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Thursday, October 8, 2009

Leaning tower of Padre Island

According to The New York Times, Sept. 21 St, 2009, Business Section, The Ocean Tower on South Padre Island, Texas Golf Cost, recently known as “The Leaning Tower of Padre Island” will be demolished. This was announced by its developer.

The Ocean Tower, considered to be the most luxurious tower in the region, a 31-story condominium project with 151 units, spa and other amenities, is structurally complete and in the interior finishing stage.

It is also sinking more rapidly than the attached parking garage structure, causing cracks in beams and columns.

Not intended to be an evaluation of this particular matter without knowledge of th
e design parameters, geotechnical conditions and applied geotechnical considerations/models, we do, however, have some input. In a tower structure with a garage attached, uneven settlements are always expected and design compensations as well as construction considerations are always provided. This is because the tower’s weight considerably exceeds the garage’s weight.

Most of us at the Construction Advisory Group have worked at the Marquis Tower, a Miami Florida project, for four years, from Preconstruction to Certificate of Occupancy. The Marquis Tower is a 67-story luxury condominium, with an attached garage, structurally similar to The Ocean Tower. As at most buildings located on beaches, the foundation system of The Marquis Tower consists of pile caps supported by friction piles/caissons. It is reasonable to assume that a similar system has been used at the Ocean Tower on South Padre Island.

On projects like this -- and because of expected differential settlements between the two structures -- the garage is built when the tower is close to completion (concrete) thus giving the necessary time for the sinking process to settle and the garage to be built on a more stable geotechnical condition. For example, at Marquis Project, we started erecting the garage when the tower was 40 stories high and when completed, the anticipated garage settlements matched with the respective elevations of the adjacent tower slabs.

Realizing that we do not know the actual field related provisions taken to prevent the Ocean Tower situation, it is a matter of speculation whether the same constructability approach was in use.

4 comments:

  1. Recently, further complications are attached to this project since the implosion appears to be questionable as a method of demolition.
    The following are data related to this project and according to ENR:
    "The 381-ft-tall tower, designed by Datum Engineers Inc. Austin, has a two-way. flat-plate slab with 4,000 PSI concrete and top and bottom reinforcing",
    "Columns have 5,000 PSI concrete at and above level 18 and 6,000 PSI below. Mechanical splices were used on lower-wall reinforcing to avoid congestions from lap splices, The core measures 22 ft x 31 ft in plan with 2.5-ft-thick walls at the base."
    "The garage is 200 ft x 237 ft in plan and has 24-in-dia. concrete columns in 27 ft-wide bays.The foundation consists of 16-in-dia augered, pressure-grouted piles, 95-ft long. Of 800-plus piles, 401 are under the tower's concrete mat"
    This is by far more information than we had at the time of our initial comments.
    According to Mr, Loizeaux of CDI, "The biggest challenge is the garage's post-tensioned, unbonded-tendon beams, which run through the tower base"
    And here comes the same question again, "Is there a expansion joint between the tower and the garaje?"
    Not a critique, just a question since we don't have a complete knowledge of the design.
    I know Mr. Loizeaux since 1980 when CDI imploded The Blenheim Hotel and Tower in Atlantic City when building Bally Casino and they are indeed the dynamite demolition contractor.
    A great demolition problem, should the implosion method be used,
    The main restriction is avoiding the tower to drop on the garage since post- tensioning anchors can fly like bullets if the tendons are suddenly releasel.
    And this is why CDI intends to tilt the tower 15 degrees away from the garage and than blast it.
    Great structural engineering indeed.
    Let's not forget one very basic fact: Demolition via implosion is the best structural design in reverse.

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  2. could any part of this project be saved if you separated the garage from the building foundation and perhaps removed 4 or 5 of the top floors to reduce the weight.
    rosemary sanders

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  3. The garage is not contributing to the 16” of settlement that has occurred in the tower. These large settlements also create major slopes in the floors that make the floors unusable. Removing floors from the top would not make the settlement spring back to create level usable floors.The attachment of the garage to the tower did not contribute to the settlement of the tower. Separation of the garage from the tower would not prevent the large tower settlement.

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  4. Augered Pressure Grouted Piles:
    Barcus solves unique problems such as Sheeting and Shoring, Pressure Grouting, Helical Foundation Anchors and other construction related problems.

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