The "Big" Dig

[Road Guy]

Designers & Contractors possibly facing criminal charges for the death of the woman (who had the concrete slabs fall on her) ??

Anyone else following this that has some more info?

link if you dont know what I am talking about

 

[EdinNO]

Interesting story.

Its probably more complicated than it seems. My understanding is that the bolts holding the tie-backs may have come loose. Did they come loose from the rock above or from the tie-backs themselves?

Who was responsible for testing their strength? What exact hardware was used? Was it according to specs? Who wrote the specs? Who inspected to see if the materials and construction met the specs? Was anyone assigned the responsibility to do the inspections? If not or if so, who was responsible to see that that happened?

I think it could go on and on and the lawyers will make a whole lot of money out of the deal. Looks like the governor is after the head of the person in charge of the the whole system.

I'm really interested in seeing how it all plays out. Problem is that by the time it all plays out to completion, I'm sure I'll be seeing all my kids off to college (newest is 2 weeks old)!

Ed

 

[petergibbons]

I think the Big Dig belongs on the "Engineering Disasters" show that comes on the History Channel. What a mess from the beginning. Way over budget and wasn't it supposed to be completed years ago?

 

[RIP - VTEnviro]

You can bet the tolls on the Mass Pike are gonna go up if the Turnpike Authority gets it's ass sued big time.

 

[Bryan]

I bet the drilled holes for the epoxied bolts were not properly brushed and blown. If this process isn't completed, the epoxy/concrete bond will not be anywhere near design value. This is very common here in Florida where we hold the top plate of residential structures down w/ drilled and epoxied all thread rods. Also, if the concrete had not had enough cure time at time of drilling, the bond would be insufficient.

Another item that caught my eye, they were putting the epoxy on the rod then pushng it into the drilled hole??? I don't see how you could do that correctly. And the rods looked extremely small (1/4"?).

Overall however, I think hanging concrete is a stupid idea.

 

[cement]

Overall however, I think hanging concrete is a stupid idea.

I should wait to hear more about this, but when I see dumb things like that, I think about the fact that consultant billings are sometimes determined as a fixed percentage of estimated construction cost. and a costly (unnecessary?) treatments like that ring that bell for me. that could also apply to cost plus design build.

I just read where there were loose bolts throughout the project. maybe it is simply shoddy construction / inspection.

 

[mizzoueng]

What I don't understand is why epoxy anchors are used in hanging loads like these. We are using them at a job now and we argued to use mechanical anchors. They are just a little more reliable than hoping that enough epoxy got in the hole, then there is the deal with making sure the epoxy is made for holes that are not smooth cored and dust free. Not to mention that the potential hazard of the epoxy or the reactive agent dripping out and getting in someones eye.

Also, I read somewhere that those slabs were basically 3 ton ductwork, is that true?

 

[EdinNO]

3 ton ductwork? Elaborate.... Not sure what you mean.

Ed

 

[cement]

in a true tunnel you would have a round bore, then place your roadway in the middle, with vetilation above the ceiling and drainage and utilities under the floor.

 

[EdinNO]

IC

 

[mizzoueng]

Yes, that is what I was trying to say, they used the massive slabs to make a ventilation area above the roadways, this was also the area I believe they used to check utilities and fire suppresion.

So you have massive 3 ton slabs of concerte doing the same job catwalks and sheet metal could have done.

:wtf:

 

[MA_PE]

The 3-ton (6000 lb) panels were 20 ft x 40 ft. Assuming 150pcf concrete you get a 6in. slab thickness. 6 in. to span 20 ft is not overly "massive". These suspended panels have to withstand gravity, and dynamic loads i.e. vibration and wind pressures generated by the 70 mph traffic below.

I get sick of seeing and hearing the yellow journalism and speculation in the local news and papers while the sensationalistic media attempts to bring "justice". The investihgation is being headed by the politicians and the FBI so the quality of the "engineering" portion of the investigation is, in my opinion, questionable.

The fact that we're in an election year makes the situation worse.

People, the media especially, need to calm down and wait for the answer. The next step is to put a price on it, because no matter what the circumstances are these days, it all comes down to dollars and cents.

Look what we pay for "homeland security" these days. And your quality of life is improved how much? by all this expenditure?

FWIW: I agree that using an adhesive anchor in direct tension in a critical application like this is a poor idea.

 

[Road Guy]

it seems crazy that "the governor" needs to assume control, like he really knows anything about it. probably just tryign to look good in the papers.

But does this seem like a design issue or a "contractor didnt install it correctly" problem?

or both?

 

[MA_PE]

Only time will tell, but my opinion at this time is that it is more probably related to poor installation, inspection/QC, than to the design decision to use this less than desirable attachment method.

 

[Bryan]

The 3-ton (6000 lb) panels were 20 ft x 40 ft.  Assuming 150pcf concrete you get a 6in. slab thickness. 

Actually, w/ 150pcf you would have a 0.6" thick slab w/ a 20x40 panel (6000/(20X40X150)). That was one of the things I noticed as well. I don't think the slabs were 20x40. I think the frames were 20'x40' with 6000 lb panels. Looking at the pictures of cleanup, it looks like 4" thick panels. So maybe 6'X20' panels??

It appears the epoxied failed, most likely due to poor installation in the epoxy mix process. Typical construction error that the engineer will be able to point out and get off the hook. However, we as engineers should take note. Use commen sense and practical reasoning when specifying a engineered system. If you don't have field experience in the construction, you will likely not have the information to make a responsible decision and it may cost somebody their life.

 

[MA_PE]

Thanks.

It's true what they say...haste makes waste. Agree with the .6 in. thickness at 150 pcf. Also, agree that images show something thicker than 0.6 in. LOL. Probably ~4+ in.

With a grid size at 20 x 40, the panels would have to span the 20 ft direction. 4 in. is likely too thin even for self-weight.

"Typical construction error that the engineer will be able to point out and get off the hook."

Don't bet on it. I believe that someone will pay for OK'ing epoxy anchors in this application.

 

[EdinNO]

It seems insanely stupid to use epoxy anchors in this type of application.

Ed

 

[Road Guy]

what firm did the design? I imagine there were several but someone had to be the prime?

 

[EL Nica PE]

They should of use Duct tape!!! would of hold longer! :hung:

 

[Slugger926]

It seems insanely stupid to use epoxy anchors in this type of application.
Ed

That is exactly what one of the construction supervising engineers stated during the construction phase. He also said that none of the bolts were holding properly in several notes to management before he resigned to work elsewhere.

There are a lot of managers and engineers that will be cringing at his paper trail. The lawyers are eating it up. :drunk: :congrats: