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Re: big dig structural failure - epoxy anchors overhead supporting gravity

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This one hits real close to home for me.  Several years ago, I was working on the big dig as a field engineer for a G/C casting tunnel roof sections about a 1/4-1/2 mile from that spot (or roughly $350million away.)  Our contract drawings specified continuous unistrut sections in numerous locations to accommodate ceiling and wall fixtures, panels, etc.  We had to meticulously prepare lift drawings for every single pour to locate these items exactly.  I had also been involved on several other projects to much lesser degrees and seem to recall that the embedded unistrut was the standard detail.
 
However, I do know through the grape vine (if my memory serves) that there were of course cases where things were missed, didn't line up, changes were made, etc, and anchors had to be installed after the fact.  At this point, the design engineer(s) were typically out of the picture and it was up to Bechtel/Parsons to approve design changes such as anchorages.  It would have been typical for changes to be approved, provided that field testing was done to verify the new condition.  But the most diligent testing aside, I also recall stories of bolts that were cut short because it was too hard to drill through the massive rebar.  There were also the occassional large voids due to either poor consolidation around the massive rebar cages (I recall numerous stacked layers of #11 bars in some cases, its no wonder) or the occasional empty soda can.
 
To clarify, the tunnel finishes, i.e. electronics, tile, panels, pavement, etc. were all installed under a separatly bid contract, typically by a different G/C than the original construction company.  I'm sure there are/were numerous claims between the finish contractor and the original G/C for these coordination issues.  I do know that these epoxy anchors were probably used in a lot of locations for various reasons.  Ultimately, I am sure they will do a survey of every single overhead connection in these tunnels.  What they do about it, who knows; I'm just glad I relocated to Pennsylvania.
 
FWIW, and AFAIK, the contractor that installed these bolts was also the G/C for the leaking tunnel sections.  I could be wrong.  The level of Q/C on our concrete sections and waterproofing installation where extremely stringent.  I am unaware of any problems with the work that we had installed, though that is a testament to B/P's oversight (on our project) as much as our own diligence.  For these problems to be so massive in other areas, there must have been some serious oversight or who-knows-what going on.
 
On a related note, I remember doing epoxy testing as G/C for post-installed anchor bolts somewhere else in the Boston area.  We prepared and cleaned the holes per the letter of the directions.  We waited the specified time, etc, had the engineer on hand, even had the product rep pull the bolts.  They slipped right out with no capacity.  No one ever figured out why, but I've been a skeptic ever since.  There are just too many variables that have to go right in the field to meet the required performance level.  I can't imagine taking that risk with an overhead component of such weight and size.
 
Jim Wilson, PE
Stroudsburg, PA
 


Mark Swingle <mtswingle(--nospam--at)rcn.com> wrote:
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