General Comparison between AISC LRFD and ASD Hamid

General Comparison between AISC LRFD and ASD Hamid Zand GT STRUDL Users Group Las Vegas, Nevada June 22 -25, 2005 1

AISC ASD and LRFD • AISC = American Institute of Steel Construction • ASD = Allowable Stress Design AISC Ninth Edition • LRFD = Load and Resistance Factor Design AISC Third Edition 2

AISC Steel Design Manuals • • 1963 AISC ASD 6 th Edition 1969 AISC ASD 7 th Edition 1978 AISC ASD 8 th Edition 1989 AISC ASD 9 th Edition • 1986 AISC LRFD 1 st Edition • 1993 AISC LRFD 2 nd Edition • 1999 AISC LRFD 3 rd Edition 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 • Static analysis is acceptable for ASD but nonlinear geometric analysis is required for LRFD • Beams and flexural members • Cb computation 4

ASD Load Combinations • 1. 0 D + 1. 0 L • 0. 75 D + 0. 75 L + 0. 75 W • 0. 75 D + 0. 75 L + 0. 75 E D L W E = = dead load live load wind load earthquake load 5

ASD Load Combinations Or you can use following load combinations with the parameter ALSTRINC to account for the 1/3 allowable increase for the wind and seismic load 1. 1. 0 D + 1. 0 L 2. 1. 0 D + 1. 0 L + 1. 0 W 3. 1. 0 D + 1. 0 L + 1. 0 E • PARAMETER $ ALSTRINC based on the % increase • ALSTRINC 33. 333 LOADINGS 2 3 6

LRFD Load Combinations • • • 1. 4 D 1. 2 D + 1. 6 L 1. 2 D + 1. 6 W + 0. 5 L 1. 2 D ± 1. 0 E + 0. 5 L 0. 9 D ± (1. 6 W or 1. 0 E) D L W E = = dead load live load wind load earthquake load 7

Deflection Load Combinations for ASD and LRFD • 1. 0 D + 1. 0 L + 1. 0 W • 1. 0 D + 1. 0 L + 1. 0 E D L W E = = dead load live load wind load earthquake load 8

Forces and Stresses • ASD = actual stress values are compared to the AISC allowable stress values • LRFD = actual forces and moments are compared to the AISC limiting forces and moments capacity 9

ASTM Steel Grade • Comparison is between Table 1 of the AISC ASD 9 th Edition on Page 1 -7 versus Table 2 -1 of the AISC LRFD 3 rd Edition on Page 2 -24 • A 529 Gr. 42 of ASD, not available in LRFD • A 529 Gr. 50 and 55 are new in LRFD • A 441 not available in LRFD • A 572 Gr. 55 is new in LRFD • A 618 Gr. I, II, & III are new in LRFD • A 913 Gr. 50, 65, & 70 are new in LRFD • A 992 (Fy = 50, Fu = 65) is new in LRFD (new standard) • A 847 is new in LRFD 10

Slenderness Ratio • Compression KL/r ≤ 200 • Tension L/r ≤ 300 11

Tension Members • Check L/r ratio • Check Tensile Strength based on the crosssection’s Gross Area • Check Tensile Strength based on the crosssection’s Net Area 12

Tension Members ASD ft = FX/Ag ≤ Ft ft = FX/Ae ≤ Ft Gross Area Net Area LRFD Pu = FX ≤ ϕt Pn = ϕt Ag Fy Pu = FX ≤ ϕt Pn = ϕt Ae Fu ϕt = 0. 9 for Gross Area ϕt = 0. 75 for Net Area 13

Tension Members ASD Gross Area Net Area LRFD Gross Area Net Area (ASD Section D 1) Ft = 0. 6 Fy Ft = 0. 5 Fu (LRFD Section D 1) ϕt P n = ϕt F y A g ϕt P n = ϕt F u A e ϕt = 0. 9 ϕt = 0. 75 14

