Performance Evaluation of Reinforced Concrete Bridge Columns through Experimental Blast Testing

Bridge columns are the most critical components of a bridge for its overall stability. At the same time, bridge columns are one of the most vulnerable components to terrorist attacks. Recent studies conducted by the University of Connecticut at the Army Corps of Engineers - Engineer Research and Development Center (ERDC) have shown that reinforced concrete (RC) columns that are subjected to large explosions may undergo significant yielding without showing any observable signs of damage, like spalling or permanent deformations. The blast overpressure acts as a confining force on the pressure side and allows the columns to instantaneously resist larger loads and deformations compared to static and dynamic loading. This condition leads officials to believe a compromised bridge column has not lost any capacity. However, once the blast pressure wave has cleared, this increased resistance due to the confining effect of blast overpressure is no longer available. The column is left with significantly reduced ductility, but without any observable damage. The results of three one-fifth scale blast tests of varying severity conducted at ERDC, combined with residual capacity tests and analytical studies conducted at Next-Generation Multihazard Resilient Infrastructure Laboratory (NGMRIL) at UConn, are used to confirm this phenomenon. Experimental results are used to quantify the proposed blast overpressure confinement effect. Subsequently, possible methodologies to assist officials in making critical bridge closure decisions after columns have been exposed to blast loading are explored.