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Re: design code

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Waterman Drinkwater wrote:

Is it possible to share your experience about how to comply with the 
following design code?
        2227.1 Connections (1997 UBC). Adequate strength of connections
to withstand calculated resultant forces and moments, and adequate 
rigidity where such is required, shall be demonstrated by calculation or 
by testing in an approved manner.
It can be seen from the code that a connection has two requirements: 
"(1) sufficient strength for forces and moments" and "(2) adequate 
Requirement "(1) sufficient strength for forces & moments"......
There is no problem with the first requirement. Most structural software 
can analyze the required forces and moments for structural professionals 
to design connections.
Requirement "(2) adequate rigidity"....
If you have design experience, is it possible to show how you comply 
with the second requirement? If your structural software cannot provide 
any information about the minimal (required) connector stiffness, how do 
you make sure your design has an adequate rigidity to comply with the 
Most structural analysis assumes each connection has a perfect rigidity 
(stiffness=infinity), and outputs a set of connection forces and 
moments. In other words, those forces and moments are valid only if the 
connector stiffness is infinite. There is no way to design a connection, 
for example, steel connection, to have an infinity stiffness. If your 
connection design does not provide a sufficient large stiffness, all the 
internal forces and moments must be redistributed. Safe or not? A safe 
design must provide an adequate rigidity for connections. Is it possible 
to share you experiences about how to comply with the second 
requirement? Thank you.
     Section 2227 of the 1997 UBC is part of Division X - Design Standard 
     For Steel Storage Racks.
     The rigidity referred to in Section 2227 refers to connection rigidity 
     consistent with your frame analysis.  If in your frame analysis 
     software you assign joint and member boundary conditions as fixed or 
     pinned, your connection design must match.  I believe the concern is 
     with engineers who treat the connections as partially restrained but 
     analyze them as fixed or pinned.  If you consider the rack connections 
     to be partially restrained, you must somehow provide an anlysis that 
     for the partial restraint, something that may not be available in 
     commercial software.
     For a more technical explanation, see Sections A2.2, J1.1 and J1.2 of 
     the AISC Specifications, ASD or LRFD.
     Rick Drake, SE
     Fluor Daniel, Irvine