Single Bridge Replaces Two Obsolete Bridges
The Beaver Drive Bridge spanning Interstate 35/80 and Beaver Creek provides a vital link across the interstate for northbound and southbound motorists moving between Johnston and Des Moines. The area directly north of the bridge mainly consists of commercial business while the southern side moves into a more residential setting. For many years, this roadway section was served by two separate, 28-foot wide bridges. A 247-foot-long, pretensioned, prestressed concrete (PPC) beam bridge spanned the interstate while a 455-foot-long PPC beam bridge traversed Beaver Creek. These two structures had become structurally deficient and functionally obsolete and required replacement.
The Iowa Department of Transportation (DOT) partnered with Shuck-Britson, a subsidiary of Snyder & Associates, to design a replacement option. Our team recommended replacing the two substandard structures with a single, 897-foot-long, 40-foot-wide PPC beam bridge to span both the interstate and the creek. The new bridge would also have a five-foot-wide sidewalk to accommodate local bicycle and pedestrian traffic.
In addition to the development of the project concept statement, the Shuck-Britson and Snyder & Associates professionals teamed to provide the preliminary bridge and roadway design plans and the final bridge and roadway design plans. A hydraulic analysis and supporting documentation were also provided to the DOT. Our services also included rapid response assistance to address issues that arose during construction, including pile driving inquiries and erosion/revetment modifications.
Unique Design Features Add Enhanced Aesthetic & Safety for Interstate Bridge
The design team incorporated several unique features and design characteristics into this lengthy structure. Stub abutments with a bridge deck expansion device were required due to the length of the bridge. Also, modified sliding bronze plate bearings were required at the south abutment due to excessive bridge movement. Aesthetic details such as special blisters to support light poles, steel pipe handrails, and exterior fencing with steel mesh panels were utilized to enhance the bridge’s appearance.
To further support pedestrian safety, a non-standard deck cross-section with a raised pedestrian sidewalk prevents ponding on the sidewalk surface. Our team developed prototypical details for the raised sidewalk and exterior fence where they interact with the deck expansion joint and stub abutment. The additional sidewalk load resulted in non-uniform beam reactions, requiring careful analysis to determine the proper bearing pad sizes.
Additionally, multiple pier types were utilized at the roadway and waterway crossing locations. The pier located in the median of the interstate was designed for vehicular collision. Construction began on this extensive project in the spring of 2016 and was completed in the fall of the same year, eliminating any commuter inconvenience during the winter months.