Bridge Restoration and Landslide Correction Using Stabilization Pier and Grade Beam Structural System

The existing Lady Bug Point Bridge within the 10 million m² Winton Woods Park in Cincinnati, Ohio was closed in Winter of 2007, as a result of ongoing landslide movements under the south bridge abutment. An initial study indicated the landslide was triggered by bridge abutment loading, recent fluctuating lake water levels, and dredging activities. An extensive rock buttress fill at the toe of the abutment extending into the lake was suggested as a remedial option from the original investigation. However, the rock fill option was deemed expensive, and the fill placement permit process with USACE could be time-consuming. Due to the fact that the abutment movements had created tension cracks and settlements of over 10 cm in a short period of time, and endangered bridge integrity and public safety, a value-engineering study was conducted using both analytical and numerical modeling methods to estimate landslide forces. A structural system, consisting of twelve drilled piers and grade beams, was designed, capable of providing both slope stabilization and abutment underpinning. The extremely narrow clear space between bridge girders added significant challenges to the pier design and construction. The unique system was installed and the bridge was reopened for use in June 2008. The design was a collaborative effort between the geotechnical and structural engineers.