bridge collapse in mn part 2

huangyhg

bridge collapse in mn part 2
the other thread was getting quite long so i thought i'd start a new one.
here's a snippet from a news report today about some of the engineering thinking about dealing with the bridge in the months preceeding the collapse:
documents obtained by the star tribune of minneapolis for a story published sunday reveal details of how officials decided to conduct periodic inspections of the bridge rather than repair it in the months before it crumbled.
according to the internal state department of transportation documents, officials were ready dec. 6 to go ahead with a plan to install steel plates at several areas on the bridge as a patchwork fix amid reports that it was structurally deficient, as recommended by an outside consulting firm. the project was shelved after the state determined the process could actually weaken the bridge.
instead, officials decided in january to go with periodic safety inspections that would look for any cracks in the beams that would warrant emergency repair. senior engineer gary peterson said contractor urs inc. assured them that any cracks could be detected before they posed a serious safety risk.
inspections of 52 steel beams began in may but were suspended when concrete repairs began earlier this summer.
the inspection strategy was also deemed to be more cost effective, but peterson and state bridge engineer dan dorgan denied that money played a role.
engineers were to have met aug. 20 to discuss whether the inspections were effective or if they had to go back to the plating idea.
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what does everyone think should have been done?  of course, 20/20 hindsight says that the bridge should have been closed and repaired back in december.  and maybe the lesson learned here is not to mess around with deficient nonredundant structures.
but put yourself in the mndot's shoes.  it must have seemed out of the question to just shut down a high volume bridge like that.  that would be a polical nightmare.  better to go out and find an expert to do a study.  if the expert tells us everything will be ok, we can all breath easy.
what would you do if you were a rank and file dot or other government engineer faced with a similar situation?
i do not know about mndot but, at my agency, there are fewer and fewer high level people who care to discuss our very real and serious engineering problems.  all they seem to be concerned about is monitoring performance based on meeting schedule milestones.  what needs to happen in government agencies to avoid these types of catastrophes?

you can bet the pressure to keep that bridge open was enormous! there is also a tendency to hire the consultant that will give you the answer that you want.
i have already been in situations where the architect has told me not to use the words "structurally deficient" in a report because the owner would not be happy and it would cause too much concern. how many others have been put into this position?
accountability is required,
in the uk they brought in corporate manslaughter laws which held the directors accountable for such incidences.
the problem is that those that hold the power are too far removed from the consequences.
they had report that it was structurally deficient but they chose not to rectify the problem. monitoring is pointless if they are not going to do anything about it when problems are found - they had already found a problem which they chose to do nothing about.
i am sure there is more to it, but (in my opinion) this senior engineer should never have recommended inspections when it was already shown that the bridge was inadequate.
i love how they claim that money was not a factor, on what basis did they make these decisions then?
it will be interesting to see how this plays out when we have all the facts.
csd
aren't the politicans there to make the hard choices ?
personally i think it's stupid (and insulting) to be told "money wasn't the issue".
i think it's possible that the repair might have weakened the bridge (but then it would be a pretty lousy repair wouldn't it !).  i'm willing to bet it was an expert's opinion, and possibly only 1/2 the message was received "as is it might weaken the bridge; if you did this as well it'd be ok".
it sounds like the discussion at nasa before challenger's reentry ... it's like they say, if you want to know the price of safety, have an accident.
how many other bridges could you compile a similar audit trail of inspections, engineering recommendations, political pressure to change recommendations, etc.?
one wonders who the gov't really works for? in my industry, aviation, the faa is supposed to promote flying and promote safety--these two goals have a conflict; almost inevitably, the faa goes with the commercial airlines, especially when it relates to accidents. accidents are almost always "pilot error." i just got an faa publication that talked about 'wake turbulence' with the rather astonishing statement that there has never been a loss of life due to wake turbulence. if you are thinking of that airbus that crashed in november 2001, you might recall one of the pilots pushed the rudder over one way then the opposite, trying to maintain control of the aircraft that was flying into severe turbulence caused by a much larger aircraft that took off right before it. because the pilot overcorrected, causing the tail to break off from the severe aero loads, the accident's cause was 'pilot error.' the wake turbulence was a 'contributing factor.' this seems ludicrous to me--if the plane had not flown into heavy turbulence, would all those people on that plane survived the take off of that airbus? i believe the answer to that question has to be "yes." or the opposite, would anyone have died if their had not been heavy turbulence? i'd say that one was "no." sounds to me like 'wake turbulence' was the accident's cause, not pilot error. but i am just a lowly engineer and a   
"i am sure there is more to it, but (in my opinion) this senior engineer should never have recommended inspections when it was already shown that the bridge was inadequate."
not practical.  a staggering percentage of the bridges in this country are "inadequate".
hg
in my opinion it is not up to the engineers doing inspections to determine what is or isn't practical, only to offer clear, unambiguous opinions of the adequacy of the structures and recommended course of action if repairs are needed.  recommending inspections vs repairs could be argued till the cows come home, but deferring maintenance in my opinion is rarely a cost effective method of managing our infrastructure.  it only increases the cost and risk to the public. management should be making the hard decisions of setting priorities for the repair work.  the politicians can then decide which departments need increased funding...
it is an old story, isn't it?  but what should a lowly engineer do when he is in the thick of it, after a鈥攅s have been covered by 鈥渄ocumenting the recommendations?鈥?nbsp; stand on his desk and scream?
this is certainly a dilemma for the engineer. aerospace is just full of similar examples--the engineer at morton thiokol who screamed and jumped up and down about the seals on the shuttle boosters; the engineer at douglas who had a similar reaction with the design of the dc-10 doors. each is considered a seminal example of management overriding engineering recommendations. on the other hand, i'll bet there are many counterexamples in which engineers 'cried wolf' so to speak, management ignored calls for change, nothing happened anyway.
cvg, what is or isn't practical is by all means a necessary consideration for any engineer.  pie in the sky is pointless.  in an ideal world, a state dot would have all the funding it needed to fix the bridges that should be fixed; replace all those that would cost more to fix than replace; repave all the roads that need repaving (dangerous surface conditions, doncha know); upgrade the guardrail that needs upgrading; replace the signage that has been stolen (for the aluminum), defaced, or weathered away; provide at least slightly competetive salaries for employees so that there can be engineers to make the kind of decisions you want them to make; upgrade to only two versions ago (instead of five) of autocad, office, windows, and other software and get computers that will run said software; and so on.  (note that things like cost-of-living raises or keeping up with healthcare costs aren't even on the list.)  
this isn't an ideal world.  ultimately a dot reports to a politician.  an executive director who sticks their neck out too far gets replaced with one who won't.  their funding priorities are not always theirs to set, and even if they are, it's not as black-and-white as you seem to imagine.  so they look at the cost of, say, replacing this bridge this year vs. replacing it next year, on engineering advice that it doesn't seem to have anything wrong with it that is of such immediate concern that it can't wait another year, and spending that money on other efforts to make other roads safer.  or on such wasteful notions as the first cost-of-living wage increase in many years for the state employees.  i could go on and on, but i've said enough.
what happened in minneapolis is awful, but i doubt it will be able to be pinned down to any specific act of negligence.
hg