/t
=
h/tw
=
95 / Fy
9536. / Fy
253 / Fy
25374. / Fy
![Page 24: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/24.jpg)
24
Compression Members
ASD KL/r
≤
C′c
(ASD E2-1 or A-B5-11)
LRFD (LRFD A-E3-2)
F
QKL r
CF
KL rC
KL r
C
ac
y
c c
12
53
38 8
2
2
3
3
/
/ /
F Q FcrQ
yc 0 658
2
.
Where C EQFc
y
2 2
Where c
yKLr
FE
c Q 15.
![Page 25: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/25.jpg)
25
Compression Members
ASD KL/r
> C′c
(ASD E2-2)
LRFD (LRFD A-E3-3)
F E
KL ra
1223
2
2
/Where C E
QFcy
2 2
c Q 15.
F Fcrc
y
08772
.
Where c
yKLr
FE
![Page 26: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/26.jpg)
26
Compression Members
LRFDF Fcr
cy
08772
. Where
cyKL
rFE
FKLr
FE
Fcr
y
y
08772
.
F E
KL rcr
0877 2
2.
/
F
EKL rcr
2017123
2
2
./
![Page 27: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/27.jpg)
27
Compression Members
ASD LRFD
Fcr
/ Fa
= 1.681
LRFD Fcr
= ASD Fa
×
1.681
F E
KL ra
1223
2
2
/ F
EKL rcr
2017123
2
2
./
![Page 28: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/28.jpg)
28
Compression Members
ASD
(ASD C-E2-2)
LRFD
λc
= Maximum of
( λcy
, λcz
, λe )
KL rK L
rK L
rKLr
y Y
y
z z
z e/ , ,
WhereKLr
EFe e
![Page 29: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/29.jpg)
29
Compression Members
LRFDWhere:
cy
y y
y
yK Lr
FE
cz
z z
z
yK Lr
FE
ey
e
FF
![Page 30: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/30.jpg)
30
Compression Members
Flexural-Torsional Buckling
F
EC
K LGJ
I Iew
x x y z
2
210.
![Page 31: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/31.jpg)
31
Qs
Computation
ASD
LRFD
When 95 195/ / / / /F k b t F ky c y c
Q b t F ks y c 1293 0 00309. . ( / ) /
When 056 103. / / . /E F b t E Fy y
Q b t F Es y 1415 0 74. . ( / ) /
k
h th t kc c
4 05 70 100.46.
// , .if otherwise
![Page 32: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/32.jpg)
32
Qs
Computation
Assume E
= 29000 ksiASD
LRFD
When 95 195/ / / / /F k b t F ky c y c
Q b t F ks y c 1293 0 00309. . ( / ) /
When 9536 1754. / / . /F b t Fy y
Q b t Fs y 1415 0 004345. . ( / )
![Page 33: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/33.jpg)
33
Qs
Computation
ASD
LRFD
When b t F ky c/ / / 195
Q k F b ts c y 26200 2/ /
When b t E Fy/ . / 103
Q E F b ts y 0 69 2. / /
![Page 34: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/34.jpg)
34
Qs
Computation
Assume E
= 29000 ksiASD
LRFD
When b t F ky c/ / / 195
Q k F b ts c y 26200 2/ /
When b t Fy/ . / 1754
Q F b ts y 20010 2/ /
![Page 35: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/35.jpg)
35
Qa
Computation
ASD
LRFD
b tf b t f
be
253 1 44 3.
( / )
b t Ef b t
Ef
be
191 1 0 34. .
( / )
Assume ksiE b tf b t f
e
29000 32526 1 57 9, . .( / )
![Page 36: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/36.jpg)
36
Compression Members
X
Y
Z FIXED JOINT
-100.o
![Page 37: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/37.jpg)
37
Compression Members•
Member is 15 feet long
•
Fixed at the bottom of the column and free at the top•
Loadings are:
•
Self weight•
100 kips compression force at the free end
•
Load combinations based on the ASD and LRFD codes
•
Steel grade is A992•
Design based on the ASD and LRFD codes
![Page 38: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/38.jpg)
38
Compression Members
ASD
W10x49
Actual/Allowable Ratio = 0.941
LRFD
W10x54
Actual/Limiting Ratio = 0.944
![Page 39: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/39.jpg)
39
Compression Members
ASDW10x49
Area = 14.4 in.2
FX
= 100.734 kips
Ratio = 0.941
LRFDW10x54
Area = 15.8 in.2
FX
= 160.967 kips
Ratio = 0.944
![Page 40: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/40.jpg)
40
Compression MembersLoad Factor difference between LRFD and ASD
160.967 / 100.734 = 1.598Equation Factor difference between LRFD and ASD
LRFD Fcr
= (1.681) ×
ASD Fa
Estimate required cross-sectional area for LRFD
LRFD W10x54 Area = 15.8 inch
Area for LRFD 14 4 160 967100 734
101681
10085
0 9410 944
16 05. ..
