I'm hoping to get some mod guidance on this. I'm working on a project where significant rooftop equipment is right above this header. See below:
As you can see in the photos, the joists have already been tripled up (notice the difference in joist width between original and modified) but I...
Yes. DCR is the Demand Capacity Ratio...and it seems original EOR economized the design (in at least the localized location of where I am checking). My structure is from 1983 where I don't have those bent bars. It's actually probably the newest pan and joist structure I've ever worked on...
Thanks for the information all. I've never heard of FRP strips before. Since my client is not the structure owner, it makes performing some of these modifications very difficult. Where can I get more information on these FRP strips?
It turns out that these joists are at a lot higher of DCR...
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Expanding this referenced thread, how have people been handling this for existing structures that weren't designed with this provision in mind? To me it seems really odd to have to say a structure that was completely fine before now is screwed over when the gravity loads (5%)...
True true. I was thinking of just saying the CMU wall didn't need to carry any of the flexure if the WT or channel (which is probably the shape I would lean towards) could carry the flexure alone. I do have a concrete pan and joist penthouse and main roof, so I feel as long as I can get the...
Thanks for the suggestions. The screen tubes don't really provide the capacity that is really needed. Even if it did, I'm struggling to get the global wall to check out (especially since it probably never checked out to current code in the first place). My issue is the penthouse has virtually...
I'm in the process of designing a wall mount to an old unreinforced hollow masonry wall. It was built in the early 60's, so I'm not surprised about the wall construction.
Anyways, my calculations are showing it needs to be grouted solid to support the needed loads. We also don't have have...
I typically analyze existing concrete/steel structures. However, on occasion, I'm tasked with analyzing an existing brick/masonry structure. I'm hoping someone can provide some feedback on this particular table.
More often than not, I am using the first section, normal to bed joints...
Thanks for the replies all. I was getting something similar with 1.2D + 1.7L but it still seemed off and thought I was missing something (which is why I posted). I was expecting to get something closer like when I use the steel bar joist tables. So for my particular project, shear is likely a...
I've got sort of an easy question (I'm hoping anyway). I'm working on an existing hollow core structure designed in 1969. I've been able to track down the load tables from the era (a 6412 that spans 22' - see attachment). This shows an allowable load of 62psf. The plans call out a 30psf live...
Thanks for everyone's help on this. I feel much more confident with the subject matter and I am now danerous. Precast/prestressed concrete just seems so different from conventional CIP concrete (even though it is more like a cousin). I just haven't touched it since school and have tried to avoid...
Thanks again for the replies. It's just not my area of expertise, but I am comfortable enough to work on it with some research. I usually work with telecommunication structures, but we do get the occasional building where our clients want to install on top of buildings. If I go the grouting...
Thanks for the replies. It's weird to me too think they can grout it solid without filling the whole span or worse yet, not completely filling the void. I assume there must be construction methods to retroactively grout a segment or a cell?
I will have double check the plans to see if they at...
I am am designing a rooftop equipment platform which is supposed to connect to the rooftop structural system. This rooftop is constructed with a system of precast planks, steel beams, and steel columns. I plan on putting the platform directly on building columns, so globally I don't see it...
Sorry I didn't make it clear enough what I had. Here is a screenshot from the slab notes. On the roof level, I have 20 gage composite deck. The general notes also say that it is a composite deck for everything above ground level. I don't have any specs on the building. I am going to reach...
I have W18x77 (which isn't even a current size W shape in today's AISC manual) partially composite beams with 58 total studs (29 on each half). I verified that the composite beam with steel and concrete is sufficient to carry the additional loads associated with my project. Now I just wanted...
Thanks for the replies. Yes, I am talking about a composite beam and I am checking the decking for a fairly large point load. I already determined that the beams are strong enough but wanted to verify the capacity of the roof decking. It is a very odd design where the CMU block penthouse wall...
I am in the process of analyzing an existing composite deck building from 1973. In the plans, it is called out to have a design roof live load of 30psf and doesn't say anything about snow load. This site is in the UP right on Lake Superior, so the ground snow load is 70psf and the balance snow...
It makes sense what hokie and Koot are saying. However, I have no idea how far the anchor rods extend down. The plans do not call it out. The one thing that is called out is a hooked anchor rod of an unknown hook length. Given my experience with appendix D, these don't usually perform that...
I did the calculations and it appears I am under the 5*sqrt(f'c). I'm not sure I want to rely on that capacity but it could explain why the foundation has lasted as long as it has. Most of the time this foundation is in compression because the tank is not empty and therefore in compression...
