Civil and Environmental Engineering


First Advisor

Joshua S. Steelman

Second Advisor

Ronald K. Faller

Date of this Version



A dissertation presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy

Major: Civil Engineering (Structural Engineering)

Under the supervision of Professor Joshua S. Steelman

Lincoln, Nebraska, December 2023


Copyright 2023, Andrew Eric Loken


When an errant vehicle strikes a bridge railing on a typical girder bridge, impact loads are transmitted downward through the railing and inward through the deck overhang to the primary superstructure elements. In this research effort, design demands for deck overhangs supporting concrete railings were characterized using physical testing and complementary modeling in LS-DYNA. Physical test and modeling results were also used to better characterize the ultimate strength of overhangs supporting post-and-beam railings. Ultimately, a novel design methodology for deck overhangs was developed and proposed for adoption to the AASHTO LRFD Bridge Design Specifications (BDS).

For overhangs with solid concrete railings, the existing BDS recommendation to use the barrier bending strength as the overhang moment demand was found to drastically overestimate actual overhang demands. In the proposed methodology, deck moment demands are calculated using the lateral impact load and an assumed longitudinal distribution pattern. Impact loads were found to effectively distribute at 45o and 60o with downward and inward transmission through the barrier and overhang, respectively.

For overhangs supporting concrete and steel posts, an alternative method of calculating the overhang capacity was developed, which produced significantly more accurate predictions of lateral post strength and deck damage than the existing BDS method. The method was also expanded to address posts mounted on curbed deck edges.

Advisor: Joshua S. Steelman