Ji Lu Investigation - Ground Motions
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The ground motions of interest for the Ji Lu Bridge were the ones closest to its geographical location.  There were four motions considered in the site specific investigation done by Professor Loh, director of the National Center for Research on Earthquake Engineering (NCREE).

The motions considered were at the stations TCU078, TCU079, TCU089, and TCU129.  

Motion Distance (km) PGAtrans (g) PGAlong (g)
TCU078 7.34 .41 .33
TCU079 12.89 .60 .43
TCU089 12.61 .37 .19
TCU129 12.46 .95 .55
Site 0 .44 .46

Image showing locations of useable ground motions
Figure 1 - Map showing ground motions used in site specific characterization and the Ji Lu Bridge.   Click yellow markers to see ground Motions
 

 
The site specific record rotated to the longitudinal direction of the Ji Lu showed a peak ground acceleration of .46g.  The integrated velocity record had a peak ground velocity (PGV) of 18.7 in/sec (Figure 2).  The velocity record, like the others, has a cyclic sinusoidal pulse of about 10 seconds.

The results of a nonlinear constant ductility spectral analysis in the longitudinal direction showed the following results:

Quantity Peak Value
Spectral Acceleration 1.0 g
Spectral Velocity 35 in/sec
Spectral Displacement 15 in
Displacement Amplification at 4 sec 1.8

The spectral displacement at 4 seconds was showing no signs of leveling out, this coupled with the large nonlinear displacement amplification at 4 seconds amounts to the large nonlinear lateral displacements.  

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

 

 
The site specific record rotated to the transverse direction of the Ji Lu had a PGA was .44 and a PGV was 14 in/sec (Figure 3).  This record also shows a cyclic type behavior in the velocity record also with a period of around 10 sec.

The results of a nonlinear constant ductility spectral analysis in the transverse direction showed the following results:

Quantity Peak Value
Spectral Acceleration 1.3 g
Spectral Velocity 35 in/sec
Spectral Displacement 12.5 in
Displacement Amplification at 4 sec 1.0

The 1.3 g spectral ordinate was at ~ .2 sec.  The displacement amplification was 1.0 for a ductility of 5 showing the equal displacement rule to be applicable.

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


[TCU078] [TCU079] [TCU089] [TCU129]