Compare ASD to LRFD ASD LRFD 1. 0 D + 1. 0 L 1. 2 D + 1. 6 L 0. 6 Fy (ASD) × (1. 5) = 0. 9 Fy (LRFD) 0. 5 Fu (ASD) × (1. 5) = 0. 75 Fu (LRFD) ASD × (1. 5) = LRFD 15

Tension Members 16

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 A 992 • Design based on the ASD and LRFD codes 17

Tension Members ASD W 18 x 46 Actual/Allowable Ratio = 0. 989 LRFD W 10 x 49 Actual/Limiting Ratio = 0. 989 18

Tension Members ASD W 18 x 46 FX = 400. 688 kips Area = 13. 5 in. 2 Ratio = 0. 989 LRFD W 10 x 49 FX = 640. 881 kips Area = 14. 4 in. 2 Ratio = 0. 989 19

Tension Members Load Factor difference between LRFD and ASD 640. 881 / 400. 688 = 1. 599 Equation Factor difference between LRFD and ASD LRFD = (1. 5) × ASD Estimate required cross-sectional area for LRFD W 10 x 49 Area = 14. 4 in. 2 20

Tension Members Code Check based on the ASD 9 and using W 10 x 49 FX = 400. 734 kips Ratio = 0. 928 Load Factor difference between LRFD and ASD 640. 881 / 400. 734 = 1. 599 LRFD W 10 x 49 Ratio = 0. 989 21

Tension Members ASD Example # 1 Live Load = 400 kips W 18 x 46 Actual/Allowable Ratio = 0. 989 LRFD Example # 1 Live Load = 400 kips W 10 x 49 Actual/Limiting Ratio = 0. 989 Example # 2 Dead Load = 200 kips Live Load = 200 kips W 14 x 43 Actual/Limiting Ratio = 0. 989 Code check W 14 x 43 based on the ASD 9 W 14 x 43 Actual/Allowable Ratio = 1. 06 22

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 23

Compression Members ASD fa = FX/Ag ≤ Fa LRFD Pu = FX ≤ ϕc Pn = ϕc Ag Fcr Where ϕc = 0. 85 24

Limiting Width-Thickness Ratios for Compression Elements ASD b/t = h/tw = LRFD b/t = h/tw = 25

Limiting Width-Thickness Ratios for Compression Elements Assume E = 29000 ksi ASD b/t = h/tw = LRFD b/t = h/tw = 26

Compression Members ASD LRFD KL/r ≤ C′c (ASD E 2 -1 or A-B 5 -11) (LRFD A-E 3 -2) 27

Compression Members ASD LRFD KL/r > C′c (ASD E 2 -2) (LRFD A-E 3 -3) 28

Compression Members LRFD 29

Compression Members ASD LRFD Fcr / Fa = 1. 681 LRFD Fcr = ASD Fa × 1. 681 30

Compression Members ASD (ASD C-E 2 -2) LRFD λc = Maximum of ( λcy , λcz , λe ) 31

Compression Members LRFD Where: 32

Compression Members Flexural-Torsional Buckling 33

Qs Computation ASD LRFD 34

Qs Computation Assume E = 29000 ksi ASD LRFD 35

Qs Computation ASD LRFD 36

Qs Computation Assume E = 29000 ksi ASD LRFD 37

Qa Computation ASD LRFD 38

Compression Members 39

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 A 992 • Design based on the ASD and LRFD codes 40

Compression Members ASD W 10 x 49 Actual/Allowable Ratio = 0. 941 LRFD W 10 x 54 Actual/Limiting Ratio = 0. 944 41

Compression Members ASD W 10 x 49 FX = 100. 734 kips Area = 14. 4 in. 2 Ratio = 0. 941 LRFD W 10 x 54 FX = 160. 967 kips Area = 15. 8 in. 2 Ratio = 0. 944 42

Compression Members Load Factor difference between LRFD and ASD 160. 967 / 100. 734 = 1. 598 Equation Factor difference between LRFD and ASD LRFD Fcr = (1. 681) × ASD Fa Estimate required cross-sectional area for LRFD W 10 x 54 Area = 15. 8 inch 43