..
..
.
..
![Page 41: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/41.jpg)
41
Compression MembersCode Check based on the ASD9 and use W10x54
FX
= 100.806 kips
Ratio = 0.845
Load Factor difference between LRFD and ASD160.967 / 100.806 = 1.597
LRFD W10x54
Ratio = 0.944
LRFD Ratio computed from ASD 0845 160 967100806
101681
10085
0 944. ..
..
..
.
![Page 42: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/42.jpg)
42
Compression MembersASD
Example # 1Live Load = 100 kips
W10x49
Actual/Allowable Ratio = 0.941LRFD
Example # 1Live Load = 100 kips
W10x54
Actual/Limiting Ratio = 0.944Example # 2
Dead Load = 50 kipsLive Load = 50 kips
W10x49
Actual/Limiting Ratio = 0.921Code check W10x49 based on the ASD9
W10x49
Actual/Allowable Ratio = 0.941
![Page 43: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/43.jpg)
43
Flexural Members•
Based on the b/t
and h/tw
ratios determine the compactness of the cross-section
•
Classify flexural members as Compact, Noncompact, or Slender
•
When noncompact
section in ASD, allowable stress Fb
is computed based on the l/rt
ratio. l
is the laterally unbraced length of the compression flange. Also, Cb
has to be computed•
When noncompact
or slender section in LRFD, LTB, FLB,
and WLB are checked•
LTB for noncompact
or slender sections is computed using Lb
and Cb
. Lb
is the laterally unbraced
length of the compression flange
![Page 44: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/44.jpg)
44
Flexural Members
ASD
fb
= MZ/SZ
≤
Fb
LRFD
Mu
= MZ
≤
ϕb Mn
Where ϕb
= 0.9
![Page 45: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/45.jpg)
45
Limiting Width-Thickness Ratios for Compression Elements
ASD
LRFD
Assume E
= 29000 ksi
d t Fw y/ / 640
b t E Fy/ . / 0 38 h t E Fw y/ . / 376
b t Fy/ / 65
b t Fy/ . / 64 7 h t Fw y/ . / 640 3
![Page 46: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/46.jpg)
46
Flexural Members Compact Section
ASD (ASD F1-1)
Fb
= 0.66Fy
LRFD (LRFD A-F1-1)
ϕb Mn
= ϕb Mp
= ϕb Fy ZZ
≤ 1.5Fy SZ
Where ϕb
= 0.9
![Page 47: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/47.jpg)
47
Flexural Members Compact Section
X
Y
Z
FIXED JOINT
-15.00
-15.00
o
o
FIXED JOINT
Braced at 1/3 Points
![Page 48: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/48.jpg)
48
Flexural Members Compact Section
•
Member is 12 feet long•
Fixed at both ends of the member
•
Loadings are:•
Self weight
•
15 kips/ft uniform load•
Load combinations based on the ASD and LRFD codes
•
Steel grade is A992•
Braced at the 1/3 Points
•
Design based on the ASD and LRFD codes
![Page 49: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/49.jpg)
49
Flexural Members Compact Section
ASD
W18x40
Actual/Allowable Ratio = 0.959
LRFD
W18x40
Actual/Limiting Ratio = 0.982
![Page 50: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/50.jpg)
50
Flexural Members Compact Section
ASDW18x40
Sz
= 68.4 in.3
MZ
= 2165.777 inch-kips
Ratio = 0.959
LRFDW18x40
Zz
= 78.4 in.3
MZ
= 3462.933 inch-kips
Ratio = 0.982
![Page 51: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/51.jpg)
51
Flexural Members Compact Section
Load Factor difference between LRFD and ASD3462.933 / 2165.777 = 1.5989
Equation Factor difference between LRFD and ASDLRFD = (0.66Sz
)(1.5989) / (0.9Zz
) ×
ASD
Zz
LRFD W18x40
Zz
= 78.4 in.3
for LRFD 68 4 3462 9332165777
0 660 9
0 9590 982
78 3. ..
..
.
..
