Performance information

• Seismic performance of pile foundations reinforced with micropiles　　　　　　　　　　　　　　　
  Rahman M.; Iwamura S.; Goit CS; Saitoh M.
  18th East Asia-Pacific Conference on Structural Engineering and Construction (EASEC-18), Nov. 2024, [Reviewed]
  English, International conference proceedings
• Effects of Soil Nonlinearity on the Seismic Behavior of Pile Foundations Reinforced with Micropiles
  Chandra Shekhar Goit; Shogo Honma; Masato Saitoh; Pujan Giri
  International Journal of Geomechanics, Volume：24, Number：10, Oct. 2024, [Reviewed]
  American Society of Civil Engineers (ASCE), English, Scientific journal
  DOI：https://doi.org/10.1061/ijgnai.gmeng-9600
  DOI ID：10.1061/ijgnai.gmeng-9600, ISSN：1532-3641, eISSN：1943-5622
• Experimental studies on the kinematic response of micropiles-retrofitted bridge foundations　　　　　　　　　　　　　　　
  Goit CS; Maruyama Y.; Saitoh M.; Ekubo S.
  18th World Conference on Earthquake Engineering, Jun, 2024, Jun. 2024, [Reviewed]
  English, International conference proceedings
• Frequency- and intensity-dependent impedance functions of laterally loaded pile groups in cohesionless soil　　　　　　　　　　　　　　　
  Naba Raj Shrestha; Masato Saitoh; Chandra Shekhar Goit; Alok Kumer Saha; Ryoya Yokota
  Soils and Foundations, Volume：63, Number：4, First page：101340, Last page：101340, Aug. 2023, [Reviewed]
  Elsevier BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.sandf.2023.101340
  DOI ID：10.1016/j.sandf.2023.101340, ISSN：0038-0806
• Vertical impedance functions of pile groups under low-to-high loading amplitudes: numerical simulations and experimental validation　　　　　　　　　　　　　　　
  Usama Zafar; Chandra Shekhar Goit; Masato Saitoh; Riku Fukuda
  EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION, May 2023, [Reviewed]
  Piles in a group experience additional displacements in soil due to pile-to-pile interactions apart from those resulting from the external loading. The effect of these interactions determined assuming soil as an elastic and/or viscoelastic material on pile head impedance functions of the pile group is studied by relating the group stiffness to the static stiffness of a single pile. However, the prevailing elastic solutions may misestimate the resulting pile group response due to the lack of consideration for either soil (material) and/or soil-pile interface nonlinearities. It is well established that soil behaves nonlinearly under moderate-to-high loading amplitudes, and besides, the soil-pile interface nonlinearity can exist even at small loading amplitudes. This study addresses the effects of these nonlinearities on the vertical impedance functions of a 3x3-pile group using numerical methods by direct analyses and superposition using pile-to-pile interaction factors. The numerical results are validated using scaled model tests under 1 g conditions. The results highlight the overestimation of pile-to-pile interactions in the pile group when assuming elastic soil conditions. The cases either by direct analyses or superposition approach involving soil and soil-pile interface nonlinearities agree well with the experimental pile group responses under close-to-elastic and nonlinear conditions.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11803-023-2183-y
  DOI ID：10.1007/s11803-023-2183-y, ISSN：1671-3664, eISSN：1993-503X, ORCID：137591569, Web of Science ID：WOS:000989841200005
• Experimental and numerical investigations on vertical dynamic pile-to-pile interactions considering soil and interface nonlinearities　　　　　　　　　　　　　　　
  Usama Zafar; Chandra S. Goit; Masato Saitoh
  Bulletin of Earthquake Engineering, Volume：20, Number：7, First page：3117, Last page：3142, May 2022, [Reviewed]
  Springer Science and Business Media {LLC}, English, Scientific journal
  DOI：https://doi.org/10.1007/s10518-021-01186-x
  DOI ID：10.1007/s10518-021-01186-x, ISSN：1570-761X, ORCID：137591564
• Influence of nonlinearities on the vertical kinematic interaction of piles　　　　　　　　　　　　　　　
  Zafar U.; Goit CS; Saitoh M.
