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Structural Analysis of 100 Year Old Structure
10

Structural Analysis of 100 Year Old Structure

Structural Analysis of 100 Year Old Structure

(OP)
I'm running into an issue on an analysis that I am doing for a 100 year old 4 story building....and I'm wondering what I could be missing that's causing it to blow up on me.

General description of the building:
- 24' x 90' rough dimensions for first two levels. Then upper levels step in on one side and building is 20' x 90'
- Steel Lumber Floor system (basically cold-formed steel back to back channels) with 6" concrete slabs on each floor
- Upper floors span the narrow direction across the building and bear on exterior masonry walls
- Exterior walls are 12" - 16" brick
- Where the building steps in, the exterior wall (and thus half of the floor load from upper floors) is supported by a pair of steel I-Beams which, in turn, frame into 4 18" deep floor girders which also span across the narrow width of the building.
- No obvious signs of structural problems...bowed floors, cracked plaster, etc.

Issue:
I've taken into account the soft steel of the 1920's. I've found good design data on the steel lumber product and deduced it was designed for the typical residential 40 psf live loads plus the weight of the concrete floor. And I've done select demolition in different parts of the building enough that I have a pretty reasonable feel for how the building was framed and how it all works.

The problem is that when I run the analysis of the steel beams which are supporting the stepped in wall, it is blowing up on me. Stress ratios 2-3 times what the allowable was for 1920 steel (16,000 psi according to old literature). So much so, that even just running a dead load case it is still 1-2 times allowable.

I refuse to believe that the building has been standing 100 years and could be this far off. Even if you include the possibility that they ignored live load, it still seems unreasonable to assume they didn't account for the building materials they used! So I believe the issue is on my end.

I also am not eager to be the engineer who cries wolf that the building is unstable when it has stood for 100 years without any visible signs of structural distress.

Anyone with experience in similarly aged structures able to lend some expertise?

RE: Structural Analysis of 100 Year Old Structure

Have you checked the possibility of a higher grade steel?

RE: Structural Analysis of 100 Year Old Structure

(OP)
Good thought...I considered it. But were such grades available in 1920's? The Carnegie Steel Pocket Reference doesn't make any mention of them.

RE: Structural Analysis of 100 Year Old Structure

Quote (pittguy12)

But were such grades <structural steel> available in 1920's?

No.

The 16,000 psi is allowable bending stress, used with Allowable Stress Design (ASD).
Are you performing your checks, using 16,000 psi, per modern techniques such as Allowable Strength Design (ASD)?

www.SlideRuleEra.net idea

RE: Structural Analysis of 100 Year Old Structure

2
I found something from AISC Steelwise, it shows steel grade from 1901 to 1968, however, it wouldn't help you much since the discrepancy is huge. The paper includes a table that shows tensile stress/yield stress/working stress. it indicates from 1923 on, the working stress is 18 ksi, but the working stress is not listed for 1901 to 1922. The paper is linked for interested party use, in case dealing with old steel structures.

Link

RE: Structural Analysis of 100 Year Old Structure

I wouldn't say that old steel was soft. The Carnegie Pocket Companion uses 16 ksi as an allowable bending stress in its examples, but 18 ksi was also common at the time and is what is in the ASTM design specification.

I don't mind using modern design equations on old structures, using the rationalization that the subsequent increase in allowable bending, from 0.5 to 0.66, for example, is based on research and improved understanding rather than on improvement of the fundamental methods of rolled steel production. You could also run coupon tests, but, none of this gets you to showing that a 3x overstressed girder is okay. I don't think that magic steel is your answer.

I think there's more information that we need here. How do the deflections work out for the pieces you're concerned about? There are more 'asking the obvious' kinds of questions like 'are you sure you're using the right girder size' and 'did you subtract the area of the windows from your wall load?' 'did you get the spacing on the girders right?" I'm only throwing these out there because it seems like we're missing something.

