Failure Mechanism of Column Components and Systems of Bridges

Bridges are a vital component of transportation facilities. Because it was revealed in past earthquakes that bridges were extremely vulnerable to seismic effects, a project on the failure mechanism of bridges was identified as one of the high priority areas of the National Institute of Earth Science and Disaster Prevention (NIED). Consequently, a five year research project on the large-scale experiments of bridges was launched at NIED in 2005. E-Defense is the world largest and powerful shake table constructed by NIED for clarifying the failure mechanism of structural components and systems under extreme ground motions, and it started its full service in 2006. Large scale experiments using E-Defense on bridge is scheduled in 2007–2009 based on NEES/E-Defense collaboration. Two types of model are proposed for bridge experiments; component model (C1 model) and system model (C2 model). C1 models are reinforced concrete columns which are tested to clarify failure mechanism of columns which collapsed or suffered extensive damage in 1995 Kobe, Japan earthquake, and verify the effectiveness of current seismic retrofit measures and seismic performace of columns designed based on the current design criteria. Reinforced concrete columns with diamter of nearly 2 m are excited by E-Defense as shown in Figure 1. C2 models are system models which are tested to clarfify progressive failure mechanism, effectiveness of advanced technology. Several pre E-Defense studies were conducted in 2005 and 2006 to evaluate necessary information prior to the large scale experiment using E-Defense. This paper shows an experimental clarification of failure mechanism on reinforced bridge columns which suffured extensive shear failure. This was the major damage of bridges in 1995 Kobe earthquake.