Experimental investigation of blast performance of seismically resistant concrete-filled steel tube bridge piers

Abstract

The terrorist threat on bridges, and on the transportation system as a whole, has been recognized by the engineering community and public officials since recent terrorist attacks. There are some similarities between seismic and blast effects on bridge structures: both major earthquakes and terrorist attacks/accidental explosions are rare events that can induce large inelastic deformations in the key structural components of bridges. Since many bridges are (or will be) located in areas of moderate or high seismic activity, and because many bridges are potential terrorist targets, there is a need to develop structural systems capable of performing equally well under both events.
The objective of this research is to present the development and experimental validation of a multi-hazard bridge pier concept, i.e., a bridge pier system capable of providing an adequate level of protection against collapse under both seismic and blast loading. A multi-column pierbent with concrete-filled steel tube (CFST) columns is the proposed concept. The work presented here experimentally investigates the adequacy of such a system under blast loading.
This report describes development of the multi-hazard pier concept, design of the prototype bridge pier under blast and seismic loading, specimen design, experimental set-up, and experimental results. Additionally, the results from the blast experiments are compared with the results from simplified method of analysis considering an equivalent SDOF system having an elastic-perfectly-plastic behavior.
It is found that prototype bridge CFST columns can be designed to provide both satisfactory seismic performance and adequate blast resistance. It is also shown that the CFST columns exhibited a ductile behavior under blast load in a series of the tests at 1/4 scale. Maximum deformation of the column could be calculated using simplified analysis considering a factor to account for the reduction of pressures on the circular column and determined from this experimental program.