Tappan Zee Bridge Deck Replacement

Project Cost: $146 million      

Tonnage: 8,000 tons of structural steel

Description: This cantilever-style bridge was first opened to traffic 1955 and it continues to serve as a major artery between New York City and Upstate New York carrying between 140,000 and 170,000 vehicles every day. Over the last 50 years, the NYSTA has completed several major projects, but the bridge was still in need of frequent emergency repairs.

Since this vital thruway could not be closed for these major repairs, an innovative approach was need. The innovation came in the form of precast steel and concrete panels that were completely fabricated off-site and installed at night.

MC Ironworks was involved in the steel refabrication for spans 2-178. Once the beams were drilled, actual measurements were taken and entered into a custom software program. This software improved placement accuracy of over 12,200 connection locations and expedited drilling on the connecting angles and Ts, saving over 30,000 manhours.

MCIW also recommended an alternative cambering option. When New York specs required heat cambering, it was quickly realized that this would have taken 550 days and pushed beyond the schedule by 1 year. Since the stringers were going to be jacked into position once in the precast frame, MCIW suggested that all the cambering be applied by the precaster. 

With these recommendations, the contractor realized a $2.0 million dollar cost savings and maintained the tight schedule. And through the coordinated efforts of the fabricating, galvanizing, precast and storage suppliers, the contractor was able to replace over 600,000 SF of the bridge's decking panels – 40% of the entire bridge – in just over an 8-month period.

Source: Perini / Tutor-Saliba III J.V.