Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil

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 5掳 and 10掳 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.

Optimization Mathematical Model of Pile Forces for Offshore Piled Breasting Dolphins

An optimization mathematical model of the pile forces for piled breasting dolphins in the open sea under various loading conditions is presented. The optimum layout with the well distributed pile forces and the least number of piles is achieved by the multiplier penalty function method. Several engineering cases have been calculated and compared with the result of the conventional design method. It is shown that the number of piles can be reduced at least by 10%～20% and the piles' bearing state is improved greatly.

Comparative Examinations of Single Bored Piles Using International Codes

This paper presents some aspects of the load-settlement behavior for large diameter bored piles using four different international codes, namely: ECP 202 [1], DIN 4014 [2], AASHTO [3] and French Code [4]. Ultimate capacities for 38 pile load tests founded in realistic multi-layered soils in Delta and Port Saidareas atEgyptare evaluated using modified Chin (1970) method and compared to ultimate load predictions obtained by the aforementioned codes. Many statistical analyses were conducted on the total pile loads and individual contributions of tip and skin resistances. Based on code predictions of ultimate pile loads, an empirical modified load-settlement model is proposed. This model will simplify to a great extent the analysis of piled-raft systems as it can effortlessly predict pile settlement due to the load on pile itself. Comparisons showed that the pile load test is an irreplaceable process for determining the ultimate capacity of piles.

Performance-based seismic assessment of a large diameter extended pile shaft in a cohesionless soil

The seismic behavior of a large diameter extended pile shaft founded on a dense sandy site is investigated in this paper. First, a deterministic analysis is conducted including both nonlinear dynamic analysis （NDA） and pushover analysis to gain insights into the behavior of the pile and make sure an appropriate modeling technique is utilized. Then a probabilistic analysis is performed using the results of NDA for various demands. To this end a set of 40 pulse-like ground motions are picked and subsequently 40 nonlinear dynamic and pushover analyses are performed. The data obtained from NDA are used to generate probabilistic seismic demand model （PSDM） plots and consequently the median line and dispersion for each plot are computed. The NDA and pushover data are also plotted against each other to find out to what extent they are correlated. These operations are done for various engineering demand parameters （EDPs）. A sensitivity analysis is done to pick the most appropriate intensity measure （IM） which would cause a minimum dispersion in PSDM plots out of 7 different IMs. Peak ground acceleration （PGA） is found to be the most appropriate IM. Pushover coefficient equations as a function of PGA are proposed which can be applied to the pushover analysis data to yield a better outcome with respect to the NDA. At the end, the pacific earthquake engineering research （PEER） center methodology is utilized to generate the fragility curves using the properties obtained from PSDM plots and considering various states of damage ranging from minor to severe. The extended pile shaft shows more vulnerability with a higher probability with respect to minor damage compared to severe damage.

桩顶荷载及温度循环对黄土地基中能量桩承载性状影响研究

为对比分析未经过温度循环的普通桩与能量桩竖向承载变形性状,开展黄土地基中能量桩温度循环试验。模型桩为现浇钢筋混凝土灌注桩,黄土为人工配制重塑黄土。研究结果表明:温度循环弱化黄土地基中能量桩桩身侧阻、增强能量桩桩底端阻,温度循环过程中桩顶工作荷载越大,桩侧阻的弱化作用及桩端阻的增强作用越大,这导致能量桩的竖向抗压承载力比普通桩有明显的提高。另外,根据模型试验结果,通过数据拟合建立桩土界面摩阻力-桩土相对位移及桩端土反力-桩端沉降双曲线函数模型,并确定模型参数,其函数计算结果与试验结果对比表明本文模型能合理反映温度循环及桩顶工作荷载大小对桩基承载力的影响。研究结果可为黄土地区能量桩的安全设计提供一定参考。

Ultimate Lateral Capacity of Rigid Pile in c–φ Soil

To date no analytical solution of the pile ultimate lateral capacity for the general c–φ soil has been obtained. In the present study, a new dimensionless embedded ratio was proposed and the analytical solutions of ultimate lateral capacity and rotation center of rigid pile in c–φ soils were obtained. The results showed that both the dimensionless ultimate lateral capacity and dimensionless rotation center were the univariate functions of the embedded ratio. Also,the ultimate lateral capacity in the c–φ soil was the combination of the ultimate lateral capacity（f;） in the clay, and the ultimate lateral capacity（f;） in the sand. Therefore, the Broms chart for clay, solution for clay（φ=0） put forward by Poulos and Davis, solution for sand（c=0） obtained by Petrasovits and Awad, and Kondner’s ultimate bending moment were all proven to be the special cases of the general solution in the present study. A comparison of the field and laboratory tests in 93 cases showed that the average ratios of the theoretical values to the experimental value ranged from 0.85 to 1.15. Also, the theoretical values displayed a good agreement with the test values.

