Structural Performance of Bridge Approach Slabs under Given Embankment Settlement

Soil embankment settlement causes concrete approach slabs of bridges to lose their contact and support from the soil. When soil settlement occurs, the slab will bend in a concave manner that causes a sudden change in slope grade near its ends. Meanwhile, loads on the slab will also redistribute to the ends of the slab, which may result in faulting across the roadway at the ends of the approach slab. Eventually, the rideability of the bridge approach slab will deteriorate. The current American Association of State Highway Transportation Officials code specifications do not provide clear guidelines to design approach slabs considering the embankment settlements. State Departments of Transportation are spending millions of dollars each year to deal with problems near the ends of approach slabs. To investigate the effect of embankment settlements on the performance of the approach slab, a three-dimensional finite element analysis was conducted in the present study, considering the interaction between the approach slab and the embankment soil, and consequently the separation of the slab and soil. The predicted internal moments of the approach slab provide design engineers with a scientific basis to properly design the approach slab considering different levels of embankment settlements. A proper design of the approach slab will help mitigate the rideability problems of the slab.