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Re: Joists & Adding Roof Mechanical Unit

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Richard,

The whole idea of clamping came about as a result of trying to avoid 
welding or drilling.  There are specialty clamps and other items not 
necessarily called clamps, e.g., Lindapters 
(http://www.lindapter.com/), which may work but I find, in most 
cases, you have to invent your own clamping system to fit the joist 
top chord or whatever else you may be dealing with.

Gary


On 1 Nov 2004 at 16:15, richard lewis wrote:

> Are there "C" clamp type bolts that would be reliable?  Drilling holes
> in the top chord of the truss would remove a lot of steel in the
> compression chord.
> 
> Rich
> 
> On Sat, 30 Oct 2004 09:32:40 -0400 "Gary Hodgson & Associates"
> <ghodgson(--nospam--at)vaxxine.com> writes:
> > Just bolt the new pipe stanchion in place with end plates already
> > welded to it.  Use 4 bolts so it is clamped in place-- no welding.
> > Gary
> > 
> > On 29 Oct 2004 at 12:39, richard lewis wrote:
> > 
> > > This sounds like it might be a feasible alternative.  So if I
> > > understand this, the roof would be opened at the locations of the 
> > pipe
> > > post.  The pipe post base would be welded to the joist from the 
> > top. 
> > > Then the roof is closed again.  I can then sit a "curb" on top of 
> > the
> > > posts.  This would minimize disruption of the office space below, 
> > but
> > > I'm sure there still would be some welding sparks dropping.  At 
> > least
> > > the equipment is on the roof.
> > > 
> > > Did I understand you correctly here?
> > > 
> > > Thanks.
> > > 
> > > Rich
> > > 
> > > On Fri, 29 Oct 2004 13:31:19 -0400 "Jordan Truesdell, PE"
> > > <seaint(--nospam--at)truesdellengineering.com> writes:
> > > > Disclaimer: I'm used to using pipe columns and pitch pockets 
> > for
> > > > rooftop curbs.  Can you afford a three-tier curb system - two 
> > rails
> > > > over the panel points, perpendicular rails on top of that to 
> > support
> > > > the curb rails at the proper spacing?  It's more steel tonnage, 
> > but
> > > > it will get you to the 
> > > > 
> > > > bearing points of the trusses without having mess around in the
> > > > ceiling.
> > > > 
> > > > At 10:49 AM 10/29/2004 -0500, you wrote:
> > > > >I have an existing roof structure where the owner wants to add 
> > a 
> > > > rooftop
> > > > >mechanical unit.  The unit weighs about 3,000 lbs.  The 
> > existing 
> > > > roof
> > > > >joists are 24H9.  I checked the roof joists and supporting 
> > girders 
> > > > and
> > > > >they are fine to support the additional load.
> > > > >
> > > > >I have a detailing question.  I know this has been done many 
> > times 
> > > > so I
> > > > >am hoping someone will share their experience with me.  I plan 
> > to 
> > > > ask
> > > > >that the unit be placed on a continuous curb that runs 
> > > > perpendicular to
> > > > >the roof joists.  My question has to do with the curb bearing 
> > on 
> > > > the roof
> > > > >joist.  First, I assume the curb will bear directly on the 
> > deck.  
> > > > No roof
> > > > >penetrations are required.  The roof deck is corrugated decking
> > > > >
> > as 
> > > > the
> > > > >joists are about 2 feet on center.  The curb will run parallel 
> > to 
> > > > the
> > > > >deck flutes.  It is typical to just run a wood plate on top of 
> > the 
> > > > deck
> > > > >to support the curb?  The curb will be a structural curb that 
> > > > spans
> > > > >between joists.  Next, in new construction when the 
> > concentrated 
> > > > load is
> > > > >put on a joist top chord at a place other than a panel point an
> > > > >
> > 
> > > > angle is
> > > > >welded from the top chord down to the bottom panel point.  The 
> > 
> > > > space
> > > > >below is occupied by office space and to weld a few angle 
> > struts 
> > > > would be
> > > > >very difficult on innocent tenants.  Is there another detail 
> > that 
> > > > might
> > > > >not involve filed welding?  Would I be able to skip the angle 
> > strut
> > > > >
> > > > if
> > > > e maximum possible point load from the curb were under 1,000 
> > lbs?
> > > > >
> > > > >
> > > > >Thanks for your help.
> > > > >
> > > > >Rich
> > > > >
> > > > 
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