This is so sad to see. :(

Steven Lake

Large solar panel collapses under weight of snow at elementary school in Teaneck, NJ

mike95490

Re: This is so sad to see.

Interesting to see if it was materials failure, or engineering's fault. Or simple overload.

Blackcherry04

Re: This is so sad to see.

It was a low angle Carport type cover with a center mount Is there any doubt that it would fail at some point with snow load on one side that would pull it out of balance ??

BB.

Re: This is so sad to see.

Running the video and I see that both the bolts pulled from the concrete and (it appears) other concrete "posts" may have snapped at ground level (possible that the earth failed--could not see due to snow).

In any case, it appears that it is simply the wrong application for use with concrete piers and anchor bolts. Too much twisting from unbalanced loads from snow (and high winds would probably have similar failures too).

Concrete is great at resisting compression, but very poor when under tension. And placing a long leveler with side loads, (non- pre or post tensioned) concrete is going to fail.

In my humble opinion, they are going to have to retrofit or pull any structures with this design. They (appear) to not be safe/well engineered for the application.

Pole mount usually seen on this forum have metal posts that extend through the concrete all the way into the base of the hole. These posts carry the entire loads to the ground and the concrete just provides weight and larger surface contact with the soil.

-Bill

offgrid me

Re: This is so sad to see.

I have never seen such bad fastening on a structural column. If just in compression it may have been ok. 6 @ 3/8" anchors only 5" into the concrete was a recipe for failure. Either the engineer or builder is in a lot of trouble. Hope their insurance was paid up.
Ned

SolInvictus

Re: This is so sad to see.

BB. wrote: »

Running the video and I see that both the bolts pulled from the concrete and (it appears) other concrete "posts" may have snapped at ground level (possible that the earth failed--could not see due to snow).

Concrete is great at resisting compression, but very poor when under tension. And placing a long leveler with side loads, (non- pre or post tensioned) concrete is going to fail.

It is possible the piers are concrete piles that do not flare out at the base and simply pulled up out of the ground after the anchor bolts pulled out of the concrete on the one that was shown in close-up. As the structure failed it probably tilted first sending more snow toward the lower edge increasing the torque and hastening the collapse.

The design in this case appears to be improper. The anchor bolts are supposed to extend to the base of the concrete pier and bend 90 degrees outward beneath horizontal rebar. The tension is all in the steel which then uplifts the concrete from the base which puts the force on the concrete in compression where it is strongest. The anchor bolts or rebar are supposed to be designed with a safety factor of 2 to withstand the reasonable worst case load. The torque equation for calculating the force and determining the tensile strength of the steel necessary to bear it are rudimentary. Based on the video, incompetent engineering is my first guess.

peakbagger

Re: This is so sad to see.

I agree the anchor bolts are entirely unacceptable, someone saved a buck and it will be up to the courts to figure out who pays for the fix. The tough part is that even if the bolts were designed correctly, the high snow loading may case some other part of the structure to fail due to excessive load. If the snow was wet, it easily could be over 30 PSF and many structures outside the snow belt may be designed for less.

The region I live in northern NH is a "black zone" for snow loads. Generally there is a loading map in the code books used to determine maximum ground snow load. Due to the potential for high snow loads in the area, the local towns have to establish snow load. My house is next to the town with the highest snow load in the state which is 110 lbs per square foot ground snow load (my town is 95 psf). There are factors used to reduce this amount for roof snow load but generally it means that houses built to code have 12" on center rafters with a couple of inches of extra depth. Many contractors from outside the area design to 40 PSF and since most of the towns do not inspect residential homes many houses get built with less than code design. I used to work in an local industrial plant that had been around for 100 plus years, many flat roofs were designed for 10 PSF. The theory was that the building were heated with no insulation so the snow would melt before the roofs loaded up. Unfortunately over the years some buildings ceased being heated and some had new roofs installed with insulation, most survived. My experience is that structures rarely fail due to the design as much as in the details. I would expect that the structure in the video was doomed from the day it was built due to either poor design or shortcuts by the contractor, which should in theory have been caught by the inspector. Unfortunately with concrete, its easy to bury the details.