RE: Structural Analysis of 100 Year Old Structure

Good article, retired13. The "AISC Iron & Steel Beams 1873 to 1952" is mentioned in it. The 1873-1952 book does not have the useful detail background info included in the article you posted.

I scanned that (public domain) 1873 - 1952 book in 2009 and posted it on my website. Later, AISC borrowed my scan and posted it themselves.
Here is a link to their posting, which downloads faster than the same scan from my site: Link

Interesting thing is that AISC claims "Design Guide 15 expands on this (1873-1952) publication and includes a summary of documents through 2000"... which is true. However, Design Guide 15 edits out much of the specific info such as which manufacturer produced a certain shape and the time period when that manufacturer had that shape in production. I prefer the older book for shapes thru 1952, Design Guide 15 for 1953 and later shapes.

www.SlideRuleEra.net idea

RE: Structural Analysis of 100 Year Old Structure

1920’s steel was mainly A7 with a yield stress of 33,000 psi and an ultimate tensile stress of 60,000 psi.

RE: Structural Analysis of 100 Year Old Structure

Another bold suggestion if every check/effort turns no result, try "composite beam". This is not a joke, the linked paper indicates successful cases since 1902. But by doing so, you need to use ASD method though.

Link

RE: Structural Analysis of 100 Year Old Structure

Quote:


I think there's more information that we need here. How do the deflections work out for the pieces you're concerned about? There are more 'asking the obvious' kinds of questions like 'are you sure you're using the right girder size' and 'did you subtract the area of the windows from your wall load?' 'did you get the spacing on the girders right?" I'm only throwing these out there because it seems like we're missing something.
.
I second this. Are you absolutely sure that all the inputs such as material properties, sections, loads, units, unbraced lengths etc are right?
Most of the time wrong input data is the reason for odd results.
I ususally check displacements if I'm not sure that the computer results are right.
Most of the time doing this points me to my error.
Also which software are you using? I've noticed this in sap2000, if the model is giving you very unlikely results, importing the .sdb file again in a fresh model usually correct those inaccuracies.

Euphoria is when you learn something new.

RE: Structural Analysis of 100 Year Old Structure

Here's a quick sanity check. look at The Carnegie Pocket Companion, what is the published safe load for the beams in question? The building is still standing, someone must have done something right. My other thought is the designer did a grillage analysis assuming some degree of continuity where the two beams frame into the four.

RE: Structural Analysis of 100 Year Old Structure

You can have a few pieces of the steel tested for relatively cheap. The contractor nips off a few pieces of flange at the beam ends and you mail them off.

RE: Structural Analysis of 100 Year Old Structure

I have always suspected that todays computer programs leave a lot to be desired. What factors of Safety are involved here??? The old timers knew a thing or two and today's computer jockeys have lost the ability to run calculations manually , while applying a critical eye on the assumptions.

On more than one occasion during my career, I have been told by consulting geotechnical engineers, " I hope you realise that this excavation , which is obviously stable , is theoretically impossible" Mind you, there were a few that were theoretically stable , which failed catastrophically.

RE: Structural Analysis of 100 Year Old Structure

"Cold-formed steel back to back channels"? 100 years ago?

RE: Structural Analysis of 100 Year Old Structure

I think that there is something basically wrong in your approach - the first thing being that instead of providing a sketch, or drawing, you are trying to describe the structural system - "Steel Lumber Floor system (basically cold-formed steel back to back channels) with 6" concrete slabs on each floor" which is confusing to start with - what is steel lumber??? Is it steel or timber? It reminds me of some of my clients, which are doing exactly the same - describing the system which they do not fully understand, or computer modelling dudes, which could not solve by hand a simple supported truss - recent Miami Bridge collapse is a classical example.
I'm almost sure that there is nothing wrong with the building structure for the vertical loads - seismic and wind could be an issue, but this will depend on which code you are using.

RE: Structural Analysis of 100 Year Old Structure

Is it the pair of I-beams or the four 18" girders that are failing? I don't think you said.

