Kyushu University [Yukihide Kajita (Associate Professor) Faculty of Engineering, ]

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Yukihide Kajita
Associate Professor
Structural Analysis and Earthquake Engineering
Faculty of Engineering
Last modified date：2024.04.18

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Graduate School of Engineering

Department of Civil and Structural Engineering
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Department of Earth Resources,Marine and Civil Engineering
School of Engineering

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Disaster Risk Reduction Research Center

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Total Priod of education and research career in the foreign country

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1.	Kunyang Wang, Yukihide Kajita and Yaoxin Yang, Bayesian RC-Frame Finite Element Model Updating and Damage Estimation Using Nested Sampling with Nonlinear Time History, Buildings, https://doi.org/10.3390/buildings13051281, 13, 5, 1281, 2023.05, This paper proposes a Bayesian RC-frame finite element model updating (FEMU) and damage state estimation approach using the nonlinear acceleration time history based on nested sampling. Numerical RC-frame finite element model (FEM) parameters are selected through nested sampling, and their probability density is estimated using nonlinear time history. In the first step, we estimate the error standard deviation and select the FEM parameters that are required to be updated by FEMU. In the second step, we estimate the probability density of the selected parameters and realize the FEMU through the resampling method and kernel density estimation (KDE). Additionally, we propose a damage state estimate approach, which is a derivative method of the FEMU sample. The numerical results demonstrate that the proposed approach is reliable for the Bayesian FEMU and damage state estimation using nonlinear time history..
2.	Mujtaba Amin, Yukihide Kajita, Taiji Mazda, Numerical Simulation of Pounding Effect on Damage Assessment of an Abutment for Highway Bridge, Proceedings of the 7th Asia Conference on Earthquake Engineering, Paper ID 0009, 2018.11, The current study mainly focuses on the impact damage assessment of the abutments considering the non-linearity of backfill soil which has not ever quantitatively estimated. The numerical simulation of pounding effect on four types of the abutments with wing wall variation in shapes and dimensions were carried out using the explicit FE code LS-DYNA. The pounding scenario was simulated by the initial impact velocity on the entire nodes of the superstructure. The numerical models are capable of simulating the nonlinearly of backfill soil, damage of concrete and yielding of reinforcement steel with strain rate effect behavior of concrete and steel reinforcement. The study indicates that the response displacement and the impact force on the back wall are affected by the non-linear backfill soil and wing wall variations. At the initial instant of impact, there is No significant effect on the impact forces whereas, for the rest of the time, the impact force on the back wall slightly decreased and the abutment displacement at the crown of back wall increased due to soil non-linearity. In the case of low impact velocity, damage only occurs at the base of the back wall whereas, in the case of maximum velocity impact, the damage spread over the entire Back wall and damage to the entire abutment was confirmed. In the design, only one impact is considered. However, in a real situation, a few or several impacts would occur during an earthquake. So, if the damage to abutment is predicted precisely, the non-linear property of backfill soil should be considered..
3.	Yukihide Kajita, A Horizontal Loading Test and Its Simulation Analysis of the Abutment Model with Backfill Soil , Proc. of the 2014 Taiwan-Japan Workshop on Structural and Bridge Engineering, 2014.05.
4.	Yukihide Kajita, Hisanori OTSUKA, Yuki Fujiyoshi, A Horizontal Test and Its Simulation Analysis of the Abutment Model with Backfill Soil , Proc. of the 15th World Conference on Earthquake Engineering, Paper No.0339(CD-ROM), 2012.09.