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Allowable Limit Contraction Scour and Abutment Scour at Bridges

Damage to riprap abutment of FM 937 bridge over Montgomery Creek.

Project Summary

Scour at bridges is the leading cause of bridge failures nationwide. Guidelines exist to estimate the scour depth at bridge supports for a given flood. By comparison, little exists to determine the maximum allowable scour depth at bridges. This is necessary to decide when to construct remedial measures for existing bridges. TxDOT already has guidance for the maximum allowable pier scour depth but not for the maximum allowable abutment scour depth or the maximum allowable contraction scour depth. The maximum allowable abutment scour depth is related to the potential failure of the abutment. This includes the abutment soil slope, the abutment deck support structure, and the embankment supporting the access roadway. The maximum allowable contraction scour depth is related to the potential failure of the bridge pier. A distinction is made between the routine maximum allowable scour depth limit and the exceptional maximum allowable scour depth limit. All issues are studied in light of available case histories, stability analyses, existing knowledge, and engineering judgement.

Project Number

0-6935

Status

Completed

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