Compression Members Code Check based on the ASD 9 and use W 10 x 54 FX = 100. 806 kips Ratio = 0. 845 Load Factor difference between LRFD and ASD 160. 967 / 100. 806 = 1. 597 LRFD W 10 x 54 Ratio = 0. 944 44

Compression Members ASD Example # 1 Live Load = 100 kips W 10 x 49 Actual/Allowable Ratio = 0. 941 LRFD Example # 1 Live Load = 100 kips W 10 x 54 Actual/Limiting Ratio = 0. 944 Example # 2 Dead Load = 50 kips Live Load = 50 kips W 10 x 49 Actual/Limiting Ratio = 0. 921 Code check W 10 x 49 based on the ASD 9 W 10 x 49 Actual/Allowable Ratio = 0. 941 45

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 46

Flexural Members ASD fb = MZ/SZ ≤ Fb LRFD Mu = MZ ≤ ϕb Mn Where ϕb = 0. 9 47

Limiting Width-Thickness Ratios for Compression Elements ASD LRFD Assume E = 29000 ksi 48

Flexural Members Compact Section ASD (ASD F 1 -1) Fb = 0. 66 Fy LRFD (LRFD A-F 1 -1) ϕb Mn = ϕb Mp = ϕb Fy ZZ ≤ 1. 5 Fy SZ Where ϕb = 0. 9 49

Flexural Members Compact Section Braced at 1/3 Points 50

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 A 992 • Braced at the 1/3 Points • Design based on the ASD and LRFD codes 51

Flexural Members Compact Section ASD W 18 x 40 Actual/Allowable Ratio = 0. 959 LRFD W 18 x 40 Actual/Limiting Ratio = 0. 982 52

Flexural Members Compact Section ASD W 18 x 40 MZ = 2165. 777 inch-kips Sz = 68. 4 in. 3 Ratio = 0. 959 LRFD W 18 x 40 MZ = 3462. 933 inch-kips Zz = 78. 4 in. 3 Ratio = 0. 982 53

Flexural Members Compact Section Load Factor difference between LRFD and ASD 3462. 933 / 2165. 777 = 1. 5989 Equation Factor difference between LRFD and ASD LRFD = (0. 66 Sz)(1. 5989) / (0. 9 Zz) × ASD Zz LRFD W 18 x 40 Zz = 78. 4 in. 3 54

Flexural Members Compact Section Code Check based on the ASD 9, Profile W 18 x 40 MZ = 2165. 777 inch-kips Ratio = 0. 959 Load Factor difference between LRFD and ASD 3462. 933 / 2165. 777 = 1. 5989 LRFD W 18 x 40 Ratio = 0. 982 55

Flexural Members Compact Section ASD Example # 1 Live Load = 15 kips/ft W 18 x 40 Actual/Allowable Ratio = 0. 959 LRFD Example # 1 Live Load = 15 kips/ft W 18 x 40 Actual/Limiting Ratio = 0. 982 Example # 2 Dead Load = 7. 5 kips/ft Live Load = 7. 5 kips/ft W 18 x 40 Actual/Limiting Ratio = 0. 859 Code check W 18 x 40 based on the ASD 9 W 18 x 40 Actual/Allowable Ratio = 0. 959 56

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 57

Flexural Members Noncompact Section ASD fb = MZ/SZ ≤ Fb LRFD Mu = MZ ≤ ϕb Mn Where ϕb = 0. 9 58

Limiting Width-Thickness Ratios for Compression Elements ASD LRFD 59

Limiting Width-Thickness Ratios for Compression Elements Assume E = 29000 ksi ASD LRFD 60

Flexural Members Noncompact Section ASD (ASD F 1 -3) (ASD F 1 -2) ASD Equations F 1 -6, F 1 -7, and F 1 -8 must to be checked. 61

