Blacksburg gym collapse
Blacksburg gym collapse
(OP)
I haven't seen this posted on the site. Can anybody shed any light? It is difficult to tell how the roof was framed. A bulb tee is seen in one photo, so probably a Tectum deck or similar.
http://roanoke.com/multimedia/bhsgymcollapse
http://roanoke.com/multimedia/bhsgymcollapse






RE: Blacksburg gym collapse
Looks like a couple of feet of snow on the roof. Considering the way it sheared rather than sloughing off, it was likely pretty well packed.
Agree with Easterling on one count...you don't often see such full collapse. His other comments are a bit presumptuous.
I'll be surprised if they take the time necessary to determine a true progression of the failure. My sense is they want to get it cleared and reconstructed ASAP.
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
http://w
RE: Blacksburg gym collapse
Now the "fun" starts. The defense will have a field day with the report. One statement in particular
will create a world of grief for the writer when the depositions come about. I understand what he means, but the defense will use the statement on its surface to discredit his other statements. (He implies that only full penetration welds meet AWS requirements). Further, he leaves out one important example of a prequalified joint profile in his list of approved ones...the single bevel, perhaps the most common after a square butt.
The next argument will be whether it was the chicken or the egg that came first. Then they'll get into the argument about whether the 9% yield strength deficiency means anything, since the design stress was a lot lower than that. And on, and on, and on....!
The cell phone photos were of good quality!
RE: Blacksburg gym collapse
I wonder what legal recourse the school board has, as the gym was built 35 years ago. The contractor, steel fabricator, and structural engineer would be in the firing line. I think the contractor still exists, but don't know about the others.
What hit me first about the report was that the investigating engineer for the school board basically just brokered a testing company to do all the work, and depended entirely on the conclusion of the testing outfit, without any further explanation or discussion of the structural behaviour of the roof system.
Based on the coach's photos, I suggest the bottom chord, supposed to be a zero force member at that point, instead placed a couple on the tube column, yielding it as the roof deflected, thus making the end unstable, resulting in the masonry distress. I would like to examine the drawing for five minutes to see if my alternative theory makes sense. I'm not a metallurgist, but I believe a case could be made that the gross distortions in the seat were due to impact when the roof came down.
RE: Blacksburg gym collapse
There are no levels of stress indicated... or I missed it on first glance. I cannot determine from the report what the consequences of the inadequate 'butt' weld are or the lack of full penetration. I also could not determine the consequences of a low Fy... and if the issue is buckling, then, other than rotation, what the consequences of the above are.
I'll try to take a more thorough gander at the report over the weekend. On first glance, there may be a bit of a problem in defending the report, other than the obvious, that the roof came down.
Dik
RE: Blacksburg gym collapse
I also agree, hokie, that the distortions were post-failure rather than concurrent or causative. That makes all the effort (and cost) to explain the metallurgical and profile issues for naught.
If the defects are latent (which they appear to be), then they might have recourse against those responsible for the defect, unless Virginia has a statute of repose as well as a statute of limitations. The way that works in my state is that the clock starts running when the defect is discovered. You then have 4 years to bring that defect to a lawsuit(statute of limitations); however, if the defect is over 10 years old, time has run out (statute of repose), even if the statute of limitations has not.
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
As far the discrepancy in the yield strength, I agree it can over rated, but even in the 70's it was standard to get between 45 and 50 ksi for A36 steel. I know that because in the nuclear business we used to get mill certs all the time. If there was one thing you could count on, it was a minimum of 36 ksi for A36 steel. The chemical analysis didn't tell me anything. What is wrong with the steel? And couldn't they get a historical version of A36? Call ASTM for god's sake. It just seems sloppy.
It seemed unusual to have a mechanical and metallurgical analysis done (or at least by a ME), but no structural. For all I know the member with the low yield strength had no force in it. What's the calculated stress vs. the allowable?
I'd like to see a better report, not for the lawyers, but for a learning experience.
RE: Blacksburg gym collapse
The only conclusion the engineer makes is that the failure was caused by a non-overload condition and reaches no conclusion as to the probable cause of the collapse!
Was there deterioration or other conditions that led to the collapse?
Oh well...read for yourselves..
RE: Blacksburg gym collapse
So the code in the 70's required a 35 psf load. What stress level did that cause? Maybe the designer missed that load case and only designed for a reduced 20 psf LL (12 psf?)based on the area.
RE: Blacksburg gym collapse
Kudos for finding the earlier "report". It would be interesting to see that photo 7, which he says shows the column bent by the bottom chord.
Jed,
You wouldn't reduce snow load in Blacksburg, Va. It really snows there. We had it drifted to 2nd story windows in the dorms in 1965.
RE: Blacksburg gym collapse
If it turned out that the maximum stresses were 7000 psi with 35 psf applied to the roof, you could move on to other causes. To blow off any design investigation because there have been greater snow accumulations in the past shows an amazing lack of curiosity. I'd like to give them the benefit of the doubt that they ran a calculation and it was obviously not the design. Plus they reroofed the gym in 1999. How did that roof weight compare to the old one?