![Page 52: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/52.jpg)
52
Flexural Members Compact Section
Code Check based on the ASD9, Profile W18x40MZ
= 2165.777 inch-kips
Ratio = 0.959
Load Factor difference between LRFD and ASD3462.933 / 2165.777 = 1.5989
LRFD W18x40 Ratio = 0.982
LRFD Ratio computed from ASD 0 959 3462 9332165777
0 660 9
68 478 4
0 981. ..
..
.
..
![Page 53: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/53.jpg)
53
Flexural Members Compact Section
ASDExample # 1
Live Load = 15 kips/ftW18x40
Actual/Allowable Ratio = 0.959LRFD
Example # 1Live Load = 15 kips/ft
W18x40
Actual/Limiting Ratio = 0.982Example # 2
Dead Load = 7.5 kips/ftLive Load = 7.5 kips/ft
W18x40
Actual/Limiting Ratio = 0.859Code check W18x40 based on the ASD9
W18x40
Actual/Allowable Ratio = 0.959
![Page 54: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/54.jpg)
54
Flexural Members Noncompact
Section
ASD•
Based on b/t, d/tw
and h/tw
determine if the section is noncompact
•
Compute Cb
•
Compute Qs
•
Based on the l/rt
ratio, compute allowable stress Fb
•
Laterally unbraced
length of the compression flange (l) has a direct effect on the equations of the noncompact
section
![Page 55: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/55.jpg)
55
Flexural Members Noncompact Section
ASD
fb
= MZ/SZ
≤
Fb
LRFD
Mu
= MZ
≤
ϕb Mn
Where ϕb
= 0.9
![Page 56: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/56.jpg)
56
Limiting Width-Thickness Ratios for Compression Elements
ASD
LRFD
65 95F b t Fy y
d t Fw y 640
0 38 083. / .E F b t E Fy L
376 57. .E F h t E Fy w y
h t Fw b 760
![Page 57: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/57.jpg)
57
Limiting Width-Thickness Ratios for Compression Elements
Assume E
= 29000 ksiASD
LRFD
65 95F b t Fy y
d t Fw y 640
64 7 1413. / / . /F b t Fy L
640 3 970 7. / . /F h t Fy w y
h t Fw b 760
![Page 58: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/58.jpg)
58
Flexural Members Noncompact Section
ASD
(ASD F1-3)
(ASD F1-2)
ASD Equations F1-6, F1-7, and F1-8 must to be checked.
F Fbt
Fb yf
fy
0 79 0 0022
. .
If minimum orL L
b
F d A Fb cf
y f y
76 20000
![Page 59: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/59.jpg)
59
Flexural Members Noncompact Section
ASD
When
(ASD F1-6)
102 10 510 103 3
CF
lr
CF
b
y T
b
y
F
F l r
CF F Qb
y T
by y s
23 1530 10
0 62
3
/.
![Page 60: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/60.jpg)
60
Flexural Members Noncompact Section
ASD
When
(ASD F1-7)
lr
CFT
b
y
510 103
F
C
l rF Qb
b
Ty s
170 100 6
3
2/.
![Page 61: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/61.jpg)
61
Flexural Members Noncompact Section
ASD
For any value of l/rT
(ASD F1-8)FC
ld AF Qb
b
fy s
12 100 6
3
/.
