Newly Constructed Gym Has Roof Collapse in New Mexico 12

[jerseyshore]

https://www.kob.com/new-mexico/gym-roof-collapses-at-charter-school-sparking-safety-concerns/

ALBUQUERQUE, N.M. — In-person classes have been canceled at a local charter school for the rest of the week after the roof of its new gym collapsed.

School officials say the new gym at the Explore Academy middle and high school campus was basically complete. They were even planning on hosting a ribbon cutting Wednesday, but that’s been canceled, as well as all in-person classes.

Parents learned about the collapse through an email from the school Sunday night.

“The students are out the whole week now,” a parent told KOB 4 anonymously. “Because they have to get inspectors to gather and, at the request of the inspectors in particular, for students to stay away until they can just look the whole thing over.”

The parent said the incident has raised many more concerns about sending her child back to school.

“Students were going to be in that building in two days, and I think one of the big questions I personally have is, did it pass the inspection already?” the parent asked.

The answer is no. KOB 4 spoke with a rep from Albuquerque’s Planning Department. They said the construction company, AIC General Contractors, failed a building frame inspection on March 6. Inspectors found the trusses bowing or bending.

The city’s Planning Department didn’t know the roof had caved in until KOB 4 called Monday afternoon.

Explore Academy leaders say, as of now, it’s just the new gym that seems to be impacted, but they aren’t taking any chances.

“They discovered the damage and evaluated the situation and decided that we would go ahead and go to asynchronous learning until we have a sign off that the entire building and structure is, in fact, safe for students to enter,” said Katia Pride, Explore Academy’s director of outreach.

Pride said there was no obvious damage to nearby classrooms. The school will also have to bring in an engineering company to create a repair plan.

The city’s Planning Department will be sending a building complaints investigator to figure out what went wrong.

 

[bones206]

There are some more photos on the GC’s Facebook page showing the installed hollowcore plank roof. I don’t have a Facebook account so it won’t let me share the link.

 

[1503-44]

Would not the tension in the bottom chord tend to direct the bottom chord to move upward from any deflected condition, but that upward movement being restricted, kicks it out laterally instead? Especially in a Pratt configuration. The bottom chord does not appear to be braced against any sideway. Additional shear deflection of the panel with the missing diagonal might have contributed to the possibility of a greater sideways tendency.

It does seem rather odd that there are a diagonals vacant for no yet apparent reason. What's up with that?

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[bones206]

Grabbed this from the GC's facebook page. You can see duct piled up on the floor.

 

[Sym P. le]

Is there a date associated with the photo or posting?

Aside from showing the viewpoint of the Facebook photo, the two a/c units supplying the gym are seen at the window elevation astride the two girder trusses. This would mean that at least some duct work is exposed beneath the ceiling though it could be turned up immediately inside the gym.

I see now - Hollow Core Concrete Panels atop the truss with insulation above.

Enhanced photo from Facebook - AIC General Contractor, Inc. (Photos were posted January 12, 2024)

 

[Sym P. le]

This photo seems odd as there are no supports for the A/C units nor openings for ducting.

 

[dik]

Try not to use the term 'negligible' in a report. Maybe, where shear is greatly reduced...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

I'm not sure what you mean. HC projects often have mech units and the precaster accommodates the weight of these in his HC design. The same thing is done for any openings in the HC slab for mech units/access.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Sym P. le]

dik, it just seems odd to me that you would cut in HVAC openings rather than block them out or place HVAC units directly on the roofing membrane rather than provide raised supports.

Below is a 2D analysis of a simple pin connected truss showing distribution of tensile and compressive forces. I included the two omitted elements, 60 and 61, to model inadequate moment connections (61) by reducing the modulus of elasticity, and adequate moment connections (60) by using full strength material. Note the diagonals are in tension, I believe a defining element of Pratt trusses.

If this is the type of deformation that was noticed prior to collapse, or even lateral deflection, it is puzzling that over a month of analysis would be required to study the situation. There is a disconnect in the ability of our design and construction personnel to recognize vulnerable structures or to react appropriately. As I stated in a previous thread, I'm quite sure that if a 2x4 could have been used to prop this thing up while they thought about it, they would have done it. However, since temporary support would require more dollars, they just commissioned a study.

If the moment connections were deformed, ....?

Edit: I misdirected references to elements 60 and 61. They are now corrected. (Still getting my ship* together)

 

[hpaircraft]

...if a 2x4 could have been used to prop this thing up while they thought about it...

Just eyeballing it, I bet 4x4 fence posts with double-beveled ends, two each wedged into the open bays, would have had enough column strength to keep that mess in the air while they got their shit together.

