chapter 7: bolted connections · 2015. 10. 9. · bolted shear connections • types of bolted...
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Chapter 7: Bolted Connections
Dr. Hasan Katkhuda
Steel Design
STEEL DESIGN
Introduction
• Types of Bolts:
1. Ordinary or Common bolts:
• Classified by ASTM as A307 bolts.
• Used in light structures subjected to static loading only.
2. High strength bolts:
• Classified by ASTM as A325, A490 bolts.
• Have tensile strengths two or more times those of ordinary bolts.
• Used in all types of structures (static + dynamic loads)
Dr. Hasan Katkhuda
Steel Design
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Introduction
• Simple Connections:
• If the line of action of the resultant force to be resisted passes through the center of gravity of the connection, each part of the connection is assumed to resist an equal share of the load.
Dr. Hasan Katkhuda
Steel Design
Introduction
• Eccentrically Loaded Connections:
• If the line of action of the resultant force to be resisted does not act through the center of gravity of the connection.
Dr. Hasan Katkhuda
Steel Design
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Bolted Shear Connections
• Failure modes:
1. Shear failure of the bolts:
Dr. Hasan Katkhuda
Steel Design
Bolted Shear Connections
2. Tension failure in the member :
• Yielding
• Fracture
• Block shear
Dr. Hasan Katkhuda
Steel Design
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Bolted Shear Connections
3. Bearing exerted by the bolts :
Dr. Hasan Katkhuda
Steel Design
Bolted Shear Connections
3. Bearing exerted by the bolts :
Dr. Hasan Katkhuda
Steel Design
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Bolted Shear Connections
• Types of bolted shear connections:
1. Bearing type connections:
• Slip is acceptable (loose in connection)
• Load will be transferred through shear in bolts and bearing in the connected parts.
2. Slip critical connections:
• No slippage is permitted (shear force < friction force)
• No shear and bearing.
• Load will be transferred through friction.
Dr. Hasan Katkhuda
Steel Design
Bearing Type Connections
1. Shear Strength:
• f v : Shearing stress on the cross-sectional area of the bolt.
• Ab : Cross-sectional area of the unthreaded part of bolt.
• Rn : Nominal strength.
• Fnv :Nominal shear stress.
Dr. Hasan Katkhuda
Steel Design
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Bearing Type Connections
Dr. Hasan Katkhuda
Steel Design
Bearing Type Connections
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Steel Design
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Bearing Type Connections
2. Bearing Strength:
• Bearing strength is independent of the type of fastener because the stress under consideration is on the part being connected rather than on the fastener.
Dr. Hasan Katkhuda
Steel Design
Bearing Type Connections
Dr. Hasan Katkhuda
Steel Design
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Bearing Type Connections
Dr. Hasan Katkhuda
Steel Design
Bearing Type Connections
• Spacing and Edge distance requirements:
Dr. Hasan Katkhuda
Steel Design
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Bearing Type Connections
Dr. Hasan Katkhuda
Steel Design
Example (Bearing Type Connections)
• Check bolt spacing, edge distances and bearing in the connection shown.
• Bolts used A325 with threads not in plane of shear.
Dr. Hasan Katkhuda
Steel Design
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Example (Bearing Type Connections)
Dr. Hasan Katkhuda
Steel Design
Example (Bearing Type Connections)
1. Shear strength:
= (60) (�)(3/4)2 / 4 = 26.46 kips
φRn = (0.75)(26.46) = 19.845 kips (for each bolt)
For four bolts:
φRn = (4)(19.845) = 79.38 kips
Dr. Hasan Katkhuda
Steel Design
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Example (Bearing Type Connections)
2. Bearing Strength:
• Tension member :
• Edge holes:
Dr. Hasan Katkhuda
Steel Design
Example (Bearing Type Connections)
• Other holes:
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Steel Design
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Example (Bearing Type Connections)
• Gusset Plate:
• Edge holes:
Dr. Hasan Katkhuda
Steel Design
Example (Bearing Type Connections)
• Other holes:
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Steel Design
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Example (Bearing Type Connections)
Dr. Hasan Katkhuda
Steel Design
Example (Bearing Type Connections)
• Tension Failure:
• Yielding:
• Φt Pn = (0.9)(36)(5)(0.5) = 81 kips
• Fracture: …………………
• Block shear: ……………………
• Control (without calculating Tension failure) = 79.38 kips
• Ru = 1.2(15) +(1.6)(45) = 90 kips
• 79.38 < 90 kips (N.G)
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Steel Design
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Slip Critical Connections
Dr. Hasan Katkhuda
Steel Design
Slip Critical Connections
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Steel Design
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Slip Critical Connections
Dr. Hasan Katkhuda
Steel Design
Example (Slip Critical Connections)
• ¾ inch diameter, A325 bolts with threads in the shear plane no slip is permitted, A36.
