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.

 

[JLNJ]

Maybe the truss designer didn't know about the heavy hollocore and used typical metal deck/membrane loads. Hollocore will triple your design loads.

 

[LittleInch]

It won't be the first time someone changed a critical component without realising the impact on the design of the roof.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bones206]

I can’t envision a scenario where the EOR was unaware of a switch from metal deck to hollowcore plank. That would have required a deletion of all the roof purlins as well. A contractor isn’t going to make that many changes on their own.

As others have mentioned, the truss end bearing looked odd - can’t really see a base plate for positive anchorage, doesn’t look like any welding was going on in that video either. Similarly, no indication in the photos of a positive connection between the truss top chord and plank. The top chord bracing would be limited to a friction force between plank and chord. It seems likely the vierendeel panels could have exacerbated things if the truss was near its ultimate capacity.

Could be an accumulation of multiple factors, as is often the case.

 

[hpaircraft]

The big question here isn't whether they could successfully use a Vierendeel moment frame for one of the bays. Clearly they could, if they used enough steel to react the vastly increased bending moments in the chords and also keep deflection to an acceptable degree. And I don't think at this point that there is much doubt that they omitted the two diagonals so that they could run HVAC ducts through the clear bays. It seems logical that for a gymnasium you'd want to keep the HVAC as close to the ceiling as possible, above the flight path of basketballs and other sportsing projectilia.

But some of the big unanswered questions here are:

* Why didn't they use multiple smaller HVAC ducts that would fit through the truss triangles?

* Why didn't they web or gusset in the corners of the open bays to reduce the bending moments there?

* Why didn't they just place the open bays at the middle of the truss, where the shear is lowest?

It seems to me like they used a crap ton of extra steel here, and still had more deflection than a much lighter conventional truss would have had, just to save a little trouble with their sheetmetal. And in the end, it couldn't even hold itself up, let alone the two or three feet of snow that Albuquerque occasionally gets.

 

[XR250]

Man those bearing conditions look really sketchy. The trusses even look small considering the weight they needed carry.

 

[bones206]

Just watched that truss setting video again. It looks like the truss was spliced with welds right at the mid span, based on the removed paint in the chords and web member.

The two construction workers were also standing directly under the truss the entire time... not where you want to be

 

[Sym P. le]

The splice is visible in the Facebook image I enhanced and posted earlier, the dark portion of the truss on the right edge of the photo. I was wondering why it was discolored.

I don't think it was a factor in the collapse since the buckling is well off to the side.

 

[dold]

But some of the big unanswered questions here are:

* Why didn't they use multiple smaller HVAC ducts that would fit through the truss triangles?

* Why didn't they web or gusset in the corners of the open bays to reduce the bending moments there?

* Why didn't they just place the open bays at the middle of the truss, where the shear is lowest?

It seems to me like they used a crap ton of extra steel here, and still had more deflection than a much lighter conventional truss would have had, just to save a little trouble with their sheetmetal. And in the end, it couldn't even hold itself up, let alone the two or three feet of snow that Albuquerque occasionally gets.

I'm guessing you don't work with architects very often...? There's no doubt the structural design would have just been standard (but long-span) joist girders, bar joists, steel deck if that were an option. No structural engineer is going to go out of their way to come up with a fancy custom truss design if they don't have to. In my perfect world, every building would be a solid square concrete box with steel framed flat roof. Sadly we do not live in my perfect world.

In jerseyshore's very first aerial photo it looks like the truss may have buckled right around the area of the Vierendeel panel?

 

[dik]

It's not difficult design and is often done. I don't know why it failed. Maybe we'll find out. On a level of difficulty with 0 being easy and 10 being difficult, this would likely rate a 2 or maybe 3.

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

-Dik

 

[azcats]

Anyone see any remnants of ductwork going thru those bays in the trusses? I don't. Maybe not yet installed? Or maybe using that inflatable fabric ductwork that was easily ripped down with the roof.

 

[3DDave]

If that roof is cast concrete hollow slab, I doubt that any duct work would withstand the impact and will be under the rubble and the remains of the roof membrane.

 

[SWComposites]

Are ideas (speculation) as to how/why the roof panels failed in a nice straight line, a line that is not at the unfailed girder? Seems odd.

 

[3DDave]

I'm rather impressed that there seems to be zero information released since April 9th. It's an obvious place to use an FPV drone to get more detailed images of the scene, but nothing from news agencies. That leads me to think there are political shenanigans to cover up some decision.

 

[SWComposites]

Political shenanigans? In NM? Nah, never happens.

 

[Sym P. le]

SWComposites - The panels fell off the truss, the membrane tore at a lap joint.

 

[1503-44]

Roof failure brought down the truss?

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

 

[LionelHutz]

And I don't think at this point that there is much doubt that they omitted the two diagonals so that they could run HVAC ducts through the clear bays.

Well, the HVAC units are installed so the ducts would be parallel to the trusses so this reason for the missing diagonals is highly doubtful at this point.

 

[LittleInch]

Those gaps in the truss are clearly intentional. Maybe they were going to string up a walkway there to use lights or hang things from the roof - who knnows?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bones206]

I'll add something for the benefit of those who may not be familiar. With hollowcore plank roofs, sometimes a 2-3" concrete topping slab is added to provide sloping to drains and to reduce the amount of tapered insulation. Hollowcore planks also have an upward camber, which has to be taken into account by the contractor installing the topping slab. There is always potential for the ponding effect, where the structure deflects during concrete placement, and more concrete is added to compensate, which further increases deflection, and so on.

 

[Oops409]

For those who don't know, and are speculating.

Large Supply and Return Trunk Duct could have been run thru the two openings in the roof trusses. Supply Trunk on one side and return trunk on other side to create distributed air flow. Registers could be on supply trunk or some branch supply ducts could have been run from trunk, parallel to roof trusses for better distribution of supply.

Duct layout all depends on where HVAC unit is located, and whether one or more units are chosen to meet requirements.

The image posted above, shows two package units mounted on roof at end of gym wall, one on each side. So that would confirm that one unit supply trunk runs length of gym on one side, and other unit on other side of gym doing same thing. Returns for both units would be in between the two units on same end of gym as package units. Thus supply is distributed and flows back to central return ducts. Therefore, clearly the truss openings were for HVAC duct work.