Bridge: Construction Staging
Stages of Construction
When a bridge is being replaced or rehabilitated, the number of construction stages should be kept to a minimum, which will reduce the bridge cost and construction duration. Consider reducing the number of lanes being maintained and lane widths to accomplish this. If possible, avoid a situation where there is a construction zone in between travel lanes. This would make construction more difficult, increase the cost, and decrease safety for construction personnel and the traveling public.
Whenever possible, the bridge should be closed during construction and traffic detoured. This provides the shortest construction duration and lowest project cost while ensuring the safest project. For example, consider a detour for projects where the bridge can be constructed over the summer months when school is not in session and traffic needs are less. A detailed Maintenance of Traffic Alternatives Analysis should be performed when a detour is considered to ensure minimum mobility thresholds can be met. Consider drive by businesses that will be bypassed by the detour as well. A contractor incentive/disincentive to open the bridge to traffic on time should also be included in the project to minimize the impacts to the traveling public.
Future Deck Replacements
In order to address maintenance of traffic during a future bridge deck replacement, all substructure units on new bridges should be designed to support full live load with portions of the superstructure completely removed. If it is not apparent how many lanes may need to be maintained in the future, assume the bridge deck will be replaced in half sections for the purpose of the design. Piers should be configured so that temporary supports of pier caps will not be needed during staged construction. Where possible, the superstructure of the bridge should be arranged so that at least three beams will be supporting the deck in each stage of construction. Supporting the deck on two beams may not be a stable configuration, especially if curved girders are involved, and should be evaluated to determine if additional supports are required.