The fourth and last test in a series of experiments on rectangular columns were performed on the shaking table at the UC Berkeley Richmond Field Station. This test is part of the E-Defense/NEES Collaborative Research Program on Earthquake Engineering and focuses on a comparison of U.S. and Japanese design practices for constructing reinforced concrete bridges, and on developing test models for subsequent tests on the E-Defense Shaking Table in Japan. (http://www.bosai.go.jp/hyogo/ehyogo/index.html)
The first two columns in the program had transverse reinforcement provided by interlocking spirals as commonly employed by Caltrans, and the second two have traditional hoops supplemented with a limited number of cross ties, as utilized in Japan. In each set of columns, the aspect ratio of column thickness to width is altered.
The fourth specimen is similar to the first three, and will be subjected to the same ground motions, except it uses the larger aspect ratio. The ground motion utilized consists of three components from the Takatori record from the 1995 Kobe (Hyogo-ken Nanbu earthquake). The tests consist of low level runs, a design level run (nominal displacement ductility of about 4), a maximum considered run (scaled to about the predicted displacement capacity of the column), a repeat of the design level event, followed by a succession of runs where the intensity of the motion is increased up to about 1.8 times the nominal design level event. Tests continue until the specimen appears to be unsafe to test further (due to excessive local damage or residual tilt).
The tests are co-supervised by Prof. Kawashima of the Tokyo Institute of Technology and Prof. Mahin of UC Berkeley. The tests are performed by a team of students from Tokyo Tech and UC Berkeley. Funds are provided by the U.S. National Science Foundation though institutional support by NEES Consortium, Inc. of the NEES@berkeley facility and the Japan Ministry of Education, Sports, Culture, Science and Technology through the National Research Institute for Earth Science and Disaster Prevention.
The next series of tests will involve a hybrid simulation where we will mimic the behavior of a shaking table test of one of these columns with seismic isolators placed on top of the columns to limit damage. The column will be tested at Kyoto University and the seismic isolators will be tested in Berkeley in the nees@berkeley laboratory.
The remainder of the bridge and its supports will be simulated numerically. The tests will involve embedding the two test specimens within the overall structural dynamic analysis model, and carrying out the tests simultaneously with the analysis via the internet. The hybrid simulation will be carried out using OpenFresco, a framework for experimentation and control developed by Profs. Fenves and Mahin of UC Berkeley and Prof. Takahashi at Kyoto University. The simulation will be carried out using OpenSees, developed by Prof. Fenves. More information on these tests will be available at a later date.
posted on October 2006