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

2. TENSION MEMBERS – TYPES Last 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. STRENGTH Failure at Main Body Failure at Connection etc
Limit States Last Time
STRENGTH
Failure at Main Body
Failure at Connection
etc

5. TENSION MEMBERS - LIMIT STATES AISC Specs Chapter D Last 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 D Last 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 )

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
Reduced diameter T g s
g = gage
s = spacing
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. a. Longitudinal welds on sides only
2. Plates
U=1.0
since cross section has one element and it is connected
Special Cases
a. Longitudinal welds on sides only

26. b. Transverse welds only (uncommon)
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 Shear Chapter 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 Shear Chapter 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 Shear Chapter D User Note -> J4.3 (p. 16.1-112)
Anv: net shear area
Ant : net tension area
For angles and gusset plates

40. Block Shear Chapter 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. Compute block shear strength per LRFD and ASD
Example
Compute block shear strength per LRFD and ASD

42. Example

43. Example

44. Example
Nominal Strength
LRFD
ASD