Did you remember to double the capacity of those I-beams since they're a pair?

The National Pressed Steel Company's 1921 handbook gives 2" as the standard slab thickness for steel lumber floors. Is yours really 6" throughout the building? That's triple the load if not actually the case which is the magnitude of your problem.

If indeed 6", is it doing something special? Maybe composite with steel beams as suggested earlier. Or carrying the upstairs wall to some degree.

RE: Structural Analysis of 100 Year Old Structure

What is the spacing between the 18" floor beams? The pair of I beams only carry the wall weigh and distributed to the floor beams at where they framed into. The I beam shares a little portion of the floor load, the floor beams carry the majority load and the wall weight. Are they failing?

RE: Structural Analysis of 100 Year Old Structure

(OP)
Lots of great responses....I'll try to address the most pertinent of them.

Am I sure of the sizes and measurements:
Beam sizes were all verified by digital calipers in multiple locations thus I'm confident I have the proper beam sizes. Overall building dimensions were also likewise checked multiple times using a laser distance finder. I'd comfortably say they are within +/- 1". The 18" beams are spaced at 16-6" OC. There are two 10" beams spaced at 6" OC which run directly under the stepped in wall and connect to the 18" girders...thus they span 16'-6".
* Also, floor thickness was confirmed in multiple test holes. Each floor is 6" concrete.

Am I applying modern ASD to working stress:
Yes...while taking into account a yield stress of 33 ksi. I also verified with the Carnegie pocket companion the safe allowable working loads and find a proportional discrepancy so I don't think the error is in my analysis technique. For instance, one of the beams in question is a B10X25.4 from Carnegie book (this is one of the two beams under the stepped in wall). This has an allowable lbs/ft load at 16 ft span of 1,024 lbs/ft...on these beams rests the 30' tall exterior 12" brick wall and 9' of trib floor for the 3rd, 4th, and roof levels. The 3rd and 4th floor each have a 6" concrete floor...so just taking a 40 psf apartment load (actually is correct for the period also) plus a 75 psf floor weight, each of these B10's would be seeing 1,035 lbs/ft. And then I still need to account for where the weight of the roof, snow, and wall load are going.

Magic steel:
I agree, this seems unreasonable. My research shows that some higher strength steel was available in 1920, but mostly used for ship building. Hardly seems reasonably for it to end up in a apartment building in West Virginia

Steel Lumber:
It is actually quite interesting. Steel lumber was developed in the late teens as a replacement for wood floor and wall framing in Massillon, OH. Some research indicates that it was to be the next big thing in construction. Less than a decade after its development though, open web trusses took hold and steel lumber was mostly forgotten. I did manage to find a design reference in the National Archives which is the only thing I could find proving its existence: https://archive.org/details/NationalPressedSteelCo.... It is essentially a cold formed steel system.

Is anything failing:
No. Nothing I can see or measure. The beams themselves look good. Plus the building is all plaster...any reasonable movement would show.

Composite beams:
I think this is interesting and I had not considered it. I do have a portion of the floor above the 18" girder open and I don't see studs or coils, but that doesn't mean they are there. Admittedly, I have do not know much about the development of composite beams and whether they were in use in the 1920's. What is interesting though, the 6" concrete floor does seem thick even when comparing some of the details in the steel lumber and Carnegie companion books. Does anyone know if composite beams were used? If so, did they utilize something other than studs or coils to transfer the load?

RE: Structural Analysis of 100 Year Old Structure

I wouldn't grasp onto the possibility of the steel being of higher strength. I'd be looking to my analysis for errors in load path or logic

For example, if you have a beam under a masonry wall, the wall is probably arching and the beam doesn't see but a fraction of the load. The wall might even be holding up the beam.

RE: Structural Analysis of 100 Year Old Structure

pittguy,

Please have a quick look on the 2nd link I provided. Interestingly, composite beam has been used in that time period successfully, and no stud, which came to the picture in a latter date.

