Bridge piers located in navigable inland waterways are designed to resist impact forces from barges and flotillas in addition to other design considerations (e.g., scour, dead and live loads, etc.). The primary design tool for estimating these forces is the AASHTO Guide Specification which provides a simple hand calculation method for determining an “equivalent impact force”. The simplicity comes at a cost of excluding the effect of the pier shape, impact duration, and interaction between barges in a flotilla. The objective of this report is to present a hand calculation method for determining barge or flotilla equivalent static impact forces on bridge piers. The primary advantage of this approach lies in its incorporation of pier geometry, interaction between barges, and impact duration. The proposed method is derived from the conduct of hundreds of finite element dynamic simulations of barges and various flotilla configurations impacting rigid and flexible rectangular and circular (or rounded end) bridge piers at different velocities. Results are presented and compared with ones derived from the AASHTO method and detailed finite element modeling. The results generated by the proposed method compare very well with ones derived from the FE modeling, while the AASHTO results are up to twice as large as one from the proposed method for the examples presented in this report.

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The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names or trade names is for identification purposes only and is not to be considered an endorsement.