TOP 10 BRIDGES: Everything in its place (No. 5)

Custom-made schedules and deck grids fit Md. bridge

Article November 04, 2011
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One of the biggest challenges in rehabilitating the Thomas J. Hatem Memorial Bridge was that each section of the grid deck had to be custom-fabricated for a specific location on the bridge. Out of the 1,728 sections made by LB Foster, the grid fabricator, only two had to be remade. In all, Fay Co. replaced over 385,000 sq ft of the old concrete-filled grid deck with a new grid deck and then filled it with lightweight concrete.
The contractor also installed 23,350 ft of new permanent median barrier and parapet; repaired cracked and deteriorated substructure concrete; strengthened structural steel members; and spot cleaned and painted the bridge steel. During construction, they discovered and repaired other structural deficiencies, all while maintaining traffic in both directions.
The deck rehabilitation and repairs were the largest improvement project since the original Hatem Bridge was completed in 1940. The 7,500-ft, 53-span bridge carries U.S. 40 over the Susquehanna River in northeast Maryland. It is Maryland’s oldest toll facility and carries 11 million vehicles a year between Havre de Grace and Perryville.
The initial survey revealed that the spacing between grid support beams was irregular, so the grid sections had to be custom-made.
After a three-month delay caused by conflicts with an adjacent project, Fay Co. was keen to catch up with its critical-path tasks. The original schedule was for one 80-ft-long concrete pour to finish before the next pour could take place. Fay began pouring concrete in two locations simultaneously. The successful demonstration showed that the contractor could revise the schedule from 192 concrete deck pours to just 60. Longer concrete pours—up to 456 ft—saved time, provided a more consistent finish and minimized joints.
The traffic-control plan allowed up to three work zones separated by two emergency pull-off zones along the bridge at each stage of construction. Crews were assigned to specific tasks, such as shielding, structural steel repairs and grid installation. Work in each zone proceeded in order. As each crew finished its task, it would move on to the next available zone. Through repeatedly performing their tasks, the task-specific crews gained proficiency and speed and also gained three months on the project schedule.
By making the most of their innovative tactics, the project team revitalized a crucial artery for residents of northeast Maryland.

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