SolarPowered

Re: This is so sad to see.

This is why in California our District of State Architects design and engineers for snow loads when there is no snow at all....LOL

Organic Farmer

Re: This is so sad to see.

BB. wrote: »

Running the video and I see that both the bolts pulled from the concrete and (it appears) other concrete "posts" may have snapped at ground level (possible that the earth failed--could not see due to snow).

Those do not appear to be anchor bolts. Those are regular carriage bolts.

My house is set on a concrete foundation. That foundation has a lot of rebar in it. Anchor bolts are in an 'L' shape. The 'L' hooks under the rebar, and is twist tied to the rebar before the concrete was poured.

Upward force on the anchor bolt transfers that force to the rebar in the concrete.

Also those carriage bolts look to be only about 8 inches long. My anchor bolts are over a foot long [I do not recall their actual length, 14" maybe?]




They do market concrete drill bits, that you can use to drill a hole into concrete, then you could screw a carriage bolt into the hole. But that does not make it an anchor bolt. That is simply a bolt screwed into concrete for light weight use; like pipe hangers. But never for anything structural.

Now they do get away using carriage bolts for street lights. But how much weight is on a street light. And I think there are other laws that require a street light to break-away easily when vehicle smacks it. Perhaps the contractor was thinking that those poles would be holding the same weight as a street light.

SolarPowered

Re: This is so sad to see.

Organic Farmer wrote: »

Those do not appear to be anchor bolts. Those are regular carriage bolts.

My house is set on a concrete foundation. That foundation has a lot of rebar in it. Anchor bolts are in an 'L' shape. The 'L' hooks under the rebar, and is twist tied to the rebar before the concrete was poured.

Upward force on the anchor bolt transfers that force to the rebar in the concrete.

Also those carriage bolts look to be only about 8 inches long. My anchor bolts are over a foot long [I do not recall their actual length, 14" maybe?]

According to California DSA requirements the bolts have to be 1-3/8" J bolts tied into the rebar. Those were some 3/4 dowel pin allthreads. I wouldn't be surprised if the contractor that built that system was to be sued, because contractors have to warranty that work for 10 years.

Organic Farmer

Re: This is so sad to see.

SolarPowered wrote: »

According to California DSA requirements the bolts have to be 1-3/8" J bolts tied into the rebar. Those were some 3/4 dowel pin allthreads. I wouldn't be surprised if the contractor that built that system was to be sued, because contractors have to warranty that work for 10 years.

'J' bolts, I guess I forget the name for them

When I saw that video, the first thing that jumped out at me was those are the wrong bolts, and where is the rebar.

ILFE

Re: This is so sad to see.

SolarPowered wrote: »

According to California DSA requirements the bolts have to be 1-3/8" J bolts tied into the rebar. Those were some 3/4 dowel pin allthreads. I wouldn't be surprised if the contractor that built that system was to be sued, because contractors have to warranty that work for 10 years.

Organic Farmer wrote: »

'J' bolts, I guess I forget the name for them

When I saw that video, the first thing that jumped out at me was those are the wrong bolts, and where is the rebar.

I agree with both of you. Talk about an accident waiting to happen!


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Randal Stanley
General Manager/News Director
News 12 New Jersey
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Edison, NJ 08837

Cariboocoot

Re: This is so sad to see.

Anyone with half a brain looking at that picture of the bolts in concrete would be wondering how the structure stood even without and snow on it. I could build better than that when I was 10 years old. Can you say "lawsuit"?

ILFE

Re: This is so sad to see.

As I recall from viewing the video before, there are "several" of these solar arrays similarly mounted at the school. I think that contractor had better get himself together.

Of course, rather than just admitting it and doing a proper install - like he should have done in the first place, he will probably hire a lawyer and tie the whole thing up in court for six months.