Analysis of dynamical response to large deformation of piles with initial displacements

In this paper, a nonlinear mathematical model for analyzing dynamical response to the large deformation of piles with initial displacements is firstly established with the arc-coordinate, and it is a set of nonlinear integral-differential equa- tions, in which, the Winkeler model is used to simulate the resistance of the soil to the pile. Secondly, a set of new auxiliary functions are introduced. The differential-integral equations are transformed into a set of nonlinear differential equations, and the differential quadrature method （DQM） and the finite difference method （FDM） are applied to discretize the set of nonlinear equations in the spatial and time domains, respectively. Then, the Newton-Raphson method is used to solve the set of discretization algebraic equations at each time step. Finally, numerical examples are presented, and the dynamical re- sponses to the deformation of piles, including configuration, bending moment and shear force, are graphically illuminated. In calculation, two types of initial displacements and dynamical loads are applied, and the effects of parameters on the dynamical responses of piles are analyzed in detail.

基于CNN和LSTM混合网络的直流充电桩功率模块优化

直流充电桩内部功率变化动态性过强,不易捕捉及计算误差过大,提出基于CNN和LSTM混合网络的功率模块优化方法。根据充电桩电路工作原理,得到电路内部各项参数间存在的直接关联,根据该点采用三相电网平衡原理设计电力稳定控制函数,计算满足电压、电流以及功率最稳的调节比例系数,并作为调节点,建立CNN和LSTM混合网络多层次模型,计算有序、无序充放电过程的电力负荷变化,利用调节比例系数按照充电、放电所需功率需求完成优化。实验结果表明,所提方法的充电桩功率稳定,对充电桩的电压偏移量实现有效改善。

面向充电桩时间分配的在线双边拍卖机制设计

随着新能源汽车的快速发展,充电时间分配问题成为关注的焦点。现有研究主要集中在根据预先规划的驾驶路线选择充电桩,但对于车主的动态需求却没有提供即时解决方案。为解决该问题,文章首先根据车主的需求量、地理位置以及充电完成度等因素设计了一种需求者优先级函数,然后将充电桩的时间分配问题建模为密封竞价在线双边拍卖,在此基础上,提出了一种真实的交易机制。理论分析证明了该机制不仅满足个体理性、预算平衡,还能够引导供需双方报告真实的到达离开时间以及物品估值。最后通过具体的实验证明了该拍卖机制的实用性和有效性。所提出拍卖机制满足双边市场中交易个体的属性偏好和在线环境的交易特征,为当前的在线充电平台提供了有益的参考。

饱和土中刚性排桩对平面SV波的隔离分析

在Biot波动理论的基础上,用单排刚性排桩作为屏障,对全空间饱和土中入射平面SV波进行了隔离分析。采用波函数展开法,将散射波的势函数展开成Fourier-Bessel级数的形式,利用一组可以求解多散射问题的圆柱坐标系统和桩土界面处位移连续的条件,以及刚性桩的动力平衡条件,得到问题的理论解。对影响排桩隔离效果的桩间距和饱和土的渗透系数等参数进行了分析,结果表明,桩间距对饱和土中排桩的隔离效果有较明显影响;与弹性土体中排桩的隔离效果相比,饱和土中排桩的隔离效果有所不同,随着饱和土渗透系数的减小,排桩的隔离效果越好。

电动汽车充电桩运营模式研究

以电动汽车民用充电桩为研究对象,在分析充电桩建设运营的政府主导模式、电网企业主导模式、汽车厂商主导模式等三种模式利弊的基础上,结合我国的实际情况,提出我国现阶段应实行汽车厂商与电网企业联盟建设充电桩的模式。建立一个考虑政府补助,建设成本和运行成本的充电桩利润函数模型,并提出充电桩运营的基本思路,为电动汽车充电桩在中国的长期发展提供思路和理论基础。