 

[Sym P. le]

LOL(as in yes)

With 4x4 supports/wedgies

 

[dik]

I'm not sure I understand the question. With HC slabs, you don't 'block out' openings. The HC slabs are extruded and the openings are placed in the plant.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

You design for the missing web diagonals; I've done this numerous times. It's easy to do. You do not have to accommodate it for erection purposes. It becomes part of the design.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

I see nothing wrong with the openings for the ventilation. No reason to suspect an "inadequate moment connection"...the top and bottom chord are continuous. Assuming pin connections and short segments is great for a freshman college course or reviewing a 150 year old bridge design, but it's not very useful for analysis of a modern building structure. With steel mills running continuous casting, the only real limit on length of members is the ability to ship them. We don't cut them up and spend money on more labor to make weaker structures. So unless your 2x4 or fence post is 28 feet tall with some amazing ability to be braced along its length, it's not going to do anything to help with propping anything up here.

Based on the negligible information available (a very rough, long distance shot from a circling helicopter), it would appear that there's not much of a positive connection between the hollow core and the truss. If there were, I'd think the truss would be a bit more deformed. If that's the case, then it could well have been an LTB type failure or a buckling failure of the top chord. Looking at the weather, looks like winds were fairly calm leading up to that weekend, and then they jumped up above 20mph. A localized gust or downburst could have been enough to trigger it in that case as it would only take a limited amount of time to start the deformation and second order effects would carry it the rest of the way.

Inadequate bearing could also be a/the cause as increased wind would cause more movement in the walls. Not a lot at that wind strength, but it if that bearing were deficient it may not take much to shift it off or tear the bearing plate out. The lack of damage to the outer walls makes me wonder how well the roof was tied in there, too. So if the truss to wall connection was the stiffest thing out there, it may have taken a much higher out of plane load than the designer might have normally assumed.

Be interesting to see more details if/when they come out. It happened 3 weeks ago, so there may not be...

 

[Sym P. le]

The wall opening for the HVAC duct is what I was referring to and vibrating units can wear the membrane which is why I thought raised supports would be used as they are for the roof hatch and skylights.

 

[Sym P. le]

phamENG, ... except for the anecdotal report that there was a dip in the truss. It sounds like a distinctly odd description.

dik, ... it has to be accomodated in the design and is every day. I don't doubt that. Without more info, we are left speculating about possible causes and we may as well itemize a few, no?

 

[phamENG]

It does sound odd. But a 'dip in a truss' is sufficiently vague as to be nearly worthless. We know that it had changed its shape - but how? Vertically? Laterally? The top chord only? The bottom chord only? At one end? At the middle? Without a report with accurate descriptions and/or measurements, it's hard to know exactly what that means.

I do agree that a Vierendeel "truss" is less stiff than a more traditional Howe or Pratt if all else is equal, but the timing makes no sense. And why only one? The next one over is just as heavily loaded - why was only one "dipping"? Could be a flaw in the fabrication of one of the trusses. I think the strength of the design is unlikely to be a concern here - stability of the truss, on the other hand, is suspect.

 

[Sym P. le]

Yes, nothing in any of the imagery says the hollow core elements were well attached to the girder.

 

[1503-44]

Less load towards the center. Why did they need any diagonals at all then?
If you can cut them out of the end panels, you can do the same for the central ones.
I think it transfers a lot of deflection towards the ends, right where too much curvature is not what you need.
My money's on those open panels.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Aesur]

It appears to me to be a bearing issue caused by the dip in the truss. I suspect the truss may have been inadequate or was designed allowing for too much deflection which occurred causing the end to rotate and slip out of the pocket, so in essence providing inadequate bearing length. The questions I have are how much bearing was required versus provided to allow the truss to be post installed after the walls and how much deflection would it take to start slipping off the bearing plate and/or potentially bowing the wall just enough to allow the truss to slip out? How were the trusses secured? I assume slip connections may have been used. Was the out of plane attachment properly secured to the hollowcore plank roof to help prevent wall rotation/movement? Were the trusses even designed for the weight of hollowcore roofing? We would need much more information to have a more definite answer, but I believe most here are probably on the right track.

As for the missing diagonals, this is quite common to allow large mechanical to pass through trusses. Could have resulted in an improper design, but I would like to think something like this was modeled/designed properly, so without more information, hard to say.

 

[1503-44]

Looks interesting, but beyond my processing capability.

https://www.istructe.org/IStructE/m...1960/0784b3ae-9145-4861-9c72-8cc209562ac5.pdf

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."