CSMIP Strong-Motion Instrumentation and Records from the I10/215 Interchange Bridge near San Bernardino

The 2540-foot long, multi-span, curved I10/215 interchange bridge near San Bernardino was extensively instrumented by the California Strong Motion Instrumentation Program (CSMIP) in cooperation with the California Department of Transportation (Caltrans). The locations of the sensors on this freeway interchange bridge were carefully planned to achieve specific instrumentation objectives. Significant sets of strong-motion records were obtained from this bridge during the magnitude 7.5 Landers and the magnitude 6.6 Big Bear earthquakes of June 28, 1992. The epicenters of these earthquakes were about 50 and 30 miles (80 and 48 km) from the bridge, respectively. The maximum ground acceleration at the bridge was about 0.10 g for both earthquakes. The relative motion of the deck across the hinges was recorded and is characterized by sharp spikes in the acceleration records with a peak value as high as 0.81 g during the Landers and 1.02 g during the Big Bear earthquake. Without the spikes the peak acceleration on the bridge would be about 0.40 g during the Landers and 0.30 g during the Big Bear earthquake. The Landers records show that the bridge structure had a period of about 1.7 seconds in the transverse direction and 1.0 second in the longitudinal direction. The maximum relative displacement between the deck and the footing of a 57-foot column was about 16 cm in the transverse direction and 5 cm in the longitudinal direction during the Landers earthquake. The maximum relative displacement across one of the hinges during the Landers earthquake was 1.2 cm in the transverse direction and 3.6 cm in the longitudinal direction.