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Tips for Successful Delegation of
Connection Design
by Clifford Schwinger, P.E.The Harman Group, Structural Engineers
King of Prussia, Pa.
Delaware Valley Association of Structural Engineers
10/8/14 breakfast seminar
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Engineers can reduce the cost of the
connections even when delegating
connection design.
A substantial percentage of structural
steel cost is related to the connections.
Why care? Why delegate?
Less work for the engineer of record
Connection design is becoming a specialty
Fabricators have different preferences
for preferred connection details
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But there is a right way and a wrong
way to delegate connection design.
5The wrong way:
“ALL SHEAR CONNECTIONS SHALL BE
DESIGNED TO DEVELOP THE FULL SHEAR
STRENGTH OF THE MEMBER.”
“ALL MOMENT CONNECTIONS SHALL BE
DESIGNED TO DEVELOP THE FULL
PLASTIC MOMENT CAPACITY OF THE
MEMBER.”
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The wrong way:
“ALL SHEAR CONNECTIONS SHALL BE
DESIGNED TO DEVELOP A SHEAR
STRENGTH EQUAL TO 0.6 x Fy x d x t”
“ALL MOMENT CONNECTIONS SHALL BE
DESIGNED TO DEVELOP THE FULL
PLASTIC MOMENT CAPACITY 0.9 x Mp OF
THE MEMBER.”
7 The wrong way: 8
The right way=.
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Follow the Code of
Standard Practice
10Rule #1
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From the commentary of AISC 303A10,
The EOR has ultimate “).responsibility for the
adequacy and safety of the entire structure).”
Follow Code of Standard Practice18
Section 3.1.1
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This is not connection design This is not connection design
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Design of stiffeners is the responsibility of the
engineer of record
Show the reactions
22Rule #2
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Wrong way #1
“ALL SHEAR CONNECTIONS SHALL BE
DESIGNED TO DEVELOP THE FULL SHEAR
STRENGTH OF THE MEMBER.”
“ALL MOMENT CONNECTIONS SHALL BE
DESIGNED TO DEVELOP THE FULL PLASTIC
MOMENT CAPACITY OF THE MEMBER”
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Wrong way #2
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Do not specify
connections be
designed using
Table 3A6
Wrong way #3
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Relying on Table 3A6 will usually result in excessively
conservative connection designs.
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Relying on Table 3A6 will usually result in excessively
conservative connection designs.
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But, relying on Table 3A6 can also result in connections with
insufficient strength
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Show member shear reactions on
framing plans, moment connection
design moments and axial loads in
brace and truss members.
(preferably factored)
The right way�.
Do not make up
connection design
requirements
32Rule #3
Do not mandate connection design
requirements more stringent than
required by the Building Code and
AISC 360
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“All bolts shall be slipAcritical”
“All connections shall be designed for the
full strength of the member”
“All holes shall be standard sized holes”
“SingleAsided shear connections are
prohibited”
Examples of arbitrary (and usually
unnecessary) requirements,
Use R=3 (where
permitted)
35Rule #4
Limit “Strength Ratio” of
tension members
36Rule #5
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37Limit strength ratio
ASAGS = Available strength at the gross section
Strength ratio =ASAGS
Required strength
Members must have sufficient strength at both the gross
and net sections
38Limit strength ratio
39Limit strength ratio
40Limit strength ratio
41Limit strength ratio
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Following this rule will reduce the likelihood that
sections will require reinforcement at the net section
Limit strength ratio
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43Limit strength ratio
44Limit strength ratio
Think about
constructability and
connection
“designability”
45Rule #6 46
Designability
The ease by which economical
connections can be designed for a
given framing configuration
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How will the connections be designed and detailed?
Are the connections “designable”?
Designability
Will the connections be easy to fabricate?
Will they be easy to install in the field?
Constructability
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Engineers have options during design
Engineers can configure the framing to
improve the “designability” of connections
Failure to consider “designability” during
design reduces options for the fabricator
during detailing
Designability
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49Designability
50Designability
51Designability
Head off steeply skewed connections
52Designability
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Configure framing so that no more than one beam frames to
any one side of a column
Designability54
Configure framing so that no more than one beam frames to
any one side of a column
Designability
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Be aware of connection interference where beams are
slightly offset from columns.
Designability
Avoid skewed beamAtoAcolumn moment connections
56Designability
Issue complete, coordinated
and wellAdetailed contract
documents
57Rule #7 58
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Show details giving concept of design.
Permit alternative details.
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Permit consideration of
alternative connection details
61Rule #8Summary
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1.Understand and follow the Code of Standard Practice
2.Show the reactions
3.Do not specify requirements in excess of the building code
4.Use R = 3 for seismic design (if permitted)
5.Limit strength ratio in tension members to 0.75
6.Think about constructability and connection “designability”
7.Issue complete & coordinated contract documents with
“designable” concept connection details
8.Permit alternative connection details
Questions?
Thank you!
Clifford Schwinger, P.E.The Harman Group, Structural Engineers
King of Prussia, Pa.
601A337A3360
