Microtremor Measurements And Fem Simulation

2.1 Vibration characteristics of the libraries

In August 2006, micro-tremor measurements were carried out at the northern library and the southern library of Bayon temple (Maeda et al. 2007). They are about 4.1m high with area of 6.6m times 14.4m, standing on a sandstone-covered manmade mound of 4.9 m high, which is made of sand, gravel, and laterite, a porous soft rock. Their appearances are similar to each other as shown in Figure 2. The northern library was fully restored in 2000 (JSA2000), by being dismantled and reassembled mostly with original materials supplemented by some new ones, while the southern library is now under similar restoration.

We have arranged accelerometers to capture horizontal translation and rocking motion of the superstructure as shown in Figure 3. Accelerometers are composed of over damped oscillators, with frequency range of 0.1 Hz to 100 Hz and the sensitivity of 1 Gal/V Acceleration is low-pass filtered at 30 Hz and sampled by 0.01 s. with 20 bit AD converter.

Figure 4 shows horizontal transfer functions ofroof level to floor level for the northern library in NS and EW directions. Clear peaks and smooth transition of phases are observed. Peak frequencies of the first modes are summarized in Table 1. In NS direction, the peaks of the transfer functions for the first mode reveal

Figure 2. Appearance of the northern library (upper panel) and the southern library (lower panel).

Figure 3. Sensor arrangements for the library.

(b) EW direction Floor level

Figure 3. Sensor arrangements for the library.

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Frequency(Hz)

(a) NS direction

Frequency(Hz)

(a) NS direction

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