Retractable Roof Facts
- Three panels elevated over the playing field and ballpark canopy.
- 560 foot span, track to track - just short of two football fields in length.
- 338,000 square feet of roof surface areas, or 7.76 acres.
- 13-minute operation time from fully closed to fully open position.
- Roof panels can be operated independently to produce micro shading effects.
- Fifth retractable roof built over a ballpark in the U.S.
An Engineering Marvel
The retractable roof consists of three metal decked operable panels: one upper panel and two lower panels. The East and West panels are at a lower elevation over the stands and the center panel is at the highest elevation with 200 feet clear over second base to allow for "pop-flies". The retractable roof mechanization system is supported by two horizontal concrete track beams approximately 548 feet apart and 750 feet long. When open, the Center Panel retracts to the west main entrance plaza and the East and West panels will retract underneath the Center panel.
The challenge is to move a combined 19 million pounds within 13 minutes, traveling at a speed of 39 feet per minute. Each of the three panels can move simultaneously or individually to provide partial shading to the field surface and patrons.
How it Works
Composed of nearly 8,000 tons of high-strength steel, the span of each retractable roof panel from rail to rail is approximately 530 feet at each lower panel and 566 feet at the upper panel. The opening created by the long span of the 45 foot deep upper panel trusses is wider than any NFL retractable roof stadium. The south track beam structure is lower than the north track beam to minimize the overall building height and allow for roof panel movement due to the effects of sun and wind.
The Mechanics - How it Moves
The concept behind how the roof moves is similar to a locomotive train. The roof mechanization system that moves the roof consists of 44 transporters each capable of supporting over 1 million pounds of load. The transporters are equipped with 88 wheels measuring 36 inches in diameter and 8 wheels measuring 15 inches in diameter that travel along parallel steel rails, similar to a locomotive. The roof mechanization is an electrically powered traction drive system with 76 motors with a capacity for 10 horsepower each (combined: 360 hp upper panel, 200 hp each lower panel).
The Roof Panels will be controlled by a single roof operator from a control room located inside the ballpark. The control system allows the roof panels to open or close with all three panels in motion simultaneously or a single panel individually to provide partial shading to the field surface and patrons.
As a LEED Gold Certified building, the energy efficiency of the retractable roof is essential. The regenerative drive systems reduces the power consumption during braking at times when the moving panel is being pushed by the wind. It is estimated that opening and closing the roof costs approximately $10 or less in electricity.
How It Was Built
Although the steel was fabricated off-site, the enormous size of each panel meant the assembly of the steel could only happen at the construction site. An innovative construction shoring removal technique was developed to assemble each truss while increasing the safety of the process. Since the roof is designed for horizontal travel, the trusses were lowered off the shoring systems by merely rolling the roof panels down the supporting ramps as the transporters moved along at the same pace. The concept is similar to launching a ship into the water, except the descent is much slower and controlled throughout the entire process. The shoring system and the associated steel erection procedure for the roof structure were also meticulously designed to resist hurricane level winds.
The maximum allowed wind condition to move the roof is 40 miles per hour.
The Roof mechanization system is designed to travel approximately 2,000 miles over its life (equivalent to the distance from Miami to Denver and a little more than four round-trips to Havana).
The Retractable Roof was designed, manufactured, and assembled in North America.
The retractable roof mechanization system contains 96 sets of automatically and manually deployed tie downs to safely secure the retractable roof to the track beam for high wind events including hurricanes. Approximately 70% of these (clamps) are automatically deployed or always active, with the remaining 30% (turn-buckles) to be manually deployed in preparation of a hurricane event only.
Want to know if the roof will be opened or closed? Roof status news are updated a couple of hours prior to every home game right on the @MarlinsPark Twitter feed.