2 Story Steel Frame Reno
2 Story Steel Frame Reno
(OP)
I have a 2 story steel frame building that we are renovating. No existing building drawings are available. The floors and roof are designed for relatively heavy gravity loads, but like a lot of steel buildings of its era there does not appear to be any defined lateral system. There are some solid exterior walls of 4" brick + 4" CMU, unreinforced, with no attachment to the steel frame, they are being removed. While they may add stiffness to the building they were not intended to be a lateral system and there is not true load path.
We are removing some structural bays and all of the perimeter masonry so we are reducing the seismic load on the building. We are not in a high seismic zone and wind would govern the design.
There is a small addition to the wind load with some short parapets at the entry.
My problem is with the intent of either IEBC or IBC chapter 34. While I am not increasing the load by their threshold limits ie 10%. The language is "lateral loading to existing structural elements is not increased beyond its capacity or more than 10%" If there are not "existing structural elements" receiving load in the first place is there anything to compare?
We are removing some structural bays and all of the perimeter masonry so we are reducing the seismic load on the building. We are not in a high seismic zone and wind would govern the design.
There is a small addition to the wind load with some short parapets at the entry.
My problem is with the intent of either IEBC or IBC chapter 34. While I am not increasing the load by their threshold limits ie 10%. The language is "lateral loading to existing structural elements is not increased beyond its capacity or more than 10%" If there are not "existing structural elements" receiving load in the first place is there anything to compare?






RE: 2 Story Steel Frame Reno
2. If it isn't, have you ruled out moment frames
3. Most people would consider Reno, NV to be high seismic
4. Just because the building code doesn't prohibit something doesn't mean it is safe
RE: 2 Story Steel Frame Reno
Removing masonry infill for conditions like that, and then assuming that the original frame didn't take any load to begin with, and then assuming that the code language doesn't get technically violated, would not be a good engineering practice. I would look for new means of introducing a lateral load path into the system.
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RE: 2 Story Steel Frame Reno
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: 2 Story Steel Frame Reno
The 4" masonry is built tight to the columns and beams but no positive connection, no dowels at the bottom, no brace at the top. The exterior brick is connected to the 4" cmu backup with ladder ties, there is a gap between wythes.
Steel connections are standard gravity connections, no attempt to create a moment connection of any type. The floor girders are connected to the columns with double angles, the roof is predominantly a cantilever beam system, so beams run over the columns.
This is an early 70's suburban office building. Not uncommon in this area to not address wind and ignore earthquake at that time.
RE: 2 Story Steel Frame Reno
How are you going to justify the foundations if there are no as-builts available?