The newest sports and entertainment arena located in downtown Los Angeles is the Staples Center. Situated on a congested site adjacent to the existing Convention Center, the arena seats up to 20,000 for professional sporting events and up to 22,000 for concert or stage events. The overall floor area is 960,000 sq ft (89,200 m2), which is about 1.5 to 2 times greater than other typical arenas with this seating capacity. Its sleek, modern design, with curved perimeter walls that slope outward from bottom to top along with the numerous offsets and curved shapes, contributes to the dynamic look and feel of the building. What is truly noteworthy about this project is that the start of excavation began on March 23, 1998 and the first public event took place on October 2, 1999, a mere 18 months after groundbreaking. In a year when at least five major arenas were opened across the U.S., the Staples Center project is the largest, most complicated, and by far the most quickly constructed of them all.

An eclectic mix of concrete systems was utilized in this arena, which contributed to the short time to completion. The superstructure of the stadium consists of a composite precast / cast-in-place system. According to Mark Josten, senior Project Manager for PCL Construction Services, Inc., this system was the key to the overall fast schedule. Work on the precast and cast-in-place systems occurred simultaneously.

Horizontal Framing

In the seating bowl, precast raker beams, stadia units (seating risers), and stairs are utilized. The horizontal framing in the "typical" bowl levels consists primarily of precast pretensioned beams and girders. Typical bays are 30 ft by 28 ft (9.1 m by 8.5 m), with the girders spaced 28 ft (8.5 m) on center and the beams spaced 15 ft (4.6 m) on center. Due to the circular and oval grid layouts, many of the beams are not parallel to each other. Typical girders and beams are 24 in. (610 mm) wide by 36 in. (915 mm) deep, and 12 in. (305 mm) wide by 24 in. (610 mm) deep, respectively. A 6-in. (150-mm) thick slab with mild reinforcement spans between the beams.

In the suite levels, the required floor-to-floor spacing limited the structural depth to 30 in. (760 mm). Thus, 48-in. (1,220-mm) wide by 21-in. (530-mm) deep prestressed girders with a 9-in. (230-mm) thick post-tensioned slab were utilized. Along the front edges of the suites, facing the arena bowl, prestressed U-shaped units (channels) serve as both the seating riser for two rows of seats at each suite and the girder carrying the front edge of the 9-in. (230-mm) slab.

Outside of the main bowl are secondary spaces referred to as "saddlebags" that house concessions, rest rooms, lobbies, and building services. Within these areas, 21-in. (530-mm) deep beams are arranged in radial directions and are supported on the inside end by the bowl shear walls or ring beams and by precast columns near the outer edge. These beams vary in width from 24 in. to 36 in. (610 mm to 915 mm). The slabs are typically 7 in. (180 mm) thick with mild reinforcement and span between the beams, which are spaced between 14 ft (4.3 m) and 20 ft (6.1 m) on center.

Cast-in-place, post-tensioned transfer girders are utilized over the loading dock and marshalling areas in the arena basement. The largest of these girders, which carries major column loads from the roof, spans 60 ft (18.3 m) has a 96-in. (2,440-mm) square cross-section, and has approximately 8 million lb (35,585 kN) of prestressing force applied through bonded, bundled tendons. These girders were originally designed in structural steel, but it was determined that steel plate girders would have been more expensive than concrete girders and that the steel fabrication could not meet the aggressive construction schedule.

Vertical Framing

Precast columns with a variety of cross-sections are used, including 42-in. (1,070-mm) elliptical, 24-in. and 36-in. (610-mm and 915-mm) circular, and a wide array of rectangular and square sections. Many of the bowl columns contain three different cross-section shapes within one precast column piece. The longest one-piece columns are approximately 110 ft (33.5 m) tall. Some of the perimeter columns are spliced, with top segments up to 50 ft (15.2 m) long on top of 102-ft (31.1-m) base segments, since they were too large to transport to the site in one piece. The columns at the front of the luxury suites include 6-ft (1.8-m) long cantilevered beams that were cast monolithically with the columns to support the precast channels at each suite level. The elliptically-shaped columns at the main entry lobbies are battered out at a 10-degree angle. Spread footings are mainly used to support the columns.

Lateral System

For seismic considerations, the lateral-force-resisting system of the main bowl area consists of four curved cast-in-place shear walls that follow the perimeter of the bowl and ten cast-in-place shear walls that are oriented along the radial lines. The curved walls, which are up to 175 ft (53.3 m) long and 160 ft (48.8 m) tall, vary in thickness from 42 in. to 48 in. (1,070 mm to 1,220 mm), while the radial walls, which are up to 50 ft (15.2 m) long, are 30 in. (760 mm) thick. Large mat-style grade beams support the walls. Cast-in-place ring beams at each floor level tie the circumferential walls to the precast columns between them. The office wing, situated between the saddlebags, utilizes three sets of concrete moment frames in the north-south direction and four shear walls in the east-west direction. The office building is tied to the arena structure at every level except at the office roof.

Team Work

A cooperative and team-oriented approach among the designers, contractors, and subcontractors enabled the project to be completed in spite of the aggressive schedule and the numerous changes that occurred right up until the end. These extensive changes could be accommodated without delays since the concrete framing system was very flexible. No other material could have provided the flexibility and economy to accomplish the myriad of functions required for this project.

Credits

Owner: Los Angeles Arena Company
Architect: NBBJ Sports & Entertainment, Marina Del Ray, CA
Structural Engineer: John A. Martin & Associates, Los Angeles, CA
General Contractor: PCL Construction Services, Inc., Glendale, CA
Precast Concrete Fabricator: AT Curd Structures (wholly owned subsidiary of PCL), Rialto, CA
Concrete Supplier: Catalina Pacific Concrete, Azusa, CA

 
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