Flexural Members Noncompact Section ASD When (ASD F 1 -6) 62

Flexural Members Noncompact Section ASD When (ASD F 1 -7) 63

Flexural Members Noncompact Section ASD For any value of l/r. T (ASD F 1 -8) 64

Flexural Members Noncompact Section LRFD 1. 2. 3. LTB, Lateral-Torsional Buckling FLB, Flange Local Buckling WLB, Web Local Buckling 65

Flexural Members Noncompact Section LRFD – LTB • • • – FLB • – 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 noncompact and slender sections 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 66

Flexural Members Noncompact Section LRFD LTB For λp < λ ≤ λr (Table A-F 1. 1) (LRFD A-F 1 -2) Where: Mp = Fy Zz ≤ 1. 5 Fy Sz Mr = FLSz λ = Lb/ry λp FL = Smaller of (Fyf − Fr) or Fyw = 67

Flexural Members Noncompact Section LRFD LTB (Table A-F 1. 1) Where: λr = X 1 = X 2 = 68

Flexural Members Noncompact Section LRFD For FLB (Table A-F 1. 1) λp < λ ≤ λr (LRFD A-F 1 -3) Where: Mp Mr λ λp λr = Fy Zz ≤ 1. 5 Fy Sz = FLSz = b/t = = FL = Smaller of (Fyf − Fr) or Fyw 69

Flexural Members Noncompact Section LRFD WLB For λp < λ ≤ λr (Table A-F 1. 1) (LRFD A-F 1 -3) Where: Mp = Fy Zz ≤ 1. 5 Fy Sz Mr = Re Fy Sz Re = 1. 0 for non-hybrid girder 70

Flexural Members Noncompact Section LRFD WLB λ (Table A-F 1. 1) = h/tw λp = λr = 71

Flexural Members Noncompact Section ASD LRFD 72

Flexural Members Noncompact Section 73

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 W 12 x 65 Loadings are: • Self weight • 12 kips/ft uniform load • Load combinations based on the ASD and LRFD codes • Steel grade is A 992 • Check code based on the ASD and LRFD codes 74

Flexural Members Noncompact Section ASD W 12 x 65 Cb = 1. 0 Actual/Allowable Ratio = 0. 988 LRFD W 12 x 65 Cb = 1. 136 Actual/Limiting Ratio = 0. 971 Code check is controlled by FLB. Cb = 1. 0 Actual/Limiting Ratio = 0. 973 75

Flexural Members Noncompact Section ASD Example # 1 Live Load = 12 kips/ft W 12 x 65 Actual/Allowable Ratio = 0. 988 LRFD Example # 1 Live Load = 12 kips/ft W 12 x 65 Actual/Limiting Ratio = 0. 971 Example # 2 Dead Load = 6 kips/ft Live Load = 6 kips/ft W 12 x 65 Actual/Limiting Ratio = 0. 85 Code check W 12 x 65 based on the ASD 9 W 12 x 65 Actual/Allowable Ratio = 0. 988 76

Design for Shear ASD fv = FY/Aw ≤ Fv = 0. 4 Fy (ASD F 4 -1) LRFD Vu = FY ≤ ϕv. Vn = ϕv 0. 6 Fyw Aw (LRFD F 2 -1) Where ϕv = 0. 9 77

Design for Shear Assume E = 29000 ksi ASD fv = FY/Aw ≤ Fv = 0. 4 Fy (ASD F 4 -1) LRFD Vu = FY ≤ ϕv. Vn = ϕv 0. 6 Fyw Aw (LRFD F 2 -1) Where ϕv = 0. 9 78

Design for Shear ASD fv = FY/Ay ≤ (ASD F 4 -2) Vu = FY ≤ ϕv. Vn = ϕv (LRFD F 2 -2) LRFD Where ϕv = 0. 9 79

Design for Shear LRFD Vu = FY ≤ ϕv. Vn = ϕv (LRFD F 2 -3) Where ϕv = 0. 9 80

Design for Shear Braced at 1/3 Points 81

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 A 992 • Braced at the 1/3 Points • Design based on the ASD and LRFD codes 82