  Proceedings of the 7th World Congress on Civil, Structural, and Environmental Engineering, Apr. 2022, [Reviewed]
  English, International conference proceedings
  DOI：https://doi.org/10.11159/icsect22.173
  DOI ID：10.11159/icsect22.173
• Numerical Modelling of the Rate-Dependent Characteristics of Laterally Loaded Single Pile in Dry Sand
  A. K. Saha; M. Saitoh; N. R. Shrestha; C. S. Goit
  Lecture Notes in Civil Engineering, First page：73, Last page：80, Oct. 2021, [Reviewed]
  Springer Singapore, English, In book
  DOI：https://doi.org/10.1007/978-981-16-5547-0_8
  DOI ID：10.1007/978-981-16-5547-0_8, ISSN：2366-2557, eISSN：2366-2565
• Frequency- and intensity-dependent impedance functions of laterally loaded single piles in cohesionless soil　　　　　　　　　　　　　　　
  Naba Raj Shrestha; Masato Saitoh; Alok Kumer Saha; Chandra Shekhar Goit
  Soils and Foundations, Volume：61, Number：1, First page：129, Last page：143, Feb. 2021, [Reviewed]
  Elsevier BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.sandf.2020.11.004
  DOI ID：10.1016/j.sandf.2020.11.004, ISSN：0038-0806, ORCID：137591558, Web of Science ID：WOS:000614212500009
• Time control and experimental verification of IoT based structural seismic monitoring　　　　　　　　　　　　　　　
  Dang J.; Zuo R.; Goit CS
  17th World Conference on Earthquake Engineering, Volume：Paper no. C001738, 2021, [Reviewed]
  English, International conference proceedings
• Effect of the joint shear resistance on the dynamic responses of steel pipe sheet pile foundations　　　　　　　　　　　　　　　
  Ullah MS; Sasaki A.; Goit CS; Saitoh M.
  17th World Conference on Earthquake Engineering, Volume：Paper no. 4c-0046, 2021, [Reviewed]
  English, International conference proceedings
• Experimental and Numerical Analysis on the Rate-Dependent Cyclic Lateral Load on a Single Pile in Sand　　　　　　　　　　　　　　　
  Naba Raj Shrestha; Masato Saitoh; Chandra hekhar Goit; Alok Kumer Saha
  International Journal of Civil Infrastructure, 2021, [Reviewed]
  Avestia Publishing, English, Scientific journal
  DOI：https://doi.org/10.11159/ijci.2021.002
  DOI ID：10.11159/ijci.2021.002, eISSN：2563-8084
• Rate-Dependent Cyclic Lateral Load Test on a Single Pile in Sand　　　　　　　　　　　　　　　
  Naba Raj Shrestha; Masato Saitoh; Alok Kumer Saha; Chandra Shekhar Goit
  Proceedings of the 5th International Conference on Civil, Structural and Transportation Engineering, Nov. 2020, [Reviewed]
  Avestia Publishing, English, International conference proceedings
  DOI：https://doi.org/10.11159/iccste20.231
  DOI ID：10.11159/iccste20.231, ISSN：2369-3002, SCOPUS ID：85097226165
• Inclined single piles under vertical loadings in cohesionless soil　　　　　　　　　　　　　　　
  Chandra Shekhar Goit; Masato Saitoh; Takumi Igarashi; Shun Sasaki
  Acta Geotechnica, Volume：16, Number：4, First page：1231, Last page：1245, Sep. 2020, [Reviewed], [Lead]
  Springer Science and Business Media LLC, English, Scientific journal
  DOI：https://doi.org/10.1007/s11440-020-01074-9
  DOI ID：10.1007/s11440-020-01074-9, ISSN：1861-1125, eISSN：1861-1133, ORCID：81544209, Web of Science ID：WOS:000572721300006
• Effective Foundation Input Motion for Soil-Steel Pipe Sheet Pile (SPSP) Foundation System
  Md. Shajib Ullah; Keisuke Kajiwara; Chandra Shekhar Goit; Masato Saitoh
  Mechanisms and Machine Science, First page：135, Last page：148, Nov. 2019, [Reviewed]
  Springer International Publishing, English, In book
  DOI：https://doi.org/10.1007/978-3-030-27053-7_14
  DOI ID：10.1007/978-3-030-27053-7_14, ISSN：2211-0984, eISSN：2211-0992, ORCID：81544215
• On the Behaviour of Raked Piles　　　　　　　　　　　　　　　
