See attached for snow drift calc.
https://res.cloudinary.com/engineering-com/image/upload/v1575309505/tips/M4325_-_STAMPED_FF_CALCS_-_02-19-19-_SEC_2071-18_ijk617.pdf
I am reviewing calculations for the design of a 5 ft cantilevered canopy on the side of a building (see attached for a wall section). The building is a large warehouse, so there is potential for significant snow drift based on the length of roof. The engineer who designed the canopy is...
Unfortunately this specific connection was omitted from the precast submittals we received.
At this point I am convinced that thermal contraction has caused the cracking. I admit this was not considered in the design, in most cases where the tube is attached to structural steel it would not be...
New piece of information. On our drawings we indicated the reaction of the tube steel beam at the precast, including vertical load, lateral load and torsion. Apparently the precast engineer made the assumption that we gave a total load and divided by 2 to get the reaction at each end of the...
The steel tube is welded directly to an embed provided in the precast. As I said, I understand that temperature change is probably a factor, although I've never had an issue before on this type of condition. Any thoughts regarding the interior space being conditioned vs. not? Are you...
I have a project currently under construction that includes a segment of storefront approximately 30 feet in length with a 5 foot cantilevered canopy attached. A steel tube was designed to span through the storefront for support and attachment of the canopy. This tube is rigidly attached to a...
Thanks dauwerda. I agree that it is odd for a supplier to object to this standard. I have a message out to the Omaha Building and Planning Department to see if they frequently approve aggregate that does not meet ASTM C33 requirements. We'll see what they have to say...
A building I designed is currently in the bid phase and is located in Omaha, NE, right on the border of Iowa and Nebraska. Our specification on this project (as well as every other project I have done in the area) requires ASTM C33 aggregate for the concrete mix. I was told by a concrete...
Thanks KootK. I was not familiar with that kind of diaphragm analysis. I have purchased a copy of the SDI Diaphragm Design Manual to assist, and plan on tackling the problem as you suggest.
KootK - Thanks for the figures, that certainly aids in the discussion. The second figure would be my assumption for how the lateral load is distributed to the shear towers. I understand that flexible diaphragms do have some amount of torsional capacity and that in reality diaphragms are...
KootK - I agree that the diaphragm cantilevers in one direction, where it spans between the two shear towers and cantilevers past to pick up the rest of the roof. However, in the other direction there is really only one support location as the two shear towers are aligned. In this case, I...
I have been tasked with site adapting a 5 story office building (originally built in Iowa) to be constructed at a new site in Nebraska. The original design (done by another engineer) utilizes two concrete shear towers for lateral, located near the center of the building at approximately third...
I don't believe the 1989 spec stated that you could assume an inflection point was a brace point, but I know that assumption wasn't prohibited by the code until AISC 360.
In my analysis I did calculate Cb based on moment variation, and I am using 50 ksi yield strength. At this point I believe...
Absolutely agree that using the inflection point as a brace point is bad engineering nowadays. The fact that it was added to the AISC 360 spec makes that clear.
Maybe this is the more interesting question. If braces are not added and there were to be an issue with the frame in the future, who...
jayrod - One of the beams is entirely above the current tenant's space. Any repair would require disturbing their space. A single brace point at the midspan is enough to get the beam to work.
WARose - I don't necessarily disagree with your comments, but to play devil's advocate, I think there...
I am above the 10% increase allowed for lateral load, so a detailed analysis is required. The analysis showed that the increase in lateral load is not a problem, but the unbraced length at the bottom flange is a potential problem based on the current codes.
I am working on a project that includes structural modifications and a small addition to an existing retail building. Part of the structural modification includes moving a braced frame approximately 10 feet, and therefore increasing the lateral load on an existing interior moment frame. In my...
JAE - I agree that a pure wedge shape (i.e. no flat area for bearing on top of the pile) would be a concern. In that case I think a repair would be required.
I calculated an approximate required bearing area of 27 square inches for the 45 kip load. In this case, there is clearly more than 27...
