WEB EXCLUSIVE: Hyper active in New Jersey

Bridge Construction Article November 17, 2008
Printer-friendly version

The fast-track rehabilitation of the Stickel Memorial Bridge, which carries I-280 over the Passaic River, two helix ramps at the western end from Rte. 21, and over Rte. 699 in Hudson and Essex counties, N.J., was one of the New Jersey Department of Transportation's (NJDOT) major hyper build projects.

The bridge serves over 90,000 vehicles a day on six lanes (two through-lanes and one auxiliary lane in each direction) without shoulders. A lane drop occurs in the westbound direction (lane addition in the eastbound direction) at the westbound access to and eastbound egress from Rte. 21. A significant amount of large truck traffic uses this corridor. The lift span provides a 200-ft clear width and a 35-ft minimum vertical clearance in the closed position and 135 ft with the span fully raised. Due to several reasons, the navigation channel use is limited.

This project included the main and approach spans, including all substructure, superstructure, deck and the fender system and mechanical/electrical systems.

The rehabilitation aimed to extend the life of the bridge by approximately 25 years. Preliminary design and final design phases were completed at an accelerated pace: eight months for preliminary and seven months for final. Substantial completion of construction was met in December 2007, and final completion was scheduled for September 2008.

An in-depth inspection was part of the preliminary design and Parsons Brinckerhoff (PB) was already under agreement with NJDOT to perform the NBIS biennial inspections for the bridge. This helped in meeting the short schedule, and furthermore, the same key staff, including the authors, were involved in the NBIS inspections and design. A significant understanding of the scope and extensive multidisciplinary coordination thus became much easier. The concepts assessed during the preliminary design were all geared towards accelerating the construction phase, with a goal to minimize traffic impacts.

Taking on the rapid

For rapid construction, four stages were used (three primary stages, one preparatory stage), with innovative techniques and materials to expedite the deck replacement work under heavy traffic. In the concept study, the focus was on retaining all six lanes in the a.m. and p.m. peak periods, with off-peak, nightly and weekend lane reductions, possibly with a six-stage scenario, one lane at a time.

Two of the early-on critical meetings the PB team had were with NJDOT Traffic Operations North (TON) region and the USCG. Because of the limited demand for navigational openings over the last 10 years, a shutdown of the span lifts for the entire duration was obtained. Subsequently, different options were presented to TON for vehicular traffic maintenance, including nightly closures with all six lanes available during peak hours and also six-, five- and four-stage construction options.

The cause of peak-hour traffic tie-ups in this corridor was the lane drop west of the bridge, which could not be improved. The eastbound acceleration lane showed only a slight increase in the ramp storage at peak hours. With this early determination, the design team presented elimination of the acceleration/deceleration lanes during construction. This staging allowed a 24-ft construction zone, while maintaining two through-lanes in each direction for the entire duration. TON concurred and other staging options were quickly eliminated.

Next, a careful evaluation of the most important bridge activities-structural and mechanical/electrical rehabilitation-was done to assess their approximate duration and to identify likely driving activities. The evaluation separated activities requiring lane outages and those without. Deck replacement, bearing replacement, lift span deck and stringer replacement clearly dominated the construction schedule. Cleaning and painting the entire bridge was another major activity, as the existing lead-based paint required extensive containment measures with work at very high elevations on the towers over live traffic. Much of the mechanical/electrical work could continue after all six lanes were reopened.

With the approximate duration for a four-stage construction estimated at 21 months as compared to a six-stage scenario at 36 months, the project could be hyper-built. The total overall design and construction schedule was now cut from approximately 60 months to about 36 months.

The design considered deck options facilitating speedy construction within the compressed schedule, confined staging work zones and minimizing weight of the lift-span decking. Land-based contractor access appeared likely, as the river only extended under a portion of the bridge. Certain existing geometric constraints and the fact that the existing steel superstructure was to be retained in the approach spans limited deck type choices in the approach spans. Weight and speed of construction drove the choice of deck types in the lift span. Retaining the superstructure, upgraded for a higher live load, while maintaining existing variable cross slopes on the deck and retaining the vertical profile, required a deck system less than 7 in. thick, which is the same as the existing span.

