Investigation of the Collapse of the Chirajara Bridge, Columbia

[Ingenuity]

Follow up on this closed thread: thread815-434353

ACI's Concrete International magazine (June 2019 issue) has a 6 page investigation paper entitled:

Investigation of the Collapse of the Chirajara Bridge. A summary of a study conducted by members of ACI Committee 133, Disaster Reconnaissance.​

Available here for ACI members: Link

For those who do not have access to ACI and CI magazine here is a summary of the conclusions:

Conclusions:
In our opinion, the West Tower of the Chirajara Bridge collapsed because post-tensioned reinforcement placed in a slab meant to act as a tie between columns was insufficient by a large margin. In contrast, in the perpendicular direction (that is, in the direction of the deck), where no large stresses would have been expected, this slab tie (or tower slab) was provided with nine times more reinforcement. Had the provided reinforcement been rotated 90 degrees, the collapse would not have occurred.

Bold added by me. Wow!

 

[12345abc6ttyui67]

Without access to the article, is the implication that the reinforcement specified by the designers was in the wrong orientation, or was it specified correctly but placed by the contractor in the wrong orientation?

 

[JAE]

I think the implied conclusion is that the design was flawed, not the construction - they state in the very last sentence "This tragic example emphasizes once again the importance of peer review of all projects..." This suggests to me that a peer review of the design was needed here.

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[12345abc6ttyui67]

Thanks JAE.

I'm no bridge or concrete guy but to me it's obvious which way the reinforcement is required at the base of the pylon. Really beggars belief there are people out there designing these things who can't see the fundamentals...

 

[JStephen]

Makes me wonder if this was a general goof, or a matter of somebody getting the steel quantities right and then detailing in the wrong direction and it didn't get caught.
I remember in the original thread, there was another similar bridge existing, wonder if it has these issues?

 

[waross]

A friend of mine in Latin America asked for my opinion on a concrete failure in his new home.
The house was designed with a cantilevered concrete canopy extending about five feet horizontally along one side of the house.
When the men started to remove the forms the canopy started to fall.
It was poured in two lifts with the break line vertically over the point of support.
The re-bar was laid on the forms and the concrete poured on top, with no attempt to raise the rebar.
The concrete was spec'ed at 2800 psi.
Test cores were taken at about 90 days and failed at about 1400 psi.
The concrete appeared to have been poured with much too much slump and seemed to have washed out in the area of the failure. The concrete wasso poor in the area of failure that it was not possible to take test cores.
I pointed out to the owner that the re-bar should have been much higher or it would not do any good.
The owner went to talk to the engineer.
The owner came back to me and reported that the engineer had said that was as it should be.
"The re-bar has to be on the bottom or the concrete will fall off."
I met a lot of very good engineers in Latin America.
I met some and saw the work of many more who weren't quite ready for prime time.
Structural, electrical, road construction, bridges.
We have heard more than a few examples in this forum of engineers looking for help to remedy engineering shortfalls.
Different culture, different rules.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[3DDave]

No different than Wright's Falling Water fiasco - Wright wanted the rebar on the bottom for the same reasons.

 

[JAE]

Wright also stated that extra rebar would weigh too much and cause further structural collapse.

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[BridgeSmith]

Wright was a great artist, I'll give him that, but as with so many, greatness in one area blinded him to his limitations in others, and led to ugly failure. At least his overextended ego didn't cost lives, as others' have.