5 SEISMIC PERFORMANCE TESTS
5.1 S HAKING T ABLE T ESTS
5.1.4 Assessments of Seismic Performance
To prevent damage of the model structure, no tests with intensity larger than 0.1g have been conducted on the bare frame (i.e. without damper). The responses of the bare frame at greater intensities (PGA=0.2g, 0.3g and 0.4g for El Centro, PGA=0.15g, 0.2g and 0.25g for both Hachinohe and Kobe) presented in this section were obtained by linear extrapolation from the recorded results for PGA=0.1g. The testing results for the damper-protected structure were recorded directly.
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81
El Centro Earthquake The comparisons of floor acceleration responses
under the El Centro earthquake are illustrated in Fig. 5.9 ~ 5.12 for intensities of 0.1g, 0.2g, 0.3g and 0.4g, respectively. As protected with damper, evident reductions of all the floor accelerations at various earthquake intensities have been observed. The peak floor responses at each testing scenario are summarized in Table 5.3. The peak accelerations are reduced except for 5F of PGA=0.1g, 0.2g, 0.3g and 0.4g, 2F of PGA=0.1g. The reduction of the 1st floor peak acceleration in the case of PGA=0.1g is 16% and increased to 38% in the case of PGA=0.4g. The controlling effects of the damper system is even more pronounced as we look into the root-mean-squares (RMS) responses of the floor accelerations, as summarized in Table 5.4. The RMS responses are reduced except for 5F of PGA=0.1g. The reduction of the 5th floor RMS acceleration in the case of PGA=0.2g is 18%, and increased to over 40% for higher intensities.The comparison of the storydrift of the 1st floor under the El Centro earthquake are illustrated in Fig. 5.13 ~ 3.16 for intensities of 0.1g, 0.2g, 0.3g and 0.4g, respectively. The controlling effects of the damper on the displacement responses have been achieved to a greater extent. The comparison of the root-mean-squares responses of the 1st floor storydrift is summarized in Table 5.5. The reduction of the RMS response is 62% in the case of PGA=0.1g and increases for higher intensities.
The dynamic characteristics of the model structure in terms of the equivalent natural frequency and damping ratio of each mode under each testing scenario were determined, using the system identification technique from the test results, and summarized in Table 5.6. It is noted that the equivalent natural frequencies of the model structure decrease as the earthquake intensity increased, while the model damping ratios increase with the earthquake intensity. This is due to involvement of more inelastic behavior of the dampers for stronger earthquake. The natural frequencies of the structure have been increased as compared with those for the bare frame from Table 5.2 due to the added stiffness by the damper. The damping ratio of the 1st mode was increased from 0.51% to 2.89% for PGA=0.1g and up to 7.49% for PGA=0.4g. Similar trends have been observed for the other modes.
Hachinohe Earthquake The comparisons of floor acceleration responses
under the Hachinohe earthquake are illustrated in Fig. 5.17 ~ 5.20 for intensities of 0.1g, 0.15g, 0.2g and 0.25g, respectively. As protected with damper, evident reductions of all the floor accelerations at various earthquake intensities have been observed, without exception. The peak floor responses at each testing scenario are summarized in Table 5.7. The reduction of the 5th floor peak acceleration in the case of PGA=0.1g is 46%, and increased slightly for higher intensities. The reduction of the 1st floor peak acceleration in the case of PGA=0.1g is 31% and increased to 49% in the case of PGA=0.25g. The controlling effects of the damper system is even more pronounced as we look into the root-mean-squares (RMS) responses of the floor accelerations, as summarized in Table 5.8. The reduction of the 5th floor RMS acceleration in the case of PGA=0.1g is 54%, and increased to over 70% for higher intensities.The comparison of the storydrift of the 1st floor under the Hachinohe earthquake are illustrated in Fig. 5.21~3.24 for intensities of 0.1g, 0.15g, 0.2g and 0.25g, respectively. The controlling effects of the damper on the displacement responses have been achieved to a greater extent. The comparison of the root-mean-squares responses of the 1st floor storydrift is summarized in Table 5.9. The reduction of the RMS response is 72% in the case of PGA=0.1g and 81% for higher intensities.
The dynamic characteristics of the model structure in terms of the equivalent natural frequency and damping ratio of each mode under each testing scenario were determined, using the system identification technique from the test results, and summarized in Table 5.10. It is noted that the equivalent natural frequencies of the model structure decrease as the earthquake intensity increased, while the model damping ratios increase with the earthquake intensity. This is due to involvement of more inelastic behavior of the dampers for stronger earthquake. The natural frequencies of the structure have been increased as compared with those for the bare frame from Table 5.2 due to the added stiffness by the damper. The damping ratio of the 1st mode was increased from 0.51% to 4.79% for PGA=0.1g and up to 10.34%
for PGA=0.25g. Similar trends have been observed for the other modes.
