Ground Motions - TCU129
Ground Motions - TCU129 |
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| The TCU129 record (N 23.878, E 120.684) was the largest in PGA of the four records under consideration and was located at an approximate distance of 12.46 km (Figure 1) from the Ji Lu and 13.54 km from the epicenter. Of the four records under consideration, this record was the farthest from the epicenter, but was very close to the fault rupture itself lying just west of the fault hanging wall. This was the only record from the west side of the fault under consideration. The other stations were east of the rupture and east of the epicenter and had PGA's and PGV's far less than the TCU129 record. |
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Figure 1 - Location of TCU129 relative to the Ji Lu |
| The corrected record rotated to the
longitudinal direction of the Ji Lu showed a peak ground acceleration of
.55g. The
integrated velocity record had a peak ground velocity of 25.9 seconds (Figure 2).
The results of a nonlinear constant ductility spectral analysis in the longitudinal direction showed the following results:
The maximum spectral displacement was at 4 sec and showed no signs of leveling off. In the periods of interest (2.1 to 3.6 seconds), displacements ranged from 6 to 12 inches. |
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Figure 2 - Rotated and Corrected acceleration and velocity records longitudinal to the Ji-Lu bridge |
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| The corrected record rotated to the
transverse direction of the Ji Lu was the largest motion recorded in the area. The
PGA was .95 and the PGV was 27.6 in/sec (Figure 3). The shape of the velocity record,
like in the longitudinal direction, was very harmonic with a cycle time of about
6 seconds. This effect may have given the bridge the low frequency energy it needed to
displace the large amplitudes that it did. This effect is still under investigation.
The results of a nonlinear constant ductility spectral analysis in the transverse direction showed the following results:
The spectral displacement at 4 seconds, like in the longitudinal direction was showing no signs of leveling out. In fact, the trend was very linear. Nonlinear amplification of displacements was greater than one at 4 sec showing increased deformations with structural nonlinearity. This nonlinear displacement amplification was also seen the TCU078 record. The spectral ordinate of 1.8 on the acceleration response spectrum was at the site period of ~ .4 sec. with a slight second peak of .5g at 1.3 sec. In the periods of interest, the spectral displacement values ranged from 9 - 18 inches. |
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Figure 3 - Rotated and Corrected acceleration and velocity records transverse to the Ji-Lu bridge |
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