Less than 10% reduction in capacity of lateral resisting elements is the code allowed rule of thumb. However, you have to check overturning forces as well and the hold down implications according to location of openings.
Example: If you have a 30' continuous wall, you can likely add a 3'...
This needs to be a cantilevered diaphragm with wood shear walls, no steel required. R=6.5 no question. Recalculating for R=6.5 you get V(low roof)=2720*(2.5/6.5)= 1046#. Chord Forces T=C=2720*9'/25'= 376#. With omega(2.5), T=C=941#. From the elevation shown, the low roof diaphragm only appears...
What is critical when designing these feature stair elements is communicating clearly with the architect and owner on what their desires and expectations are. If this is an artistic feature, and vibrations/stiffness are not of concern, then you can push code limits and help provide the desired...
Where I have seen this specifically referenced is in the Seismic Design Manual Section D.2(a) requiring bolted connections in the SFRS to be designed with deformation as a design consideration.
Sorry, AISC 341-16.
"unless you consider this to be the maximum moment that can be transferred to the connection)."
That is exactly the case. In Part 4 (Moment Frame Section) it gives a similar list of limiting aspects of the system, including overstrength seismic load (AISC 341-16) or R=1...
While it appears they are trying to discourage this type of design, AISC 341-18 Section 4.2(b) allows for the "overstrength seismic load" to be the limiting design moment for OMF connections. This is similar and replacing the R=1 option from AISC 341-10.
I don't think it is a take it or leave it situation. It is a get an engineer to assess it and provide their recommendation as to how to proceed. If they come back with recommendations for 15k of repairs, get another engineer to assess it. Don't just ignore it, but also don't feel backed into...
Yes, sistering on additional framing in a reasonable way would help eliminate any cause for concern, and that would be my recommendation if this were a concern. That should be possible to do without any demo or excavation. They got somebody down there to take the photo, and the work required is...
I quit stressing over issues like this long ago. There are other potential structural deficiencies that I have seen over the years that keep me up at night, and I will not let a not let a single-story, lightly loaded floor beam be a concern. What does a real failure look like in this case...
I have considered that option before, but never put it into practice. This might be the best solution though. I don't do as much residential work anymore so I don't battle this everyday like I used to.
sandman21, I thought this was the answer I have been searching for for all these years, but unfortunately for typical residential stem walls (8" width), this method is not effective.
A couple things that I have been able to get to work is reducing my overturning forces using FTAO or resolving...
One important clarification: the structures I am referring are industrial facilities which rely heavily on the ability to modify and upgrade equipment as quickly as possible to avoid shutdown time (this was understood by all parties prior to design). This also comes with working on existing...
Pham,
Thanks for the reply and the article. I like the idea of a mechanical zone, and I will be using that in the future. As a follow-up, I agree that loading the chords away from panel points is not the most economical, but what would you do when the unit location is modified and is to be...
Regarding mechanical equipment loading on prefabricated steel roof joists, I am wondering what your experience is with mechanical units being located in their proper locations in the field. Typically, I see units shown on roof plans with dimensions and total load. I ask this because I know the...