  Goit CS
  Proceedings of the 6th International Conference on Engineering, Energy and Environment, First page：249, Last page：254, Nov. 2019, [Reviewed]
  English, International conference proceedings
• Earthquake motion filtering effect by pile foundations considering nonlinearity of soil and piles　　　　　　　　　　　　　　　
  Yudai Hochi; Yoshitaka Murono; Masato Saitoh; Chandra Shekhar Goit
  Soil Dynamics and Earthquake Engineering, Volume：125, First page：105748, Last page：105748, Oct. 2019, [Reviewed]
  Elsevier BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.soildyn.2019.105748
  DOI ID：10.1016/j.soildyn.2019.105748, ISSN：0267-7261, eISSN：1879-341X, ORCID：67386451, Web of Science ID：WOS:000483627900046
• Frequency and intensity dependent dynamic responses of soil-steel pipe sheet pile (SPSP) foundation-superstructure system　　　　　　　　　　　　　　　
  Md. Shajib Ullah; Keisuke Kajiwara; Chandra Shekhar Goit; Masato Saitoh
  Soil Dynamics and Earthquake Engineering, Volume：125, First page：105730, Last page：105730, Oct. 2019, [Reviewed]
  Elsevier BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.soildyn.2019.105730
  DOI ID：10.1016/j.soildyn.2019.105730, ISSN：0267-7261, eISSN：1879-341X, ORCID：67386435, Web of Science ID：WOS:000483627900035
• Development and Experimental Verification of IoT Sensing Based Structural Health Monitoring System　　　　　　　　　　　　　　　
  Zuo R.; Dang J.; Goit CS
  Proceedings of the 5th International Conference on Experimental Vibration Analysis for Civil Engineering Structures, Volume：8, First page：99, Last page：107, 2019, [Reviewed]
  English, International conference proceedings
• On the verification of superposition method of kinematic interaction and inertial interaction in dynamic response analysis of soil-pile-structure systems　　　　　　　　　　　　　　　
  Md. Shajib Ullah; Hiroki Yamamoto; Chandra Shekhar Goit; Masato Saitoh
  Soil Dynamics and Earthquake Engineering, Volume：113, First page：522, Last page：533, Oct. 2018, [Reviewed]
  Elsevier BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.soildyn.2018.06.023
  DOI ID：10.1016/j.soildyn.2018.06.023, ISSN：0267-7261, eISSN：1879-341X, ORCID：58919101, Web of Science ID：WOS:000447086000042
• Single pile under vertical vibrations in cohesionless soil
  C. S. Goit; M. Saitoh
  Géotechnique, Volume：68, Number：10, First page：893, Last page：904, Oct. 2018, [Reviewed]
  The vertical response of a fixed-head floating single pile embedded in sand is obtained experimentally under 1g conditions. Specifically, pile head stiffnesses and axial strains generated along the pile length for a range of static and dynamic pile head loadings are measured. To account for the effects of soil non-linearity on the static response of the pile, a range of low- to high-magnitude static displacements is considered. Likewise, for the dynamic response, varying amplitudes of vertical harmonic accelerations for a wide range of frequencies are considered. Results obtained from the experiments under both the static and dynamic loading conditions indicate that the pile head stiffness is dependent on the direction of pile head loading – that is, whether the pile is pushed or pulled. To gain further insight into such direction-dependent pile head stiffness, three-dimensional non-linear finite-element analyses are carried out. Numerical results show very good agreement with the experimentally measured pile head stiffnesses. Axial strains generated along the pile length due to head loadings, on the other hand, depend on the amplitude of both the static and the dynamic loadings.
