Bonner Bridge (Outer Banks NC) Collapse During Demo

[ImminentCollapse]

https://www.obxtoday.com/federal-in...YGlmTkwhj1gFcRG8HBnnxmQlbcd0m2BDb4nu2EhR5vcJE

I don't think that link is going to work......just Google for yourself.

I'll be interested to hear more details. Taking down simple spans is not out of the ordinary in the bridge world even though the site is difficult. Looks like it hinged at mid-span.

IC

 

[waross]

PCL Constructors is the lead contractor on both the construction of the Marc Basnight Bridge and demolition of the Bonner Bridge.

PCL is a strange company;
They have been in the top ten of several surveys of "The Ten Top Companies to Work For."
Those surveys invariably only include the managers and supervisors (Who own the company. When they retire they must sell their shares.) and office staff.
The surveys don't include the thousands of tradesmen who do the actual work for them.
Among most tradesmen they are rated the worst.
PCL has bragged about their safety record.
They play every dirty trick in the book to avoid accepting responsibility for workers injuries.
One trick whan a worker suffers a painful but not life threatening injury is to give the worker some powerful pain medication with instructions not to take the pills until instructed to.
The injured man is then left sitting in a room by himself, in pain, looking at some pain medication.
After several hours a drug test is given.
If the worker has taken any of the medication, he is fired and his claim disallowed on the basis of drug use.
I have seen this first hand.
Some years back, PCL refused to abide by a WorkSafe rule that all temporary power circuits on a construction site must have GFCI protection.
Citing a general regulation that "A better alternative" was allowed, PCL claimed that their "Better alternative" was an assured grounding program.
This involved a labourer with no electrical training using a receptacle tester every three months to check all extension cords.
Tools were not checked.
The authorities chose not to enter a protracted legal battle over this.
They chose a quicker and cheaper solution.
The next copy of the regulations had a slight revision.
In the section on GFCI protection, one line was added.
"This rule does apply to PCL."
What is the moral and purpose of mentioning this?
Don't believe any information given by PCL as true.
They will lie and cheat.
They don't play by the rules.
Cover Your ASSets is SOP and more important than the truth to PCL management.
Every manager is an owner and every manager is watched by the other owners.
"Don't worry. It's not your money."
In PCL it is the manager's money and the money of the other managers watching.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Pete_K]

Couple years ago, while working on the new bridge, PCL cause a power outage for the entire Hatteras seashore because while setting a pile to the side for storage, cut thru the buried power cable. In the height of rental season.

 

[FacEngrPE]

Ocracoke Island is at the end of an 82 mile long feeder. When driving along the access road, ir feels like you are driving out into the Atlantic ocean.

Here is a screenshot of the north termination of the cable that was cut in 2017, - now repaired.

This is the south termination post repair.

Here is some history

http://www.villagecraftsmen.com/news022117.htm

This was reported at the start of the 2017 outage

https://www.13newsnow.com/article/n...ras-ocracoke-estimated-1-2-days/291-460210009

Access to the island was disrupted from July 27 to Aug 5 2017 (power was restored Aug 4)

https://www.sunrealtync.com/hatteras-island-july-2017-power-outage-updates

Ocracoke Island is one location where having a "microgrid" able to continue to carry part of the islands loads is almost a necessity. They still have a 3MW diesel alternate power plant.

https://www.utilitydive.com/news/ho...-most-of-the-lights-on-during-last-mo/503806/

 

[phamENG]

FacEngrPE - have you been out there recently? I took the ferry across in October around high tide. They've lost so much of the beach between the terminal and the airport that the surf was crashing over jersey barriers sitting on the shoulder.

 

[FacEngrPE]

No - actually have been just local for the last year, perhaps this summer I will get a chance.

Last time I drove NC5, 3 years ago, there were spots where ocean water was getting on the roadway. The problem of course is that barrier islands want to move and our structures do not. Eventually nature wins.

 

[phamENG]

Eventually nature wins.

Don't try to tell the Army Corps that.

I love the lighthouse and I think the system they worked up to move it was brilliant, and I love going out there every summer (I have a big OBX sticker on the wind shield of my old Jeep), but trying to keep those islands where they are is already expensive and is going to become ruinously so in no more than a generation or two - quite possibly less.

 

[Lomarandil]

I'm curious about how the right hand support pancaked down. I think that the girder hinge at midspan is more likely a secondary failure point -- with at least some cross bracing in place, the girders should have most of the original capacity in strong-axis bending (with much less demand), and the collapse doesn't seem to be a result of a significant lateral event.

My uninformed guess would be that the right hand pancake could not occur without some preliminary column demolition. Which would be an odd sequencing choice with deck segments & workers remaining on the span (even if all panelized).

Maybe the schedule pressure led to some ill-advised attempts at "crashing". That term might take on new meaning.



----
just call me Lo.

 

[waross]

From the original news report;

Shoaling along the ocean sandbar slowed the Bonner demolition process which was expected to only take around 6 to 8 months after N.C. 12 was moved to the new span.
The conditions prevented barges from leaving the inlet with the concrete remains that were being placed along several artificial reefs offshore.
As the bridge was being dismantled, the concrete road deck and guardrails were cut apart and stacked on the support beams. It was then loaded on to barges, followed by the steel beams.

Speculation:
As the spans were removed, the concrete was stockpiled ahead waiting for the barges to load out the concrete.
The last span may have been overloaded with concrete waiting to be removed.

A question for the structural gurus:
Are the spans connected together rigidly, and if so, would the removal of an adjacent span lessen the load capacity of the remaining span?

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Lomarandil]

The tapered profile indicates that this was originally a continuous span girder. So yes, the removal of the adjacent span would shift and increase the moment demand profile on the remaining span (although not technically reducing the capacity).

That should have been accounted for in the demolition sequence (and less significant than the design live load of the bridge, which is no longer present). It's one of the basic principles of this sort of work -- but I don't know who PCL hired as their demolition engineer.

----
just call me Lo.

 

[waross]

Don't forget that they were increasing the loading by stacking demoed concrete on the span and were months behind schedule offloading the concrete.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Lomarandil]

I get that, but I've run the calcs to demolish very similar bridges, and some stacked up deck panels usually just aren't that significant until you're putting heavy equipment on the deck or cutting out the cross bracing.

----
just call me Lo.

 

[waross]

Thanks Lo.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!