Also, does the height of the brick wall above exceed one half of your beam span? If so, you may consider to take advantage of arch action - assume the wall has cracked diagonally, thus the load above is passed to the more rigid end supports (a heavy concentrate load on the 18" beam). I learnt this from an old colleague, not through practices. For your case, rather than call it magic beam right way, the use of some bold methods approaches should be acceptable/justified.

RE: Structural Analysis of 100 Year Old Structure

2

Quote (And then I still need to account for where the weight of the roof, snow, and wall load are going.)


Allow me to muddy the waters...

The attached is an excerpt from the first AISC Manual, published in 1923. On the second page under "5 ALLOWABLE STRESSES" it says maximum static stresses. In school I was taught static = dead. On the first page of the attachment "4 LOADING" contradicts Section 5. Perhaps I'm just having a bad day but this is puzzling. I've been going through the manual but I can't find anything.

Also, in the Manual, it does permit a 30% live load reduction for a 4 story building.

RE: Structural Analysis of 100 Year Old Structure



Quote (OP)

Where the building steps in, the exterior wall (and thus half of the floor load from upper floors) is supported by a pair of steel I-Beams

Where is the step-in occurred, and how that exterior wall is supported laterally - no intermediate supports along entire 90' length?

RE: Structural Analysis of 100 Year Old Structure

Are you sure there aren’t steel beams and columns framing up above your transfer floor and buried in the masonry out of site?

RE: Structural Analysis of 100 Year Old Structure

OP
I'm not clear if the failure is under a full design load or just the dead load and I wonder if the actual design load is something that is not ever realized. Not saying that should not be a concern, just trying to understand the load case.

I think I understand that the "failure" is in the double beam that is spanning 16'-6" located about 4 ft in from one of the side walls and that is supporting brick walls and floor (etc.) above.
The double beam is referred to as a Steel Timber" beam and is a cold formed steel product.

I would go along with the suggestion that some form of composite behavior and arching action is happening. Curious that they are 6" apart and I wonder if there is something located in there that is contributing to the needed shear transfer.

Very interesting condition. A couple of photos might be helpful.

RE: Structural Analysis of 100 Year Old Structure

Even if arching action was happening the end connections of the beams would still take the majority of the load. Arching tends to only help flexure, not shear if the end of the arch is also the end of the beam.

And arching wouldn’t matter a whit to the supporting perpendicular beams.

RE: Structural Analysis of 100 Year Old Structure

It is highly unlikely that a meaningful steel-concrete composite floor was intentionally used in a 1920's house in WV (I read the attached paper). However, I won't dispute that composite action could (unintentionally) be taking place. With that said, I would not rely on composite action several reasons, here is one:

It's the 1920's. Concrete is proportioned by volume, say 1:2:4 (cement:fine aggregate:course aggregate), and it mixed on the job site. Some of this concrete can be surprisingly good... say on bridge projects with skilled workers. For residential type work... I would not count on it. Has the OP tested the concrete? What were the result?

www.SlideRuleEra.net idea

RE: Structural Analysis of 100 Year Old Structure

JAE and SRE
I'm not disagreeing with you but I AM wondering how the structure is behaving "so well".
Not saying it is a reliable system either (although we all know how difficult it can be to defend unintentional structural systems that appear to work fine but that we don't want to rely on).

Sounds like the system is not very redundant so... I'm just wondering about it.

I have not considered what stresses ought to be but I assumed OP was referring to bending stress on the double 10" tall beams that ar 6" apart.

RE: Structural Analysis of 100 Year Old Structure

If I remember correctly, 1:2:4 mix can produces a concrete strength of approximately 2500 psi. 1:3:6 mix can produces 2000 psi concrete. The actual strength depends largely on quality control then.

