Fujikura and Bruneau 2008
This paper presents the development and experimental validation of a multihazard bridge pier concept, i.e., a bridge pier system capable of providing an adequate level of protection against collapse under seismic and blast loading. A multicolumn pier-bent with concrete-filled steel tube columns is the proposed concept. The adequacy of this system is experimentally investigated under blast loading. This paper describes simplified blast analysis, multihazard design of bridge piers, and blast experimental program results.
Experimental Study, Results, and Discussion
The simplified analysis procedure introduced in this study considers and equivalent single-degree-of-freedom system having an elastic-perfectly plastic behavior, and assumes that all the energy imparted to the system by the blast loading is converted into internal strain energy. The energy imparted to the system is considered impulsive loading. The blast scenario considered in this paper concerns a blast source of an explosive device located in a car at the base of a bridge pier. The pier concepts considered were designed and analyzed assuming that they are part of a typical three-span continuous highway bridge as described in Dicleli and Bruneau (1996). Pier columns were designed as CFT columns and utilized the foundation proposed by Marson and Bruneau in 2004 which consisted of concrete embedded C channels linked to the columns through steel plates.
Two identical multicolumn bents were fabricated and a series of blast tests were performed. Test specimen dimensions were set to be quarter scale of the prototype bridge piers. Each specimen consisted of three piers with different diameters of 4, 5, and 6 inches connected to steel beams embedded in the cap beam and foundation beam. The bent frames were braced in what would correspond to the bridge longitudinal direction at the level of the cap beams. Cap beams were not connected to the frame but were only in contact with the frame. The main test parameters were weight, standoff distance from pier, and height of the explosives.
Specimens showed no sign of breaching and spalling after testing, demonstrating the effectiveness of CFT columns as blast resistant structures. Tests showed that CFT columns exhibited a satisfactory ductile behavior under blast loading. The foundation connection concept applied in this experiment allowed the composite strength of CFT columns to develop under blast loading.
Reference
Fujikura, S., Bruneau, M., and Lopez-Garcia, D. (2008). ”Experimental Investigation of Multihazard Resistant Bridge Piers Having Concrete-Filled Steel Tube under Blast Loading.” Journal of Bridge Engineering, 13(6), 586–594. doi: 10.1061/(ASCE)1084-0702(2008)13:6(586)