  Thomas Telford Ltd., English, Scientific journal
  DOI：https://doi.org/10.1680/jgeot.17.p.020
  DOI ID：10.1680/jgeot.17.p.020, ISSN：0016-8505, eISSN：1751-7656, ORCID：58919058
• Influence of pile radius on the pile head kinematic bending strains of end-bearing pile groups　　　　　　　　　　　　　　　
  Mostafa Faghihnia Torshizi; Masato Saitoh; Guillermo M. Álamo; Chandra Shekhar Goit; Luis A. Padrón
  Soil Dynamics and Earthquake Engineering, Volume：105, First page：184, Last page：203, Feb. 2018, [Reviewed]
  An analytical solution is developed for the kinematic response of a group of end-bearing fixed-head cylindrical vertical piles embedded in a homogeneous elastic stratum subjected to vertically-propagating harmonic shear waves. Pile-soil interaction, incorporating group effects in a pile group, is represented through a simplified beam-on-dynamic-Winkler-foundation (BDWF) model with realistic frequency-dependent springs and dashpots. Expressions for interaction factors and curvature ratios atop the foundation are presented considering different boundary conditions at the tip of the piles. To investigate the fundamental characteristics of kinematic bending in end-bearing pile groups when kinematic interaction dominates, kinematic bending strains at the head of each pile are expressed in terms of the slenderness ratio. The methodology is verified by comparison against results of a coupled finite element-boundary element (FE-BE) model. Obtained results indicate that kinematic bending strains of end-bearing single piles and piles in a group follow the same trend, with values being almost coincident in the case of slender piles. In addition, boundary conditions at the pile tip markedly affect the kinematic bending at the pile head.
  Elsevier Ltd, English, Scientific journal
  DOI：https://doi.org/10.1016/j.soildyn.2017.10.007
  DOI ID：10.1016/j.soildyn.2017.10.007, ISSN：0267-7261, eISSN：1879-341X, ORCID：58919103, SCOPUS ID：85037538875, Web of Science ID：WOS:000423893000017
• Dynamic Pile-to-Pile Interaction Factors for Inclined Pile Groups　　　　　　　　　　　　　　　
  Goit CS; Saitoh M.
  Proceedings of the 5th International Conference on Engineering, Energy and Environment, First page：165, Last page：170, Nov. 2017, [Reviewed]
  English, International conference proceedings
• Pile-to-pile kinematic interaction factors for vertically-incident shear waves　　　　　　　　　　　　　　　
  Álamo GM; Saitoh M.; Goit CS; Padrón LA; Aznárez JJ; Maeso O.
  2nd Global Conference on Applied Computing in Science and Engineering, Jul. 2017
  English, Symposium
• Experimental approach on the pile-to-pile interaction factors and impedance functions of inclined piles　　　　　　　　　　　　　　　
  C. S. Goit; M. Saitoh
  GEOTECHNIQUE, Volume：66, Number：11, First page：888, Last page：901, Nov. 2016, [Reviewed]
  Dynamic tests on model soil-pile systems under 1g (natural gravity) conditions are carried out to assess the effects of soil non-linearity on the horizontal pile-to-pile interaction factors of inclined piles. This paper examines 2 x 2 symmetric free-head floating inclined pile groups embedded in cohesionless soil and subjected to a low-to-high amplitude of lateral harmonic pile head loadings for a wide range of frequencies. Piles with head level centre-to-centre spacing of five times the pile diameter with three practical pile inclinations of 0 degrees (vertical), 5 degrees and 10 degrees aligned parallel to the direction of loading are reported. Results from the experiments indicate a significant impact of soil non-linearity on the horizontal interaction factors. Moreover, utilising such experimentally measured interaction factors in conjunction with available experimental solutions for horizontal impedance functions of inclined single piles, the principle of superposition is assessed in obtaining the horizontal impedance functions of inclined pile groups. Comparison between the results based on the principle of superposition and experimentally available solutions shows a good agreement for the low-to-intermediate range of loading frequency. At higher frequencies, however, loading-direction-dependent soil-pile interface non-linearities developed for inclined piles cannot be captured in a straightforward way. To this end, a multiplication factor is proposed for the superposition method.
