Vibration characteristics of the pile foundation building with different pile length are investigated by microtremor measurement and earthquake observation. Different pile length reflects on the fact that the depth of pile supporting layer (soft surface soil layer) is fluctuating. The effect is observed in the data that the rocking motion of the superstructure increases. Regarding earthquake observation data, amplitude dependence of natural frequency of the building is also observed including nonlinear response.
Seismic wave propagation in basin structure is investigated by microtremor measurement. It is known wave propagation in basin structure is complicated to understand by irregular engineering and seismic bedrock, and surface wave generated by basin edge etc. We conducted dense microtremor measurement in Yamagata and Yonezawa basin and analyze earthquake observation data. Based on the results, we are discussing the complicated wave propagation characteristics.
Tohoku region of Japan is well known the heavy snow area and snow load produced by snow accumulation in winter gives severe effect to the building in this region. The natural frequency of the wooden house or building may be shifted towards ground motion predominant frequency in some cases. We are conducting long term structural health monitoring by microtremor and earthquake observation in three story wooden building and Japanese traditional temple and multi-layer pagoda. It turns out that daily and seasonal fluctuation of natural frequency of the structures cannot be negligibly important with respect to structural design.
Mitsuji K. and Adachi H. (2020), Variation of Dynamic Characteristics of Multi-Layer Wooden Building Based on Continuous Observed Records, 17th World Conference on Earthquake Engineering, Paper No.C001887, 10pp.
Mitsuji K., Ohno S. and Motosaka M. (2018), Estimate of Local Site Effect with Irregular Seismic Bedrock for Earthquake Engineering Based on Microtremor Measurement, 16th European Conference on Earthquake Engineering, Paper No. 11407,9pp.
Mitsuji K., Motosaka M., Ohno S. and Tadokoro M. (2017), Dynamic Behavior of a Pile-foundation Building with the Effect of Irregular Pile-supporting Stratum, 16th World Conference on Earthquake Engineering，Paper No.1922, 12pp.
Motosaka M. and Mitsuji K. (2012), Building damage during the 2011 off the Pacific coast of Tohoku Earthquake，Soils and Foundations, Vol. 52 No.5, pp.929-944