Mathews Bridge Breaking News

[Tacachale]

According to the paper the ship normally docks at Blount Island, and was being moved so the channel could be worked on. That required going under the bridge, but another ship from the same place went under just fine a few days ago. There's still no word exactly what happened, hopefully we'll hear soon.

[strider]

The 152 FT clearance number is the clearance at MEAN HIGH TIDE. basically meaning that the clearance is 152 feet at the average or median of all recorded high tides.  So if we have a higher than normal high tide, the clearance would be less but that is an unusual situation.  For Thursday at about 2:00 PM, it is pretty average and not yet high tide so at least the 152 feet and maybe even a foot or two extra.

The other consideration is the ship itself.  What is the clearance of it loaded to what is it empty?  Seems likely that someone either didn't bother to check at all or they used a loaded number.  A friend was close by and said he heard one of the tugs giving horn signals so I suspect at least one person saw it coming and tried to do something about it but a ship that big moving at all is a lot to stop. The bridge itself couldn't do it.

Frankly, from the damage and some of the descriptions I have heard, it would not surprise me if the state came back and said it had to be replaced.  I would not be looking for one side to be used in anyway as the damage is very severe and typically that type of structure works because of the small pieces making up the whole and if you remove one piece, all of it is weaker and easily can fail. 

[thelakelander]

So much for Lake Ray's theory of using the eastbound lanes.....

Standing at the top of a Mathews Bridge devoid of motor vehicles, Florida Department of Transportation bridge maintenance officer Will Watts summed up the damage he was looking at.

"This is as severe as it can get without a bridge collapse," Watts said. "Right now it's in such a state that we can't even put service vehicles up here."

Read more at Jacksonville.com: http://jacksonville.com/news/crime/2013-09-27/story/mathews-bridge-repairs-will-cost-plenty-and-take-least-month#ixzz2gBvoGIYz

[Ralph W]

It's commendable that they will be over cautious, keeping all traffic off the bridge. No one should fault that decision keeping in mind that although the vehicular traffic continued until someone reacted and closed the span and nothing happened during that time, that strike took out what appears to be a major chord and undoubtably weakened adjacent connections which could further deteriorate with added pounding by use even on the opposite side.

I'd like to believe that the original engineering took into account the possibility of an accident like this and the structure is braced accordingly and methods of repairs have already been precalculated.

[strider]

It's commendable that they will be over cautious, keeping all traffic off the bridge. No one should fault that decision keeping in mind that although the vehicular traffic continued until someone reacted and closed the span and nothing happened during that time, that strike took out what appears to be a major chord and undoubtably weakened adjacent connections which could further deteriorate with added pounding by use even on the opposite side.

I'd like to believe that the original engineering took into account the possibility of an accident like this and the structure is braced accordingly and methods of repairs have already been precalculated.

Luck played a part in all this.  The bridge could have come down from a hit like this.  I think the issue with assuming anything about the design loads and possible repairs are the facts that in many cases, today's traffic loads are way over anything imagined in 1950's and the issue of fatigue.  The bridge moves all the time.  Eventually, things get worn out from age and with this damage, the repair could be higher than the cost of replacing it.  Don't look at one damaged member, think the multitude of members damaged and twisted to some degree, including the damage you can't see but is there on the "good" side of the bridge. Even a little twist in a truss type structure can change the loads enough to reduce the load capacity of the structure significantly.   I am thankful they closed it in time.

[Ocklawaha]

EXACTLY, this is WAY bigger then the local media or the DOT boys are letting on. My immediate concern is the fact that the structure is 60 years old, and has had a long history of varied and increasing loads. Heres a little primer:

Whenever a steel object such as a bridge (or railroad car) is subjected to a tensile, cyclic load, a situation that occurs with vibration, rocking, or other slight movements, you will find 'METAL FATIGUE'. Metal Fatigue is a slow growth of cracks, many barely detectible by the human eye, throughout the structure.

The cracks grow very slowly at first but can dramatically increase with age. They are generally sped up by an increase of stress at the top of the cracks. Keep in mind with two opposing pieces of steel, both subject to metal fatigue, the mutual support is affected by an ever diminishing cross section of material.