  ICE PUBLISHING, English, Scientific journal
  DOI：https://doi.org/10.1680/jgeot.15.P.192
  DOI ID：10.1680/jgeot.15.P.192, ISSN：0016-8505, eISSN：1751-7656, ORCID：40209803, Web of Science ID：WOS:000385390600003
• Principle of superposition for assessing horizontal dynamic response of pile groups encompassing soil nonlinearity　　　　　　　　　　　　　　　
  Chandra Shekhar Goit; Masato Saitoh; George Mylonakis
  SOIL DYNAMICS AND EARTHQUAKE ENGINEERING, Volume：82, First page：73, Last page：83, Mar. 2016, [Reviewed]
  Model tests on fixed-head floating piles embedded in dry cohesionless soil (Gifu sand) are carried out under 1-g conditions on a shaking table, to investigate the effects of local soil nonlinearity on the dynamic response of pile groups. Results obtained from these tests are employed to assess the applicability of Poulos' superposition method in determining the pile group response under different levels of material nonlinearity. A wide range of head loading amplitudes inducing low-to-high levels of soil strain are employed for a broad range of frequencies. Utilizing the aforementioned superposition method, horizontal impedance functions of a closely spaced 3 x 3-pile group are computed based on: (1) experimentally-measured values of horizontal impedance functions for a single pile, and (2) experimentally-measured pile-to-pile interaction factors. Comparisons between computed and measured impedance functions show good agreement for low to intermediate loading amplitudes, suggesting that the superposition method is valid even under moderately nonlinear conditions. (C) 2015 Elsevier Ltd. All rights reserved.
  ELSEVIER SCI LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.soildyn.2015.11.001
  DOI ID：10.1016/j.soildyn.2015.11.001, ISSN：0267-7261, eISSN：1879-341X, ORCID：40209804, Web of Science ID：WOS:000371361300007
• Expanded superposition method for impedance functions of inclined-pile groups　　　　　　　　　　　　　　　
  M. Saitoh; L. A. Padron; J. J. Aznarez; O. Maeso; C. S. Goit
  INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Volume：40, Number：2, First page：185, Last page：206, Feb. 2016, [Reviewed]
  This paper presents a superposition method expanded for computing impedance functions (IFs) of inclined-pile groups. Closed-form solutions for obtaining horizontal, vertical, and rocking IFs, estimated by using pile-to-pile interaction factors, are proposed. IFs of solitary inclined piles, crossed IFs, and explicit incorporation of compatibility conditions for pile-head movements are also appropriately taken into consideration. All of these factors should be known in advance and will be computed and shown for the most relevant cases. The accuracy of the proposed closed-form solutions is verified for 2 x 2 and 3 x 3 square inclined-pile groups embedded in an isotropic viscoelastic homogeneous half-space soil medium, with hysteretic damping. The pile-to-pile interaction factors are computed by means of a three-dimensional time-harmonic boundary elements-finite elements coupling formulation. The results indicate that the IFs obtained from the proposed method are in good agreement with those obtained from the coupling formulation. Furthermore, crossed vertical-rocking IFs of solitary piles need to be appropriately considered for obtaining rocking IFs when the number of piles is small. Copyright (C) 2015 John Wiley & Sons, Ltd.
  WILEY-BLACKWELL, English, Scientific journal
  DOI：https://doi.org/10.1002/nag.2389
  DOI ID：10.1002/nag.2389, ISSN：0363-9061, eISSN：1096-9853, ORCID：40209802, Web of Science ID：WOS:000368153800002
• Effects of soil nonlinearity on the lateral impedance functions of inclined single piles　　　　　　　　　　　　　　　
  Goit CS; Saitoh M.
