Right Hand Fork Pedestrian Bridge Final Report

Author

Ren Gibbons, Utah State University

Date of Award

5-2015

Degree Type

Thesis

Degree Name

Departmental Honors

Department

Civil and Environmental Engineering

Abstract

Right Hand Fork is a tributary canyon whose stream enters the Logan River nine miles east of the mouth of Logan Canyon near Logan, Utah. The access bridge to a popular recreational area, the Hobbit Caves, was damaged in 2011 by flooding. We propose that a new bridge be designed and constructed for the Forest Service to replace the current structure to ensure public safety and minimize environmental impact. We plan to use a longer bridge span that will situate the abutments higher on the stream bank and reduce possible water damage during flood events. Bridge costs will be minimized and will meet required construction and aesthetic standards required by the Forest Service.

The current bridge is a 15-foot timber span placed on existing earth footings. High runoff discharges in 2011 caused the northern earth abutment to shear and settle due to scour. The bridge span now sags at approximately 20°. While still usable, the bridge's structural integrity has been compromised, and the footing will presumably continue to settle until the bridge fails. Figure 1 shows the extent of the damage done to the bridge.

We have completed a topographical survey and hydrological report to determine the best location for the structure to prevent future water damage. We performed structural analysis and design for a safe and cost-effective replacement pedestrian bridge. We independently prepared a steel bridge and a timber bridge design. The preferred alternative for structural materials is a 40-ft timber glulam girder span and Gabion foundations. We propose that construction will begin as early as fall 2015. We also propose biannual inspections beginning once construction is complete to ensure proper maintenance and a 50-year life as required by the Forest Service.

Recommended Citation

Gibbons, Ren, "Right Hand Fork Pedestrian Bridge Final Report" (2015). Undergraduate Honors Capstone Projects. 561.
https://digitalcommons.usu.edu/honors/561