桩基-非线性框剪结构相互作用体系(上)──群桩阻抗函数的求取

为研究桩基－非线性框剪结构相互作用体系的地震反应，需要求解群桩基础的动力阻抗函数。本文利用单桩阻抗和群桩动力相互作用因子计算群桩动力阻抗函数，计算并讨论了不同构形群桩阻抗函数在软、中和硬土地基中的变化规律和特点。研究表明：群桩阻抗表现出很强的频率相关性，随土体剪切波速的增大，群桩阻抗有较大幅度的增加，但土体剪切波速的变化对群桩效率（规格化阻抗函数）影响不大．

西安地区单桩荷载传递双曲线模型与工程应用

选用双曲线荷载传递函数分析单桩的荷载传递规律。通过分析各参数对传递函数的影响,认为桩土间的极限位移是双曲线传递函数的主要参数。然后以西安地区的26个工程钻孔灌注桩的现场试桩资料为基础,利用Matlab提供的优化工具箱对荷载传递函数中的参数进行了优化,得到各工程中的传递函数的参数,同时发现桩土间极限位移离散程度在各参数中最大,这与理论分析相一致。最后与工程实例进行了对比验证,结果表明,把利用该优化方法得到的双曲线荷载传递函数的参数作为西安地区的经验参数是可靠的。

扭转波应用于低应变动力测桩的理论研究

给出层状土中多缺陷桩在桩顶冲击扭矩作用下桩顶扭转响应的解。考虑了桩土相互作用。应用Laplace变换和传递矩阵 ,解桩的满足初始条件和边界条件的一组偏微分方程 ,导出桩土系统的传递函数 ,得到桩顶某点扭转振动速度的频率响应函数和频率域表达式。该点扭转振动速度时程由快速Fourier逆变换计算。用这种解研究桩的扭转波特征 。

基于改进荷载传递函数的自平衡数据转换

考虑土体的连续性,提出基于改进荷栽传递函数的自平衡测试数据转换方法,并通过应用实例验证其准确性。

水泥土桩的承载机理研究

利用传递函数法对水泥土桩的承载机理进行了研究 ,并对桩侧摩阻力的发展规律及单桩承载力的影响因素进行了讨论 ,其结论对水泥土桩的理论研究及工程应用具有一定的意义。

考虑桩土动力相互作用时群桩阻抗函数的分析

桩与土体的动力相互作用不仅改变了桩基的承载力,也影响了上部结构对动荷载的响应,因此在进行上部结构的动力响应分析时必须考虑桩土动力相互作用的影响。对这种动力相互作用效应研究的基础是确定桩土系统的阻抗函数,文章对考虑桩土系统动力相互作用时群桩的阻抗函数进行了细致的分析,明确了影响桩土系统动力相互作用阻抗函数的各种主要参数,为进一步研究桩土结构相互作用打下基础。

考虑桩土动力相互作用时阻抗函数分析

对考虑桩土系统动力相互作用时的阻抗函数进行了细致的分析,以单桩为例导出了各参数对整体阻抗函数的贡献,明确了影响桩土系统动力相互作用阻抗函数的各种主要参数,如各层土的剪切波速;桩的半径和长度;土与桩的密度;土的泊松比等,为进一步研究桩土结构相互作用打下基础。

基于自平衡法后压浆灌注桩荷载传递函数的变化分析

通过对实际工程自平衡试桩资料的分析,根据自平衡试桩的特点提出上下段桩选取不同荷载传递函数模型及压浆前后采用不同荷载传递函数模型,并采用Mindlin位移解与荷载传递法混合求解来考虑土体连续性的影响进行承载特性分析,最后通过一个工程实例验证了该模型的合理性。结果表明,荷载传递函数模型选取是正确合理的,考虑压浆后桩的荷载传递函数模型的变化影响更符合实际工程;土体连续性对超长桩的承载力及沉降计算有着较大影响,考虑土体连续性的桩顶位移比未考虑土体连续性的要大,结果偏安全。

基于Kano模型的充电桩功能需求研究

由于电动汽车日益增多,其配套充电设施的建设也要随之进行。充电桩作为充电设施的重要组成部分,目前正处于产品探索发展阶段,其功能开发的创新度及用户对其功能的需求度仍比较模糊。本文将运用户访谈法、观察法、焦点小组法等挖掘用户需求,制作产品功能需求列表;并结合kano模型对用户需求进行分析,构建反映充电桩各功能需求类型及重要度的产品功能塔,以确定用户的重点需求,以此作为充电桩功能发展方向的理论依据。