Aspects of the stability of jack-up spud-can foundations

A three-level procedure for assessing jack-up foundation stability for more or less homogenous soils is described. The objective is to provide a rational framework for these assessments that ensures their safe operation in extended year-round operations and enables their use in deeper waters than at present.

The three levels of the procedure have to be entered successively as long as foundation stability cannot be proven. The first level is a screening exercise and essentially replaces the well-known preload check. The second level compares factored foundation loads resulting from a structural analysis with foundation capacities obtained with ultimate bearing capacity formulae. The most refined third level assesses whether the displacements associated with these loads lead to an acceptable situation, i.e. capacity increase and/or load redistribution that does not result in collapse of the jack-up unit.

Since, for maximum benefit, this third-stage analysis requires a non-linear foundation model to be linked with the structural package used: such a tool is provided in the paper. Examples are given to demonstrate the impact of the assessment procedure.

This procedure forms part of the overall in-house approach to the assessment of jack-ups and has already been offered to the jack-up industry as part of the continuing efforts towards establishing common and accepted standards for jack-up assessments. Further developments have been identified and will be pursued.     

应用空间有限元模型进行船舶总振动特性的研究

本文以17500吨货船“海建”号为实例研究应用空间有限元模型计算船舶总振动的方法。对于实际船舶结构中的板,提出用平面应力元简化,以减少计算自由度数,由此产生的问题采用节点主从关系的方法解决。在编制的计算程序中,根据质量矩阵高度稀疏的特点,采用了稀疏存储技术,从而使船舶整体空间模型的振动分析能在国产中小型机器上实现。实例计算结果和测量结果的比较表明,这种计算模型合理、可靠。本文还对船舶总振动计算的梁模型、平面有限元模型、空间有限元模型作了比较和讨论。     

Sensitivity analysis of side-slip angle observer based on a tire model

We investigated the sensitivity of an observer based on a tire model using simulation in linear and nonlinear regions. In the linear region, we investigated the influence of vehicle speed by doing the same simulation at three speed levels. In the nonlinear region, the simulation condition was set such that the vehicle became unstable. In the linear region, steering input and cornering stiffness have a relatively large effect on the estimation error because these quantities determine tire side force. In the nonlinear region, the road surface's friction coefficient becomes a crucial factor. In both the regions, the observer is sensitive to yaw rate and longitudinal speed.     

那吉航运枢纽溢流坝断面及坝下冲刷试验

采用比尺为 1∶30水工断面模型 ,进行溢流坝断面设计方案的过流能力、坝面压力及坝下消能局部冲刷试验 ,经优化提出的坝面曲线及消能工方案 ,改善了消力池水流条件、减小了冲刷、节约了工程量     

The impact of major road developments on the spheres of urban influence of Japanese cities

This study aims to measure the impact of major road developments on the spheres of urban influence of Japanese cities.First, the sphere of urban influence is defined by application of an individual behavior model. The model explains the number of trips to representative cities in regions from the residential place of each individual using the following factors; the attractiveness of cities, the travel time to cities and the individual's free time. Development of major roads shortens the travel time, and this causes the change in the sphere of urban influence. The model we propose has the structure to explain this phenomenon.Second, this method is applied to all of Japan where expressways are now being rapidly constructed and, how they change spheres of urban influence is explained. In the application, as a measure of attractiveness of cities, population, commercial and industrial activity, etc. are considered. From these points of view, the impacts of construction of expressways in Japan are estimated.     

交流异步电机直接转矩控制理论的研究

直接转矩控制是异步电机交流传动中一种新型控制方法，它充分利用逆变器的开关特点，引入容差控制概念，通过一些简单的计算和调节使异步电机的磁链和转矩在动态时按要求快速变化，因而具有高动态性能，控制电路简单的优点。对直接转矩控制系统的原理与理论作了深入的研究与探讨。     

外高桥新港区顺岸码头工程水环境质量影响预测数学模型

本文在外高桥顺岸码头工程水环境现状评价的基础上,采用沿水深积分平均的二维水流水质数学模型,结合一定的定解条件,建立了预测该项工程对周围水环境影响的水质数学模型。采用ADI数值计算方法离散控制方程,考虑到顺岸码头下游3km的上海合流污水竹园排放口工程,预测计算工程建成后产生的污染源对评价区水域的水质影响。计算时,主要讨论了化学耗氧量(COD_(Mn))的浓度增量。本模型也可以推广应用于其他河口、海岸流场和浓度场的计算预测研究。     

路基设计CAD中排水设施的自动设置方法

将数字地形模型引入路基设计ＣＡＤ中，可有效地解决路基排水设施的设置等关键问题；本文详细介绍基于横断面系统数字地形模型和交互式图形睡堤排水沟设置的方法。本文所介绍的方法同样适用于基路ＣＡＤ中天沟等排水设施的设置。