Category:503 Bridge Approach Slabs
A bridge approach slab is used to provide a smooth and structurally sound transition from the pavement to the bridge. The area between the roadway embankment and the bridge end bent frequently receives inadequate compaction or a different degree of compaction than the roadway fill. Another cause of differential settlement between roadway pavement and the bridge structure is subsidence of compressible original soil layers under the new approach roadway fill's weight, while the bridge is normally founded on more unyielding foundation of solid rock or piling. In order to prevent pavement failure, an unacceptable differential elevation between the pavement and the bridge pavement, and excessive loading on the end bent, a bridge approach slab is constructed to span from the end bent over the roadway embankment.
Bridge approach slabs are included in the bridge plans prepared by the Bridge Division. Payment for bridge approach slab is included in bridge estimated quantities.
Major Roads. In site-specific circumstances, the project core team may decide a bridge approach slab is not needed on a major road. In those cases, a design exception is required. When the decision is made to include a bridge approach slab in the project plans, Construction personnel will not underrun the item nor will the contractor be allowed to remove it by a Value Engineering proposal.
Minor Roads. In light of their expense, bridge approach slabs on minor roads have shown less than satisfactory in-service performance. In keeping with the true purpose and need of the project, bridges on minor roads will be constructed without bridge approach slabs. In order to maintain an acceptably smooth pavement, maintenance forces may need to fill or patch pavement adjacent to the bridge end as settlement occurs.
Drainage. When a bridge approach slab is included in the plans, the roadway items of curb and drain basin as shown on Standard Plan 609.40 are also specified. When the bridge approach slab is not needed, a method of moving drainage away from the bridge end will be necessary. In most cases, Type A curb and drain basin will be sufficient. The project core team is to make recommendations for handling drainage as necessary.