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83
Kobe Earthquake The comparisons of floor acceleration responses under
the Kobe earthquake are illustrated in Fig. 5.25 ~ 5.28 for intensities of 0.1g, 0.15g, 0.2g and 0.25g, respectively. Similarly, as protected with damper, evident reductions of all the floor accelerations at various earthquake intensities have been observed, without exception. The peak floor responses at each testing scenario are summarized in Table 5.11. The reduction of the 5th floor peak acceleration in the case of PGA=0.1g is 45%, and increased slightly for higher intensities. The reduction of the 1st floor peak acceleration in the case of PGA=0.1g is 21% and increased to 28% in the case of PGA=0.2g. The controlling effects of the damper system is even more pronounced as we look into the root-mean-squares (RMS) responses of the floor accelerations, as summarized in Table 5.12. The reduction of the 5th floor RMS acceleration in the case of PGA=0.10g is 72%, and increased to 75% in the case of PGA=0.25g.The comparison of the storydrift of the 1st floor under the Hachinohe earthquake are illustrated in Fig. 3.29~3.32 for intensities of 0.1g, 0.15g, 0.2g and 0.25g, respectively. The controlling effects of the damper on the displacement responses have been achieved to a greater extent. The comparison of the root-mean-squares responses of the 1st floor storydrift is summarized in Table 5.13. The reduction of the RMS response is 85% in the case of PGA=0.1g and 81% for higher intensities.
The dynamic characteristics of the model structure in terms of the equivalent natural frequency and damping ratio of each mode under each testing scenario were determined, using the system identification technique from the test results, and summarized in Table 5.14. It is noted that the equivalent natural frequencies of the model structure decrease as the earthquake intensity increased, while the modal damping ratios increase with the earthquake intensity. This again is due to involvement of more inelastic behavior of the dampers for stronger earthquake. The natural frequencies of the structure have been increased as compared with those for the bare frame from Table 2.2 due to the added stiffness by the damper. The damping ratio of the 1st mode was increased from 0.51% to 7.56% for PGA=0.1g and up to 9.26%
for PGA=0.25g. Similar trends have been observed for the 2nd mode.
-0.3 0.0 0.3
5F Ac cel er at io n ( g )
Experimental Acc.
El Centro 0.1g w/ USD Fixed
-0.3 0.0 0.3
4F A ccel er at io n (g )
-0.3 0.0 0.3
2F A cc ele ra ti on ( g )
-0.3 0.0 0.3
3F A ccel er at io n (g )
0 5 10 15 20
Time(sec) -0.3
0.0 0.3
1F A ccel er at io n (g )
Fig. 5.9 Comparison of floor acceleration responses (El Centro, PGA=0.1g)
w/ damper w/o damper
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85
-0.3 0.0 0.3
5F Acceleration (g)
Experimental Acc.
El Centro 0.2g w/ USD Fixed
-0.3 0.0 0.3
4F Acceleration (g)
-0.3 0.0 0.3
2F Acceleration (g)
-0.3 0.0 0.3
3F Acceleration (g)
0 5 10 15 20
Time(sec) -0.3
0.0 0.3
1F Acceleration (g)
Fig. 5.10 Comparison of floor acceleration responses (El Centro, PGA=0.2g)
w/ damper w/o damper
0.5 0.0 -0.5
5F Acceleration (g)
Experimental Acc.
El Centro 0.3g w/ USD Fixed
-0.5 0.0 0.5
4F Acceleration (g)
-0.5 0.0 0.5
2F Acceleration (g)
-0.5 0.0 0.5
3F Acceleration (g)
0 10 20 30 40
Time(sec) -0.4
0.0 0.4
1F Acceleration (g)
Fig. 5.11 Comparison of floor acceleration responses (El Centro, PGA=0.3g)
w/ damper w/o damper
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87
-0.5 0.0 0.5
5F Acceleration (g)
Experimental Acc.
