Saturday, October 10, 2009

Ocean Tower Settlement and Implosion


In 2006 construction began on the 31-story condo building known at the "Ocean Tower" . The hi-rise included a 4-level parking garage immediately adjacent and connected to it. In 2008 construction was halted when large cracks were observed in parking garage walls and in beams in the hi-rise.

In July 2008 the developers filed a $125,000,000 lawsuit against Raba-Kistner geotechnical engineers and the structural engineer and the general contractor Zachary Construction. Zachary however was later dismissed from the lawsuit.

Although the facts of the case are not disclosed and difficult to obtain, the lawsuit does reveal that the exploratory borings were no deeper than 100 feet, and the design pile depth was 95 feet in the final construction drawings. I think 401 16-inch diameter auger-cast piles were revealed to be under the hi-rise building footprint. Settlement of the structures was indicated to be 4" to 8" under the garage, and 8" to 16" under the hi-rise, which is catastrophic so the "leaning tower of Padre" is actually a reasonable moniker.

I would love to see the calculations by Raba-Kistner and by the structural engineer to find out the root cause of the flawed design (errors and omissions anyone). I can hypothesize, maybe Raba's engineer(s) thought the piles would be 100% skin friction piles but over-estimated the skin friction developed? Or maybe they did include end bearing capacity but didnt realize that the piles would end up 95 feet deep, just 5 feet above deepest exploration depth? Or maybe Raba did not analyze "group pile" settlement models? I also question the length to diameter ratio, it is pretty slender (95/1.33 = 71). Who knows, right now all i can say is that a geotechnical report for a project of this magnitude is usually written by one engineer and reviewed by another more senior engineer. I don't know whose 2 signatures were on the Raba report, but i would never hire these guys to be geotechs on my projects.

In late 2009 the owner hired Controlled Demolition Inc to start planning the implosion of the building since it was too costly and impractical to try and repair the structure, much less get anyone to move in considering the stigma now associated with the building.

See photos here:
http://texasgeotechnicalengineer.blogspot.com/2010/01/ocean-tower-implosion-photos.html


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