Design for Shear ASD W 18 x 40 LRFD W 18 x 40 (Check shear at the end of the member, equation “F 4 -1 Y”) Actual/Allowable Ratio = 0. 8 (Check shear at the end of the member, equation “A-F 2 -1 Y”) Actual/Limiting Ratio = 0. 948 83

Design for Shear ASD W 18 x 40 FY = 90. 241 kips Ay = 5. 638 in. 2 Ratio = 0. 8 LRFD W 18 x 40 FY = 144. 289 kips Ay = 5. 638 in. 2 Ratio = 0. 948 84

Design for Shear Code Check based on the ASD 9, Profile W 18 x 40 FY = 90. 241 kips Ratio = 0. 8 Load Factor difference between LRFD and ASD 144. 289 / 90. 241 = 1. 5989 Equation Factor difference between LRFD and ASD LRFD = (0. 4)(1. 5989) /(0. 6)(0. 9) × ASD LRFD W 18 x 40 Ratio = 0. 948 85

Design for Shear ASD Example # 1 Live Load = 15 kips/ft W 18 x 40 Actual/Allowable Ratio = 0. 8 LRFD Example # 1 Live Load = 15 kips/ft W 18 x 40 Actual/Limiting Ratio = 0. 948 Example # 2 Dead Load = 7. 5 kips/ft Live Load = 7. 5 kips/ft W 18 x 40 Actual/Limiting Ratio = 0. 83 Code check W 18 x 40 based on the ASD 9 W 18 x 40 Actual/Allowable Ratio = 0. 8 86

Combined Forces ASD fa /Fa > 0. 15 (ASD H 1 -1) (ASD H 1 -2) LRFD Pu /ϕPn ≥ 0. 2 (LRFD H 1 -1 a) 87

Combined Forces ASD fa /Fa ≤ 0. 15 (ASD H 1 -1) LRFD Pu /ϕPn < 0. 2 (LRFD H 1 -1 a) 88

Combined Forces 89

Combined Forces • 3 D Simple Frame • • 3 Bays in X direction 2 Bays in Z direction 2 Floors in Y direction 3 @ 15 ft 2 @ 30 ft 2 @ 15 ft Loadings • • Self weight of the Steel Self weight of the Slab Other dead loads Live load on second floor Live load on roof Wind load in the X direction Wind load in the Z direction 62. 5 15. 0 50. 0 20. 0 psf psf psf 90

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 > < W 10 x 33 2. 1600 E+03 2. 0974 E+04 5. 9418 E+00 12 > < W 12 x 58 1. 4400 E+03 2. 4480 E+04 6. 9352 E+00 4 > < W 12 x 65 1. 4400 E+03 2. 7504 E+04 7. 7919 E+00 4 > < W 12 x 72 2. 1600 E+03 4. 5576 E+04 1. 2912 E+01 12 > < W 6 x 9 3. 2400 E+03 8. 6832 E+03 2. 4600 E+00 18 > < W 8 x 40 1. 4400 E+03 1. 6848 E+04 4. 7730 E+00 4 > < W 8 x 48 1. 4400 E+03 2. 0304 E+04 5. 7521 E+00 4 > <<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> < ACTIVE UNITS WEIGHT KIP LENGTH INCH > < TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS > < LENGTH = 1. 3320 E+04 WEIGHT = 4. 6566 E+01 VOLUME = 1. 6437 E+05 > <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> 91

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 > < W 10 x 33 3. 6000 E+03 3. 4956 E+04 9. 9030 E+00 16 > < W 10 x 39 1. 4400 E+03 1. 6560 E+04 4. 6914 E+00 4 > < W 10 x 49 7. 2000 E+02 1. 0368 E+04 2. 9373 E+00 4 > < W 12 x 45 1. 4400 E+03 1. 9008 E+04 5. 3850 E+00 4 > < W 6 x 9 3. 2400 E+03 8. 6832 E+03 2. 4600 E+00 18 > < W 8 x 31 1. 4400 E+03 1. 3147 E+04 3. 7246 E+00 4 > < W 8 x 40 1. 4400 E+03 1. 6848 E+04 4. 7730 E+00 8 > <<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> < ACTIVE UNITS WEIGHT KIP LENGTH INCH > < TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS > < LENGTH = 1. 3320 E+04 WEIGHT = 3. 3874 E+01 VOLUME = 1. 1957 E+05 > <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> 92

