Norihiko Yamashita
Environmental Development Engineering major, Graduate School of Engineering
1. Research topics① Research related to dynamic interaction among foundations, ground andstructural systems
Numerous structures absorbed tremendous damage during the 1995 Southern
Hyogo Prefecture Earthquake, which also greatly impacted Japan’s
quakeproofing designs. New quakeproofing design standards were subsequently
established, and great strides were made on quakeproofing designs, mainly
performance-based methods. Many unresolved issues remain, however. Amongthese issues, the interaction between foundations and the ground, as well as theinteractions during a large earthquake, have likely not been made clear enough.
Moreover, as techniques for analyzing dynamic interaction grow moresophisticated, they have become harder to understand, and have been slow togain acceptance among technicians. With that in mind, we have been performing
dynamic response analyses on overall foundation, ground and structural systems,
sorting the results from these in an attempt to express the effects of these
dynamic interactions in a simple way.
② Research regarding the evaluation of soil structures using surface wave
methodsProposed surface wave evaluation methods include measurement techniquesthat involve using a) an exciter and two or three geophones, or b) a seismic
impulse source and multiple geophones. The former measurement technique has
been simplified, but it is not used much because some technicians question its
reliability, so the latter method prevails. However, the lengths of the lines
measured with the latter method tend to get longer because multiple geophones
are used. That is a minus because it means a wider space is needed, so we havebeen using equipment designed for the former method for measurements andthe finite element method to conduct dynamic response analyses as part of ourefforts to improve precision by clarifying soil survey mechanisms and analyticalprocesses.
③ Research regarding the evaluation of the residual seismic capacity ofstructures supported by foundations
There is a need to accurately assess the seismic capacity of reinforced concrete
structures before earthquakes and after absorbing quake damage to assess theirrelative level of safety during aftershocks as well as to promote the drafting ofrational recovery plans. There is also a need to establish methods for accurately
assessing quake-damaged structures’ residual seismic capacity to be able toquantitatively establish seismic performance based on safety, serviceability andreparability with regard to performance-based seismic design. With this in mind,
we have adopted damage indices that quantitatively express the damage levelsof structures at the time of an earthquake as residual seismic capacity—whichrepresents the seismic capacity of structures. Rates of residual seismic capacity
will be reviewed through dynamic response analyses using models of actualbridges.
2. List of published articles
・N. Yamashita and T. Shimabukuro: Residual Seismic Performance Evaluation
Of Highway Bridges Using The Damage Index, Journal of Japan Society of CivilEngineers, Division A (Structural and Earthquake Engineering and Applied
Mechanics), Vol. 70, No. 4 (pp. I 1144–1154). 2014.
・N. Yamashita, R. Fujita, T. Shimabukuro and T. Harada: Asymmetry Of Seismic
Displacement Response Of Highway Bridge Supported By Spread Foundation,
Journal of Japan Society of Civil Engineers, Division A (Structural and Earthquake
Engineering and Applied Mechanics), Vol. 68, No. 4 (pp. I 470–478). 2012.
・Y. Hata, K. Ichii, S. Kano, T. Tsuchida, L. Li and N. Yamashita: A Simple and Easy
Calculation Method to Seismic Response of Embankment considering Horizontaland Vertical Interaction, Journal of Japan Society of Civil Engineers, Division A(Structural and Earthquake Engineering and Applied Mechanics), Vol. 65, No. 1 (pp.
156–165). 2009.
・S. Saito, T. Harada, G. Mori, H. Wang, and N. Yamashita: A Method of Estimationof Subsurface Ground Structure and Elastic Soil Properties Using VerticalHarmonic Loading on Ground Surface and Its Numerical Verification, JSCE
Journal of Earthquake Engineering, Vol. 29 (pp. 279–286). 2007.
・N. Yamashita, and T. Harada: A Study Of Nonlinear Response Analysis Of
Buried Foundation Considering P-Delta Effect Of Superstructure, JSCE Journal ofEarthquake Engineering, Vol. 28 (pp. 1–8). 2005.
3. Corporate affiliations
None