  17th JSCE International Summer Symposium, Sep. 2015
  English, Symposium
• Model Tests on Horizontal Impedance Functions of Fixed-Head Inclined Pile Groups under Soil Nonlinearity　　　　　　　　　　　　　　　
  Chandra Shekhar Goit; Masato Saitoh
  JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING, Volume：140, Number：6, Jun. 2014, [Reviewed]
  The effects of soil nonlinearity on the dynamic behavior of fixed-head floating inclined pile groups are investigated experimentally in the form of horizontal impedance functions (IFs) and internal forces in piles. A 2x2 model of inclined pile groups embedded in dry cohesionless soil and subjected to a broad range of lateral harmonic loadings at the pile-cap level are examined. Piles with a spacing-to-the-diameter ratio (s/d) of 5 with practical pile inclinations of 0, 5, and 10 degrees along the direction of loading are reported. Results show a profound impact of local nonlinearity and resonance of soil on the horizontal impedance functions. The inclined pile groups show higher values of horizontal IFs than the vertical pile group, in accordance with the general understanding. Influence of pile inclinations on the horizontal IFs is further examined through the variation of soil reactions along the depth of the piles. Semiempirical expressions for estimating the soil reactions, as a function of pile inclinations, are proposed. As for the internal forces in piles, bending strains for the inclined piles are smaller than the vertical pile; the axial strains show an opposite behavior. (C) 2014 American Society of Civil Engineers.
  ASCE-AMER SOC CIVIL ENGINEERS, English, Scientific journal
  DOI：https://doi.org/10.1061/(ASCE)GT.1943-5606.0001127
  DOI ID：10.1061/(ASCE)GT.1943-5606.0001127, ISSN：1090-0241, eISSN：1943-5606, ORCID：40209806, Web of Science ID：WOS:000336250200019
• 近傍地盤の局所非線形性を考慮した斜杭基礎の動的水平インピーダンス特性に関する実験的研究　　　　　　　　　　　　　　　
  齊藤正人; Goit CS
  First page：3772, Last page：3777, 2014
  Japanese, Symposium
• NONLINEAR KINEMATIC INTERACTION RESPONSE OF BATTER PILE^|^mdash;CENTRIFUGE VIBRATION TESTS
  Takashi TAZOH; Jiho JANG; Yoichi TAJI; Hiroyuki KIMATA; Yasunobu SAKAI; Masato SAITOH; Chandra GOIT
  Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering ^|^ Earthquake Engineering (SE/EE)), Volume：70, Number：1, First page：51, Last page：66, 2014, [Reviewed]
  Japan Society of Civil Engineers, Japanese, Scientific journal
  DOI：https://doi.org/10.2208/jscejseee.70.51
  DOI ID：10.2208/jscejseee.70.51, ISSN：2185-4653, eISSN：2185-4653, ORCID：58919021
• Effects of soil nonlinearity on the active length of piles embedded in cohesionless soil: model studies　　　　　　　　　　　　　　　
  C. S. Goit; M. Saitoh; H. Oikawa; H. Kawakami
  Acta Geotechnica, Volume：9, Number：3, First page：455, Last page：467, Jun. 2013, [Reviewed]
  Springer Science and Business Media LLC, English, Scientific journal
  DOI：https://doi.org/10.1007/s11440-013-0257-0
  DOI ID：10.1007/s11440-013-0257-0, ISSN：1861-1125, eISSN：1861-1133, ORCID：40209805, Web of Science ID：WOS:000336262100008
• Applicability of principle of superposition in obtaining horizontal impedance functions of pile groups under soil nonlinearity　　　　　　　　　　　　　　　
  Chandra S. Goit; Masato Saitoh; George Mylonakis
  ECCOMAS Thematic Conference - COMPDYN 2013: 4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Proceedings - An IACM Special Interest Conference, First page：1145, Last page：1151, Jun. 2013, [Reviewed]
  The effects of soil nonlinearity on the pile-to-pile horizontal interaction factors and horizontal impedance functions of piles through model testing are investigated. Separate experiments with a solitary pile and closely spaced 3×3-pile groups with spacing to diameter ratio of 2.5 embedded in cohesionless soil, are considered. Lateral harmonic pile-head loadings in the form of accelerations with amplitudes of 0.2, 0.5, 1 and 2 m/s2 for a wide range of frequencies are reported. Results obtained from model soil-pile systems encased in a laminar shear box show that local nonlinearity and resonant behavior of soil have a significant impact on both the interaction factors and the impedance functions. Utilizing the measured values of horizontal impedance functions of a single pile and the horizontal pile-to-pile interaction factors, Poulos' superposition method is assessed in obtaining the horizontal impedance functions of the pile group. Comparisons between computed and experimentally measured values show very good agreement, suggesting that the principle of superposition is applicable under nonlinear conditions.