Combined Forces ASD WEIGHT = 46. 566 kips LRFD WEIGHT = 33. 874 kips 93

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 > < W 10 x 33 2. 1600 E+03 2. 0974 E+04 5. 9418 E+00 12 > < W 12 x 58 1. 4400 E+03 2. 4480 E+04 6. 9352 E+00 4 > < W 12 x 65 1. 4400 E+03 2. 7504 E+04 7. 7919 E+00 4 > < W 12 x 72 2. 1600 E+03 4. 5576 E+04 1. 2912 E+01 12 > < W 14 x 43 1. 4400 E+03 1. 8144 E+04 5. 1402 E+00 4 > < W 14 x 48 1. 4400 E+03 2. 0304 E+04 5. 7521 E+00 4 > < W 6 x 9 3. 2400 E+03 8. 6832 E+03 2. 4600 E+00 18 > <<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> < ACTIVE UNITS WEIGHT KIP LENGTH INCH > < TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS > < LENGTH = 1. 3320 E+04 WEIGHT = 4. 6933 E+01 VOLUME = 1. 6566 E+05 > <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> 94

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 > < W 10 x 33 2. 1600 E+03 2. 0974 E+04 5. 9418 E+00 12 > < W 10 x 49 1. 4400 E+03 2. 0736 E+04 5. 8745 E+00 8 > < W 10 x 54 7. 2000 E+02 1. 1376 E+04 3. 2228 E+00 4 > < W 12 x 40 1. 4400 E+03 1. 6992 E+04 4. 8138 E+00 4 > < W 14 x 43 2. 8800 E+03 3. 6288 E+04 1. 0280 E+01 8 > < W 14 x 48 1. 4400 E+03 2. 0304 E+04 5. 7521 E+00 4 > < W 6 x 9 3. 2400 E+03 8. 6832 E+03 2. 4600 E+00 18 > <<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> < ACTIVE UNITS WEIGHT KIP LENGTH INCH > < TOTAL LENGTH, WEIGHT AND VOLUME FOR SPECIFIED MEMBERS > < LENGTH = 1. 3320 E+04 WEIGHT = 3. 8345 E+01 VOLUME = 1. 3535 E+05 > <<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> 95

Deflection Design ASD WEIGHT = 46. 933 kips LRFD WEIGHT = 38. 345 kips 96

Compare Design without and with Deflection Design ASD Without Deflection Design With Deflection Design WEIGHT = 46. 566 kips WEIGHT = 46. 933 kips LRFD Without Deflection Design With Deflection Design WEIGHT = 33. 874 kips WEIGHT = 38. 345 kips 97

Design same example based on Cb = 1. 0 Code and deflection design with Cb = 1. 0 ASD Compute Cb Specify Cb = 1. 0 WEIGHT = 46. 933 kips WEIGHT = 51. 752 kips LRFD Compute Cb Specify Cb = 1. 0 WEIGHT = 38. 345 kips WEIGHT = 48. 421 kips 98

Design Similar example based on Cb = 1. 0 and LL× 5 • Code and deflection design with Cb = 1. 0 and increase the live load by a factor of 5. • Area loads are distributed using two way option instead of one way • Also change the 2 bays in the Z direction from 30 ft to 15 ft. ASD WEIGHT = 25. 677 kips LRFD WEIGHT = 22. 636 kips Difference = 3. 041 kips 99

Design Similar example based on Cb = 1. 0 and LL× 10 • Code and deflection design with Cb = 1. 0 and increase the live load by a factor of 10. • Area loads are distributed using two way option instead of one way • Also change the 2 bays in the Z direction from 30 ft to 15 ft. ASD WEIGHT = 31. 022 kips LRFD WEIGHT = 29. 051 kips Difference = 1. 971 kips 100

