Field Study of Integral Backwall with Elastic Inclusion

Report No: 05-R28

Published in 2005

About the report:

Jointless construction is considered an effective design option to reduce bridge maintenance costs and resist seismic loads. Although these attributes make the integral bridge an increasingly popular choice, soil-structure interaction issues unique to this type of design remain unresolved. Of particular concern is the excessive settlement of approach embankments, resulting from the repetitive, thermally induced cyclic movements of the superstructure. In many cases, rectifying this condition can be expensive because the integral bridge approach slab (if provided) cannot be overlaid with pavement. To address this soil-structure interaction problem, the Virginia Department of Transportation conducted a study designed to test the feasibility of using elastic inclusion at the integral backwall. The design was completed in mid-1997, and the bridge was opened to traffic in October 1999. The bridge was constructed with elasticized expanded polystyrene (EPS) attached to the backwall. The structure has been monitored continuously for 5 years. Significantly attenuated lateral earth pressures have been recorded at the backwall, and the settlement of the approach fill has been tolerable. Field data indicate that the elasticized EPS layer has been functioning effectively in allowing the superstructure to interact with the adjoining select backfill material. The use of elasticized EPS in conjunction with a well-compacted granular backfill offers a cost-effective way of minimizing settlements at bridge approaches.

Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.

Last updated: November 29, 2023

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