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Maximum stiffener width bf−tw
214 −0. 5
26. 75 in.
Compute the compressive strength:
LcKL 0. 757757. 75 in.
Lc
r57. 75
3. 008 19. 20
From AISC J4.4, for compression elements with Lc/r25, the nominal strength is
RnFyAg509. 0450. 0 kips
cRn0. 90450. 0405. 0 kips 294. 8 kips (OK)
Because the stiffener was sized for dimensional constraints, it cannot be made any
For a 1.5-in. length, Rn1. 513. 9220. 88 kips
Required spacing:
Rn
20. 88
sVuQ
Ix
13. 5 Vu824. 3
83730 ,Solutionis:Vu157. 1 kips
Shear at first interior load, left of load, 295. 8 −5. 56922173. 3 kips, so
20. 88
10 Vu824. 3
83730 ,Solutionis:Vu212. 1 kips
This occurs where 295. 8 −5. 569x212. 1, Solution is: x15. 03 ft.
Check middle third of span. Shear on right side of load 173. 3 −112. 0 61. 3 kips
sRnIx
2in.
Welds for bearing stiffeners at the supports (1/2 6):
Minimum weld size 3
16 in. (AISC Table J2.4, based on a thickness of 1/2 in.)
Minimum length 43
16 0. 75 in. 1.5 in., use 1.5 in.
25. 05
s3. 944
s6. 351 in.
For a center-to-center spacing of 6 1
4in., the clear spacing is 6. 25 −1. 5 4. 75 in
25. 05
16. 75 −1. 5 15. 25 in.9 in. max. (9 1. 5 10. 5 in. c-c)
10.7-8
(a) Assume a girder weight of 600 lb/ft.
wu1. 2wD1. 6wL1. 20. 3 0. 61. 60. 72. 2 kips/ft
Pu1. 2PD1. 6PL1. 2501. 6150300. 0 kips
137. 3 115
137. 3 0. 837 6 in.
[10-43]
232. 0 115
232. 0 0. 495 7 in.
Try a 3
2. 5 10. 46 in.
Try a 2 1
2in. 15 1
2in. flange, Af2. 515. 538. 75 in.2
Girder weight 0. 75115238. 750. 490
144
Tension flange: MnFySxt 5060433. 022 105in.-kips
Compression flange: Check FLB:
bf
2tf
15. 5
22. 53. 1, p0. 38 E
Fy
0. 38 29, 000
50 9. 152
Since p,Fcr Fy50 ksi
0. 7Fy
0. 750345. 7 in. 28.81 ft
Since LpLbLr,
Fcr CbFy−0. 3Fy
Lb−Lp
≤Fy
2. 5Mmax 3MA4MB3MC
12. 517750
28. 81 −8. 442 41. 70 ksi (controls)
Compute the bending strength reduction factor.
Rpg 1−aw
1200 300aw
hc
tw
−5. 7 E
Fy
≤1. 0
1. 10 kvE
Fy
1. 10 5. 73529000
50 63. 44
tw
1. 10 kvE
Fy
h
tw
153. 3 0. 413 8
Vn0. 6FyAwCv10. 650900. 41381117 kips
vVn0. 9011171005 kips 560 kips (OK)
No intermediate stiffeners (other than the bearing stiffeners) are required.
(b) Intermediate stiffeners: Intermediate stiffeners are not required.
Rn0. 75675506. 3 kips VL560 kips (N.G.)
Try two plates, 3
4in. 7 in., with 1-in. cutouts.
Apb 7−10. 7529. 0 in.2
Rn1. 8FyApb 1. 8509810. 0 kips
3. 413 25. 27
r
4. 71 E
Fy
4. 71 29000
50 113. 4
Rn0. 90FcrAg0. 9047. 7217. 25740. 9 kips 560 kips (OK)
Use 2 PL 3
47 with 1-in. cutouts for bearing stiffeners at the supports.
2. 083 41. 41
r
4. 71 E
Fy
4. 71 29000
50 113. 4
Rn0. 90FcrAg0. 9044. 1120. 06796. 4 kips 300 kips (OK)
Ix
3. 626 1053. 517 kips/in.
