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Washington, DC 20590
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Improving Connectivity: The Custer Interchange Project

Appendix C Structures Skill Set

Idea Name Detailed Description Implementation Details (barriers, skills set coordination, etc.)
Lateral Skidding Bridge will be moved laterally into place using skidding equipment.
  • The new superstructure will be built alongside the existing structure on temporary supports. The new superstructure will be used as a temporary bridge during demolition of the existing bridge.
  • Construct abutments and center pier prior to repositioning new structure.
  • Moving the new structure into place will require a short closure (2-3 days) of Custer Ave.
  • Lateral skidding requires specialized equipment and contractor.
  • Possibly more expensive than conventional construction.
45 to 90 day Custer Avenue Closure The Custer Ave. bridge will be closed for 45 to 90 days while the bridge is replaced.
  • Using precast elements for the majority of the structure elements will allow for more rapid construction.
  • Closing the site to traffic will create safer working conditions.
  • Facilitates efficiency in other construction operations. (Installation of utilities, reduced traffic control, inspections, reduced construction duration, easier delivery of materials).
  • This idea appears to be the most cost effective solution (excluding user costs).
Phased Construction The project will be constructed in phases without closure of Custer Avenue.
  • Using precast elements for the majority of the structure elements will reduce the duration of each stage.
  • It would be possible to build the bridge in one to two construction seasons.
  • The Frontage Road would need to be realigned prior to the rest of the project to provide room for construction.
  • Phased construction would require temporary roadway approach modifications.
  • This idea can be used for either conventional or accelerated construction techniques.
Offsite Prefabrication Construction of the superstructure will be completed before or during other site work and will require minimal (weekend) roadway closures.
  • The superstructure will be constructed off to the side of the project and moved into place after the approaches and substructures have been completed.
  • Self Propelled Modular Transporters (SPMT) will be used to move entire superstructures into and out of place.
  • SPMT's may not be readily available.
  • This idea is more appropriate for superstructure replacement only.
  • The cost of using SPMT's may be high. (additional $1,000,000 for technology).
Structure Depth Investigate ways to shorten the proposed bridge span lengths for the purpose of minimizing structure depth.
  • The purpose of this idea is to lower the profile grade and minimize fill heights within the interchange.
  • This idea is applicable to all previous construction options.
  • Consider using full height abutments to shorten span lengths.
  • This idea would lower the grade of the Custer Ave. bridge by approximately 1 ft.
  • Larger wingwalls would be required.
  • Structure is not as efficient.
  • Additional structure cost will need to be offset by approach fill savings.
Structure Components The Structures Skill Set discussed and documented options for all structural components.
  • Both Full Depth and Partial Depth Precast Concrete Decks were considered. Precast deck panels should be pre-tensioned and post-tensioned to reduce cracking and leaking. Cast panels approximately half the deck width and connect with a closure pour.
  • Parapets could be precast with the deck slab or precast separately and grouted to deck. Bolt down barriers similar to the Vermont or New Hampshire barrier were considered. Parapets could be built behind temporary Jersey Barrier in order to open the bridge to traffic more quickly.
  • Girder options included pre-stress concrete AASHTO girders, butted Bulb-T's, Steel girders, and butted box beams.
  • Bearing options included steel rocker shoes and elastomeric bearings.
  • Abutments options included precast integral abutments and precast full height abutments. Short wingwalls or "flying" wingwalls could be used at this location. The span lengths could be shortened if full height MSE walls were utilized.
  • Wall piers were discussed but may present difficulties in seismic design.
  • Both spread and pile footings were discussed.
Constructability Study A Constructability Study is recommended for all options.
  • All options presented would be fleshed out.
  • All aspects of the project would be considered, not just the bridge.
  • Overall project costs will be calculated.
  • Local concerns may drive final decision.
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Updated: 10/31/2013
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000