RE: Structural Analysis of 100 Year Old Structure

2
HouseBoy - Sorry for any confusion I caused. I was addressing the OP's question, but failed to say so:

Quote (pittguy12)

Does anyone know if composite beams were used? If so, did they utilize something other than studs or coils to transfer the load?

From the attached paper, in the USA, here is the one and only worthwhile step towards development of satisfactory composite construction during the 1920s:



Well, here is Mr. Kahn's patent.

If the OP wants to go on a wild goose chase... do some exploration in the slab looking for the "bent-up flange cut-outs" shown in the patent.
If the detail does exist in this house... be sure to submit this house for inclusion as an ASCE Historic Landmark.

www.SlideRuleEra.net idea

RE: Structural Analysis of 100 Year Old Structure

I would look more into the arching action JAE is suggesting.

http://www.nceng.com.au/
"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

RE: Structural Analysis of 100 Year Old Structure

Quote (pittguy12)

I would look more into the arching action JAE is suggesting.
Absolutely. How could it not be behaving like this?

If I understand it correctly, you have an extremely stiff wall sitting on some very flexible beams across their full length. The assumption of uniformly distributed load goes out the window the second the beam starts to deflects slightly and the stiff wall doesn't.

RE: Structural Analysis of 100 Year Old Structure

2
One other aspect of this to consider, when talking about a supposed arching action - is that with 100 year old brick, you've got masonry with much softer units that what is used today along with a very much softer mortar.

So instead of a highly rigid wall you actually have masonry that tends to slowly deform when its support moves, rather than crack.
Look at old masonry and sight down the mortar joint lines and you'll see this kind of effect. No control joints needed in these old masonry walls because they aren't rigid/brittle like today's hard units with high strength mortars.

This would slowly negate some of the arching action as the wall deformed downward onto the supporting beams.

Also - just to clarify - I wasn't suggesting that arching action was occurring but I was saying that if it does arch, then the full loading (dead and live loads from the walls and floors/roof above) will still come down on the ends of the steel support beams and are probably then taken by the beam end connections to the columns.

I still wonder if there isn't hidden steel columns and beams in the stories above and the beams that are reportedly failing here on the "transfer" level are only taking the weight of the single story wall directly above it.

RE: Structural Analysis of 100 Year Old Structure

In the early development days of composite beam (a clip from paper linked above). Shear connector was invented/used in the later date as pointed out by SRE.

Another example is Mathias Koenen’s (1849–1924) flat-soffit, later (from about 1892) ribbed, floor in which the underlying steel sections carry the tension and the arching concrete infill sections are solely responsible for carrying the compression. Despite the lack of shear connectors, tests confirmed Koenen’s assumptions regarding the structural behaviour (Christophe 1902).

RE: Structural Analysis of 100 Year Old Structure

(OP)
I'm following the arching action concept and believe it is probably happening...though I don't think that could be something intentionally built into the design of the building. What makes it even more difficult to assess...I do know that there is at least a course of terra cotta clay block used in that wall that I've observed from some of my test holes. But to what extent that is used is hidden behind plaster walls. Unfortunately, one major limitation of this whole effort is that I cannot rip down all the plaster to expose everything. The labor cost involved in removing plaster, which is all tied to metal lathe interestingly enough, would quickly exceed the total value of the building.

Similarly with the composite beam idea. I think there is probably some composite action happening...but do I make the leap to assume that is how it was designed?

Based on the exploration I have done, I'm reluctant to assume there are hidden beams and columns at work that I can't see. I've exposed enough of the wall and the beam pockets where the steel bears on the wall to know that they aren't there...or, if they are, are not located in the areas that would make the most sense for them to be!

Some progress sketches attached.

RE: Structural Analysis of 100 Year Old Structure

During your field investigations, did you measure the deflected shape of the framing? If the building is currently empty and is essentially nothing but dead load right now, you can fine tune your analysis until the calculated deflected shape closely approximates the measured deflected shape. That will tell you that your current loading assumptions are at least tolerably accurate.

