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Re: Definition of a Collector

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I consider collectors as David said, being elements spanning openings or other discontinuous (in your case) shear walls areas where your angle or other member would be free spanning between shearwalls. If the angle is continuously connected and transferring lateral directly to the adjacent shearwall, I would not say this is a collector. 
 
 Normally I see collectors at the roof level. Also when your building is not square in plan, and has a projecting rectangular area that requires the roof diaphragm to be dragged back into the main building through a deck angle or beam. As long as the shearwall is capable of taking the lateral directly off the the angle along its length, I don't see it as a collector. Is that what you are asking?
 
 
Will Haynes

 
On 2/9/07, David Topete <dtopete(--nospam--at)gfdseng.com > wrote:

I'll take a shot…  You definitely have a collector if the opening between wall elements is relatively large.  Say you have 8- 20ft panels = 160ft at the rear, but only 2 panels on either side of an 80ft opening at the front, then you'll need to collect/drag the accumulated diaphragm force into the shearwalls.  And, those forces are amplified.  If you have a series of smaller openings, than the required force transfer is nominal, amplified or not.

See 9.5.2.7.1 for the design of the collector element.  Do a shear diagram along the line of resistance, multiply that force by Omega, and design that connection to pilaster/panel accordingly.  Hope this helps.

 

David A. Topete, SE


From: Chuck Hanson [mailto: Chuckh(--nospam--at)dpsdesign.org]
Sent: Friday, February 09, 2007 7:30 AM
To: seaint(--nospam--at)seaint.org
Subject: Definition of a Collector

 

I'm trying to resolve a disagreement in my office. The background is that we are designing a three story tilt-up building in Seismic Design Category C. It is regular and rectangular in plan and the perimeter concrete walls are acting as shearwalls. The floors are metal deck slabs. Our floor slabs have an edge angle, tied to the slab with closely spaced headed anchor studs, which is welded to embedded plates on the wall panels at approximately 4 feet on center. Each embedded plate will have multiple headed anchor studs.

 

The definition of collector elements in 9.5.2.6.3.1 of ASCE 7-02 describes them as elements capable of transferring forces originating in other portions of the structure to the element providing resistance to those forces. One side says these edge angles are doing exactly that while the other side says they are simply diaphragm to wall connections.

 

The million dollar question is: Should the slab diaphragm to wall connections described above be designed to resist amplified collector forces? If so, does anyone have a code reference that tells me to do this?

 

Thank you.

Chuck Hanson, PE