Minimum weld size 1
4in. (AISC Table J2.4)
Minimum length 41
For a 1.5-in. length, Rn1. 511. 1416. 71 kips
Required spacing:
Rn
16. 71
sVuQ
Ix
13. 5 Vu2277
3. 626 105,Solutionis:Vu197. 1 kips
Shear at first interior load, left of load, 560 −2. 225505. 0 kips, so maximum
spacing will not be used in the first third of the span.
Spacing required at left side of first interior load:
RnIx
4in. 11
2in. intermittent E70 fillet welds.
67 spaces at 4 1
2in. each end.
Spacing between interior loads 12 1
2in.
33. 41
s4. 956, Solution is: 6. 74 in.
For a center-to-center spacing of 6 1
2in., the clear spacing is 6. 5 −1. 5 5. 0 in.
25. 05
s2. 655, Solution is: s9. 435 kips/in.
For a center-to-center spacing of 9 in., the clear spacing is
10.7-9
(a) Assume a girder weight of 875 lb/ft.
wu1. 2wD1. 6wL1. 21. 9 0. 8751. 62. 87. 81 kips/ft
137. 3 114
137. 3 0. 830 3 in.
From h
≤11. 7 E
12. 0 29000
Try a 0. 75 in. 114 in. web.
h
tw
114
0. 75 152. 0, Aw0. 75114 2390. 0 in.2
0. 9hFy
63823012
0. 911450−90
674. 43 in. 2
bf≥74. 43
324. 81 in.
Trya3in.28 in. flange, Af32884. 0 in.2
[10-51]
cIx
h/2 tf667500
114/2 31. 113 104in.3
Tension flange: MnFySxt 501. 113 1045. 565 105 in.-kips
Compression flange: Check FLB:
bf
28
0. 38 29, 000
Compute the bending strength reduction factor.
Rpg 1−aw
1200 300aw
hc
tw
−5. 7 E
Fy
≤1. 0
awhctw
bfctfc
1140. 75
2831. 018 10
h
tw
152 61. 22 ∴Cv1
1. 10 kvE
Fy
h
tw
61. 22
152 0. 402 8
Vn0. 6FyAwCv10. 650900. 40281088 kips
h4st
1.3
Fyw
1.5
Ist h4st
1.3
40
Fyw
E
1.5 11441
40
50
29000
1.5 302. 3 in.4
Try two 5/16 12 plates.
16 in. 12 in. 9 ft-2 in. for intermediate stiffeners.
(c) Design bearing stiffeners for the concentrated loads of Pu403. 2 kips
Maximum stiffener width bf−tw
228 −3/4
213. 63 in.
Try b7 in. and t≥1. 79bFy
A18. 753/4279/1621. 94 in.2
rI
A151. 1
21. 94 2. 624 in.
[10-54]
Compute the compressive strength:
2. 624 32. 58
r
4. 71 E
Fy
4. 71 29000
50 113. 4
Ix
6. 675 1057. 899 kips/in.
Minimum weld size 1
4in. (AISC Table J2.4)
Minimum length 41
41. 0 in. 1.5 in., use 1.5 in.
Shear at first interior load, left of load, 1073 −8. 3730821. 9 kips, so the
maximum spacing will not be used in the first quarter of the span.
Spacing required at left side of first interior load:
sVuQ
Ix
13. 5 Vu4914
6. 675 105Vu169. 1 kips
Let Vu1073 −7. 81x−403. 2 169. 1 x64. 11 ft
Distance past first interior load 64. 11 −30 34. 11 ft (slighty past midspan).
Try an intermediate spacing of 10 inches. This will be required where
VuRnIx
and from C to D.
Welds for intermediate stiffeners 5
16 in. 12 in. :
Minimum weld size 3
16 in. (AISC Table J2.4)
25. 05
s10. 65 kips/in. s2. 35 in.
For a center-to-center spacing of 2 1
4in., the clear spacing is 3 −2. 25 0. 75 in.
Use continuous 3
22. 27
s3. 6 kips/in. s6. 186 in.
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