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RE: Canvas patio covers and the code????[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Canvas patio covers and the code????
- From: "Dennis S. Wish PE" <wish(--nospam--at)cwia.com>
- Date: Fri, 28 Aug 1998 10:40:11 -0700
Ed, thanks for your comments - I concure about the live load, but since I did not have to prove the structure and was only hired to deal with the uplift it became a moot point. In our area it is much harder to get the depth of the foundation due to the extremly rocky conditions. Most of our soils is decomposed granite culminating in bedrock condition farther down. This results in a sandy soil with a lot of larger than stone size fragments. In addition, if I exceed 5' of depth, the contractor must conform to OSHA regulations for shoring. It's much easier to create a shallow pad than a deep pier. Expansive soil is not an issue in "most" of our valley although liquification area's do exist which might do better with a deeper foundation if this were other than a secondary structure. BTW, I did go to the site yesterday to see the non-conforming structure that was to be replaced. After seeing it, I would not recommend that the system be used. It is surely not conforming and is simply a welded 1" sq x 1/16" thk tube steel parallel chord "ladder-truss" sturcture that is constructed in two sections 10' x 20'. The two sections joined by tack weldw at the 20' side and the column at the junction of the two panels was omitted at the front side to allow easier acess to the car. Although there was no noticible deflection parallel to the front, there was a deflection at the sides that was compensated by adding two temporary columns. I should add that the canvas had not been installed as yet since the structure will be modified to accomodate the pads, a connection to the house and the setback required by the city. I stood on one end and literally shook the structure to see how flimsy it was. I would question how it will behaves laterally with as much flexibility as I was able to create. Considering the potential cyclic motion, I wonder (without having to run the numbers) if it will hold up in an earthquake. I suspect it will since it is extremely lightweight. After reviewing the system, I would recommend that it not be connected to the residence but remain free-standing to allow it to fail rather than tear away from the residence. The columns are TS2x2x1/8" from what I can see. This is a real looser as far as I'm concerned and wonder how this company survived for so long. I can only guess that they never pulled permits and never got caught - imagine their luck! Dennis -----Original Message----- From: Ed.Haninger(--nospam--at)fluordaniel.com [mailto:Ed.Haninger(--nospam--at)fluordaniel.com] Sent: Thursday, August 27, 1998 10:14 AM To: seaint(--nospam--at)seaint.org; Dennis S. Wish PE Subject: Re: Canvas patio covers and the code???? Dennis, Just as a point of reference, I designed a canvas covered wood frame structure for a school in central Orange County. I remember using ASCE 7 with a design speed of 85 mph (3 second gust) which resulted in about 15 psf uplift. I used a 1.5 uplift factor to provide the proper stability ratio. (BTW - some don't feel the 1.5 factor applies - I do) I remember getting foundation loads and sizes about what you have. We used 1 ft dia by 6 ft deep drilled piers. The worst column had about a 225 SF tributary area. The building department had a consultant check it over. The consultant thought that the roof live load should be 20 psf (like a solid roof), but I talked him into accepting the 5 psf load I used. Other, than that the building dept was happy. This was a one-of-a-kind design so the owner did not have any "under-designed" structures to compare to. They were happy. Ed Haninger Fluor Daniel ______________________________ Reply Separator _________________________________ Subject: Canvas patio covers and the code???? Author: "Dennis S. Wish PE" <wish(--nospam--at)cwia.com> at fdinet Date: 8/26/98 6:08 PM (snip)....Am I missing something or is there a specific code requirement (UBC) that makes structures like this exempt from code requirements? If the numbers are typical of other canvas installations, how do the local engineers address the political side of the issue so that we are not accused of trying to create a market or putting some merchant out of business? Dennis Wish PE
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