…enough to accommodate the anticipated variations in support geometry without overstressing the structure or its supporting wheels, or a suspension system for the retractable roof structure and its supporting wheels should be provided.

Wheel Suspensions and Load Distribution

• Considerations for weather sealing must be incorporated into the design from the very beginning, which includes a reasonable cost budget for these specialty systems. The seal design must account for relative movements of long span structures, construction tolerances, stopping position tolerances, required clearances, and the effects of externally applied loads. In addition, access must be provided for inspection, repair, and replacement of seals.

Miller Park Bulb Seals

• A reasonable means must be provided to inspect, maintain, repair, and replace every mechanical and electrical system component. Jacking points or temporary strut connections should be included to provide a secondary load path in order to facilitate removal of mechanical components. A means to hoist and handle replacement parts is also required, along with safe and reasonably convenient personnel access and working space for operation, inspection, maintenance, repair, and replacement.

• Time and money must be budgeted to test everything reasonably possible, using proven technologies whenever possible. Prototype tests should be executed on new technologies and applications for function, life cycle performance, and structural integrity. Every manufactured mechanical and electrical component is potentially flawed, and should be tested before it is put into service. It is much less expensive to find and correct a problem in the shop than it is to repair or replace components when they are supporting a multimillion pound structure.

• Float is required in the manufacturing schedule to allow for recovery from schedule setbacks such as delinquent vendor delivery or replacement of flawed or damaged components. Because these systems are custom designed and manufactured electromechanical assemblies with thousands of components, it is almost inevitable that some will be delivered later than expected and some will be delivered with flaws. Having a Plan B is a must. Where practical, a small number of manufacturing spare parts should be included in the budget and ordered to keep manufacturing on schedule in the event that a single part is flawed or damaged during shipment, storage, handling, or assembly.

Every step of manufacturing should be verified. It is likely that the thousands of components for the system will be manufactured and provided by a multitude of vendors. For custom designed and manufactured components, the design team should provide manufacturing quality assurance check sheets to identify critical dimensions and the minimum quality assurance requirements. Where practical, the design engineer should audit the manufacturers’ quality assurance process, and inspect the first article manufactured of each component. When manufactured parts are received at assembly facilities, they should be immediately checked for damage and inspected for compliance with the specified requirements. Test fit assemblies for components should be performed as early as possible as a further verification of component adequacy.

The design engineers should participate in the first article assembly of all assemblies and subassemblies. Wherever possible the operation and performance of completed assemblies should be tested in the shop by the design engineer.

The budget should include cost contingencies for rework and surprises in both the manufacturing and construction phases of the project. A15 to 20 percent contingency should be carried before the design is completed, and a 10 percent contingency should be carried after design is completed. Regardless of the precautions taken, unanticipated costs will inevitably arise during the process of delivering these large and complex custom designed and manufactured systems.

Adequate schedule time must be provided for the system supplier to execute a safe and deliberate regiment of startup and testing sequences, in order to verify the performance of each feature of the control system and the safety system, and each mechanical component. Two to three months should be allowed for the startup and commissioning of retractable roof stadiums. The roof should be completed and the supplier must have free reign to operate the roof during this period. (In other words, other trades should not be scheduled to work on the roof during this period.) Regardless of the precautions taken, this process normally results in some small control program changes and mechanical adjustments. The supplier needs time to make required changes, and to identify and replace any components that are subject to “infant mortality” prior to handing the system over to the owner. This startup and commissioning period is critical to a smooth and successful handover to the owner, and the owner’s operator should participate with the supplier in much of this process as an opportunity to learn about the system and gain experience in its operation.

The project should include a modern control system with onscreen status indicators, diagnostics, and troubleshooting. Often times these systems have hundreds or thousands of electromechanical components located at remote positions spread out over several acres of area. If a single sensor or component fails, the control system must tell the operator where the failure is and how to correct it.

