The Earthquake Engineering Online Archive

Field testing of bridge design and retrofit concepts: Part 2 of 2: Experimental and analytical studies of the Mt. Diablo Blvd. bridge

Gilani, Amir S.; Chavez, Juan W.; Fenves, Gregory L.

UCB/EERC-96/02, Earthquake Engineering Research Center, University of California, Berkeley, 1996-06, 140 pages (520.6/F53/1996)

Field testing and dynamic analysis of an elevated curved bridge arose out of the reconstruction and demolition activities of the Interstate 680/Route 24 interchange in Walnut Creek, California. Prior to its demolition, the bridge was subjected to forced vibration tests and ambient measurements. During the forced vibration tests, vibration generators placed on the deck of the bridge were used to excite the bridge in its principal directions. The resulting steady state response was recorded and used to evaluate the dynamic properties of the entire bridge. For the ambient measurements, response to factors such as wind and local traffic were determined. After the beginning of the demolition sequence, ambient response of partial frames of the bridge were measured. The collected field data were used to determine the dynamic properties (mode shapes, modal frequencies, and damping ratios) of the bridge, and the frequencies of the partial structures. Analytical models were developed according to the computed properties, and linear dynamic analyses were carried out to verify the measured dynamic properties. From analysis of experimental data, a total of ten superstructure modes were identified. The analytical models were calibrated from the test data for the partial frames. These data aided in identification of effective column heights, stiffness reduction factors, and boundary conditions.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-96-02.pdf (20 MB)