Need a book? Engineering books recommendations...

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

Re: Shear in NDS

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Which version of RISA are you using?  And how do you model the members
(i.e. material and section sets)?  

I ask because newer versions of RISA have glulam materials that allow you
to actually do glulam members rather than having to do a "custom wood
species".  The "custom wood species" in older versions could be used to
"jury rig" a glulam, but you have to be careful as I believe RISA treated
those as regular lumber NOT glulams.

And current versions CAN handle fractions...older versions could only do
nominal dimensions...and if I remember could do integer dimensions.  More
current versions can do full sawn (i.e. actual dimensions, including
fractions...use them all the time when doing timber framing) dimensions.

If you want, feel free "offline" to send me your model and I will take a
look at it.  You can also have RISA support take a look at the model.  RISA
has _VERY_ good support.  When I have gotten strange results, they have
always been more than helpful in figuring the problem with the model.  You
might need to be current on your support agreement, however.

Regards,

Scott
Adrian, MI

On Thu, 26 Feb 2009 15:42:55 -0500, "Timothy Hilton"
<thilton(--nospam--at)lhcengineers.com> wrote:
> Hello All,
> 
>  
> 
> I'm new on the list and I've been enjoying reading it.  Here is my
> question.
> 
> 
>  
> 
> I'm working on an outdoor pavilion/shelter that covers three basketball
> courts.  We are framing the whole thing with Glulams.  We have a few
places
> with long cantilevers and I'm getting shear to control my designs.
> 
>  
> 
> The question is this: I've analyzed the structure in RISA software and it
> has a feature where you input design values and it will perform design
> calcs.  As my members were failing in shear so much I started poking
> around.
> 
> 
>  
> 
> My controlling V is 19.256k for one beam.  My shape is 7"x27" (the
program
> can't handle fractional dimensions).  RISA's reports seem to be pretty
> lame,
> so I can't get to all the numbers, but it gives me a shear check of
1.906.
> This is interesting because by hand I get a fv of 19,256/(7*27)*(3/2) =
> 152.83 psi.  I gave the program Fv of 200 and I've neglected the load
> duration factor for the time being, so I thought the check should be
> 152.83/200 = .764.  This caught my attention because it's off by a factor
> of
> exactly 2.5.  
> 
>  
> 
> So all this to say, is there some 2.5 safety factor somewhere in the NDS
> that I've never heard of?  It seems extremely conservative to me.  Or
have
> I
> done something stupid?
> 
>  
> 
> Thanks a ton,
> 
>  
> 
>  
> 
> Timothy K. Hilton, E.I.
> 
> Engineering Intern
> 
>  
> 
> LHC STRUCTURAL ENGINEERS
> 
> P.O. Box 10567
> 
> 1015 Wade Avenue
> 
> Raleigh, NC 27605-0567
> 
>  
> 
> 919.832.5587 x 20
> 
> thilton(--nospam--at)lhcengineers.com
> 

******* ****** ******* ******** ******* ******* ******* ***
*   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 
******* ****** ****** ****** ******* ****** ****** ********