Effects of Bridge Pile Bent Geometry and Levels of Scour and $P$ Loads on Bent Pushover Loads in Extreme Flood/Scour Events

A common substructure for highway bridges over streams and creeks consists of a group of steel HP piles with a length above ground up to the level of a concrete bent cap, which supports the bridge superstructure. The use of three, four, five, or six such piles in a row with the two end piles battered constitutes a very common bridge bent configuration. In streams subject to significant flooding and scour, a critical load condition for these bents can be a gravity dead and live loading in conjunction with a horizontal flood water loading acting near the top of the bent. Such a loading may cause a pushover failure of the bent and, in turn, failure of the bridge. Pushover loads for such pile bents of various heights, bracing conditions, levels of gravity loading, and levels of scour are presented in this paper. A procedure is also presented for determining the maximum applied flood water loading acting on a bent, for determining the bent’s adequacy against a pushover failure.