Performance of Bridge Approach Slabs under Void Formation – Experiment and Simulation

Abstract

In the US practice, approach slabs are frequently used to provide a smooth transition between the roadway and highway bridge. Current approach slabs use a cast-in-place reinforced concrete slab that is anchored to the abutment at one end, and may be dowel-connected to the pavement slab at the other end. Maintenance of bridges however often requires repair or replacement of approach slabs due to damage from traffic, washout of fill materials, and settlement of the approach embankment etc. This paper describes a full-size approach slab test of California design, and examines the performance of these slabs deteriorated by washout using a modified beam-on-elastic-foundation model. Simulation results from the model under the AASHTO truck load show good agreement with the deformations measured during the full-size test. Increased internal force demands as a result of the washout are used to assess the performance of the slabs under the service load. It is found that the slab is able to retain a significant portion of its original stiffness even under a severe washout condition. Although the analysis is based on approach slabs in California, the model can be readily adapted for approach slabs in other states and elsewhere.

Keywords:

• Approach Slab
• Washout
• Bridge Maintenance
• Slab-soil Interaction
• Winkler’s Foundation