Less than 10 year old, 25 story McGuire PT building in Seattle that was demolished back in 2010 ...

[Ingenuity]

I recall the 'shenanigans' of the McGuire apartment building in Seattle back in 2010 (Link 1 and Link 2). Summary ==> 9 yo, 25 level PT building that had some strand corrosion issues at tendon ends due to water/moisture penetration from live-end grout pockets...fast forward to 2010/11 and it was demolished! I don't recall if it was discussed here at Eng-Tips at the time.

Well I just read this report Link3 by Bondy, Poston et. al, and whilst the authors do not mention the McGuire building by name (to protect the innocent/guilty?) it is obvious it is indeed the project they refer.

Always interesting in getting the 'other side' of the opinion.

 

[hokie66]

Why continue to use a system which has so many pitfalls, when bonded post-tensioning largely eliminates these workmanship issues? Unbonded PT is not allowed in Australia, for good reasons. But we need to be vigilant to keep it out.

 

[Trenno]

"Pitfalls" as in "Pitting" as in "Corrosion" ??? Haha

 

[msquared48]

It was an unsafe condition that had to be rectified, and quickly, and it was cheaper to demolish the structure than fix the problem. It was a major local story at the time.

Mike McCann, PE, SE (WA)

 

[CELinOttawa]

Stupid waste.

 

[asixth]

Had some interesting info in there though. I had something similar a few years back when performing a comprehensive testing procedure for "temporary" rock anchors that had been tying back retaining walls for years. These were unprotected strand and underwent some similar deterioration.

 

[Ingenuity]

I have been directly involved with the design, construction and repairs of both BONDED and UNbonded PT for bridges and buildings, and both systems have their own "issues", but on this project it appears that the owner's (part of the local carpenter's trade union) agenda was they just wanted it demolished.

I have seen some totally screwed up UNbonded PT structures (with massive tendon blowouts and spalls, some with deflections that were of magnitude of 50% of the slab depth, others with 75% of the tendons corroded in a single band etc etc) but they were usually 25+ years old and they were repairable - economically repaired (but not cheap) compared to demolition. Certainly seems like a drastic step to tear it down.

One engineering side treats it like terminal cancer and the other engineering side takes a totally different rationale - and the lawyers win regardless!

 

[msquared48]

The problem has encouraged local engineers to become more bonded.

Mike McCann, PE, SE (WA)

 

[JStephen]

So did they rebuild it? Is it still in litigation?

 

[Ingenuity]

An out-of-court settlement was reached in 2011, and it was disassembled from the top down, floor by floor, with demolition completed about mid-2012.

The owner's intend to re-build, however, I am not sure if they are/have to date.

An engineering firm retained by the Owner's (Carpenter's Tower, LLC) concluded earlier this year that cables were likely to start breaking next year, and about one-third would fail by 2019.

After reviewing that and other engineering reports, Jonathan Siu, the Department of Planning and Development's principal engineer and building official, said in an April 9 letter to Kennedy that "the building does not appear to be unsafe at this time."

But Siu also wrote that the city intends to issue an order later this year declaring the McGuire unsafe, ordering that it be repaired or vacated by Dec. 31, and requiring that it be demolished if it's not fixed.

Seattle Times link of above quote.

I am not sure how the owner's "...engineering firm concluded that cables will likely start breaking next year and about one-third would fail by 2019", but I do know we shall never know, in this instance!

 

[Ingenuity]

This 'corroded' strand was removed from the building and tested to failure at a load (stress) of 258 ksi (min UTS of new strand is 270 psi).

Hard for me to comprehend that this resulted in a 25 story building being demolished.