From there, you can apply your new loading and see what the building will do. If you can still get it to pass serviceability requirements but stresses are too high, then try some material sampling and testing.

RE: Structural Analysis of 100 Year Old Structure

I think it's time to tell the owner about the columns they need to add. It's as if they built to the second floor and said, "you know what?, let's add a light well and some windows on this side" and added the 10" beams to support the upper floors and wall.

The 18" beam looks about right at the ground floor, right? Then the same shape was used at the second floor with a significant additional point load! You don't know the original camber of the beam, but if those second floor 18" beams are at what you think they should be for dead load, then I think that confirms your assessment.

I'll add that I don't usually buy the argument that "it's been fine for 100 years" because you don't know the load it's seen. In this case, live load just pushes the stresses closer to yield. If you're thinking about testing the steel, take your coupons from the ground floor level.

RE: Structural Analysis of 100 Year Old Structure

phamENG - good point but you should keep in mind there could have been specified initial camber in the beams, and or natural camber, so your fine tuning calcs will have to be in a rough range anyway to acknowledge that the initial beam, before any loading, might not have been perfectly straight.

RE: Structural Analysis of 100 Year Old Structure

(OP)
Thank you everyone. I actually sent a summary to the owner this morning explaining where I was with everything and what would be needed to take this further.

I've done a lot of history renovations and assessments in my career...this was the most interesting.

RE: Structural Analysis of 100 Year Old Structure

pittguy12,

Definite can be one of the hall of fame for structural engineering and building construction. You might want to get some knowledgeable tech persons involved to get their opinions too. Keep us posted, if new clue emerges. Thanks for sharing :)

RE: Structural Analysis of 100 Year Old Structure

JAE - very true. Do you (or anyone) have any good information on the history of beam cambering? I was under the impression that intentional camber in buildings wasn't really a "thing" until about 50 years ago. But as this impression is based more on ignorance of information to the contrary, I will be happy to be proven wrong. As for natural camber and other mill tolerances, are there good resources for that going back to at least the early 20th century? A6 only seems to go back about 20 years.

RE: Structural Analysis of 100 Year Old Structure

I looked at the AISC fifth edition (1951) that I have (I'm not THAT old, though) and it talks about intentional cambering there - but not sure about the 1920's.

Even without intentional cambering there might be natural mill roll camber (either up or down) that could alter a calibration calculation attempt to some extent.

RE: Structural Analysis of 100 Year Old Structure

Thanks to AISC's Historic Steel Manual page, the first mention of intentional cambering was in the first printing of the 2nd edition (ca. 1934). Not that it wasn't possible before then, of course. But it is probably worth mentioning that in that manual, the minimum beam size they show is a 24" deep wide flange, and the minimum length to camber it was 34 feet. Even the 1951 manual only gives you W21 at 25 feet. So I think it's safe to say it was unlikely that these beams would have received intentional camber.

Natural mill camber was limited to 1:1000, so for a 24' beam you're looking at 0.29 inches.

RE: Structural Analysis of 100 Year Old Structure

Quote:

The 3rd and 4th floor each have a 6" concrete floor...so just taking a 40 psf apartment load (actually is correct for the period also) plus a 75 psf floor weight, each of these B10's would be seeing 1,035 lbs/ft.

pittguy12,

Let's have a sanity check on the 10" beam load, using the weigh you provided earlier w = 40+75 = 115 psf.



Calculate areas tributary to the beams:

Aleft = 0.5*16.5*(16.5/2) = 68 sf
Aright = 0.5*4*16.5 = 33 sf
Atrib = 68+33 = 101 sf
Beam load = 115*101 = 11615 lbs/2 beams = 5807.5 lbs/beam
Convert to uniform linear load w = beam load/beam length = 5807.5/16.5 = 352 plf/beam

Is this what you got? Or there is mistake in my calculation?