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Steel Design
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Example (Slip Critical Connections)
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Steel Design
Example (Slip Critical Connections)
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Example (Slip Critical Connections)
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Steel Design
Example (Slip Critical Connections)
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Example (Slip Critical Connections)
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Steel Design
Example (Slip Critical Connections)
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Design Example
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Steel Design
Design Example
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Design Example
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Steel Design
Design Example
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Steel Design
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Design Example
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Steel Design
Design Example
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Design Example
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Steel Design
Design Example
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Steel Design
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Design Example
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Design Example
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Design Example
Dr. Hasan Katkhuda
Steel Design
Bolts Subjected to Shear and Tension
• The vertical component f the force will put the bolts in shear, while the horizontal component will cause tension on the bolts.
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Steel Design
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Bolts Subjected to Shear and Tension
• Bearing Type connection:
Dr. Hasan Katkhuda
Steel Design
Bolts Subjected to Shear and Tension
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Example (Bolts Subjected to Shear and Tension)
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Example (Bolts Subjected to Shear and Tension)
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Example (Bolts Subjected to Shear and Tension)
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Steel Design
Example (Bolts Subjected to Shear and Tension)
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Example (Bolts Subjected to Shear and Tension)
Dr. Hasan Katkhuda
Steel Design
Bolts Subjected to Shear and Tension
• Slip critical connections:
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Example (Bolts Subjected to Shear and Tension- slip critical connection)
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Steel Design
Example (Bolts Subjected to Shear and Tension- slip critical connection)
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Eccentric Connections (Shear Only)
• Elastic Analysis:
Dr. Hasan Katkhuda
Steel Design
Eccentric Connections (Shear Only)
• Elastic Analysis:
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Steel Design
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Eccentric Connections (Shear Only)
• fv : Shearing stress in each bolt.
Dr. Hasan Katkhuda
Steel Design
Eccentric Connections (Shear Only)
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Steel Design
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Eccentric Connections (Shear Only)
Dr. Hasan Katkhuda
Steel Design
Example (Eccentric Connections (Elastic Analysis)
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Steel Design
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Example (Eccentric Connections (Elastic Analysis)
Dr. Hasan Katkhuda
Steel Design
Example (Eccentric Connections (Elastic Analysis)
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Steel Design
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Eccentric Connections (Shear Only)
• Ultimate Strength Analysis:
Dr. Hasan Katkhuda
Steel Design
Eccentric Connections (Shear Only)
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Steel Design
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Eccentric Connections (Shear Only)
Dr. Hasan Katkhuda
Steel Design
Example (Eccentric Connections (Ultimate Analysis)
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Steel Design
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Example (Eccentric Connections (Ultimate Analysis)
Dr. Hasan Katkhuda
Steel Design
Example (Eccentric Connections (Ultimate Analysis)
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Steel Design
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Example (Eccentric Connections (Ultimate Analysis)
Dr. Hasan Katkhuda
Steel Design
Example (Eccentric Connections (Ultimate Analysis)
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Steel Design
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Example (Eccentric Connections (Ultimate Analysis)
Dr. Hasan Katkhuda
Steel Design
Example (Eccentric Connections , Ultimate Analysis, Tables)
• Bolts are ¾ inch
• A325 bearing with threads in plane of shear.
• Bolts are in single shear.
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Steel Design
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Example (Eccentric Connections , Ultimate Analysis, Tables)
Dr. Hasan Katkhuda
Steel Design