Origin–destination missing data estimation for freight transportation planning: a gravity model-based regression approach

This paper develops a log-linear regression approach to estimate missing data in a sparse origin–destination (O–D) matrix assuming the sampled or observed O–D trips follow a good gravity pattern. The approach is tested with randomly selected samples from the known portions of 1997, 2002, and 2007 US Commodity Flow Survey (CFS) O–D value and tonnage matrices and validated with 2007 US O–D tonnage matrix at the state level. The missing data are also estimated for the 2007 CFS tonnage matrix with the best intercept and coefficients obtained using all known entries of the matrix. The concept of the approach can be extended beyond the gravity model to any strong mathematical pattern embedded in the known set of a sparse O–D matrix to estimate its missing cells.     

桥墩及桥台设计思路探讨

桥梁设计时,要求墩身拥有良好的结构造型,既要符合结构力学要求,又要符合经济适用的原则.通过对现代技术手段的调研及相关桥梁设计实践经验总结,总结了桥梁设计中常用的桥墩及其桥台形式,详细地分析了不同形式对桥梁设计的影响.     

重力式挡墙稳定性可靠度分析

目前我国重力式挡土墙采用安全系数法进行挡土墙稳定性分析,而在实际施工过程中由于存在诸多不确定因素,导致其分析偏差较大引发许多工程事故。结合山西省某挡土墙工程,分别采用安全系数法和可靠度分析方法对其稳定性进行对比分析。分析表明:采用挡土墙可靠度分析方法进行挡土墙稳定性判断,更为合理地反映其结构的安全程度,其设计理论合理可行。     

重力式U型桥台开裂原因

U型桥台是桥梁工程中常采用的结构物,主要受力部分为前墙,前墙的设计对整个桥台的结构尤为重要。我国设计规范从结构的整体抗力、抗滑和抗倾稳定性、地基承载力验算等方面进行验算,但是没有验算其产生的土压力对侧墙、前墙的影响。现实中,桥台前墙和侧墙连接处出现裂缝,许多桥台的开裂正是由于台内填料的土压力引起的,为此本文将通过专业软件考虑土压力的影响,采用实体单元,进行分析得到填料土压力对前墙作用的影响。     

重力式挡士墙的施工质量问题与防治

对重力式挡土墙在施工中出现的质量问题，要尽可能因地制宜、因时而异地进行具体分析，采用科学的处理方法，从而保证施工质量。     

重力式码头块石基床的水下爆炸夯实技术

结合重力式码头基床、地基及水文的实际情况,总结码头基床水下爆炸夯实技术的设计、施工工艺、质量控制及爆破的安全控制,可供类似工程参考。     

重力式码头胸墙变形缝缺陷防治

分析重力式码头变形缝的缺陷,结合营口港鲅鱼圈港区四期工程54#～56#集装箱泊位施工,提出防治措施,防治效果很好。     

重力式码头后方构筑物周边地面沉降过大缺陷防治

重力式码头后方构筑物周边地面沉降过大,将影响码头的正常使用。结合工程实践,对出现该问题的原因进行分析,并提出预防措施。     

某港重力式墩台压顶方块开裂原因分析

通过对某港重力式墩台压顶方块开裂原因的分析,阐述了一种罕见的支撑状态改变引起墩台上构件破损的因素。     

Effect of the combined centre of gravity on the running safety of freight wagons

ABSTRACT

This paper presents an analysis of loaded freight wagon dynamics in curve alignments. We investigate the effects of the combined centre of gravity (CCOG) on the running safety of freight wagons and examine proper position of the CCOG. A simple wagon-rail model is implemented using the multibody dynamics software ADAMS/Rail. The simulation model is operated on curve tracks with various radii and velocities and the curving performances are evaluated. The results indicate that the CCOG can be located within a flexible and accurate range. The longitudinal offset is good for the curving performance and the permissible lateral offset should be assessed based on the curve radius and cant deficiency.