明挖地铁车站主体结构最不利设计水位分析

我国华南、华东、华中地区及沿海城市地下水丰富,地下水压力是影响地铁车站主体结构受力的重要因素,随着水头高度的变化结构受力会随之发生改变。为了研究不同的水位对车站主体结构受力的影响,结合众多地下水丰富的地铁工程实例,选取多种水位进行数值模拟计算,结果表明:影响顶板、中板、底板及侧墙的最不利水位并不是统一的水位。为了方便设计,通过将众多正常使用中的地铁车站结构受力情况对比分析,认为:选取工程场地内最高水位进行车站结构受力计算,然后对部分构件配筋面积进行调整,能够满足车站结构安全的要求。     

公路施工时的基层压实度探析

分析了公路基层施工时石灰土施工时混合料配比不均对其最大干密度的影响,回归分析了混合料配比与其松容重和最大干密度的线性关系,建立松容重-最大干密度的压实度控制方法,从而保证了基层的强度。     

Extreme value prediction of nonlinear ship loads by FORM using Prolate Spheroidal Wave Functions

In this study, a method for predicting the extreme value distribution of the Vertical Bending Moment (VBM) in a flexible ship under a given short-term sea state is presented. The First Order Reliability Method (FORM) is introduced to evaluate the Probability of Exceedances (PoEs) of extreme VBM levels. The Karhunen-Loeve (KL) representation of stochastic ocean wave is adopted in lieu of the normal wave representation using the trigonometric components, by introducing the Prolate Spheroidal Wave Functions (PSWFs) to formulate the wave elevations. By this means, reduction of the number of stochastic variables to reproduce ocean wave is expected, which in turn the number of computations required during FORM based prediction phases is significantly reduced. In this study, the Reduced Order Model (ROM), which was developed in our previous studies, is used to yield the time-domain VBMs along with the hydroelastic (whipping) component in a ship. Two different short-term sea states, moderate and severe ones, are assumed. The FORM based predictions using PSWF for normal wave-induced VBM are then validated by comparing with those using the normal trigonometric wave representation and Monte Carlo Simulations (MCSs). Through a series of numerical demonstrations, the computational efficiency of the FORM based prediction using PSWF is presented. Then, the validation is extended to the severe sea state where the whipping vibration contributes to the extreme VBM level to a large degree, and finally the conclusions are given.     

基于DEA的交叉效率模型在公路建设适应性评价中的应用

由于经济、地域等原因，全国公路建设的发展极不平衡，地区差距与建设的适应性也存在较大差异。本文利用基于DEA的交叉效率模型来评价各地区的公路建设适应性情况，结果表明各地区的公路建设适应性差异明显。     

城市轨道交通CBTC系统车载ATP仿真研究

介绍了基于无线的城市轨道交通CBTC仿真系统的车载ATP子系统,设计了一种车载ATP模型,阐述了此模型的原理及算法,并以上海轨道交通10号线的线路及列车参数为例,对提出的ATP模型进行了仿真。     

Required test durations for converged short-term wave and impact extreme value statistics — Part 1: Ferry dataset

For the design of maritime structures in waves, the extreme values of responses such as motions and wave impact loads are required. Waves and wave-induced responses are stochastic, so such responses should always be related to a probability. This information is not easy to obtain for strongly non-linear responses such as wave impact forces. Usually class rules or direct assessment via experiments or numerical simulations are applied to obtain extreme values for design. This brings up questions related to the convergence of extreme values: how long do we need to test in order to obtain converged statistics for the target duration? Or, vice versa: given testing data, what is the uncertainty of the associated statistics? Often the test or simulation duration is cut up in ‘seeds’ or ‘realisations’, with an exposure duration of one or three hours based on the typical duration of a steady environmental condition at sea, or the time that a ship sails a single course. The required number of seeds for converged results depends on the type of structure and response, the exposure duration, and the desired probability level. The present study provides guidelines for the convergence of most probable maximum (MPM) wave crest heights and MPM green water wave impact forces on a ferry. Long duration experiments were done to gain insight into the required number of seeds, and the effect of fitting. The present paper presents part 1 of this study; part 2 [1] presents similar results for wave-in-deck loads on a stationary deck box.