In high seismicity areas, it is important to consider kinematic effects to properly design pile foundations.Kinematic effects are due to the interaction between pile and soil deformations induced by seismic waves. One...In high seismicity areas, it is important to consider kinematic effects to properly design pile foundations.Kinematic effects are due to the interaction between pile and soil deformations induced by seismic waves. One of the effect is the arise of significant strains in weak soils that induce bending moments on piles. These moments can be significant in presence of a high stiffness contrast in a soil deposit. The single pile kinematic interaction problem is generally solved with beam on dynamic Winkler foundation approaches(BDWF) or using continuous models. In this work, a new boundary element method(BEM)based computer code(KIN SP) is presented where the kinematic analysis is preceded by a free-field response analysis. The analysis results of this method, in terms of bending moments at the pile-head and at the interface of a two-layered soil, are influenced by many factors including the soil-pile interface discretization. A parametric study is presented with the aim to suggest the minimum number of boundary elements to guarantee the accuracy of a BEM solution, for typical pile-soil relative stiffness values as a function of the pile diameter, the location of the interface of a two-layered soil and of the stiffness contrast. KIN SP results have been compared with simplified solutions in literature and with those obtained using a quasi-three-dimensional(3D) finite element code.展开更多
出行时间价值(Value of Travel Time.VOTT)对于城市交通设施建设和交通政策的经济价值评估和政策决策具有重要的作用。国外学术界已对VOTT内涵、影响因素及计算方法、模型、案例应用等方面进行了较多研究,但国内这方面的研究还较少见,...出行时间价值(Value of Travel Time.VOTT)对于城市交通设施建设和交通政策的经济价值评估和政策决策具有重要的作用。国外学术界已对VOTT内涵、影响因素及计算方法、模型、案例应用等方面进行了较多研究,但国内这方面的研究还较少见,处于国外理论借鉴学习阶段。本文运用意愿偏好法(Stated Preference.SP)计算原理,然后通过SP调查法的问卷调查,以重庆市轨道交通出行人群为例进行实证研究,研究结果表明:重庆市居民轨道交通出行的平均VOTT为9.29元/h;出行时间价值受收入水平、出行时段、性别等因素影响显著;收入水平较高,通勤性、商务性、高峰期出行人群,其时间价值相对较高;男性出行时间价值略高于女性。展开更多
基金Acknowledgements This study is supported by the National Natural Science Foundation of China （grants 40302001 and 40232019） a foundation for the Author of National Excellent Doctoral Dissertation of China （200429）.
文摘In high seismicity areas, it is important to consider kinematic effects to properly design pile foundations.Kinematic effects are due to the interaction between pile and soil deformations induced by seismic waves. One of the effect is the arise of significant strains in weak soils that induce bending moments on piles. These moments can be significant in presence of a high stiffness contrast in a soil deposit. The single pile kinematic interaction problem is generally solved with beam on dynamic Winkler foundation approaches(BDWF) or using continuous models. In this work, a new boundary element method(BEM)based computer code(KIN SP) is presented where the kinematic analysis is preceded by a free-field response analysis. The analysis results of this method, in terms of bending moments at the pile-head and at the interface of a two-layered soil, are influenced by many factors including the soil-pile interface discretization. A parametric study is presented with the aim to suggest the minimum number of boundary elements to guarantee the accuracy of a BEM solution, for typical pile-soil relative stiffness values as a function of the pile diameter, the location of the interface of a two-layered soil and of the stiffness contrast. KIN SP results have been compared with simplified solutions in literature and with those obtained using a quasi-three-dimensional(3D) finite element code.
文摘出行时间价值(Value of Travel Time.VOTT)对于城市交通设施建设和交通政策的经济价值评估和政策决策具有重要的作用。国外学术界已对VOTT内涵、影响因素及计算方法、模型、案例应用等方面进行了较多研究,但国内这方面的研究还较少见,处于国外理论借鉴学习阶段。本文运用意愿偏好法(Stated Preference.SP)计算原理,然后通过SP调查法的问卷调查,以重庆市轨道交通出行人群为例进行实证研究,研究结果表明:重庆市居民轨道交通出行的平均VOTT为9.29元/h;出行时间价值受收入水平、出行时段、性别等因素影响显著;收入水平较高,通勤性、商务性、高峰期出行人群,其时间价值相对较高;男性出行时间价值略高于女性。
基金Supported by the National Natural Science Foundation of China(51175001)Anhui University Provincial Natural Science Research Project(KJ2012B020,KJ2013B036)
