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Earthquake Engineering Research - HKU Libraries - The University ...

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569<br />

ADXL210 Frequency Response Function (30Hz)<br />

5 10<br />

Frequency (Hz)<br />

15<br />

Figure 4 - Frequency response function denved from the structural acceleration response<br />

ADXL210 Measured Absolute Acceleration Response to White Noise Input<br />

30<br />

Time (sec)<br />

Figure 5 - Absolute acceleration response of fifth-story to a white noise input excitation<br />

<strong>The</strong> time history acceleration response of the structure as measured in this manner is relatively<br />

stationary with zero mean and a standard deviation of approximately 1 1 g <strong>The</strong>refore, the record is<br />

suitable to fitting an auto-regressive time series model<br />

After recording the acceleration response of the test structure, an auto regressive model of 10<br />

coefficients is tit to the measurement data of Figure 5 After logging the coefficients an identical<br />

analysis is performed using Burg s auto-regressive function provided by MATLAB to compare the<br />

accuracy of the coefficients determined by the wireless sensing unit <strong>The</strong> coefficients determined by<br />

the wireless sensing unit and MATLAB, as presented in Table 1 are identical<br />

Table 1 - Coefficients of a fitted auto regressive model to stationary structural response<br />

bi<br />

1><br />

b 3<br />

5 4<br />

b s<br />

be<br />

b 7<br />

b s<br />

b 9<br />

bio<br />

PowerPC<br />

166M)<br />

13009<br />

047D2<br />

01171<br />

06756<br />

15212<br />

12646<br />

0^989<br />

01498<br />

00891<br />

AR 10<br />

MATLAB<br />

16650<br />

13009<br />

04752<br />

0 1171<br />

06756<br />

15212<br />

12646<br />

05989<br />

01498<br />

00891

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