Larimer County Road 80 Bridge Rehabilitation

Challenge

An Engineering Judgment Rating was assigned to the County Road 80C bridge over the North Fork of the Cache La Poudre River to account for observed long-term deterioration as no design or as-built plans were available. In its current state, this judgment rating would restrict vehicle traffic on the roadway, which saw nearly 100 vehicles per day, with 23% of those being truck traffic. To avoid this limitation and continue usual traffic flow, Larimer County selected SEH to provide engineering services for the load capacity assessment and rehabilitation of the bridge.

Solution

SEH collaborated with Intermountain Testing Company to conduct X-ray examinations of the bridge's main girders. This provided crucial insights into the structure's composition, including the number, size, and positioning of prestressing strands and reinforcing steel. Concrete cores were also extracted from the deck to assess compressive strength and unit weight, which are essential parameters for structural analysis.

SEH engineers performed a thorough analysis, determining that the existing girders possessed sufficient capacity to support a reinforced concrete topping slab. This bolstered the bridge's load-carrying capability and protected the remaining underlying structure, significantly extending its service life. Notably, the proposed solution allowed for the removal of load restrictions, restoring full functionality to the bridge, and ensuring unrestricted traffic flow for the community.

By opting for a topping slab instead of costly bridge replacement, the county achieved substantial cost savings without compromising on safety or performance, and the removal of load restrictions has allowed unrestricted traffic flow and enhanced the overall efficiency of the transportation network.