Investigation of Seismic Design of Slab-on-Girder Bridge Details in Alabama

Abstract

The Alabama Department of Transportation (ALDOT) requested assistance to simplify and evaluate the process of designing typical slab-on-girder bridges for seismic loads. First, the determination of the seismic hazard in Alabama was made more expedient by providing hazard maps by each county within the state. Second, standard details were created to aid in the design of the plastic hinge zone within reinforced concrete columns. Third, the procedure for calculating the required support length at bents was studied. Next, the superstructure-to-substructure connection was investigated to determine whether adequate load path and capacity are provided to transfer seismic loads. Finally, the end diaphragms of steel girder bridges were designed for seismic loads to determine whether the current design methodology provides adequate resistance. It was determined that the superstructure-to-substructure connection did not provide adequate load path and anchor bolt strength, therefore improvements were recommended for future use in ALDOT’s designs. The end diaphragms were determined to be adequate with the inclusion of seismic loads in design.