Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: seaint Digest for 6 Jun 2010

[Subject Prev][Subject Next][Thread Prev][Thread Next]
It would be pretty easy to rig a test fixture and do a tension test on the roof panels.  Put down blocking over the purlins in four places,  run a couple of 4x's between each pair of blocks, parallel to the roofing ribs.  Set a heavy step ladder resting on the 4x's.  Hang a small block and tackle from the top of the ladder.  Hang a spring scale from the block and tackle.  Put a cee clamp on the high of the roof rib halfway between the purlins (midspan, worst case) and fasten it to the spring balance.  pull on the rope through the block and tackle and run it up to whatever value you calculate will be the uplift load on the connection.

Then you'd know. / eric

admin wrote:
******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 
                       seaint Digest for 6 Jun 2010

Topics covered in this issue include:

   1: Part II Re: Wind Loads on Roof Mounted Solar Panels
             by Paul Ransom <ad026(--nospam--at)hwcn.org>
   2: Part II Re: Wind Loads on Roof Mounted Solar Panels
             by Paul Ransom <ad026(--nospam--at)hwcn.org>
   3: RE: Wind Loads on Roof Mounted Solar Panels
             by "Conrad Harrison" <sch.tectonic(--nospam--at)bigpond.com>
   4: RE: Wind Loads on Roof Mounted Solar Panels
             by "Conrad Harrison" <sch.tectonic(--nospam--at)bigpond.com>
   5: RE: Wind Loads on Roof Mounted Solar Panels
             by sch.tectonic(--nospam--at)bigpond.com<BR>To: seaint(--nospam--at)seaint.org<BR>Subject: RE: Win=



--------------------------------------------------------------------------
1                                Message:0001                            1
--------------------------------------------------------------------------
Subject: Part II Re: Wind Loads on Roof Mounted Solar Panels
From: Paul Ransom <ad026(--nospam--at)hwcn.org>
To: <seaint(--nospam--at)seaint.org>

  
From: "Thor Matteson" <thorm(--nospam--at)sti.net>
    
  
plus uplift due to the Bernoulli effect of moving air above the panels.  But
the uplift from the "scoop" pressure on the panels is counteracted by the
wind stagnation pressure against the existing roof that is created by the
panels' acting as scoops--potentially the rafters are not going to have any
increase in uplift.
    
  
This may have nothing to do with the code or what you need, but I've had to
point this sort of thing out in the past.
    
  
Thor Matteson, SE
www.shearwalls.com
    
Thanks, Thor.

The counteracting forces are valid, from the perspective of the truss &
down. However, there may be much higher forces than anticipated passing
through the point of concern ... the fastener into the truss/panel holding
the solar panel onto the roof. Also, as you point out, this may be extremely
location sensitive (windward/leeward/side edges).

Screw the code, this is REAL engineering.

Regards
Paul