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Vertical impedance functions of pile groups under low-to-high loading amplitudes:numerical simulations and experimental validation

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Earthquake Engineering and Engineering Vibration 2023年第3期22卷 647-666页

作者： usama zafar Chandra Shekhar Goit Masato Saitoh Riku Fukuda School of Science and Engineering Saitama University255 Shimo-OkuboSaitamaJapan

piles in a group experience additional displacements in soil due to pile-to-pile interactions apart from those resulting from the external *** 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 ***,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 *** 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 *** study addresses the effects of these nonlinearities on the vertical impedance functions of a 3×3-pile group using numerical methods by direct analyses and superposition using pile-to-pile interaction *** numerical results are validated using scaled model tests under 1 g *** results highlight the overestimation of pile-to-pile interactions in the pile group when assuming elastic soil *** 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.

关键词： impedance functions numerical simulations model-scale experiment superposition approach soil-pile interface nonlinearity

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A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium

A multi-proxy reconstruction of spatial and temporal variati...

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中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： Feng Shi Quansheng Ge Bao Yang Jianping Li Fengmei Yang Fredrik Charpentier Ljungqvist Olga Solomina Takeshi Nakatsuka Ninglian Wang Sen Zhao Chenxi Xu Keyan Fang Masaki Sano Guoqiang Chu Zexin Fan narayan p.gaire.muhammad usama zafar Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences College of Global Change and Earth System Science Beijing Normal University Joint Center for Global Change Studies China Meteorological Administration Training Centre Department of History Stockholm University Bolin Centre for Climate Research Stockholm University Institute of Geography Russian Academy of Sciences Tomsk State University Central Department of Environmental Science Tribhuvan University

To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer(June–July–August;JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization(RegE M) algorithm with truncated total least squares(TTLS), under a point-by-point regression(ppR) framework. The temperature index reconstructions show that the late 20 th century was thewarmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11 th and 13 th centuries, and in western Asia during the 12 th century, were significantly higher than those in other regions, and comparable to levels in the 20 th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial timescales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison project phase 5(CMIp5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function(EOF) from the GISS-E2-R and MpI-ESM-p model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal res

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