A conventional cast-in-place deck slab, requiring a greater total thickness, was eliminated. Vertical clearance above deck had to be maintained; therefore increasing the profile was neither desirable nor feasible. During this time, the Exodermic deck system, until then a proprietary design/manufacture product, began licensing out their product for a royalty; in discussions with the Exodermic manufacturer and local contractors, it appeared that competitive bids could be expected for this option. More importantly, this largely prefabricated and lighter weight deck type would allow for the desired higher live-load capacity and could be made composite with the existing steel, all while retaining the existing profile.

Prefabricated standardized panels for the bulk of the construction were feasible, especially since the staged construction widths were identical or similar for the three primary stages. Thus, these immediate advantages clearly favored its use. A precast option may have led to more time savings, but the variable cross slopes and accommodations of scuppers and deck flare-out in spans one and four would definitely negate the savings, in addition to the larger weights to be handled for installation. Hence, an Exodermic deck with cast-in-place lightweight concrete was specified.

For the lift span, PB recommended open-steel grid decking, as weight was a concern in this movable span. In order to expedite construction, standard offsite fabrication with repetitious deck panels and identical steel stringers that spanned between equally spaced floorbeams helped immensely. The connection of the grid to stringers was made using shear studs on the stringer flange and cast-in-place concrete only along the stringer line. This resulted in multifold benefits; a speedier construction as compared to cumbersome field welding; elimination of fatigue concerns at the connections; an increased stiffness of the deck-stringer connection; protection to the underlying steel stringers; and an improved rideability, as many of these concrete fill lines coincided with wheel paths in the lift span.

The early part of the preliminary design included a fiber-reinforced polymer (FRP) deck system for the lift span, with nightly partial replacements. PB was working with a major FRP manufacturer for its design, and installing test panels at the bridge site was considered. Approximately three months into the preliminary design phase, NJDOT chose not to pursue FRP decking. Although a setback to the design schedule, it could be absorbed without significant impact as PB had already considered several conventional deck designs with the primary objective of maintaining the existing span weight. To speed up construction, PB retained the same spacing as the existing steel stringers and set the new stringers at the same vertical location as the existing to reuse the existing connection holes in the floor beams. As there were 16 stringers in each of the nine bays, time was saved in not having to field-drill new holes. Attention to such simple details proved fruitful, as the lift span redecking went off ahead of schedule.

The bridge was deemed historic by the State Historic Preservation Office (SHPO) and is on the state register. SHPO mandated the use of an open railing system on the bridge curb lines to retain the original open pedestrian railing perception, as the original sidewalk and pedestrian railing were to be retained. PB utilized a crash-tested steel open rail system mounted to the curb. From a speedier construction perspective, the standardized rail sections being fabricated offsite definitely helped. Pre-fabricated components that the contractors are familiar with and fairly simple conventional details also helped the construction schedule.

All the bearings required replacement. Minimizing the number of different types and standardizing the bearing types helped, and pot bearings were chosen by the contractor, with a repetitious, simple method for jacking. Jacking with minimal loads with the deck off in each stage and standardizing the jacking loads helped achieve a standard jacking system that could be repeatedly used.

In the lift span there was a steel shell NJ-shaped median barrier installed in 1978, and its condition was acceptable. An analysis indicated that with minor strengthening of the connections the barrier could be reused. Therefore, to save time, the metal barrier was removed in Stage I, stored, cleaned, painted offsite and reused. The barrier was reinstalled very quickly in Stage IV and matched up well with the rest of the bridge paint color.

As this challenging project nears completion, one can look back at the initial concern of the entire team: the maintenance of traffic. The most important decision made was to allow two of the lanes to be shut for construction. That opened up options for the ultimate hyper design/hyper build approach that was embraced by the team. While this philosophy will no doubt work, the key to it is a buy-in from all decision-makers and stakeholders at the outset.

Generally, a major rehabilitation of movable bridges is very complex because of unforeseen problems that typically arise during the mechanical and electrical component's rehabilitations and/or retrofits that traditionally tend to take the longest to resolve. Extensive information up front is required, as many of these older structures may have undergone maintenance and/or repairs not always well documented. To be able to hyper design complex movable bridges and to be able to hyper build them will be a big challenge for future projects. However, if one evaluates the duration of lane outages, and the time from start of construction to reopening all lanes, as a measure of the effectiveness of hyper build, then it can work.

About the author: 
Anella and Krishnagiri are project managers with Parsons Brinckerhoff Inc., Princeton, N.J. Patel is a project manager with the NJDOT.
Overlay Init