By Mark Rea

Houston's new downtown arena fits nicely into the city's long history of innovative, state-of-the-art sports and entertainment facilities.

Located just a few blocks south of the George R. Brown Convention Center and Minute Maid Park, the new arena will be a key part of the continued revitalization of downtown, drawing more than 2 million patrons to 200-plus events a year.

The new downtown arena, designed by Kansas City, Mo.-based HOK Sport+Venue+Event and Morris Architects of Houston, will seat up to 18,500 people for basketball games, and feature 85 luxury suites on two different levels and 2,900 club seats with access to luxury amenities. The two main seating bowls are served by two concourses, with the main concourse at street level. The large, sunken lower bowl contains over 55 percent of the overall seating, the largest of any major arena, bringing fans closer to the game and allowing for walk-down seating.

Amenities include a 150-seat restaurant, ledge dining overlooking the playing court, two club-seat lounges, banquet space and significantly increased concession and restroom counts in contrast to Compaq Center. For suite and club-seat ticket holders, parking is provided in an adjacent 2,500-vehicle parking garage with a skybridge link to the arena.

The architectural design of the arena presented numerous challenges for the Houston-based structural engineering design team of Walter P. Moore & Associates Inc. and associate engineer Nathelyne A. Kennedy & Associates Inc. One of the most significant was the large sunken lower bowl, which places the playing court nearly 32 ft. below street level over four city blocks.

Excavated from the site were 315,000 cu. yds. of soil, the largest such excavation ever performed in Houston. A concrete drilled-pier retention system with 36-in. diameter piers at 44 in. on center and two levels of tiebacks were used to allow for excavation to the court level. The drilled piers were incorporated into the completed structure as the foundation for the exterior columns.

A shotcrete "skin" wall was applied to the piers and served as the final basement wall.
The depth of the excavation resulted in portions of the playing court being approximately 16 ft. into the water table.

Ulrich Engineers Inc. of Houston worked with the design team to develop temporary and permanent systems that allowed 250 gallons of water per minute to be dewatered from the site.

The ice slab for the Houston Aeros hockey team is supported on a 10-in., two-way structural slab over void forms with 18-in. drilled piers at 28 ft. on center each way.

Vehicle access to the event floor could not be accommodated on the site, therefore a ramp and tunnel from the adjacent arena garage provides access by going under Bell Street and into the arena.

Cast-in-place concrete was used to structure the elevated floors of the arena. The main and upper concourse levels use a 25-in. deep pan joist system. Limited floor-to-floor heights below the suite level necessitated that this level be structured with 10-in.-thick, two-way flat plates to maximize the plenum space and ceiling heights in the suites.

The seating bowls consist of conventional precast seating units with cast-in-place raker beams for the suite seating and upper bowl, and steel raker beams for the lower bowl. The lower bowl construction had to be delayed until the completion of the main roof to maximize the lay-down space for the roof trusses. Instead of concrete rakers, steel raker beams were used to allow for faster erection of the lower bowl after completion of the roof.

The arena has an oblong, shallow-domed main roof that projects above the concourse roofs. The main structure of the roof is one of the signature architectural features. Tapered steel-box-trussed supercolumns rise from the four corners of the arena to support the main roof trusses that run diagonally from the supercolumns, crisscrossing to form a prominent "X."

The main trusses, spanning 390 ft., are steel box trusses made up of W14 chords and diagonals with an overall depth of 26 ft. at the ends to nearly 36 ft. at midspan. At approximately the quarter point of each of the main trusses is a secondary planar truss - also made up of W14s - that spans 153 ft. on the east-west side and 110 ft. on the north-south side between truss legs.

The remainder of the roof is infilled with planar WT truss girders and steel joists. The roof is stabilized by eight pairs of steel-braced frames along the length of the perimeter steel ring beam.

In addition to the challenges of solving the complex geometry of the roof, it also had to be designed to resist 110-mph hurricane winds. Fort Collins, Colo.-based Cermak Peterka Peterson Inc. performed extensive wind-tunnel testing to determine the design wind pressures for the roof.

The results indicated significant downward pressures on the main roof, which would have not been required by the wind provisions of the building code. Because of the sensitivity of long-span roofs to internal pressures, the effects of broken glass during a hurricane event were also considered.

Suspended from the main roof are two rings of catwalks, a huge scoreboard and speaker cluster and end-panel scoreboards. Also hanging from the north and south ends of the main roof are two 1,500-sq.-ft. mechanical rooms that house the main air handler units for the arena bow.

The roof structure also supports a distributed rigging grid designed for up to 120,000 lbs. of rigging load from an end-stage or center-stage configuration, accommodating the heaviest of today's concerts.

When the new Toyota Center opens this fall, it will be one of the city's premier destinations. With complete accommodations for NHL hockey, the new building will be key element to Houston's attempt to attract a NHL team.

The arena will also allow Houston to pursue hosting national and regional events such as the Big XII basketball tournament, early rounds of the NCAA Tournament and the NBA All-Star game. Coupled with Minute Maid Park and Reliant Stadium, the new arena will complete the cycle for Houston with three new sport facilities.

Dennis M. Wittry, PE, SE, is managing director of Walter P. Moore & Associates Inc.'s Houston structural engineering operations.