![Page 62: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/62.jpg)
62
Flexural Members Noncompact Section
LRFD
1. LTB, Lateral-Torsional Buckling
2. FLB, Flange Local Buckling
3. WLB, Web Local Buckling
![Page 63: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/63.jpg)
63
Flexural Members Noncompact
Section
LRFD–
LTB
•
Compute Cb•
Based on the Lb
, compute limiting moment capacity. Lb
is the lateral unbraced
length of the compression flange,λ
= Lb
/ry•
Lb
has a direct effect on the LTB equations for noncompactand slender sections
–
FLB•
Compute limiting moment capacity based on the b/t
ratio of the flange, λ
= b/t–
WLB
•
Compute limiting moment capacity based on the h/tw
ratio of the web, λ
= h/tw
![Page 64: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/64.jpg)
64
Flexural Members Noncompact Section
LRFD LTB (Table A-F1.1)
For λp
< λ
≤
λr
(LRFD A-F1-2)
Where:Mp
= Fy
Zz
≤
1.5Fy Sz
Mr
= FL
Sz
FL
= Smaller of (Fyf
−
Fr
) or Fyw
λ
= Lb
/ry
λp
=
M C M M M Mn b p p rp
r pp
176. E Fyf
![Page 65: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/65.jpg)
65
Flexural Members Noncompact Section
LRFD LTB (Table A-F1.1)
Where:
λr
=
X1
=
X2
=
XF
X FL
L1
221 1
S
EGJA
z 2
42C
ISGJ
w
y
z
![Page 66: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/66.jpg)
66
Flexural Members Noncompact Section
LRFD FLB (Table A-F1.1)
For λp
< λ
≤
λr
(LRFD A-F1-3)Where:
Mp
= Fy
Zz
≤
1.5Fy Sz
Mr
= FL
Sz
FL
= Smaller of (Fyf
−
Fr
) or Fyw
λ
= b/tλp
=λr
=
M M M Mn p p rp
r p
0 38. E Fy
083. E FL
![Page 67: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/67.jpg)
67
Flexural Members Noncompact Section
LRFD WLB (Table A-F1.1)
For λp
< λ
≤
λr
(LRFD A-F1-3)Where:
Mp
= Fy
Zz
≤
1.5Fy Sz
Mr
= Re Fy
Sz
Re
= 1.0
for non-hybrid girder
M M M Mn p p rp
r p
![Page 68: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/68.jpg)
68
Flexural Members Noncompact Section
LRFD WLB (Table A-F1.1)
λ = h/tw
λp
=
λr
=
376. E Fy
57. E Fy
![Page 69: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/69.jpg)
69
Flexural Members Noncompact Section
ASD
LRFD
C M M M MM M
M M M C
b
b
175 105 0 3 2 3
10
1 2 1 22
1 2
1 2
. . . .
, .maxIf between and
CM
M M M MMMM
bA B C
A
B
C
12 52 5 3 4 3
..
max
max
absolute value of moment at quarter pointabsolute value of moment at centerlineabsolute value of moment at three quarter point
![Page 70: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/70.jpg)
70
Flexural Members Noncompact Section
X
Y
Z
Roller
-12.00
-12.00
o
o
Pin
![Page 71: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/71.jpg)
71
Flexural Members Noncompact
Section
•
Member is 12 feet long•
Pin at the start of the member
•
Roller at the end of the member•
Cross-section is W12x65
•
Loadings are:•
Self weight
•
12 kips/ft uniform load•
Load combinations based on the ASD and LRFD codes
•
Steel grade is A992•
Check code based on the ASD and LRFD codes
![Page 72: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/72.jpg)
72
Flexural Members Noncompact Section
ASDW12x65
Cb
= 1.0Actual/Allowable Ratio = 0.988
LRFDW12x65
Cb
= 1.136Actual/Limiting Ratio = 0.971
Code check is controlled by FLB.Cb
= 1.0
Actual/Limiting Ratio = 0.973
![Page 73: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/73.jpg)
73
Flexural Members Noncompact
Section
ASDExample # 1
Live Load = 12 kips/ftW12x65
Actual/Allowable Ratio = 0.988LRFD
Example # 1Live Load = 12 kips/ft
W12x65
Actual/Limiting Ratio = 0.971Example # 2
Dead Load = 6 kips/ftLive Load = 6 kips/ft
W12x65
Actual/Limiting Ratio = 0.85Code check W12x65 based on the ASD9
W12x65
Actual/Allowable Ratio = 0.988
![Page 74: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/74.jpg)
74
Design for Shear
ASD
fv
= FY/Aw
≤
Fv
= 0.4Fy
(ASD F4-1)
LRFD
Vu
= FY
≤
ϕv
Vn
= ϕv
0.6Fyw Aw
(LRFD F2-1)
Where ϕv
= 0.9
h t Fw y/ 380
h t E Fw yw/ . / 2 45
![Page 75: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/75.jpg)
75
Design for ShearAssume E
= 29000 ksi
ASD
fv
= FY/Aw
≤
Fv
= 0.4Fy
(ASD F4-1)
LRFD
Vu
= FY
≤
ϕv
Vn
= ϕv
0.6Fyw Aw
(LRFD F2-1)Where ϕv
= 0.9
h t Fw y/ 380
h t Fw yw/ . / 417 2
![Page 76: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/76.jpg)
76
Design for ShearASD
fv
= FY/Ay
≤
(ASD F4-2)
LRFD
Vu
= FY
≤
ϕv
Vn
= ϕv
(LRFD F2-2)
Where ϕv
= 0.9
h t Fw y/ 380
2 45 307. / / . /E F h t E Fyw w yw
FF
C Fvy
v y 2 89
0 4.
.
