Need a book? Engineering books recommendations...

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

Re: Simpson Titen Screws in Existing Concrete Stemwall

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Simpson would be the best place to ask, really. Trying to calculate the capacity of a hanger from standard engineering principles is about as easy as holding onto a greased watermelon. They almost never match what you would expect, and it isn't always in the same direction (above or below calc'd values seems to depend on the particular item).  Simpson may (I say may) have tested this particular hanger to get the values, so it would be entirely empirical.
Jordan


Bill Allen wrote:

I'm doing a residential addition and I 'm trying to connect a new girder to an existing stemwall footing.

 

Looking at the Simpson 2008 catalog, page 140, I see that there is a tabulated capacity of 3,950 lbs for a HU46 using (12)-1/4" diameter x 2-3/4" Titen Screws. This comes to a little over 300 lbs per screw. According to the tabulated values, the full capacity of the screw is 400 pounds each. However, in the literature on the website (http://www.simpsonanchors.com/catalog/mechanical/titen/loads_sheartension.html), there is a reduction in shear capacity if the anchors are spaced closer than 3" down to half the capacity at 1-1/2". I downloaded the HU46 hanger from the Simpson website and the spacing of the holes is 1", which is less than the minimum spacing for the screw.

 

Am I missing something?

 

Alternatively, I have considered using a LGUM46 with (4)-3/8" diameter x 4" long Titen HD screws. Using Simpson's ASD tables, I get a full capacity of 1,585 lbs per anchor. The reduction factor for spacing is 0.804. I looked at the reduction factor for edge distance using the minimum value of 1-3/4" and that factor is 0.24. The load is due to gravity, therefore the shear load is not towards the edge. I'm not sure if I should consider this reduction factor or not. I know that ACI 318 Appendix D would use 2x the capacity if the load is not towards the edge, but I don't know the basis of the ASD tables. I guess I should/could use the Simpson calculator, but I haven't yet.

 

Should I consider the 0.24 factor for edge distance? If so, this reduces the capacity to below my design load in a few cases.

 

Regards,

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
 
V (949) 248-8588 F(949) 209-2509

 

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