El Centro 0.4g w/ USD Fixed
-0.5 0.0 0.5
4F Acceleration (g)
-0.5 0.0 0.5
2F Acceleration (g)
-0.5 0.0 0.5
3F Acceleration (g)
0 10 20 30 40
Time(sec) -0.5
0.0 0.5
1F Acceleration (g)
Fig. 5.12 Comparison of floor acceleration responses (El Centro, PGA=0.4g)
w/ damper w/o damper
0 10 20
Time (sec)
-1.0
0.0 1.0
1F D rif t (c m ) Fixed
w/ USD
Fig. 5.13 Comparison of storydrift of the 1st Floor (El Centro, PGA = 0.1g)
0 10 20
Time (sec)
-2.0
0.0 2.0
1F D rif t (c m ) Fixed
w/ USD
Fig. 5.14 Comparison of storydrift of the 1st Floor (El Centro, PGA = 0.2g)
w/ damper w/o damper
w/ damper w/o damper
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89
0 10 20 30 40
Time (sec)
-3.0
0.0 3.0
1F D rif t (c m ) Fixed
w/ USD
Fig. 5.15 Comparison of storydrift of the 1st Floor (El Centro, PGA = 0.3g)
0 10 20 30 40
Time (sec)
-3.0
0.0 3.0
1F D rif t (c m ) Fixed
w/ USD
Fig. 5.16 Comparison of storydrift of the 1st Floor (El Centro, PGA = 0.4g)
w/ damper w/o damper
w/ damper w/o damper
-0.4 0.0 0.4
5F Acceleration (g)
Experimental Acc.
Hachinohe 0.1g w/ USD Fixed
-0.4 0.0 0.4
4F Acceleration (g)
-0.4 0.0 0.4
2F Acceleration (g)
-0.4 0.0 0.4
3F Acceleration (g)
0 4 8
Time(sec) -0.4
0.0 0.4
1F Acceleration (g)
Fig. 5.17 Comparison of Floor Acceleration Responses (Hachinohe, PGA = 0.1g)
w/ damper w/o damper
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91
-0.5 0.0 0.5
5F A cc el era ti on (g )
Experimental Acc.
Hachinohe 0.15g w/ USD Fixed
-0.5 0.0 0.5
4F A cce le ra ti on ( g )
-0.5 0.0 0.5
2F A cc ele ra ti on (g )
-0.5 0.0 0.5
3F Ac ce le ra ti on (g )
0 5 10 15
Time(sec) -0.5
0.0 0.5
1F A cc el er atio n ( g )
Fig. 5.18 Comparison of Floor Acceleration Responses (Hachinohe, PGA = 0.15g)
w/ damper w/o damper
-0.8 0.0 0.8
5F A cc el er at io n ( g )
Experimental Acc.
Hachinohe 0.2g w/ USD Fixed
-0.8 0.0 0.8
4F Ac ce le ra ti on ( g )
-0.8 0.0 0.8
2F Ac ce le ra ti on ( g )
-0.8 0.0 0.8
3F A cc ele ra ti on (g )
0 5 10 15
Time(sec) -0.8
0.0 0.8
1F A cce le rat io n (g )
Fig. 5.19 Comparison of Floor Acceleration Responses (Hachinohe, PGA = 0.20g)
w/ damper w/o damper
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93
-1.0 0.0 1.0
5F A cc el er at io n ( g )
Experimental Acc.
Hachinohe 0.25g w/ USD Fixed
-1.0 0.0 1.0
4F A cc ele ra tio n (g )
-1.0 0.0 1.0
2F A cc el er at io n (g )
-1.0 0.0 1.0
3F A ccele ra ti on ( g )
0 5 10 15
Time(sec) -1.0
0.0 1.0
1F A cc el er atio n (g )
Fig. 5.20 Comparison of Floor Acceleration Responses (Hachinohe, PGA = 0.25g)
w/ damper w/o damper
0 4 8
Time (sec)
-3.0 0.0 3.0
1F D rif t (c m ) Fixed
w/ USD
0 5 10 15
Time (sec)
-3.0 0.0 3.0
1F Dr if t (c m ) Fixed
w/ USD
w/ damper w/o damper
w/ damper w/o damper Fig. 5.21 Comparison of Storydrift of the 1st Floor
(Hachinohe, PGA = 0.1g)
Fig. 5.22 Comparison of Storydrift of the 1st Floor (Hachinohe, PGA = 0.15g)
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0 5 10 15
Time (sec)
-4.0 0.0 4.0
1F Dr if t (c m ) Fixed
w/ USD
0 5 10 15
Time (sec)
-5.0 0.0 5.0
1F Dr if t (c m ) Fixed
w/ USD
w/ damper w/o damper
w/ damper w/o damper Fig. 5.23 Comparison of Storydrift of the 1st Floor
(Hachinohe, PGA = 0.2g)
Fig. 5.24 Comparison of Storydrift of the 1st Floor (Hachinohe, PGA = 0.25g)
-0.4 0.0 0.4
5F A cce le ra ti on (g )
Experimental Acc.
Kobe 0.1g w/ USD Fixed
-0.4 0.0 0.4
4F A cce le ra ti on ( g )
-0.4 0.0 0.4
2F A cc el era ti on (g )
-0.4 0.0 0.4
3F A cc ele ra ti on ( g )
0 5 10 15 20 25
Time(sec) -0.4
0.0 0.4
1F A cc el era ti on (g )
Fig. 5.25 Comparison of Floor Acceleration Responses (Kobe, PGA = 0.1g)
w/ damper w/o damper
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97
-0.5 0.0 0.5
5F A cc el era ti on (g )
Experimental Acc.
