Natural frequencies evaluation on existing reinforced concrete bridges using microtremor testing
Most bridges in Malaysia do not take earthquake loadings into their structural design consideration. Structure constructed without the consideration of seismic design is generally more vulnerable to ground shaking during seismic event. Even though Malaysia is located on the stable Sunda shelf wit...
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| Format: | Thesis |
| Language: | English English English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/654/1/24p%20NURUL%20SHAZWIN%20IDRIS.pdf http://eprints.uthm.edu.my/654/2/NURUL%20SHAZWIN%20IDRIS%20COPYRIGHT%20DECLARATION.pdf http://eprints.uthm.edu.my/654/3/NURUL%20SHAZWIN%20IDRIS%20WATERMARK.pdf http://eprints.uthm.edu.my/654/ |
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| Summary: | Most bridges in Malaysia do not take earthquake loadings into their structural design
consideration. Structure constructed without the consideration of seismic design is
generally more vulnerable to ground shaking during seismic event. Even though
Malaysia is located on the stable Sunda shelf with low to medium seismic activity
level, effects of tremors due to Sumatran earthquakes have been reported several
times. Identification of natural frequencies is important to avoid bridge resonance
which could happen when frequency of excitation coincides with a bridge natural
frequency. Resonance can cause failure to bridges. Therefore, it is important for
newly constructed and old bridges to be tested using simple dynamic test such as
microtremor test in order to determine the natural frequencies of the bridges.
Microtremor is also known as ambient vibration test. The test is a non-destructive
test and easy to be conducted with less labor, time and cost. From the testing,
„ambient‟ vibration excitation experienced by a structure under normal operating
conditions can be determined. The aim of this study was to determine the natural
frequencies of two different lengths of reinforced concrete bridges crossing Sungai
Sembrong and Sungai Simpang Kiri. By using GEOPSY software, Fourier Spectra
Amplitude Ratio (FSA) analysis used for determining bridge natural frequencies and
Horizontal-To-Vertical-Spectra-Ratio (HVSR) analysis for ground natural
frequencies, fo. The natural frequency results for Sungai Sembrong Bridge (70
meter) was 2.2 Hz and for Sungai Simpang Kiri Bridge (75 meter) was 2.0 Hz, while
the ground natural frequencies were 1.4 Hz to 2.1 Hz at Sungai Sembrong and 1.0 Hz
to 1.5 Hz at Sungai Simpang Kiri. The frequency values for both bridges were almost
the same. The bridge with longer span length had a lower frequency value compared
to the one with shorter span. The frequency results were verified by calculating and
developing empirical equation from previous researchers and code of practice. |
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