Big Dig Boston ceiling collapse 21

[mark3333]

folks, following is a message i posted to the seaint list server two days ago. i just heard of this website, so thought i'd share my post.

some of this has been discussed on this thread already, but rather than edit, thought i'd just send as is. next i will send a follow-up i just sent earlier today.
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Folks,

I lived in California for 13 years, including 3 years in the construction industry and 10 years practicing structural engineering. According to my recollection, I never met, worked for, or worked with ONE SINGLE engineer who would specify anchors grouted with epoxy to be used in an overhead application supporting gravity loads. And yet, that is what was apparently used in some areas of the big dig to anchor the concrete hung ceiling to the tunnel's concrete roof. Frankly, I am shocked that epoxy anchors were used. Perhaps I am wrong about this. I would appreciate comments on this.

If that system IS acceptable, I will state categorically that the Boston area is not the place to do it. This is due to the culture of the Boston area. After my 13 years in California, I have spent the last six years in construction management (of buildings, not highways!) in Massachusetts. My experience over the last six years points to a PROFOUND difference in culture and mentality with respect to attention to plan review, professional collaboration, compliance with building codes, inspection quality, use of new technologies, and commitment to excellence.

In my work here, I attempt to hold all of us to the highest standards of design and construction, and yet on a daily basis I am met with incredulity by my colleagues, and by the architects, engineers, and contractors involved in construction of buildings here.

During the last six years in Massachusetts I have never seen an evaluation report for a manufactured item, such as an epoxy anchor. It simply isn't done here, in my experience. The typical process is this: the engineer will be vague in the specs, indicating say epoxy OR mechanical anchors. Then there may be a submittal, maybe not. If there is, there is no follow-up. The contractor is free to install them as he sees it. There is no inspection required by the authorities having jurisdiction. The inspection firms sometimes may be asked to inspect, but in general the particular individuals are not qualified to inspect such a thing.

For instance, yesterday when I read in the paper that the epoxy had "pulled out cleanly", I told some colleagues that it seemed to me the only way that could happen was if the threaded rod was NOT galvanized. Plain steel comes from the supplier with a coating of oil. Incompatible with epoxy grout. Now it looks like that's what happened. Only in Boston could this happen with the culture we have here.

As another example, in six years I have never seen a list of plan check comments. It simply isn't done. If I ever question some aspect of the design during the construction phase, no one will look into my comments, but instead the reaction will be "we have a building permit, so your question doesn't matter". Or I am met with a stone wall of puzzled looks. "Who are you to question the engineer?" "Well, the engineer has his stamp on it, so it's OK." "That's the way we've always done it." But NEVER an answer to the question.

This mentality in Massachusetts covers ALL aspects of construction, not just structural, but also HVAC, fire protection, civil design, egress requirements, accessible design, etc etc etc.

My experience in California was completely different. Plans are checked, comments are made, professionals revise the drawings, building inspectors require inspections, building inspectors require inspections by the professionals, etc etc etc. Questions raised are viewed as an OPPORTUNITY.

Any thoughts?

Mark Swingle

 

[mark3333]

folks, perhaps i overstepped on the galvanized vs not-galvanized, but i still think it makes no sense to use plain steel (due to the coating of oil and/or rust). it may be allowed, but i never would. following is what i sent earlier today to the seaint website. these were my thoughts after seeing the photos.

all for discussion. . . .
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Folks,

Now that I've seen the picture, I have a few more points for discussion.

1. Based on the relative capacities of the four anchor rods (if installed correctly) and the cable, it appears there was no consideration of ultimate strength design. the basic design of this should have considered that the only ductile failure would be the cable yielding in tension, so it should be the weakest link by a reliable factor. Just based upon experience it is clear that those four anchor rods would fail in tension (if installed correctly) well before the cable yields. Result is a brittle and sudden failure with no warning. If the connection system had been designed such that the cable yielded first, there would likely have been warning (sagging ceiling) and possible redistribution of the gravity loads to other members. Less likely to kill someone.

2. The anchor rods in each group should have been drilled at an angle, so that they are not parallel to each other, and are not parallel to the primary tension force. Failure would then require combined shear and tension, or combined bending of the anchor and fracture of concrete. Drilling far enough into the concrete such that the rebar cage is engaged would help prevent the brittle fracture mode. I realize this is more expensive to install, but engineers are supposed to enforce public safety.

