TITech and UCB Joint Research on the
Seismic Performance of Bridge Columns
Based on NEES and E-Defense Collaboration
A total of four columns were tested, comparing bridge construction details commonly used in Japan and California. Two of the columns were rectangular in cross-section, with transverse reinforcement provided by rectangular hoops and cross ties. These were representative of Japanese construction. Two other columns had transverse reinforcement provided by a pair of interlocking spirals. In one case, the centers of the spiral cages were separated by 1.0 times the radius of the spiral, and in the other case the centers were separated by 1.33 times the radius of the individual spiral cages. Such columns are frequently used by Caltrans. The two rectangular columns had the same outer dimensions at the two columns with interlocking spirals, but the corners of the columns with spiral reinforcement have been chamfered. There was used a time history recorded in Kobe, Japan during the 1995 Hyogo-ken Nanbu earthquake at a site (Takatori) close to heavily damaged highway structures. The test schedule included several low level elastic range tests to characterize the dynamic properties of the specimen (and check instrumentation), followed by a yield level run, design level run, maximum credible event level run, and a repeat of the design level run. These tests examined the behavior of the specimen under earthquake events similar to those considered in design. To examine the endurance and ultimate failure characteristics of the column, testing was continued using the maximum level excitation and a slightly larger event until it was considered no longer safe to continue testing.
A project web site has been established by the Tokyo Tech researchers also. It can be seen at: http://seismic.cv.titech.ac.jp/TIT-UCB/. This research was part of a US-Japan collaborative research program between NEES and E-Defense. It focuses on experiments and analyses needed by Japanese researchers to develop major experiments involving bridge columns and structures to be performed later on the new E-Defense shaking table at the Hyogo Earthquake Engineering Research Center in Miki-City, Japan. This shaking table permits nearly full-size bridge models to be subjected to earthquakes as large as any recorded in Japan or the US during the Kobe and Northridge earthquakes.
The portion of the collaborative work being done at UC Berkeley involved (1) testing, analyzing and comparing columns representative of current California and Japanese construction practice, (2) developing and validating computer simulation models based on this data, and (c) carrying out hybrid simulations of more complex, seismically isolated and non-isolated bridges were portions of the bridge will be simultaneously tested or numerically at Kyoto University, Tokyo Institute of Technology, UC Berkeley and elsewhere. The research was conducted in conjunction with Prof. Kawashima of the Tokyo Institute of Technology, Prof. Takahashi of Kyoto University and Prof. Mahin at UC Berkeley. The first phase of this effort focused on shaking table testing and computer modeling by a team of students from Tokyo Tech working collaboratively with a group of students at UC Berkeley. The second phase of the effort relates to hybrid simulation and this will be carried out later this year. It involves students and researchers from the Disaster Prevention Research Institute of Kyoto University and UC Berkeley.
Funding for the nees@berkeley contribution of the phase 1 effort was provided by a contract from the Tokyo Institute of Technology as well as support from the Earthquake Engineering Research Center of UC Berkeley and nees@berkeley. nees@berkeley is supported by a contract with NEESinc though a cooperative agreement with the US National Science Foundation. Funding on the Japan side was provided by the Japanese National Institute for Earth Science and Disaster Prevention through a grant from the Japan Ministry of Education, Culture, Sports, Medicine, Science and Technology.