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Tension Members Last Time

Tension Members Last Time. Structural Elements Subjected to Axial Tensile Forces. Trusses. Bracing for Buildings and Bridges. Cables in Suspension and Cable-Stayed Bridges. TENSION MEMBERS – TYPES Last Time. TENSION MEMBERS – TYPES Last Time. Structural Shapes & Build Up Members

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Tension Members Last Time

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  1. Tension MembersLast Time Structural Elements Subjected to Axial Tensile Forces Trusses Bracing for Buildings and Bridges Cables in Suspension and Cable-Stayed Bridges

  2. TENSION MEMBERS – TYPESLast Time

  3. TENSION MEMBERS – TYPES Last Time Structural Shapes & Build Up Members rigidity, small lateral loads, load reversal Slenderness L/r > 300 AISC Spec D1 Does not apply to rods in tension

  4. Limit States Last Time STRENGTH • Failure at Main Body • Failure at Connection • etc

  5. TENSION MEMBERS - LIMIT STATES AISC Specs Chapter DLast Time Failure at main body if connection is strong enough After yielding deformations become too large and member does not serve its design purpose. Failure at yielding nominal strength Pn=FyAg Fy = Yielding Strength, Ag = Gross Area

  6. TENSION MEMBERS - LIMIT STATES AISC Specs Chapter DLast Time Failure at Connection if connection is weak it will fracture Failure at ultimate strength nominal strength Pn=FuAe Fu = Ultimate Strength, Ae = Effective Area

  7. Gross Area – Specs D3.1 p 16.1.27 Last Time Gross Area Ag: Total Area of Main Body of Member

  8. Net Area – Specs D3.2 p 16.1.27 Last Time Net Area An : Welded Connections An = Ag Bolded Connections An = Ag - Area of Holes

  9. Net Area Last Time Size of hole is larger than size of the bolt dh=db +1/16” Additional 1/16” of material is damaged during drilling or punchning of holes (Commentary D3.2 p 16.1-250)

  10. Staggered Fasteners Geometry Constraints Space Limitations

  11. Staggered Fasteners Inclined Fracture Path

  12. Net Area - Effect of Staggered Holes AISC Specs D3.1 Last Time T T T p Reduced diameter T g g = gage s = spacing s Failure paths on net section

  13. Example Last Time 11 holes 8/11 of load Different failure lines may be subjected to different loads!

  14. Net Area - Gage Distance for an Angle Unfold Angle and Visualize as a plate

  15. Net Area - Gage Distance for an Angle For holes on different legs

  16. Example

  17. Example

  18. Example

  19. Effective Net Area – Specs D3.3 p 16.1.28 Ae=AU A = Area that depends on type of connection A=Ag for welded A=An for bolted U = shear lag coefficient (accounts for eccentricities)

  20. U Accounts for eccentricities U AISC D3.3 Table D3.1

  21. Shear Lag Factor • General category for any type of tension member except plates and round HSS with • Plates • Round HSS with • Alternative values for single angles • Alternative values for W,M,S and HP shapes

  22. 1. General category for any type of tension member except plates and round HSS with Distance from centroid of connected area to the plane of the connection l Length of the connection

  23. 1. General category for any type of tension member except plates and round HSS with

  24. 1. General category for any type of tension member except plates and round HSS with

  25. 2. Plates U=1.0 since cross section has one element and it is connected Special Cases a. Longitudinal welds on sides only

  26. 2. Plates U=1.0 since cross section has one element and it is connected Special Cases b. Transverse welds only (uncommon) An net area of directly connected members

  27. 3. Round HSS with

  28. 4. Alternative values for single angles 2 or 3 fasteners in direction of loading 4 fasteners in direction of loading

  29. 5. Alternative values for W,M,S and HP shapes Connected through flange with 3 or more fasteners in direction of loading

  30. 5. Alternative values for W,M,S and HP shapes Connected through flange with 3 or more fasteners in direction of loading

  31. 5. Alternative values for W,M,S and HP shapes Connected through web with 4 or more fasteners in direction of loading

  32. Example Determine Effective Net Area

  33. Example

  34. Example Only one element is connected Net area must be reduced

  35. Example Alternatively 3 bolts in direction of load

  36. Block Shear

  37. Block ShearChapter D User Note -> J4.3 (p. 16.1-112) Failure occurs by rupture on the shear area and rupture on the tension area Both surfaces (shear and tension) contribute to total strength

  38. Block ShearChapter D User Note -> J4.3 (p. 16.1-112) Both surfaces (shear and tension) contribute to total strength Anv: net shear area Ant : net tension area

  39. Block ShearChapter D User Note -> J4.3 (p. 16.1-112) Anv: net shear area Ant : net tension area For angles and gusset plates

  40. Block ShearChapter D User Note -> J4.3 (p. 16.1-112) Anv: net shear area Ant : net tension area AISC Ubs=1 for angles, gusset plates and most coped beams See AISC Commentary J4.3 for other less common cases

  41. Example Compute block shear strength per LRFD and ASD

  42. Example

  43. Example

  44. Example Nominal Strength LRFD ASD

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