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8/12/2019 Design of Concentrically Braced Frames
1/22
4/16/20
Desi n of Concentricall
Braced Frames
Anindya Dutta, Ph.D., S.E.
Example Configurations
X-Braced Inverted V (Chevron) 2 Story X-Braced
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Example Configurations
V (Inverted Chevron) Zipper
Special Concentrically Braced Frames
Primary location of energy dissipation are the
Braces dissipate energy by tension yielding
and compression buckling
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Special Concentrically Braced Frames
Special Concentrically Braced Frames
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Special Concentrically Braced Frames
Column Axial Load Distribution
Special Concentrically Braced FramesColumn Axial Load Distribution
8/12/2019 Design of Concentrically Braced Frames
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Special Concentrically Braced Frames
Beam Design Axial Load
Special Concentrically Braced FramesBeam Design: Flexure
8/12/2019 Design of Concentrically Braced Frames
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Special Concentrically Braced Frames
Basic Design Procedure
Calculate the demand based on ASCE 7
Analyze the structure; find brace forces
Size the fuses i.e. braces
Capacity design other non yielding members
Special Concentrically Braced FramesBasic Design Procedure
Use expected brace capacity
Eliminate conservative design assumptions
Do not use factors for expected strength
. y
8/12/2019 Design of Concentrically Braced Frames
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8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Requirements for Member Design
Brace Effective Length
Requirements for Member DesignBrace Effective Length
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Requirements for Member Design
Brace Effective Length: End Fixity
Requirements for Member DesignBrace Effective Length
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Requirements for Member Design
Required Strength
If UAntRyFyAg
Max load indicated by analysis that can be
transferred to the brace by the system
Requirements for Member DesignLateral Force Distribution
All compression or tension
system (generally not allowed)Sum of horz. Comp. on either
compression or tension 0.7V NG
70% of the force is to be resisted by brace in tension
Exception allowed when compression braces are designed
for Amplified () load combinations of ASCE 7
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Requirements for Member Design
Lateral Force Distribution
0.3V Tension 0.7V 0.3V Tension 0.7V
0.3V Compression 0.7V
OK
0.3V Compression 0.7V
OK
Members to be seismically compact. Follow
Requirements for Member DesignWidth-Thickness Limitations
- -
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Requirements for Member Design
Local Buckling
Design of SCBF Connections
Connections to be designed for expected
This force need not exceed the max load
indicated by analysis that can be transferred
to the brace by the system
8/12/2019 Design of Concentrically Braced Frames
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Design of SCBF Connections
Design of SCBF Connections
8/12/2019 Design of Concentrically Braced Frames
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Design of SCBF Connections
Pin ended
Fixed ended
Design of SCBF Connections
8/12/2019 Design of Concentrically Braced Frames
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Design of SCBF Connections
Design flexural strength of the connection
xe
Design compressive strength of the
pyn MRR 1.1
detailingnyn PRR 1.1
Design of SCBF Connections2t Offset
8/12/2019 Design of Concentrically Braced Frames
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Design of SCBF Connections
2t Offset @ Concrete Filled Deck
Design of SCBF ConnectionsTearing of Gusset: No Hinge Zone
8/12/2019 Design of Concentrically Braced Frames
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8/12/2019 Design of Concentrically Braced Frames
18/22
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Design of SCBF Connections
Gusset Compression
Design of SCBF ConnectionsGusset Compression
8/12/2019 Design of Concentrically Braced Frames
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Design of SCBF Connections
Gusset Compression
Design of SCBF ConnectionsGusset Compression
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
2
Design of SCBF Connections
Design of gussets
Design of SCBF ConnectionsDesign of gussets: Uniform Force Method
Ruc
u
Pusin-Aub
eb
wp
Aub
ec
Ruc+Rub-Pucos
8/12/2019 Design of Concentrically Braced Frames
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2
Design of SCBF Connections
Design of gussets: Uniform Force MethodPuVuc u
cucuuc P
eHPV ==
Hub
Vub
Huc
Vub
ub
ubuub Pr
eVP
rH
rr
==
where
Rub
Pusin -AubRub -Vub
Pusin -Aub -Hub( ) ( )22
bc eer +++=
Design of SCBF: Specials for Chevron
8/12/2019 Design of Concentrically Braced Frames
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4/16/20
Design of SCBF: Specials for Chevron
Design of SCBF: Specials for Chevron