Delicate Arch Road Rehabilitation (Salt Valley Wash) MRC Structural

Team: Asher Neitsch, Joseph Stringham, Wyatt Chadwick, Austin Olsen, Maximilian Masek and Daniel Dastrup

Sponsor: Federal Highway Administration

Introduction

Delicate arch is one of Utah’s most visited geological features with over 1.5 milllion visitors each year. Reliable public access to and from Delicate Arch preserves the arch’s cultural and geologic splendor.

arch

The problem: Undersized culverts cause Salt Valley Wash to flood Delicate Arch Road too frequently, inhibiting travel to and from the Arch.

flood

Our task: Develop rehabilitation plans for a new crossing over Salt Valley Wash.

Criteria

  • 2-ft freeboard during the 20-year storm event.
  • Adequately transport sediment under the crossing during flash flood events.
  • Have enough space under the crossing in which a skidsteer can remove flood debris.
  • Blend with the natural landscape as to not interrupt visitors’ experiences.

Design Summary

Roadway

Roadway: The roadway was realigned to allow water to flow under the new bridge to prevent scour and provide the necessary freeboard for a 20-year flood.

Girder

Girder: Our girder design consists of a 48"x 33" boxshaped concrete beam with 37 prestressed internal cables. To carry the vehicle and superstructure loads, each of the four girders contains over 2,800 feet of prestressed cable and 2300 feet of rebar.

Connection

Connection: Our connection is designed to withstand over 120,000 lb of shear force in addition to vehicular loading.

Abutment and Wingwall

Abutment and Wingwall: The abutment transfers the load from the girders and deck to the foundation. The wingwalls are attached to the abutment and hold in the soil underneath the approach to the bridge.

Drilled Shaft

Drilled Shaft: Eight total three ft diameter 46-ft drilled shafts support each end of the four girders. The deep foundation is designed to hold 190 tons only using side friction, as per AASHTO recommendations.

Armoring

Armoring: Rock armoring (riprap) was used to protect the bridge from scour and erosion. The bridge will be built over a river channel bend, with the left bank experiencing higher flow velocities than the right. The left bank riprap was designed to be more robust to counteract forces.

Final Design

Final rendering in Civil 3D forward view

Final rendering in Civil 3D:

Final rendering in Civil 3D side view

Bridge cross section:

Bridge cross section:

Acknowledgements

We thank the following for their support:

  • Isaiah Norman, Jim Kerrigan, and the rest of the FHWA
  • Central Federal Lands team
  • Dr. Mohsen Zaker Esteghamati
  • Professor Austin Ball
  • Our family and friends