Screening tool to assess adequacy of bridge timber pile bents during extreme scour events

Abstract

Timber substructure bridges supported by three, four, or five piles were commonly used in Alabama in the past for secondary and county highway bridges. Because of the large number of such bridges in the state, the Alabama DOT recently developed a screening tool to assist its engineers in assessing the adequacy of bridge pile bents for extreme flood and scour events. The evaluation procedure employed in the screening tool is presented in this paper through the following sequence: (1) preliminary or general checks; (2) possible kick-out or plunging failure; (3) bent pile buckling failure; (4) transverse pushover failure from combined vertical gravity and lateral floodwater loadings; and (5) bent upstream pile beam-column failure from combined vertical gravity and lateral debris raft loadings. This paper discusses the theoretical background for the equations used to evaluate each failure mode in the timber screening tool, in addition to describing the flow of the screening process.