Minnehaha County Inverted-T Bridge
CDI was selected by Minnehaha County to perform all work necessary to replace a structurally deficient 39’ two span simple I-beam bridge over West Pipestone Creek on County Highway 114. CDI performed all bridge inspections for the Minnehaha County Highway Department in 2012 and recommended major rehabilitation or replacement of this structure due to the poor condition of the steel I-beams, abutments, and bent. CDI performed a hydraulic survey and completed a hydraulic analysis to size the structure. CDI also presented two options for replacement, a 54’ Prestressed Inverted-T Girder Bridge and a 120’ Hollow-Core Slab Bridge. The Inverted-T Girder design option was proposed by Minnehaha County and the 120’ Hollow-Core Slab option was proposed as an option to meet SD DOT Secondary Roads Plan for Bridges and recommended by CDI. The 54’ Prestressed Inverted-T Girder Bridge was chosen by Minnehaha County due to the excessive costs of the 120’ Hollow-Core slab bridge and the large re-grading limits. Hydraulic information proved the 54’ Prestressed Inverted-T Girder Bridge to satisfy the minimum requirements required by Minnehaha County.
The use of 19 ½” Prestressed Inverted-T Girders and cast-in-place deck superstructure allowed for a minimal road grade raise helping reduce the overall project cost. This was the first structure of its kind in the state of South Dakota and is planned to be used for future structure replacements by the Minnehaha County Highway Department. CDI completed construction plans along with the structure and grading design and administered construction administration and construction observation services for the Minnehaha County Highway Department during construction. The project was completed in September 2015 at an overall construction cost of $460,000.