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Development of an Improved integral Abutment-to-Approach Slab Connection

Thin bronze gauge installed on a bridge

Installed girder gauge


Principal investigators:

Co-principal investigators:

Student researcher:

Project status


Start date: 03/01/05
End date: 04/30/07


Report: Integral Bridge Abutment-to-Approach Slab Connection (9.7 mb pdf) June 2008

Tech transfer summary: Integral Bridge Abutment-to-Approach Slab Connection (434 kb pdf) Jun 2008


Sponsor(s): Iowa Department of Transportation

About the research

Abstract: The Iowa Department of Transportation has long recognized that approach slab pavements of integral abutment bridges are prone to settlement and cracking, which manifests as the ?bump at the end of the bridge?. A commonly recommended solution is to integrally attach the approach slab to the bridge abutment. Two different approach slabs, one being precast concrete and the other being cast-inplace concrete, were integrally connected to side-by-side bridges and investigated. The primary objective of this investigation was to evaluate the approach slab performance and the impacts the approach slabs have on the bridge. To satisfy the research needs, the project scope involved a literature review, survey of Midwest Department of Transportation current practices, implementing a health monitoring system on the bridge and approach slab, interpreting the data obtained during the evaluation, and conducting periodic visual inspections.

Based on the information obtained from the testing the following general conclusions were made: The integral connection between the approach slabs and the bridges appear to function well with no observed distress at this location and no relative longitudinal movement measured between the two components; Tying the approach slab to the bridge appears to impact the bridge; The two different approach slabs, the longer precast slab and the shorter cast-in-place slab, appear to impact the bridge differently; The measured strains in the approach slabs indicate a force exists at the expansion joint and should be taken into consideration when designing both the approach slab and the bridge; The observed responses generally followed an annual cyclic and/or short term cyclic pattern over time.