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Re: Single Plate Connection of Collectors Procedure

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The failure modes involved are never irrelevant.  They are the key to the
seismic provisions of the various building codes.

The seismic provision of the various building codes are designed to force
favorable limit states such as yielding and plastic hinging.  At the same
time, they are trying to prevent unfavorable limit states such as fracture,
local buckling, and global buckling.  Whenever the seismic provisions
requires that an item or connection be designed for omega-sub-zero forces,
it is acknowledging that it is associated with unfavorable limit states
that should be kept closer to elastic behavior.  This in turn, allows the
favorable limit states in the adjacent members to be reached first.

In the case of collectors, they are being kept closer to elastic to allow
the frames that they are connecting to reach their ductile limit states
first.

Rick Drake, SE
Fluor Daniel, Aliso Viejo, CA

******



                                                                                                                                       
                      Keith Fix                                                                                                        
                      <kefix(--nospam--at)yahoo.com>        To: seaint(--nospam--at)seaint.org                                                                   
                      11/26/02 07:48 AM                                                                                                
                      Please respond to        cc:                                                                                     
                      seaint                                                                                                           
                                               Subject:  Re: Single Plate Connection of Collectors Procedure                           
                                                                                                                                       
                                                                                                                                 ..... 
                                                                                                                                       




Does the failure mode become irrelevant because the design forces are
higher?

-Keith Fix, PE
-Little Rock, Arkansas

--- Rick.Drake(--nospam--at)Fluor.com wrote:
>
> Collectors should not be designed for ductile limit states.  They should
be
> designed for omega-sub-zero forces.  Reference  1997 UBC, Sec. 1633.2.6
or
> 2000 IBC Sec. 1620.1.6.
>
> Rick Drake, SE
> Fluor Daniel, Aliso Viejo, CA
>
> *********
>
>
>
>
>

>
>                       Markajohn(--nospam--at)cs.com

>
>                       11/25/02 09:40 PM        To: seaint(--nospam--at)seaint.org

>
>                       Please respond to

>
>                       seaint                   cc:

>
>

>
>                                                Subject:  Single Plate
> Connection of Collectors Procedure
>

>
>

>                                                    .....
>

>
>
>
>
>
> Hello,
>
> I have an analysis problem that must be fairly common.
>
> I am analyzing some existing connections of W18 and larger collectors
into
> columns.  They are one-sided plate connections with connection plate held
> by
> stiffeners on top and bottom similar to Fig. 10-25 on page 10-158 and
Fig.
> 10-28 on page 10-159 of the 3rd ed AISC LRFD manual.  The difference is
> that
> with my connections, there would be a large axial load in the beams as
well
>
> as gravity loads.
>
> The design would need to take into account beam-end rotation like Table X
> in
> the old ASD 9th ed, but also account for the axial loads.  In addition,
the
>
> governing limit state must be ductile because I am in Seismic Zone 4.
>
> I haven't seen a design procedure that address this situation.  I would
> appreciate any Ideas on procedures or approaches
>
> TIA
> Mark Johnson PE
>
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