Structural Design and Construction Issues of Approach Slabs

Abstract

Approach slabs have been used by many state transportation agencies as a means to prevent settlement problems on embankments leading to a bridge. However, many problems have reduced the effectiveness and life of the approach slabs or required excessive maintenance. Although the primary cause of approach slab problems is largely geotechnical in nature, the structural design of the approach slab is important to ensure that it performs its functions to an acceptable level over its service life and that said service life is reasonably long. A review of the literature reveals some of the approach slab problems and their causes, current design features, conclusions regarding design and maintenance, and recommendations that have been made to improve performance and service life. In this study, both the published literature and standard drawings available from state agencies are reviewed. This paper contains the results of this review, focusing on the structural design and construction issues of the approach slab. Currently, design guides are not available, requiring practicing engineers and state departments of transportation to rely upon experience and frequent maintenance. It is recommended that such a document be compiled to begin the process of standardizing the design of bridge approach slabs.