Minneapolis I35W Bridge Collapse

[Bob Buchanan]

Am watching the news report of the collapse of this bridge.

The pic I have attached looks very frightening to me. Note that the entire water span was supported by four concrete pillars. Also, note that the distrubution of all that weight was being handled by the steel connectors atop each pillar. And the bridge I understand was as much as 40 year old. Over the years, more and more stress is added to these old structures and it appears in this case, they just tried to add too much.

I pray for those that were on that bridge this evening.

 

[Tom]

Bob,

I too have been following the reports. I'm continually reminded of the potential for bridge collapse as we drive around the state and the country. Just recently we crossed a very narrow bridge to a campground on the American River. When I subsequently viewed the structure and supports from below, I was looking for an alternate way out of the campground. The steel appeared to be under-engineered and the concrete supports had eroded to the point of exposing the rebar within. Very scary.

 

[Ned]

We just crossed that bridge with the motorhome last May and have crossed it numerous times before.  That's could cause a real traffic problem in downtown MPS although there is a way around it.

 

[Tom]

Have bridge inspections stopped or has their frequency changed?

Edit: Here's some info on Federal bridge inspection standards, but I haven't had a chance to digest it.

 

[Summersky121]

We just crossed that bridge with the motorhome last May and have crossed it numerous times before.  That's could cause a real traffic problem in downtown MPS although there is a way around it.

Do you know if that area is prone to small earthquakes?  I wonder if tremor could have set it off. 
It's so sad, people waiting to hear from their kids and loved ones.  Very hard to absorb.

 

[Ron]

Have bridge inspections stopped or has their frequency changed?

Edit: Here's some info on Federal bridge inspection standards, but I haven't had a chance to digest it.

Maybe the payoff are getting larger. ;D ;D ;D

 

[Tom]

It's hard to believe that folks are still in the water. An uninformed local (SF Bay Area) newscaster commented that "the night is young". It was past 6.00pm PT when she said that and I guess she hasn't figured out the time difference. They interviewed a Bay Area fire chief and he made some recommendations on how the response should be handled (e.g. get the untrained/voluntary responders out of the way and let the pros deal with it).

 

[Ron]

Really looks bad.  Bet we will all think of this when we drive across bridges for some time.  Very unfortunate incident.

 

[Tom]

Ron,

Following the 1989 Loma Prieta earthquake in the San Francisco Bay Area, I "think of this" every time I go under a freeway overpass. If traffic comes to a halt, I try not to be stuck under the overpass, but sometimes there's no alternative and I can't wait to get out from underneath. It's almost 18 years later and they're still working on retrofitting Bay Area bridges and overpasses.

 

[Ron]

I knew some folks that  refused to go over the Narrows Bridge by Tacoma Wash after they saw pictures of the first one comeing apart.

 

[Tom]

Do you know if that area is prone to small earthquakes?  I wonder if tremor could have set it off.

It's not clear if you're asking about the bridge we crossed in Northern California or the one that collapsed in Minnesota. If the former, I honestly don't know, but would think it's out of the predominant fault areas. If the latter, I doubt they had an earthquake in Minnesota.

 

[Ron]

We will just have to wait till they investigate and find the cause.

 

[Tom]

Death toll is up to 7. Thank goodness the 60 kids got off the bus OK.

It's getting dark and rescue workers are reportedly giving up until tomorrow.

 

[Mike (ex-f-221)]

I'm just looking the live stream at MyFox Twin Cities. Before they showed the transmission of 7pm. Could be much worse - but it is bad enough.

 

[wrenster7]

From what I have heard this morning- there have been bridge inspections. If we really knew how many bridges are bad, we wouldn't be driving across any of them. In 2001 this bridge had a rating of 4 out of scale 0-9. 9 is the best. So if this is the case, think about how time can change this number. May God bless the families that had people who passed from this disaster.

 

[Ned]

The inspections in 2005 and 2006 showed the bridge needed repairs and the governor vetoed the funding.  This according to Fox News this AM.

We have quite a bit of family in the area but all are safe and were not involved, thankfully.

 

[Ron]

The inspections in 2005 and 2006 showed the bridge needed repairs and the governor vetoed the funding.  This according to Fox News this AM.

Then if that is true the govenor should be held accountable for all injuries, fatalities, and damages to personal property.

We have quite a bit of family in the area but all are safe and were not involved, thankfully.

Glad to hear that.

 

[Ned]

The bridge was not found to be unsafe in those inspections, but was to be watched and eventually repaired or replaced.

 

[John From Detroit]

Then if that is true the govenor should be held accountable for all injuries, fatalities, and damages to personal property.

I agree Ron, even if the bridge was found "Safe but in need of repair" the Governor who vetoed funding should answer for it.


Alas, never happen

 

[Bob Buchanan]

From what I have heard, stress fractures were found on some of the steel truss members in the '04 inspection. After looking up at the bridge from the pic I posted, I just can't believe it was still in service. The span across the water is a simple steel truss supported by only four concrete columns, and that design is just not used anymore for those distances. Note and compare the structure of the newer bridge upstream. It's not only a double arched concrete structure, but also has a third abutment in the center of the river.

The NTSB was on scene this AM and will be conducting the search for cause of failure. While with the Bur Reclamation during the 60's, I was a civil engineer and programmer involved for a number of months in their huge Denver materials testing laboratory. When a structure such as a steel transmission tower failed, they would disassemble each steel member and force it's failure in their testing machines.  Steel takes tension whereas concrete takes compression. A column can made of steel if it's large enough, but generally, concrete will be used if possible -- because it's cheaper. In a truss bridge, whenever a steel member goes into compression, another takes over in tension (as the live vehicle loads move across). BurRec labs had testing machines that could pull a 10 inch diameter steel bar apart in straight tension. As they failed each member, they would compare the actual tensile strength to the design strength -- and eventually, the culprit members would be known. Would imagine that is what the NTSB will be doing -- if only on suspect members. They may even send them to BurRec Denver labs, as other agencies have done over the years.

With the years of experience and the methods they have developed, am sure they will pin point exactly why this happened -- and who is to blame. I agree the governor is in deep trouble if they find something that could have been fixed were it not for a funding veto.