mixed_westinThe Westin Diplomat Resort and Spa in Hollywood, Florida, consists of five main buildings, surrounded by additional site structures, creating a beachfront resort complex that opened in February, 2002. The original Diplomat Resort was a popular tourist destination in the late 1950s and ‘60s. It eventually lost its luster, and by 1990 had almost entirely shut down. In 1998, the site was acquired by the pension fund of the United Association of Plumbers and Pipefitters, who demolished the old Diplomat in order to clear the way for a new world class resort.

The resort is anchored by a 41-story Westin Hotel, with a cutout in the middle acting as a “window” to the Atlantic Ocean. The hotel is adjacent to an eight-story convention center, including a column-free exhibition space almost the size of a football field. The pool deck behind the hotel contains both an elevated swimming pool and a pool at grade level, both surrounded by cabanas.

A pedestrian bridge crosses Florida route A1A, linking the hotel to a complex of retail stores and dining establishments along the Intracoastal Waterway. These shops form the base of a pair of eight-story parking garages. A two-story energy plant alongside the garage houses mechanical, electrical, and plumbing systems for the resort. Eventually, two condominium towers will be built, one along the Atlantic and one along the Intracoastal.

The hotel is a conventionally reinforced flat plate structure. Flying table forms were used to cast 9-inch-thick typical floor slabs on a three-day cycle. In order to protect against chloride intrusion resulting from the ocean environment, a corrosion inhibiting admixture was used in the balcony slabs. Shear walls, varying from 18- to 24-inches thick, surround the service cores and extend as outriggers to the building perimeter, providing lateral stability. Column and shear wall concrete was specified with a compressive strength of 10,000 psi at the base of the building.

The curved surfaces, reminiscent of sails or waves, are parchitectural features of the hotel. Sloped columns were provided to allow slab edges to step back from floor to floor. The 10-story-high cutout in the middle of the hotel left 24 stories unsupported above. In order to carry these loads, four, two-story-deep transfer girders span approximately 80 feet. These girders are 140 feet above the ground, precluding conventional forming techniques, which would have necessitated the erection of an enormous scaffolding tower. Instead, four steel trusses were lifted into place. These trusses supported the girder formwork and a temporary hanging work platform, and were encased inside the girders.

The convention center incorporates multiple structural systems. The roof over the upper level exhibition space spans 155 feet, using steel joists. The real challenge, however, was the floor. In order to provide the desired flexibility for event planners, a 200-psf live load capacity was needed. Concerns about wave action from a hurricane storm surge dictated that this space be elevated, rather than located on grade, as is often done with convention centers.
Post-tensioned girders up to 9 feet deep span up to 135 feet. The heaviest girders contain 195 prestressing tendons. Steel beams were used to support the formwork, since the weight of the girders precluded the use of conventional shoring systems. Hollow core precast, prestressed plank spans between the post-tensioned girders, avoiding the need to erect slab formwork 35 feet above the floor.

The ballroom level below the exhibition space spans 62 feet, supporting 150-psf live loads. Post-tensioned girders 48 inches deep were designed to support both post-tensioned and conventionally reinforced slabs. Parking levels below the ballroom were built using a keystone joist system popular in Florida due to economy and speed of erection. In the keystone joist system, precast, prestressed joists span 62 feet between beams. The beams have a 6.5-inch deep precast bottom with embedded stirrups. The joists and beam soffits were set on shoring, after which the slab bottoms and beam sides were formed. The slabs and beams were then poured monolithically.

The two garages are separated by a glass canopy supported by a steel space frame. This space frame sits on 48-inchdiameter concrete columns. The space frame-to-column connections included a significant number of sliding connections designed to allow the space frame to move without inducing forces in the frame. This meant that the frame could not be relied upon to brace the tops of the columns. Therefore, the columns had to be designed as fixed-base cantilevers.
In order to make these columns more rigid, they were post tensioned. Each column had six ducts, each containing nineteen, 0.6-inchdiameter tendons, inducing compressive force of 3,800 kips (a kip is a non-SI unit of force which equals 1000-pounds force)  .

With a combination of different framing systems, concrete provided the much needed flexibility to accommodate the varied layouts, functional requirements and prominent architectural features of the building for this project.


Nichols, Brosch, Sandoval & Associates, Coral Gables, Florida

Structural Engineer:
DeSimone Consulting Engineers, New York, New York

Concrete Trade Manager:
B&R Building & Renovation, New York, New York

Concrete Contractors:
Form Works
Quality Concrete and Rental