0 62 45
.. /
/F A
E F
h tyw wyw
w
![Page 77: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/77.jpg)
77
Design for Shear
LRFD
Vu
= FY
≤
ϕv
Vn
= ϕv
(LRFD F2-3)
Where ϕv
= 0.9
307 260. / /E F h tyw w
A E
h tw
w
4 522
./
![Page 78: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/78.jpg)
78
Design for Shear
X
Y
Z
FIXED JOINT
-15.00
-15.00
o
o
FIXED JOINT
Braced at 1/3 Points
![Page 79: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/79.jpg)
79
Design for Shear•
Same as example # 3 which is used for design of flexural member with compact section
•
Member is 12 feet long•
Fixed at both ends of the member
•
Loadings are:•
Self weight
•
15 kips/ft uniform load•
Load combinations based on the ASD and LRFD codes
•
Steel grade is A992•
Braced at the 1/3 Points
•
Design based on the ASD and LRFD codes
![Page 80: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/80.jpg)
80
Design for Shear
ASD (Check shear at the end of the member, equation “F4-1 Y”)
W18x40
Actual/Allowable Ratio = 0.8
LRFD (Check shear at the end of the member, equation “A-F2-1 Y”)
W18x40
Actual/Limiting Ratio = 0.948
![Page 81: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/81.jpg)
81
Design for Shear
ASDW18x40
Ay
= 5.638 in.2
FY
= 90.241 kips
Ratio = 0.8
LRFDW18x40
Ay
= 5.638 in.2
FY
= 144.289 kips
Ratio = 0.948
![Page 82: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/82.jpg)
82
Design for ShearCode Check based on the ASD9, Profile W18x40
FY
= 90.241 kips
Ratio = 0.8Load Factor difference between LRFD and ASD
144.289 / 90.241 = 1.5989Equation Factor difference between LRFD and ASD
LRFD = (0.4)(1.5989) /(0.6)(0.9) ×
ASD
LRFD W18x40 Ratio = 0.948
LRFD Ratio computed from ASD 08 144 28990 241
0 40 6
100 9
0 948. ..
.
...
.
![Page 83: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/83.jpg)
83
Design for ShearASD
Example # 1Live Load = 15 kips/ft
W18x40
Actual/Allowable Ratio = 0.8LRFD
Example # 1Live Load = 15 kips/ft
W18x40
Actual/Limiting Ratio = 0.948Example # 2
Dead Load = 7.5 kips/ftLive Load = 7.5 kips/ft
W18x40
Actual/Limiting Ratio = 0.83Code check W18x40 based on the ASD9
W18x40
Actual/Allowable Ratio = 0.8
![Page 84: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/84.jpg)
84
Combined Forces
ASD fa
/Fa
> 0.15
(ASD H1-1)
(ASD H1-2)
LRFD Pu
/ϕPn
≥ 0.2
(LRFD H1-1a)
fF
C f
fF
F
C ffF
a
a
my by
a
eyby
mz bz
a
ez
1 110.
fF
fF
fF
a
y
by
by
bz
bz0 610
..
PP
MM
MM
u
n
uy
b ny
uz
b nz
89
10.
![Page 85: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/85.jpg)
85
Combined Forces
ASD fa
/Fa
≤
0.15
(ASD H1-1)
LRFD Pu
/ϕPn
< 0.2
(LRFD H1-1a)
fF
fF
fF
a
a
by
by
bz
bz
10.
PP
MM
MM
u
n
uy
b ny
uz
b nz210
.