RE: Blacksburg gym collapse
Here's a link to the report and all the photos...
http://www.mcps.org/forcon/
RE: Blacksburg gym collapse
The columns were wide flange sections, not tubes as I thought. And there was nothing bracing the tops of the columns, if you don't count the unreinforced blockwork, which I don't.
I still haven't seen a photo showing the connection or lack of such between the bottom chord and the column. If that connection didn't allow rotation, I think it would have initiated the collapse.
This building obviously has had problems before, as evidenced by crack monitoring of walls and concrete beams, also permanent steel props.
RE: Blacksburg gym collapse
The final report relies on the metallurgy and physical testing which are irrelevant if the loading was not more than has been seen in the past, since there was no indication of a fatigue implication. They clearly do not believe that overload is the cause; yet how can they deny that as an implication...after all, if the snow had not been present, it isn't likely that the failure would have occurred. I suspect they have underestimated the actual loading at the time of failure.
Interesting!
RE: Blacksburg gym collapse
I made up a PVC pipe 'plug cutter' that I use to sample the depth of snow in various locations.
Without knowing what the overall framing was, the collapse photo appears to be an overload; if it were a local condition, then I would suspect there would be a redistribution of forces that would normally preclude a collapse... but, I'm not sure based on info presented.
Dik
RE: Blacksburg gym collapse
In this case, there were two trusses, spanning 150', which carried most of the roof. So when one of those became unstable at one end, down she came. There was still a lot of snow and ice on the fallen roof after the collapse, so I think they would have known if excessive snow buildup was the problem.
The investigators attributed the collapse to web crippling of the truss seat, which they just called buckling. That could be, as there was little bracing the top of the trusses at the end from twisting. Maybe a combination of web crippling with prying due to the bottom chord being in contact or connected to the column. The webs were certainly crippled, but it's anybody's guess as to whether that happened first or not.
RE: Blacksburg gym collapse
The structural engineering states that the design snow load was 35 psf and that the snow load on the day of collapse was only "23 pounds" (I'm assuming this should be 23 psf). He also states that there have been significantly greater snow accumulations in the past that have not resulted in collapse, thus ruling out excessive loading.
The structural engineer preliminarily concludes that the failure was not a result of an overload condition and defers to the metallurgical analysis to identify the failure and building collapse.
The mechanical and materials engineer then concludes that the cause of failure was the snow event in combination with a pooly designed and manufactured main truss support.
If there have been significantly greater snow accumulations in the past, then why did the roof not fail then in combination with the poor truss support?
Something is not right. The reports are too ambiguous. I'm assuming FORCON was hired to determine the cause of collapse, which they haven't done. But then again, maybe they only provided as much detail as the insurance company allowed them to since they were hired by the insurance company.
It's not going to be a fun trial for FORCON.
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
By the time the Structural Engineer got there, they building was partailly demolished.
I checked Forcon's website http://www.forcon.com/ and they seemed to be a company that provides a) Surety consulting services and b) Forensic Engineering.
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
My question is given the historical issue with the strucutre which can be seen from the crack monitoring and permanent shoring. Does anyone think it would be wise to try and repair this structure or shoudl it be demolished and replaced?
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
Sure glad I didn't write them.
Even the loading and wind loading is suspect... and who was looking after the site from Feb 13 to Mar 5... and how was the site protected/secured.
Real interesting that there was an engineer on site at the time of the collapse... nothing in the report has a comment about his observations... I generally note that the report is a compendium of information received from others and note where this is consistent or inconsistent with observations made... to reiterate... sure glad I didn't write them.
Wish I had more time to do a critique. It could be a hoot.
Dik
RE: Blacksburg gym collapse
I assume that Forcon does this routinely, as implied by their website. Those reports are going to be an absolute nightmare for the author during deposition and trial, if it gets there. For a company that specializes in construction forensics, those reports are amateurish.
RE: Blacksburg gym collapse
Among the 'shortcomings', the report doesn't reference who prepared the 'As Built' documents or the name of the engineer that sealed the them (assuming that happened).
Was OVPR on site because they were called in to look at the collapse because they were the original engineers/architects?
Dik
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
I think if they 'go after' the builder or fabricator, they will have a much tougher nut to crack, IMHO (not so humble at times <G>). Even going after the engineer could be formidable... based on the lack of information in the reports and some discrepancies.
There is no mention of advising all parties of demolition of the structure or, with the exception of OVPR, the fabricator/erector even of the collapse.
With most collapse report I've done, I generally include informing all parties and also give them an opportunity to remedy the problem, if they consider they may be at fault (can be used as a 'hook', too). I also inform them of the intent to demolish the damage so that they can post any objection.
Dik
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
RE: Blacksburg gym collapse
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Blacksburg gym collapse
Dik
RE: Blacksburg gym collapse