既有桥梁承载力动力评估方法综述

用动力法评估既有桥梁承载力是一种较有前途的桥梁承载力评估方法,在介绍各种动力评估方法的基础上,对它们进行比较分析,其结果可为相关工作人员提供一定的参考.     

Variation in predicting pantograph–catenary interaction contact forces,numerical simulations and field measurements

The contact force between the pantograph and the contact wire ensures energy transfer between the two. Too small of a force leads to arching and unstable energy transfer, while too large of a force leads to unnecessary wear on both parts. Thus, obtaining the correct contact force is important for both field measurements and estimates using numerical analysis. The field contact force time series is derived from measurements performed by a self-propelled diagnostic vehicle containing overhead line recording equipment. The measurements are not sampled at the actual contact surface of the interaction but by force transducers beneath the collector strips. Methods exist for obtaining more realistic measurements by adding inertia and aerodynamic effects to the measurements. The variation in predicting the pantograph–catenary interaction contact force is studied in this paper by evaluating the effect of the force sampling location and the effects of signal processing such as filtering. A numerical model validated by field measurements is used to study these effects. First, this paper shows that the numerical model can reproduce a train passage with high accuracy. Second, this study introduces three different options for contact force predictions from numerical simulations. Third, this paper demonstrates that the standard deviation and the maximum and minimum values of the contact force are sensitive to a low-pass filter. For a specific case, an 80?Hz cut-off frequency is compared to a 20?Hz cut-off frequency, as required by EN 50317:2012; the results show an 11% increase in standard deviation, a 36% increase in the maximum value and a 19% decrease in the minimum value.     

中外钢管桩内力验算方法对比

钢管桩作为一种多轴对称的钢结构,性能稳定,受力机理相对明确,在国内外港口工程中主要用于高桩码头的基础结构和板桩码头的主体结构。通过对比研究国标、欧标、美标API和美标AISC共4种国内外规范对于钢管桩内力验算方法,探究4种规范验算方法的差异性,为海外港口工程钢管桩内力验算方法选取提供参考建议。以某港口高桩墩台结构为例对比4种规范钢管桩内力验算方法,结果表明:1) AISC规范计算结果最小,即其充分考虑发挥结构的性能,偏安全。2)欧标计算的结果最大,相对保守。3)国标和API规范计算结果介于AISC规范和欧标之间。     

高强度洋流作用下沉管的力学性能研究

沉管水下沉放中,管节与船舶采用缆索连接吊放下沉.为解决外海复杂海况条件下,船管缆系耦合受力的状态与水下管节的位移不受控和缆力超限的问题,通过数值仿真计算和物模试验相结合的方式,分析了不同沉放深度的沉管沉放过程中,船舶受外载荷和管节水下受水动力双重作用时的动力响应情况.通过计算和试验,开展了自由状态下的衰减试验、系泊系统下模型单自由度运动衰减试验、作业状态下沉管和安装船运动响应及各缆绳的受力测量,得到系泊缆、沉管吊缆和安装缆,在浪、流组合作用下的受力和水下运动位移情况,选取了适用于本项目管节沉放施工缆系的关键力学取值,并进行了工程应用验证和对比分析,证明了该研究成果的正确性,研究成果可为类似工程大型构件水下精确沉放和施工提供技术依据.     

基于改进社会力的单向流电动自行车行为建模研究

电动自行车作为一种便捷高效的出行工具，已在许多国家被广泛使用，但对电动自行车微观行为的研究仍十分有限。在上海海事大学对电动自行车驾驶行为进行观测实验，提取电动自行车轨迹数据，以纵向间距、速度差、侧向净距、水平间距作为特征变量，利用CART(Classification and Regression Tree)决策树分类结果建立电动自行车骑行决策行为规则。然后，基于社会力模型，分别引入超越力、跟随力等改进行为力模拟电动自行车的超越、跟随等骑行决策行为。考虑公式超越力、固定值超越力和临时目标点超越力这3种超越力形式，通过实际观测数据和仿真结果比较进行参数标定和模型验证，选取单向流电动自行车行驶场景开展数值仿真分析。结果表明：临时目标点超越力的改进社会力模型在超越过程中的轨迹误差最小，电动自行车超越时所需要的横向间距与超车时横向速度、超车完成时间成正比，最佳超车横向间距为2 m。     

The kinematic wave model with finite decelerations: A social force car-following model approximation

This paper derives a five-parameter social force car-following model that converges to the kinematic wave model with triangular fundamental diagram. Analytical solutions for vehicle trajectories are found for the lead-vehicle problem, which exhibit clockwise and counter-clockwise hysteresis depending on the model’s parameters and the lead vehicle trajectory. When coupled with a stochastic vehicle dynamics module, the model is able to reproduce periods and amplitudes of stop-and-go waves, as reported in the field. The model’s stability conditions are analysed and its trajectories are compared to real data.     

高桩承台桩基计算

根据现行规范及桩基计算理论,编写了计算程序,通过算例分析比较,程序计算结果比较精确,可以使用程序方便地计算高桩承台桩基的位移以及内力,从而为工程设计提供依据。     

五弯矩方程在半悬挂舵舵杆受力计算中的应用

根据《钢质海船入级与建造规范》（简称“钢规”）规定的半悬挂舵的计算模型直接进行计算。半悬挂舵舵杆及挂舵臂组合体视为变截面梁，并将变截面梁分割成4段等截面的单跨梁，用五弯矩理论进行求解。     

An analytical mathematical method for calculation of the dynamic wheel–rail impact force caused by wheel flat

The simplified method to determine a vertical impact force of wheel with flat and rail interaction is presented in this article. The presented simplified method can be used to identify maximum contact force and its distribution in the contact length between the damaged wheel and the rail. The vertical impact force depends on geometrical parameters of the rail and wheel with flat, speed of vehicle and the angle of deviation of rail. This article demonstrates the influence of wheel with flat geometrical parameters, speed of vehicle to maximum contact force and its distribution in the contact zone. The obtained values of the simplified method for determination of a vertical contact force are compared with the results obtained from field measurements.     

客车侧翻生存空间仿真评价方法研究

为了能更直观地评价客车侧翻生存空间的侵入状况,提出以接触力作为评价指标的仿真分析方法。根据法规ECE R66要求,建立某客车骨架及生存空间的有限元模型,并进行侧翻仿真分析,评价其上部结构的变形及其侵入乘员生存空间的状况。基于仿真分析结果,验证了该仿真评估方法是简单实用、准确可靠的。