3. Note one of the photos in the link provided below shows some of the rods are bent. Apparently some anchor rods failed before others and the T section rotated before the remaining rods failed. Of course the investigators will have to verify this.

4. I still maintain that using non-galvanized threaded rod is a problem. I agree that it appear the epoxy engaged the threads somewhat, so it would never be a truly "clean" break. However, the non-galvanized rods have a coating of oil and rust which is likely not compatible with the epoxy. It would get mixed in with the epoxy, and probably reduce the bond strength. Time will tell on that one, but I would like to hear your opinions.

5. Clearly mechanical, rather than chemical, anchors should have been considered. [of course i am assuming cast-in-place anchors were somehow out of the question.] Expansion anchors and undercut anchors require less inspection effort and are more difficult to install INCORRECTLY. As long as the hole is the proper length and diameter, it is fairly hard to mis-install these. And at least in an overhead application, you don't have a pile of dust sitting at the BOTTOM of the hole!

6. I predict the epoxy manufacturer will be held second-most liable (after the engineer of record). This amount of epoxy clearly was not bought off the shelf at Home Depot or Lowe's. The supplier would have provided free technical advice and their engineer would have been involved in reviewing the application (if not the actual design) and in reviewing the installation & testing.

My points above are some pretty basic engineering principles that have been taught in engineering school, studied, researched, and practiced for decades. I still maintain that the culture in Boston (see my email from Friday 14 July 2006) contributed to the lack of care for proper engineering, proper construction practices, and proper inspection practices.

I do want to make it clear there are glaring examples TO THE CONTRARY in the Boston area. There are many firms and individuals who practice state-of-the-art engineering and demand excellence and accountability. Sadly, however, I believe they are in the minority.

Mark Swingle

 

[Tomfh]

"As long as the hole is the proper length and diameter"

But you simply cannot know that.

Amongst many other "interesting" fixes, I've seen the boys fix mechanical anchor slop by wrapping them in cardboard, so I for one am not getting on this "mech anchors would have saved the day" bandwagon.

Bottom line is that all anchors are succeptible to poor installation. You have to assume it in the design.

 

[dik]

Anyone have an idea of what epoxy system was spec'd? It would be nice to be able to review design loads as well as recommended installation or any caveats about use...

Just some idle speculation....

There's a likelihood that the anchors were properly designed ,based on information provided by the anchorage supplier... whether or not he was was ever consulted. For liability reasons, the engineer is not likely going to recant his choice of anchorage although he may have initially recommended a more costly mechanical anchorage (contrition is not necessarily good for the soul). If he's used any specifications it likely contains the provisions that installation should occur in accordance with the suppliers recommendations, and,as well, testing procedures may have been specified. For something this critical, the engineer might take a hit for not following through with testing; it may, however, be the contractual responsibility of the installer to arrange for testing. The engineering company is rather large and savvy...

In addition, the anchorage supplier likely has data coming out his kazoo regarding the adequacy of his system. In addition suppliers usually have recommended installation procedures that address temperature, preparation of the hole and any deleterious material on the object to be anchored. I suspect the anchorage supplier is carefully reviewing his installation procedures to see if there are any 'holes' or contraindications to the use...

That only leaves the installer... and based on information so far available, it appears that the anchorages were not properly installed as per the design as well as the recommendations of the supplier.

The issue of it being HDG might come into play if corrosion were the issue or cause. If the threaded rod had a coating to reduce corrosion this should be reviewed in light of the supplier's recommendations.

As far as installation of hangers on an angle, I've used this for bonding a surface so that any movement pulls the sufrace closer to the backing. With respect to hangers, the added moment from the inclined installation may cause stress risers (for fatigue) as well as additional tensile stresses from bending... not necessarily good things for either method of anchorage.

 

[Ingy]

Heynewp,

Yes, I was on the big dig for four years. I agree that unless every hole is inspected, you just don't know. As the old saying goes, you don't know what you don't know.

Having worked in Boston for several years on heavy civil projects and now in California for the past 8 years on more heavy civil projects as a general contractor with a PE, I feel I can speak with some authority of how things are done in both locations. I did not work on commercial building in Boston but have in San Francisco. I agree that the general attitude and certainly the production rates of the craft workers are different. I can also say that regardless of what the press and politicians like to say, there was a huge amount of oversight and inspection on the all aspects of the CA/T project.

