The Robbins Nest Covered Bridge is a 57-ft-long, single-span structure that spans over the Jail Branch of the Winooski River. The bridge, constructed in 1962 by Robert Robbins, is 12 ft, 10 inches wide and utilizes Queen Post truss framing. During routine bridge repairs, the contractor uncovered and exposed the lower portions of the bridge trusses, which revealed significant deterioration of a truss chord member. DuBois & King bridge engineers worked with the contractor to provide fast-track field observations, assessments, and in-depth truss analysis, in order to provide engineering and design for truss chord repairs. Repairs included:

Removal of deteriorated section of lower truss chord
Reused truss members that were in good condition
Design of tension splice for chord member interface
Design for total truss capacity of 3 tons (live load)

Principles of the Secretary of the Interior’s Standards of Rehabilitation and the Burlington Charter were applied to truss repair.

The Town of Hartford and Village of Quechee, Vermont, faced a serious problem in the wake of Tropical Storm Irene: what to do with the severely damaged and impassable Quechee Covered Bridge. The bridge was left sitting above the Ottauquechee River on unstable abutments, with no connection to either roadway approach. The massive flooding destroyed both roadway approaches; siding; the cantilever sidewalk; and the water, sewer, and communications lines carried under the bridge. The bridge is a landmark for the community and a vital transportation link connecting the Village business district to US Route 4, facilitating traffic to the economic center of the Village. In the aftermath of Irene, a 2.8-mile detour was established, but the Town needed a functional bridge quickly and developed a fast track schedule to restore the bridge to limit any long-term economic impacts to the Village.

DuBois & King provided engineering evaluation, design, and construction phase services for the replacement of the 69 ft Quechee Covered Bridge #6. The scope of work included public meetings and development of a report outlining feasibility, costs, and timelines to construct a temporary bridge, a permanent rehabilitation, or replacement structure. The Town and Quechee Village residents agreed with D&K’s recommendation to replace the bridge with a new traditional looking covered bridge on the same alignment.

Precast concrete stringers with a cast-in-place concrete deck and a timber roof structure was the preferred alternative due to cost and construction duration considerations. The replacement bridge was lengthened to 85 ft for improved hydraulics and to minimize risk of damage from future flooding. Developed 3D conceptual renderings for the look of the new covered bridge and conducted a public outreach campaign to solicit input on the final appearance. The framing of the timber roof was analyzed using a three-dimensional analytical model generated within Ram Elements, a finite element software package produced by Bentley Systems, and the framing was designed to have the appearance of a multiple Kingpost truss system. Professional services include:

Condition assessment
Alternatives evaluation
Public engagement
Design
Hydrologic/hydraulic analysis
Utility design
Permitting/SHPO approval/Section 106 clearance
Preparation of contract documents
Construction inspection

The project received a Merit Award in the ACEC/VT Engineering Excellence Awards program.