ODOT (13) 0058
E.S. Wagner Co. was the prime contractor on a multi-year contract to rehabilitate ODOT’s only remaining suspension bridge, the Anthony Wayne Bridge, located in Toledo, Ohio. The first construction season was spent preparing and planning the 570 day closure period. In that time, a safety platform, consisting of corrugated metal decking and a series of supporting cables, was engineered and installed just beneath the two main stiffening girders of the suspension spans. In order to not impede shipping traffic, the platform had to be set at a clearance of no more than six inches from the lowest portion of existing structure within the 200’ shipping channel and no more than two feet everywhere else. The concrete chipping and patching of the substructure also started during the first construction and continued for more than two years, totaling roughly 750 cubic yards.
Early in the project’s second season, the bridge was closed to traffic, commencing a maximum 570 day closure period. For the next nine months the main focus was to completely remove the existing concrete deck, repair deteriorated structural steel, and pour a new lightweight concrete deck in a series of nine stages within the suspension spans. Due to construction staging and loading requirements on the suspension spans, work began in the middle of the center span, and progressed both symmetrically and simultaneously about the transverse and longitudinal centerline. The staging was required as to not overstress the stiffening girders and maintain the structural integrity of the suspension spans. All concrete components within the suspensions spans utilized a specialized mix, incorporating a lightweight aggregate known as Haydite, in order to help reduce stresses in the structural steel, suspender cables, and main cables. Due to the progressing deterioration of the structural steel, the suspension spans required many additional repairs, which required on time delivery of the new structural steel. Upon removal of the existing deck in each stage, an inspection was conducted to determine the condition of the structural steel. Once the required repairs were identified, details were drawn up by the structural steel supplier using the original plans dated 1929-1930. The shop drawings were then reviewed, sealed by an engineer, and sent back to the supplier for fabrication. After fabrication, the repair steel was delivered directly to the jobsite for installation. In all, a process that typically takes several weeks to execute was done in a little as a few days in order to maintain schedule. After nineteen deck pours, the three suspended spans totaling 1,252 feet in length were completed and the next phase of construction could begin.
Demolition of the existing 200’ truss spans coming off each end of the suspension span took place in the fall of the project’s second season. This work consisted of deck and sidewalk removal, and a total demolition of the structural steel trusses and its secondary members. During this removal process, tremendous consideration was taken in order to protect the suspension’s main cables, which provided a mere six feet of clear space between the main cable and the existing truss. Each truss span consisted of two 25’ deep by 200’ long Warren Trusses, each weighing 225,000 pounds. In total, over one million pounds of existing structural steel was repurposed during the truss demolitions. When the truss spans were removed, the anchorage concrete demolition and substructure construction began concurrently with the construction of new piers required to accept the proposed steel superstructure. The new pier and anchorage construction took place in the winter and spring of the year, and were a part of a thermal control plan required for concrete structures considered to be mass concrete. The thermal control plan provides specific guidelines for required insulation and constant temperature monitoring to ensure proper curing without thermal cracking. The truss spans were replaced with a two-span slab on steel plate girder superstructure. With the main cables’ close proximity to the replacement spans, much like the truss span demolitions, careful planning and execution was required to successfully erect nearly 700,000 pounds of plate girders and cross frames.
After the truss span demolition and prior to replacement span erection, and nearly eight months in to an E. S. Wagner Company driven reengineering effort to remedy a non-constructible design, the most technical aspect of the work was set to begin. Repairs were to be made to each of the four hold downs located at the four corners of the suspension span. The main cable hold-down retrofit repair required the installation of a temporary main cable jacking system to apply roughly 300,000 pounds of downward force on the main cable in order to destress the wire ropes, thus relieving the tension on the existing structural steel embedded into the concrete pier below. At the same time, a smaller jacking system was installed to support the bottom side of the stiffening girder, applying roughly 75,000 pounds of upward force in order to relieve the structural steel below of all compressive forces. The top 3.5’ of the concrete pier was removed to further expose the structural steel to be repaired. Once the existing structural was cut out to its removal limits, the new steel was installed and spliced to the existing steel. New concrete was placed at the top of the pier to replace the top 3.5’ removed earlier. At that point, the temporary jacking systems could be released and dismantled.
As soon as demolition of the anchorages were complete, demolition of the approach spans’ concrete deck began, starting at the anchorages and working towards the abutments. Structural steel repairs under the deck were completed as the concrete deck removals progressed. Again, on time delivery of structural steel repairs, as with the suspension span work, were paramount to maintaining schedule. Deck pours on the approach and replacement spans began in June with the eighth, and final, pour taking place in August. Subsequent activities included median wall, sidewalks, refurbished pedestrian railing, guardrail, sealing of superstructure and substructure concrete, and asphalt paving. Finally, the project team opened the bridge to traffic in October - 26 days ahead of schedule.