Ground Motions - TCU078

The TCU078 record (N 23.812, E 120.845) was the closest to the Ji Lu at an approximate distance of 7.34 km (Figure 1). The strong motion sensor was also the closest recording to the epicenter at a distance of 5.96 km.
	Figure 1 - Location of TCU078 relative to the Ji Lu

The corrected record rotated to the longitudinal direction of the Ji Lu showed a peak ground acceleration of .33g. The integrated velocity record had a spike of 10 in/sec at 39 seconds into the record (Figure 2). Nonlinear spectral analysis was done on the ground motions in the transverse and longitudinal directions at constant ductilities. The Results, longitudinally, showed a maximum spectral amplitude of approximately 1g at a period of .4 sec. In the periods of interest (2.1 to 3.6 seconds), the spectral values for accelerations, velocities, and displacements were .1 g, 15 in/sec, and 6 in, respectively. In the range of interest, the nonlinear spectral displacement values were mostly lower than the linear (elastic) values.

	Figure 2 - Rotated and Corrected acceleration and velocity records longitudinal to the Ji-Lu bridge

The corrected record rotated to the transverse direction of the Ji Lu showed a peak ground acceleration of .41g. Just over that recorded in the longitudinal direction. The integrated velocity record had a peak of 16.8 in/sec (Figure 3). The shape of the velocity record shows a distinct long period sine pulse that could have had a significant contribution to the large lateral bridge movement observed during the event. This is still under investigation. The Results in the transverse direction showed a maximum spectral ordinate of approximately 1.7g at a period of .25 sec. In the periods of interest (2.1 to 3.6 seconds), the spectral values for accelerations, velocities, and displacements are .1 g, 17 in/sec, and +/- 8 in, respectively. The displacement values vary widely between the range of interest with 8 inches being the average. In opposite to the longitudinal analysis results, the nonlinear displacement ordinates in the range of interest were LARGER than the elastic values. This is unusual; but, could help to explain the large transverse displacements. As the structure yields, displacement are not preserved, but rather they are amplified.

	Figure 3 - Rotated and Corrected acceleration and velocity records transverse to the Ji-Lu bridge