Bridge Approach Slabs for Missouri DOT: Looking at Alternative and Cost Efficient Approaches

The objective of this project is to develop innovative and cost effective structural solutions for the construction of both new and replacement deteriorated Bridge Approach Slabs (BAS). A cost study and email survey were performed to identify states whose BAS are lower in costs compared to Missouri and perform adequately. Finally, it was decided to recommend slabs with a span of 20 feet and 12 in. thickness for new construction. An analytical beam on elastic foundation analysis based software has been developed and designs presented. A detailed three dimensional finite element analysis of BAS models was carried out in SAP to determine design moments. For slabs that need replacement, an innovative pretensioned precast slab with transverse ties is presented. The costs of both the new cast in place and precast slabs are around 25% cheaper than the current Missouri Department of Transportation (MoDOT) slab and hence even the precast pretensioned solution could be tried out for new slab construction. A preliminary study on the usage of Controlled Low Strength Material (CLSM) as a replacement for the currently used practice of compacted soil and aggregate base, which could possibly be both cost effective and mitigate void issues under the slab, is presented. Life cycle cost analyses have been performed for the proposed solutions.