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Reliant Stadium Control Screen

• The control system should be designed and supplied to allow online real time technical support from the supplier’s control engineers at remote locations. The system should be supplied such that a technician from a remote location can observe the same operating screen as the operator on a real time basis and provide technical support and trouble shooting support via telephone.

• As much as practical, drive systems should be designed with operational redundancy. Higher operational reliability can be achieved with systems that have a multitude of small motors, and that allow for one or two motors to fail without rendering the system inoperable, rather than having a single large motor. The smaller drive components can also be much easier to replace than larger components. As an example, the University of Phoenix retractable field incorporates a total of 500 steel wheels. Seventy six of the perimeter wheels are driven by one horsepower motors, and two motors on each side of the field can fail and the system will remain operational.

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University Of Phoenix Retractable Field � Cross Section at Edge

• Turnover procedures and acceptance testing criteria should be identified as early in the project as possible so that all parties understand how the job will end before it becomes an issue.

• The design engineers should prepare training materials for the owner that provide the operators and maintenance staff with all appropriate design background, system behaviors, safety considerations, operating information, and maintenance instructions. The supplier should provide an initial training program and leave behind training documentation for the owner to use for training subsequent generations of operators and maintenance staff.

• Clear, complete, user friendly operation and maintenance manuals are an essential part of the delivery package.

• A budget should be included to provide a reasonable spare parts inventory as part of the supply contract. Many of the system components are custom manufactured parts with very long lead times. If a component were to fail with no replacement spare in stock, it might render the system inoperable for several weeks. Also, it is more cost effective to provide spares of custom manufactured components during the original production run of the components as apposed to buying one or two copies at the end of the job.

• Where practical the owner should be provided with any special tools that are required to operate, maintain, or repair the system.

• For large complex systems such as stadium retractable roofs, the system supplier should budget for and provide the first year maintenance, first year warranty, and full time on site technical assistance to the owner for some period of time (first season of operation) as transition period for the owner to take over the system. This provides for a smooth turnover and a happy owner.

• Operation and maintenance costs should be included in the budget. In order to ensure reliable operation of any mechanized system, the owner must operate and maintain the system in accordance with the designer’s requirements.

The use of these best practices combined with teamwork, good engineering practices, and attention to detail have produced many trouble free sports venue projects that incorporate kinetic architecture. These successful projects have laid a solid foundation for the future of kinetic architecture in stadia.

It Won’t Get Any Easier

The success of these projects combined with an increased demand for functional flexibility and architectural significance is resulting in owners and architects demanding an ever more challenging mix of new and complex motions, shapes, and materials for the mechanized elements of stadiums. For example, the new Cowboys stadium set to open in 2009 incorporates a retractable roof that climbs a 24 degree slope on an arched rail and the world’s tallest (125 foot tall) moving glass wall panels.

Cowboys Stadium Retractable Roof & Operable End Zone Walls

A recent proposal in Asia called for a ballpark roof that opens like flower pedals with mechanized roof elements having cantilevered spans of two to three hundred feet. The Devil Rays have recently unveiled plans for a new MLB ballpark in St. Petersburg, Florida. This design calls for several acres of fabric to be deployed and tensioned over a cable net structure in the event of rain. When not in use, this fabric roof is collapsed and stored under the inboard edge of the sunscreen structure that covers the seating area.

Devil Rays Ballpark Concept

These design challenges call for a variety of new and innovative materials, structural systems, and mechanization methodologies. The keys to the success of integrating large mechanized components into these future stadiums will be much like those of the past. Proven methodologies and technologies should be used when possible. When the design calls for something new and innovative; ample computer modelling/analysis, reduced scale modeling, and full scale prototype testing is imperative in order to validate design concepts and theories as they develop. The limits of this kinetic architecture revolution are bounded only by the vision of the owners, the creativity of their architects, and technical innovativeness of the engineers and constructors that bring these archictectural icons to life.