  National Technical University of Athens, English, International conference proceedings
  SCOPUS ID：84898940390
• Model tests on horizontal pile-to-pile interaction incorporating local non-linearity and resonance effects　　　　　　　　　　　　　　　
  Chandra Shekhar Goit; Masato Saitoh; George Mylonakis; Hideji Kawakami; Hiroki Oikawa
  SOIL DYNAMICS AND EARTHQUAKE ENGINEERING, Volume：48, First page：175, Last page：192, May 2013, [Reviewed]
  Dynamic experimental studies on horizontal interaction factors for laterally loaded model soil-pile systems subjected to low-to-high amplitude pile head loading are reported, focusing on the effect of dynamics and local non-linearity. Results obtained from dynamic experiments with different amplitudes of harmonic lateral loading on instrumented model soil-pile systems conducted on a shaking table indicate that the resonance of soil-pile system shows a profound impact on the horizontal interaction factors. Furthermore, behavior of the soil-pile system becomes highly non-linear with increasing amplitude of loading, as the extent of local non-linearity around the pile increases. Consequently, group effects cannot be predicted by using established approximate equations based on the assumption of linear viscoelastic behavior. To this end, new semi-empirical equations are proposed for obtaining the horizontal interaction factors, as an extension of available approximate equations to incorporate the local non-linear behavior of soil-pile system for both small and large pile spacings. (C) 2013 Elsevier Ltd. All rights reserved.
  ELSEVIER SCI LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.soildyn.2013.02.002
  DOI ID：10.1016/j.soildyn.2013.02.002, ISSN：0267-7261, ORCID：40209808, Web of Science ID：WOS:000317877900014
• Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil　　　　　　　　　　　　　　　
  Chandra Shekhar Goit; Masato Saitoh
  EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION, Volume：12, Number：1, First page：143, Last page：154, Mar. 2013, [Reviewed]
  Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant characteristics. Two practical pile inclinations of 5A degrees and 10A degrees in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are considered. Results obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of piles. Horizontal impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination increases. Distinct values of horizontal impedance functions are obtained for the 'positive' and 'negative' cycles of harmonic loadings, leading to asymmetric force-displacement relationships for the inclined piles. Validation of these experimental results is carried out through three-dimensional nonlinear finite element analyses, and the results from the numerical models are in good agreement with the experimental data. Sensitivity analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11803-013-0158-0
  DOI ID：10.1007/s11803-013-0158-0, ISSN：1671-3664, ORCID：40209807, Web of Science ID：WOS:000316213800013
• Seismic Behavior of Batter-Pile Foundation: Centrifuge Tests and Analytical Study　　　　　　　　　　　　　　　
  Tazoh T.; Sato M.; Jang J.; Taji Y.; Kimata H.; Kobayashi N.; Saitoh M.; Goit CS; Gazetas G.
  The 3rd International Symposium on Advances in Urban Safety, Nov. 2012
  English, Symposium
• Model tests on validation of principle of superposition in obtaining pile groups’ horizontal impedance functions under soil non-linearity　　　　　　　　　　　　　　　
  Goit CS; Saitoh M.; Mylonakis G.
  Proceedings of the International Symposium on Earthquake Engineering, Japan Earthquake Engineering Association, Volume：1, First page：191, Last page：198, 2012
  English, Symposium
• Advanced numerical modelling in tunnel design – The example of a major project in the UK　　　　　　　　　　　　　　　
  Goit CS; Kovacs A.; Thomas A.
  2nd International FLAC/DEM Symposium, 2011
  English, Symposium
• Experimental Studies on Non-Linear Response of Soil-Pile-Structure Systems Subjected to Strong Ground Motion　　　　　　　　　　　　　　　
  Goit CS; Saitoh M.; Kawakami H.; Nishiyma S.