RE: Structural Analysis of 100 Year Old Structure

Slightly. And probably a bit more useful for the pre-calculator days. That comes out to 0.3" for a 24' beam rather than the 0.288" you get from a 1/1000. You'd have to hold you laser really straight to notice the difference.

RE: Structural Analysis of 100 Year Old Structure

(OP)
Retired13 ... I, admittedly, and not good at following along with someone's calculations. But let me do your sanity check a different way...

3rd floor load 115 psf
Trib span of floor to north wall = 10'
distributed load on beams = 115 psf * 10'-2" = 1150 lbs/ft

4th floor load 115 psf
Trib span of floor to north wall = 10'
distributed load on beams = 115 psf * 10'-2" = 1150 lbs/ft

Total load on beams = 2,300 lbs /ft
Divided by 2 beams = 1150 lbs / ft

RE: Structural Analysis of 100 Year Old Structure

pittguy12 - I assume you also have the self-weight of the wall included in your calculations as well in addition to the 1150 plf you show above.

RE: Structural Analysis of 100 Year Old Structure

oittguy12,

I see where I got it wrong, I was thinking about the 2nd floor only. In this sense, the 18" beam at the 2nd floor may not fare very well either. Have you checked one to see if it works?

RE: Structural Analysis of 100 Year Old Structure

(OP)
JAE - In my actual calculations, yes...that has been included. But this was just a check of the floor load to show how strange even just this weight was when compared with the allowable lb/ft load in the Carnegie manual.

Retired - Yes, the 18" beams are showing the same level of overstress as the 10" beams. It is also proportional...which is comforting because its consistent with the 10" thus maybe I've computed things correctly haha...but also just as confusing.

RE: Structural Analysis of 100 Year Old Structure

Yes, confusing. By a quick calculation, assuming Fb = 18 ksi, and Sx = 25 in3, I got an allowable uniform load of 1.1 klf per beam, not very impressive compared to the loads you have :) (For 20' wall height, assume a unit weight of 120 psf, you got 1.2 klf/beam, then the 1.15 klf of floor loads above, and 0.35 klf of the 2nd floor load, a total of 2.7 klf)

RE: Structural Analysis of 100 Year Old Structure

(OP)
Retired...I agree. And 1.1 klf is very close to the published allowable as well. But it is all just very odd.

For any still following it, after discussing it with the owner and explaining the shortcoming of my assessment and the possible need to engage in further select demo, material testing, etc to reach a more substantial conclusion, we have agreed to wrap up this phase of the report with a 'if we ever look to change occupancy maybe we will talk again'. In the time I've been doing this, they received an offer to sell the building so I think are just fine letting the next owner deal with it. My report will become part of the sales agreement with the caveat that more testing is needed.

But I am in sincere appreciation of the the sounding board this group has offered!

RE: Structural Analysis of 100 Year Old Structure

Sad to see the "once a life time" puzzle slip away. But I think that's maybe the best choice for everybody directly involved.

But I still think there are hidden framing inside of the masonry work that we couldn't see through. I did a quick calculation to prove the duel beams can support one story height of wall, and its own floor weight. Here is:

Assume 12' wall height @ 120 psf, ww = 120*12 = 1440 plf/2 beams
Tributary floor load (calculated before), wfl = 350 plf/beam
Load on one beam, w = ww+wfl = (1440/2)+350 = 1070 klf/beam ≅ Fb = 1100 klf allowable load calculated before.

This calculation implies there are structural beams under the roof and the 3rd floor, and there are columns (aligned with the 18" beams) to carry the beam loads directly to the foundation. So the duel beams only carries the 2nd floor wall weight and floor load. Make sense?

Hope this can help a little on your final report. Good luck.

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This paper will focus on the quantification of the complexity related costs in harness variations in order to model them, allowing automated algorithms to optimize for these costs. A number of real world examples will be provided as well. Since no two businesses are alike, it is the aim of this paper to provide the foundational knowledge and methodology so the reader can assess their own business to model how variation complexity costs affect their business. Download Now

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