The one point I really want to get across is that it is highly unlikely that one engineer was involved and if there is an error it was systematic. The ceiling panels are similar throughout the project which, as we all know, was built over 15 years. Lots of engineers and reviewers and differing design firms were involved.

That being said, I would be very curious to know what time of year the failed anchor assemblies were installed. The project was always under extreme schedule pressure and a lot of work was done in the winter. Epoxy does not cure very well cold conditions. Like I said before, I hope we get some very good forensic analyis out of this.

 

[haynewp]

I think the red sleeve is a hole plug used for overhead applications, like this:

http://www.ramset-redhead.com/RH/accessories.asp

 

[JAE]

Yes, that looks like those red things in the photos.

 

[UcfSE]

I agree with Tomfh about expansion anchors versus epoxy anchors. I've never head anyone suggest mechanical anchors were more reliable than epoxy anchors. It looks like it should have been cast-in-place as others have said previously, or outrageously over designed.

Hopefully this will prompt a change in what mark3333 views as standard procedure in MA. I've never been or worked there myself but I understand the mentality having run into it before.

 

[daveh6729]

This brings back memories of the Kansas city hotel walkway debacle! (although it was a different failure) Why not just cast in weld plates with studs or slotted channels into the ceiling and weld or bolt the hanger brackets to them in the first place?

 

[Ingenuity]

"The anchors were made by Hilti."

unclesyd,

From you reference at

http://www.telegram.com

it implies that the NEW reduntant anchors to be installed will be HILTI, not the existing anchors are HILTI.

 

[unclesyd]

Ingenuity,

I was in error in making that statement. Hilti is making the replacement anchors.

 

[minorchord2000]

Does anyone know if the tunnel concrete is shotcrete or gunite? Or is it cast in place from above?

 

[hokie66]

The holes were reportedly cored rather than percussion drilled because of the quantity of reinforcement. Coring leaves a much smoother surface. If the problem is failure of the epoxy/concrete interface, this would be a likely reason. Don't know if that is the case or not.

Loading on the bolts would not be just dead load. Overpressure due to the ventilation system could contribute significantly.

 

[hacksaw]

what sort of annual inspection proceedures would normally be called for before and now after the failure?

proper design and installation is only part of the equation

 

[JAE]

hokie66 - the reports were that the bolts pulled out clean. That would indicate that the failure was in the bolt-epoxy interface and not in the epoxy-concrete interface.

 

[Tomfh]

Apparantly there is a more straightforward explanation for the clean bolts - There was never any epoxy in the first place:

http://news.bostonherald.com/localRegional/view.bg?articleid=148547&format=text

This wouldn't surprise me. On some of our jobs I've seen the amount of epoxy per hole drop off to near nothing when someone is trying to stretch out their remaining cartridges/sausages.

 

[JAE]

So let me pose a question here.

Bolts with no epoxy, bolts with some epoxy, holes not adequately cleaned before installation, etc. These are all workmanship issues are they not? In light of the "criminal" investigation, how does the blame get distributed among the parties involved?

I don't know all the contractual relationships in this large project, but I assume there would be the state, city, or whoever would be considered the "Owner". Then there is the general contractor, the sub-contractors, etc.
Also - there could be a construction project manager (Parsons?). Also the bolt manufacturer who supplied the bolts and epoxy. Then you'd have the design engineers.

For the 100's of bolts, was there a full time inspector there watching the drilling, installation? How could the design engineer get blamed if the overhead bolt design "worked" on paper - which assumed "good" workmanship practices?

I'm just reflecting on the "criminal" aspect of this. Are we engineers subject to criminal penalties if we design something that gets put in poorly and falls down?

 

[cvg]

JAE

From past experience, I can tell you that the attorneys don't care who was at fault, they will name everyone even remotely connected to the project and then let the chips fall where they may. It will be guilty until proven innocent and you will have to defend yourself regardless of your level of involvement or guilt. The more parties involved, the bigger the purse.

 

[haynewp]

I don't see how the engineer could be criminally charged if he was not onsight during the installation of these particular bolts. I would expect civil wrongful death suits being distributed around the hiring companies and the engineer may get dragged in on that.

I would think the actual "criminal" (the guys that end up in jail) charges would be against the field installers individually (and possibly the full time inspectors). The actual workers that installed the bolts are probably headed back for the border right now.

 

[haynewp]

Different area, mostly different system, shutdown.

http://www.msnbc.msn.com/id/13955493/