  14th World Conference on Earthquake Engineering, 2008, [Reviewed]
  English, International conference proceedings

• 2015 - Present, Japan Society of Civil Engineers

• Significance of nonlinear soil-structure interaction (SSI) on the seismic performance of micropiles-retrofitted pile foundations　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Apr. 2022 - Mar. 2025
  Goit Chandra, Saitama University
  Grant amount(Total)：4160000, Direct funding：3200000, Indirect funding：960000
  Grant number：22K04280
• Highly accurate evaluation of dynamic response of foundations subjected to large earthquake ground motions based on small earthquake events　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Apr. 2021 - Mar. 2024
  Masato Saitoh; Goit Chandra, Saitama University
  Grant amount(Total)：17030000, Direct funding：13100000, Indirect funding：3930000
  Grant number：21H01414
• Highly accurate computational method for dynamic response of structure systems supported by pile foundations allowing yielding behavior in capacity design　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Apr. 2018 - Mar. 2021
  Saitoh Masato; Goit Chandra, Saitama University
  Grant amount(Total)：13000000, Direct funding：10000000, Indirect funding：3000000
  In recent years, there have been reported that several cases in which foundations were severely damaged during earthquake events. An increase in the amplitude of loading transmitting to soil-foundation systems is attributed to inelastic behavior of the system, thus leading to intricate combination of failure mechanisms and wave propagations. This research conducted experimental and numerical studies of single piles and pile groups for prevailing the relation between yielding procedures and frequency-dependent characteristics in the systems. This study proposed a new phenomenological model that can consider both the intensity and frequency dependencies of the systems. The model was verified by comparing the impedance functions and their convergence trends with the amplitude of loadings obtained from the experiments. This study finally proposed the applicability of the proposed model based on the yielding level.
  Grant number：18H01517
• Impedance functions of an interlocking Steel Pipe Sheet Pile (SPSP) caisson foundation under nonlinear soil-structure interaction (SSI)　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Young Scientists (B), 01 Apr. 2017 - 31 Mar. 2019
  Goit Chandra, Saitama University
  Grant amount(Total)：4290000, Direct funding：3300000, Indirect funding：990000
  Nonlinear dynamic response of a Steel Pipe Sheet Pile (SPSP) foundation is studied through model testing under 1g conditions, accounting for the effects of soil-structure interactions (SSI). A circular 1/16.5 model SPSP foundation comprising of 20 hollow circular aluminum pipes (outer diameter = 30 mm and wall thickness = 2 mm) with lengths of 960 mm, embedded in dry cohesionless soil, was considered. Specifically, the kinematic and inertial responses of the foundation were obtained in the form of kinematic interaction factors (KIF) and head level horizontal impedance functions (hIFs) under a low-to-high level of dynamic loading for a broad range of frequencies. Results obtained through this work show that both the KIF and hIFs (essential components for SSI calculations) are dependent on soil nonlinearity. In the light of such, it can be inferred that the general methodologies that assumes soil as an elastic or visco-elastic material may not be conservative for the analysis and design.
  Grant number：17K14713
• 強震時における高層建物支持機構の解明と非線形メカニカルインターフェースの創成　　　　　　　　　　　　　　　
  24 Apr. 2015 - 31 Mar. 2016
  Grant amount(Total)：1200000, Direct funding：1200000
  Grant number：15F14367
• Experimental Evaluation of Pile-to-Pile Interaction and Impedance Functions with Local Nonlinearity in Soils　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), 2011 - 2013
  SAITOH Masato, Saitama University
  Grant amount(Total)：5460000, Direct funding：4200000, Indirect funding：1260000
  This study dealt with impedance functions (IFs) of pile groups subjected to strong vibrations due to earthquakes. IFs are defined as dynamic stiffness and damping representing dynamic characteristics at the interface between superstructure and soil-foundation systems. In general, impedance functions have been evaluated under linear-elastic conditions of soils. However, in accordance with the recent earthquake events, strong ground motions and resultant high amplitude of structural response may generate strong nonlinearity in soils near the piles. Therefore, this study conducted model tests on fixed-head floating piles embedded in cohesionless soil carried out under 1-g conditions, to investigate the effects of local soil nonlinearity on the impedance characteristics of pile groups. Results obtained from such tests indicate that soil nonlinearity markedly change impedance characteristics.
  Grant number：23560562