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 rigidity, small lateral loads, load reversal Slenderness L/r > 300 AISC Spec D1 Does not apply to rods in tension

STRENGTH Failure at Main Body Failure at Connection etc Limit States Last Time STRENGTH Failure at Main Body Failure at Connection etc

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

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

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

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

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)

Staggered Fasteners Geometry Constraints Space Limitations

Staggered Fasteners Inclined Fracture Path

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

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

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

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

Example

Example

Example

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)

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

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

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

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

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

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

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

3. Round HSS with

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

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

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

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

Example Determine Effective Net Area

Example

Example Only one element is connected Net area must be reduced

Example Alternatively 3 bolts in direction of load

Block Shear

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

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

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

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

Compute block shear strength per LRFD and ASD Example Compute block shear strength per LRFD and ASD

Example

Example

Example Nominal Strength LRFD ASD