The 1.2 million-square-foot Denver Convention Center Hotel rises 438 feet and is the first high-rise building to be constructed in the downtown Denver area in many years.
The 1,100-room, five-star hotel building is composed of two towers joined at the elevator cores standing above a five-story “podium” whose footprint fills an entire city block. One guestroom tower rises to 37 stories above the street level and is capped off with a three-story, glass-enclosed beacon illuminated from within at night. The other guestroom tower extends to 27 stories above the street and is finished with a lounge on top that features northwest views of the city and mountains. The podium contains the hotel services, lobby, guest drop-off, and back-of-house functions. Underlying the building are three levels of underground parking along with mechanical rooms and the hotel laundry. Underground storm water detention vaults were also constructed as part of the parking garage.
The typical tower floor slab is a 7½-inch post-tensioned flat slab supported on rectangular concrete columns. The column sizes were varied, with the largest column having dimensions of 40-by-40-inches at the base. The stacking of different uses such as guestrooms, hotel services, and parking created many challenges necessitating the strategic location and transferring of columns.
The lateral-load-resisting system consists of concrete shear walls. The shear walls sit on a 73-by-73-by-6-foot thick concrete mat supported by 58, 42-inch-diameter concrete drilled piers. The building shear walls, that surround the guest elevators and brace the building against wind and seismic loads, are located at the extreme end of the upper guestroom floor plates. During preliminary design, it was discovered that this eccentricity produced an undesirable twist of the building during high wind loading. An additional shear wall at the far end of the floor plate, combined with stiffening of the core using high-strength concrete (8,000 psi), reduced the movement to acceptable levels.
With specified concrete strengths from 4,000 to 10,000 psi, this unique and complex project afforded many opportunities for innovation and for the use of specialized concrete admixtures. The concrete specifications were performance based to ensure the durability of the below grade, post-tensioned parking garage floors. The concrete supplier developed a mix design to limit the expected shrinkage to 0.05 percent. Through a collaborative effort with the contractor, slab support details were modified and improved to allow the slab to shorten with minimal restraint. As a result, the garage floors (which measure 400 feet in length by 200 feet in width without an expansion joint) are crack free and expected to perform without maintenance for many years.
The pace of this fast-track construction schedule had the contractor forming, pouring, and stripping one floor level every four days.
The hotel facilities complement the new convention center located across the street. Amenities include grand and junior ballrooms, meeting rooms, a full-service restaurant featuring a display kitchen, a convention bar, and a business center for guest use. Additional features include a health club with a lap pool, whirlpool, and outdoor terraces on the fifth floor.
The first floor beam-and-slab structure had to be designed to support a truck dock and a porte cochere/guest drop-off. The truck dock and porte cochere areas consist of a sloped concrete topping slab over a drainage mat and waterproofing membrane over an 8-inch thick, one-way concrete floor slab supported on concrete beams.
This unique and complex project afforded many opportunities for innovation and the use of specialized concrete admixtures. Specified concrete strengths ranged from 4,000 to 10,000 psi. Boral Micron3, a highly reactive pozzolan, was used to reduce permeability of concrete and corrosion of rebar for the underground post-tensioned slab parking garage. Agilia was used for self-consolidation and to improve flowability for the 8,000-psi and 10,000-psi mixes.
The enormous amount of concrete required to construct the hotel superstructure spurred efforts to minimize ready-mix costs without sacrificing performance. To accomplish this, the ready-mix supplier was allowed to develop concrete mixes free from the usual prescriptive constraints of the project specifications. Performance-based concrete mix specifications were developed that allowed the mix supplier freedom to create mixes that best suited the conditions of the project.
Performance criteria were specified for strength, durability, and shrinkage. It was left to the mix supplier (in collaboration with the contractor) to develop the appropriate water/cement ratios, slumps, cement contents, aggregate gradation, and addition of admixtures to satisfy all performance criteria as well as the contractor’s requirements for pumping, placement, and finishing.
Performance requirements limiting concrete shrinkage were especially important to ensure the proper performance and durability of the below-grade, post-tensioned parking garage floors. To minimize cracking of the slab due to concrete shrinkage, the mix supplier developed a concrete mix that limited the expected shrinkage to 0.05 percent. Cracking of concrete can also occur in post-tensioned slabs as a result of restraint stresses due to shortening caused by prestressing. Through a collaborative effort with the contractor, slab support details were modified and improved to allow the slab to shorten with minimal restraint. As a result, the garage floors (which measure 400 feet in length by 200 feet in width without an expansion joint) are crack free and expected to perform without maintenance for many years.
Denver Convention Center Hotel Authority, Denver, Colorado
Architect (Joint Venture):
Klipp Colussy Jenks Dubois Architects, P.C., Denver, Colorado
Brennan Beer Gorman Architects, LLP, New York, New York
Harold Massop Associates Architects, P.C., Denver, Colorado
The Roybal Corporation, Architects, Denver, Colorado
S. A. Miro, Inc., Denver, Colorado
Hensel-Phelps, Greeley, Colorado
Faulkner USA, Austin, Texas
Lafarge Construction Materials, Denver, Colorado