![Page 86: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/86.jpg)
86
Combined Forces
X
Y
Z
![Page 87: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/87.jpg)
87
Combined Forces•
3D Simple Frame
•
3 Bays in X direction
3 @ 15 ft•
2 Bays in Z direction
2 @ 30 ft•
2 Floors in Y direction
2 @ 15 ft
• Loadings
•
Self weight of the Steel•
Self weight of the Slab
62.5 psf•
Other dead loads
15.0 psf•
Live load on second floor
50.0 psf•
Live load on roof
20.0 psf•
Wind load in the X direction
20.0 psf•
Wind load in the Z direction
20.0 psf
![Page 88: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/88.jpg)
88
Combined Forces ASD
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< Active Units Weight Unit = KIP Length Unit = INCH >< >< Steel Take Off Itemize Based on the PROFILE >< Total Length, Volume, Weight, and Number of Members >< >< Profile Names Total Length Total Volume Total Weight # of Members >< W10x33 2.1600E+03 2.0974E+04 5.9418E+00 12 >< W12x58 1.4400E+03 2.4480E+04 6.9352E+00 4 >< W12x65 1.4400E+03 2.7504E+04 7.7919E+00 4 >< W12x72 2.1600E+03 4.5576E+04 1.2912E+01 12 >< W6x9 3.2400E+03 8.6832E+03 2.4600E+00 18 >< W8x40 1.4400E+03 1.6848E+04 4.7730E+00 4 >< W8x48 1.4400E+03 2.0304E+04 5.7521E+00 4 ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< ACTIVE UNITS WEIGHT KIP LENGTH INCH >< >< TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS >< >< LENGTH = 1.3320E+04 WEIGHT = 4.6566E+01 VOLUME = 1.6437E+05 ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
![Page 89: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/89.jpg)
89
Combined Forces LRFD
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< Active Units Weight Unit = KIP Length Unit = INCH >< >< Steel Take Off Itemize Based on the PROFILE >< Total Length, Volume, Weight, and Number of Members >< >< Profile Names Total Length Total Volume Total Weight # of Members >< W10x33 3.6000E+03 3.4956E+04 9.9030E+00 16 >< W10x39 1.4400E+03 1.6560E+04 4.6914E+00 4 >< W10x49 7.2000E+02 1.0368E+04 2.9373E+00 4 >< W12x45 1.4400E+03 1.9008E+04 5.3850E+00 4 >< W6x9 3.2400E+03 8.6832E+03 2.4600E+00 18 >< W8x31 1.4400E+03 1.3147E+04 3.7246E+00 4 >< W8x40 1.4400E+03 1.6848E+04 4.7730E+00 8 >< ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< ACTIVE UNITS WEIGHT KIP LENGTH INCH >< >< TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS >< >< LENGTH = 1.3320E+04 WEIGHT = 3.3874E+01 VOLUME = 1.1957E+05 ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
![Page 90: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/90.jpg)
90
Combined Forces
ASD
WEIGHT = 46.566 kips
LRFD
WEIGHT = 33.874 kips
![Page 91: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/91.jpg)
91
Deflection Design ASD
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< Active Units Weight Unit = KIP Length Unit = INCH >< >< Steel Take Off Itemize Based on the PROFILE >< Total Length, Volume, Weight, and Number of Members >< >< Profile Names Total Length Total Volume Total Weight # of Members >< W10x33 2.1600E+03 2.0974E+04 5.9418E+00 12 >< W12x58 1.4400E+03 2.4480E+04 6.9352E+00 4 >< W12x65 1.4400E+03 2.7504E+04 7.7919E+00 4 >< W12x72 2.1600E+03 4.5576E+04 1.2912E+01 12 >< W14x43 1.4400E+03 1.8144E+04 5.1402E+00 4 >< W14x48 1.4400E+03 2.0304E+04 5.7521E+00 4 >< W6x9 3.2400E+03 8.6832E+03 2.4600E+00 18 ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< ACTIVE UNITS WEIGHT KIP LENGTH INCH >< >< TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS >< >< LENGTH = 1.3320E+04 WEIGHT = 4.6933E+01 VOLUME = 1.6566E+05 ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
![Page 92: ASD vs LRFD - · PDF file01/06/2016 · 3 ASD and LRFD Major Differences • Load Combinations and load factors • ASD results are based on the stresses and LRFD results are based](https://reader033.fdocuments.net/reader033/viewer/2022042505/5aa1527e7f8b9ac67a8b9f2c/html5/thumbnails/92.jpg)
92
Deflection Design LRFD
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< Active Units Weight Unit = KIP Length Unit = INCH >< >< Steel Take Off Itemize Based on the PROFILE >< Total Length, Volume, Weight, and Number of Members >< >< Profile Names Total Length Total Volume Total Weight # of Members >< W10x33 2.1600E+03 2.0974E+04 5.9418E+00 12 >< W10x49 1.4400E+03 2.0736E+04 5.8745E+00 8 >< W10x54 7.2000E+02 1.1376E+04 3.2228E+00 4 >< W12x40 1.4400E+03 1.6992E+04 4.8138E+00 4 >< W14x43 2.8800E+03 3.6288E+04 1.0280E+01 8 >< W14x48 1.4400E+03 2.0304E+04 5.7521E+00 4 >< W6x9 3.2400E+03 8.6832E+03 2.4600E+00 18 ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>< ACTIVE UNITS WEIGHT KIP LENGTH INCH >< >< TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS >< >< LENGTH = 1.3320E+04 WEIGHT = 3.8345E+01 VOLUME = 1.3535E+05 ><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>