Kobe 0.15g w/ USD Fixed
-0.5 0.0 0.5
4F Accel er at io n ( g )
-0.5 0.0 0.5
2F A cc ele ra tio n ( g )
-0.5 0.0 0.5
3F A cc el era ti on (g )
0 5 10 15 20 25
Time(sec) -0.5
0.0 0.5
1F A cc el era ti on (g )
Fig. 5.26 Comparison of Floor Acceleration Responses (Kobe, PGA = 0.15g)
w/ damper w/o damper
-0.8 0.0 0.8
5F A cc el era ti on (g )
Experimental Acc.
Kobe 0.2g w/ USD Fixed
-0.8 0.0 0.8
4F Ac cel er at io n (g )
-0.8 0.0 0.8
2F A cce ler at io n ( g )
-0.8 0.0 0.8
3F Ac cel er at io n (g )
0 5 10 15 20 25
Time(sec) -0.8
0.0 0.8
1F A ccel er at io n (g )
Fig. 5.27 Comparison of Floor Acceleration Responses (Kobe, PGA = 0.2g)
w/ damper w/o damper
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-0.8 0.0 0.8
5F Acceleration (g)
Experimental Acc.
4F Acceleration (g)
-0.8 0.0 0.8
2F Acceleration (g)
-0.8 0.0 0.8
3F Acceleration (g)
0 5 10 15 20 25
Time(sec) -0.8
0.0 0.8
1F Acceleration (g)
w/ USD w/o USD
Fig. 5.28 Comparison of Floor Acceleration Responses (Kobe, PGA = 0.25g)
w/ damper w/o damper
w/ damper w/o damper
w/ damper w/o damper Fig. 5.29 Comparison of Storydrift of the 1st Floor
(Kobe, PGA = 0.1g)
Fig. 5.30 Comparison of Storydrift of the 1st Floor (Kobe, PGA = 0.15g)
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101
w/ damper w/o damper
w/ damper w/o damper Fig. 5.31 Comparison of Storydrift of the 1st Floor
(Kobe, PGA = 0.2g)
Fig. 5.32 Comparison of Storydrift of the 1st Floor (Kobe, PGA = 0.25g)
Table 5.3 Comparison of Peak Floor Acceleration Responses in the El Centro Series of Tests
Input = El Centro Earthquake
PGA = 0.1g PGA = 0.2g
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Table 5.4 Comparison of Root-Mean-Squares Floor Acceleration In the El Centro Series of Tests
Input = El Centro Earthquake
PGA = 0.1g PGA = 0.2g
Table 5.5 Root-Mean-Squares of 1st Floor Storydrift In the El Centro Series of Tests
Input= El Centro Earthquake RMS Response of Storydrift
(cm)
Table 5.6 Equivalent Natural Frequency and Damping Ratio of the damper-Protected Model Structure
El Centro Earthquake Record
PGA = 0.1g PGA = 0.2g PGA = 0.3g PGA = 0.4g
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Table 5.7 Comparison of Peak Floor Acceleration Responses in the Hachinohe Series of Tests
Input = Hachinohe Earthquake
PGA = 0.10g PGA = 0.15g
Table 5.8 Comparison of Root-Mean-Squares Floor Acceleration In the Hachinohe Series of Tests
Input = Hachinohe Earthquake
PGA = 0.10g PGA = 0.15g
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Table 5.9 Root-Mean-Squares of 1st Floor Storydrift In the Hachinohe Series of Tests
Input= Hachinohe Earthquake RMS Response of Storydrift
(cm)
Table 5.10 Equivalent Natural Frequency and Damping Ratio of the damper-Protected Model Structure
Hachinohe Earthquake Record
PGA = 0.1g PGA = 0.15g PGA = 0.2g PGA = 0.25g
Table 5.11 Comparison of Peak Floor Acceleration Responses in the Kobe series Tests
Input = Kobe Earthquake
PGA = 0.10g PGA = 0.15g
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Table 5.12 Comparison of Root-Mean-Squares Floor Acceleration for Kobe Series of Tests
Input = Kobe Earthquake
PGA = 0.1g PGA = 0.15g
Table 5.13 Root-Mean-Squares of 1st Floor Storydrift for Kobe Series of Tests
RMS of 1F Drift for Kobe Earthquake Record (cm) RMS of 1F Drift (cm)
Table 5.14 Equivalent Natural Frequency and Damping Ratio of the damper-Protected Model Structure
Kobe Earthquake Record
PGA = 0.1g PGA = 0.15g PGA = 0.2g PGA = 0.25g
Chapter 5 Seismic Performance Tests