Metal Fatigue is often found at a point of extreme movement, load bearing, or  where ever sharp corners, points, pins and such encounter the surface. Thus under a rail car for example, the 'center plate' where the car sits on the truck bolster is going to be a problem site, the car rocks and hunts and so does the truck, the center plate takes the brunt of the forces. This is why ships have round port holes rather then square ones. All of this is kind of hard to pull off on a bridge made of 90 degree steel beams. Even simple bolts and bolt holes can hasten the occurrence of Metal Fatigue.

It is often possible to find the source of the Metal Fatigue cracks, and some metals like mild steel are much less likely to develop cracks if engineered properly. Put those same forces or loads on aluminum and your toast!

Another factor that could well play into a disaster such as the recent one in the Twin Cities, is METAL FLAWS. There are two main types of flaws, systematic and statistical. Systematic flaws are usually fixed long before a product reaches market. These are flaws due to poor mold practices and the flaws themselves become predictable. Think of it as pressing a piece of clay against the same shard of broken glass, over and over again. You will always get an image of that same broken glass.
Statistical Flaws are the most dangerous and left undetected they can and have resulted in horrible death and destruction.

The statistical type of flaw includes gas cavities and non-metalic inclusions. These are encapsulated within the structural member itself and are IMPOSSIBLE to see. There are detection devices that use ultrasonic waves and a few other methods of scanning the structural members but on a bridge, the job would be daunting.

Add to these, a very hard hammer blow, and consider that hammer blow traveled the length and breadth of that bridge, and we've got a recipe for a major catastrophe. GO SLOW BOYS. WEAR YOUR PARACHUTES! 

Here is what a railroad rail flaw looks like onboard a 'Herzog Railroad Flaw Detector Car.'

[YellowBluffRoad]

That's the ironic thing, this bridge was in good shape, they'd actually just wrapped up refurbishing it during most of 2012 at significant expense, which is why it was closed half the time until relatively recently. Just in time to get hit by a ship.

And if it's closed for a month or more, that'll probably be just in time for them to move the ship back to its original berth east of the bridge, eh? They have to get a second shot at the bridge at some point. 

[YellowBluffRoad]

Not a good day for bridges yesterday:
http://www.cnn.com/2013/09/26/us/wisconsin-bridge-sagging/?hpt=hp_t2

Not a good week for bridges in general:
http://www.actionnewsjax.com/content/topstories/story/Sailboat-strikes-Bridge-of-Lions/Rd9kyjEDeEODKdZhRBp1RQ.cspx

[tufsu1]

EXACTLY, this is WAY bigger then the local media or the DOT boys are letting on.

do you know something they don't?

[spuwho]

A couple of months ago I tried to pull back up the FDOT/COJ website for the Mathews Bridge Replacement Project.

The site has been down for several years. I found parts of it on Rewind, but I wouldn't be the least bit surprised if it mysteriously reappears in the next week or so.

[Ocklawaha]

EXACTLY, this is WAY bigger then the local media or the DOT boys are letting on.

do you know something they don't?

Spoke with my bridge engineer friends at a social function tonight here in WGV. They've basically said it's going to be bid like next week and they are pushing for replacement and reopening within a couple of weeks. But when they saw what I wrote above, they all FULLY AGREED and added: 'They will HAVE TO REPLACE IT NOW for safety.' And... 'Expect a Cable-Stayed bridge with a clear center span.'

So maybe I do... We'll see!

[Scrub Palmetto]

And... 'Expect a Cable-Stayed bridge with a clear center span.'

I hope I'm not sounding facetious, because this is a sincere question: what is a clear center span, as opposed to an unclear one?

[simms3]

And... 'Expect a Cable-Stayed bridge with a clear center span.'

I hope I'm not sounding facetious, because this is a sincere question: what is a clear center span, as opposed to an unclear one?

I believe exactly what is sounds like.  See SF's new eastern span of the Bay Bridge for a recent example:





http://www.sfgate.com/bayarea/article/Bay-Bridge-made-to-withstand-major-earthquake-4778622.php#photo-5112243

[thelakelander]

Hmm. If that happens, I hope they can at least make room for transit, bike and ped. Also, that would mean the closure would last a few years and funding would have to be shifted from several other projects.

[billy]

You mean this incident could lead to replacing the Mathews?