Safespan's system is comprised of overlapping corrugated 3' (0.9 m) x 11' (3.4 m) steel decking, attached to parallel cables spaced 5' (1.5 m) apart using special fasteners. Various steel structural members are employed to support the system as necessary.

     Safespan's external platform design split the bridge in half. Its installation crew first brought cables from the bottom diaphragm to 20' (6.1 m) beyond the centerline of the arch, allowing as much as 10' to 15' (3.0 m to 4.6 m) of sag. They attached the cables to foot-square steel plates anchored into the concrete at both ends. After seven tie-up cables were installed 20' (6.1 m) apart, they pre-tensioned the cables to follow the perimeter of the concrete arch. Once the vertical cables were in place, they installed the steel decking longitudinally across the parallel cables to conform to the curve of the arch and applied final tensioning. They then attached angled steel pieces to the deck clips vertically and horizontally to form a series of steps, and installed plywood along the horizontal members to provide the actual external working surface. Once the eastern half of the bridge was decked in this way, the crew repeated the process for the western half.

     The company's design included a unique debris chute that led to a landside solid waste collector. Crane-Hogan crews averaging 15 to 20 workers per side removed approximately 120 cubic yards (91 m3) of concrete from the underside of the arch using this debris chute.

     To provide internal access for Crane-Hogan's crews, Safespan designed and installed three cable-suspended stacked steel horizontal "roadways," with approximately 24' (7.3 m) headroom, between the main arch's internal reinforced concrete columns and beams. As outside, the internal decks provide access not only for various crews and inspectors, but also for the equipment needed to complete the job. The project specifications called for a loading of 50 psf (244 kg/m2), although loads up to 200 psf (976 kg/m2) may be accommodated with the Safespan system.

     With the platform system in place, up to 40 Crane-Hogan employees in multiple trades are working inside or under the arch at one time. Use of the Safespan system is providing a room-like atmosphere for work that is taking place at heights up to 165' (50.3 m) outside, and up to 160' (48.8 m)or so inside. This means that project workers are not only less apprehensive, but also much more productive than they would be under "normal" bridge rehabilitation working conditions.

     According to Crane-Hogan's project superintendent Frank J. Fisher, because of the greatly improved productivity stemming from the more secure working environment, actual labor hours are expected to come in considerably under original budget. This should result in significantly increased profitability for Crane-Hogan on this unit price job.

     Fisher remarked: "We looked at this project as unique from a safety standpoint. ... There were problems of access, problems with the gorge's slope. Safespan's system helped us overcome these problems and keep our men working safely and securely." NYSDOT's project engineer Thomas L. Mialki added: "I don't know how this project could have been done without such a system. It is easier for everybody involved."

Article © 1998, Group III Communications (used with permission)