Stiffness Analysis versus Nonlinear Analysis • Stiffness Analysis – Load Combinations or Form Loads can be used. • Nonlinear Analysis – Form Loads must be used. Load Combinations are not valid. • Nonlinear Analysis – Specify type of Nonlinearity. • Nonlinear Analysis – Specify Maximum Number of Cycles. • Nonlinear Analysis – Specify Convergence Tolerance. 101

Nonlinear Analysis Commands • NONLINEAR EFFECT • TENSION ONLY • COMPRESSION ONLY • GEOMETRY AXIAL • MAXIMUM NUMBER OF CYCLES • CONVERGENCE TOLERANCE • NONLINEAR ANALYSIS 102

Design using Nonlinear Analysis Input File # 1 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Geometry, Material Type, Properties, Loading ‘SW’, ‘LL’, and ‘WL’ FORM LOAD ‘A’ FROM ‘SW’ 1. 4 FORM LOAD ‘B’ FROM ‘SW’ 1. 2 ‘LL’ 1. 6 FORM LOAD ‘C’ FROM ‘SW’ 1. 2 ‘WL’ 1. 6 ‘LL’ 0. 5 FORM LOAD ‘D’ FROM ‘SW’ 0. 9 ‘WL’ 1. 6 DEFINE PHYSICAL MEMBERS PARAMETERS MEMBER CONSTRAINTS LOAD LIST ‘A’ ‘B’ ‘C’ ‘D’ $ Activate only the FORM loads STIFFNESS ANALYSIS SAVE 103

Design using Nonlinear Analysis Input File # 2 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. RESTORE LOAD LIST ‘A’ ‘B’ ‘C’ ‘D’ SELECT MEMBERS SMOOTH PHYSICAL MEMBERS DELETE LOADINGS ‘A’ ‘B’ ‘C’ ‘D’ SELF WEIGHT LOADING RECOMPUTE FORM LOAD ‘A’ FROM ‘SW’ 1. 4 FORM LOAD ‘B’ FROM ‘SW’ 1. 2 ‘LL’ 1. 6 FORM LOAD ‘C’ FROM ‘SW’ 1. 2 ‘WL’ 1. 6 ‘LL’ 0. 5 FORM LOAD ‘D’ FROM ‘SW’ 0. 9 ‘WL’ 1. 6 LOAD LIST ‘A’ ‘B’ ‘C’ ‘D’ STIFFNESS ANALYSIS CHECK MEMBERS STEEL TAKE OFF SAVE 104

Design using Nonlinear Analysis Input File # 3 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. RESTORE LOAD LIST ‘A’ ‘B’ ‘C’ ‘D’ SELECT MEMBERS SMOOTH PHYSICAL MEMBERS DELETE LOADINGS ‘A’ ‘B’ ‘C’ ‘D’ SELF WEIGHT LOADING RECOMPUTE FORM LOAD ‘A’ FROM ‘SW’ 1. 4 FORM LOAD ‘B’ FROM ‘SW’ 1. 2 ‘LL’ 1. 6 FORM LOAD ‘C’ FROM ‘SW’ 1. 2 ‘WL’ 1. 6 ‘LL’ 0. 5 FORM LOAD ‘D’ FROM ‘SW’ 0. 9 ‘WL’ 1. 6 105

Design using Nonlinear Analysis Input File # 3 (continue) 1. 2. 3. 4. 5. 6. 7. 8. 9. NONLINEAR EFFECT GEOMETRY ALL MEMBERS MAXIMUM NUMBER OF CYCLES CONVERGENCE TOLERANCE DISPLACEMENT LOAD LIST ‘A’ ‘B’ ‘C’ ‘D’ NONLINEAR ANALYSIS CHECK MEMBERS STEEL TAKE OFF SAVE 106

General Comparison between AISC LRFD and ASD Questions 107