纤维塑料筋混凝土梁长期性能研究进展

对国内外纤维塑料筋(FRP筋)混凝土梁长期性能试验、时随分析和设计计算方法的研究进展进行综述与分析:首先介绍不同种类FRP筋的应力松弛试验,研究表明AFRP筋的应力松弛较CFRP筋更为显著;总结预应力与非预应力FRP筋混凝土梁长期性能试验,研究表明采用AFRP筋或较低强度混凝土时,梁的长期变形相对较大;分别阐述基于截面时随曲率的非预应力FRP筋混凝土梁时随分析方法和基于龄期调整有效模量的预应力FRP筋混凝土梁截面时随分析方法;介绍非预应力FRP筋混凝土梁和预应力FRP筋混凝土梁长期变形的设计计算方法;最后对今后FRP筋混凝土梁长期性能研究的发展趋势进行展望。     

上海崇明越江通道长江大桥钢结构防腐施工技术

介绍了上海崇明越江通道长江大桥钢结构防腐涂装体系的设计及规范标准,着重阐述了当今大型跨江、海桥梁钢结构的长效防腐技术方法:电弧喷铝防腐技术。总结了电弧喷铝施工控制的关键工序,保证金属涂层与钢结构基体的结合力平均可达到12.0MPa,高于国家标准,金属涂层的使用寿命达到30～50年。     

基于海况参数分析的船体梁载荷预报方法研究

利用三维势流理论在频域内计算载荷频率响应函数,在此基础上对船舶波浪载荷长短期预报方法进行了研究,分析了现有的长期预报方法,并提出只针对特定的一部分短期海况进行分析,以确定船舶在营运寿命期内航行于实际海况中的波浪载荷特征最大值。同时提出了一种基于多项式拟合的波浪载荷预报方法,建立了短期响应的最可能极值关于海浪有义波高与海浪平均向上跨零周期的函数,可以方便地确定响应的特征值。结果表明,提出的方法能够有效进行波浪载荷的预报,可供有关专业人员参考。     

The Contribution of Benefit-in-Kind Taxation Policy in Britain to the ‘Peak Car’ Phenomenon

Car use per person has historically grown year-on-year in Great Britain since the 1950s, with minor exceptions during fuel crises and times of economic recession. The ‘Peak Car’ hypothesis proposes that this historical trend no longer applies. The British National Travel Survey provides evidence of such an aggregate levelling off in car mileage per person since the mid-1990s, but further analysis shows that this is the result of counter trends netting out: in particular, a reduction in per capita male driving mileage being offset by a corresponding increase in female car driving mileage. A major contributory factor to the decline in male car use has been a sharp reduction in average company car mileage per person. This paper investigates this aspect in more detail. Use of company cars fell sharply in Britain from the 1990s up to the 2008 recession. Over the same period, taxation policy towards company cars became more onerous, with increasing levels of taxation on the benefit-in-kind value of the ownership of a company car and on the provision of free fuel for private use. The paper sets out the changes in taxation policy affecting company cars in the UK, and looks at the associated reductions in company car ownership (including free fuel) and patterns of use. It goes on to look in more detail at which groups of the population have kept company cars and in which parts of the country they have been most used, and how these patterns have changed over time. A preliminary investigation is also made of possible substitution effects between company car and personal car driving and between company car use and rail travel. Clearly, the role of the company car is only one of many factors that are contributing to aggregate changes in levels of car use in Great Britain, alongside demographic changes and a wide range of policy initiatives. But, company car use cannot fall below zero, so the effect of declining year-on-year company car mileage suppressing overall car traffic levels cannot continue indefinitely.     

海岸地区长周期地貌模型研究进展

海岸地区的长周期地貌演变关系到了人类对海岸带资源的合理开发、保护及可持续利用。研究者不断改进和提高了海岸地区长周期地貌模型的适用性和可靠性。文章从发展概况、时空尺度、计算原理、信息约减技术以及模型应用等方面简述了海岸地区长周期地貌模型的研究进展,并认为模型的理论、技术还可进一步提高,模型的应用范围还可拓展到更大尺度。     

土工格栅筋材施工机械损伤折减系数研究

土工格栅的最不利状态并不是在使用环节,而是在土工格栅铺设过程中,因此在确定土工格栅的长期强度时必须考虑的主要因素是土工格栅在铺设施工和填料碾压过程中受到的损伤。通过分析国内的一些土工格栅施工机械损伤试验数据和影响损伤的不同因素,给出了计算土工格栅机械损伤折减系数的分项系数,并提出了计算土工格栅施工机械损伤折减系数的计算公式和修正方程。研究成果对确定土工格栅的长期强度具有指导意义。     

循环荷载下水泥土桩复合单元体变形特性及其地基长期沉降计算方法

对于软土地区的路基工程,若路基处理不当,在长期交通荷载作用下,容易导致服役期路面开裂、不均匀沉降等问题。水泥土搅拌桩法是软土地区最常用的路基加固方法之一。研究循环荷载下水泥土桩复合地基的变形特性,对于指导交通荷载下软土地基长期沉降控制具有重要意义。然而,现有研究主要集中在软土和水泥土单一介质,对于水泥土桩复合体的研究较少。通过开展水泥土桩复合单元体大型动三轴试验,分析围压、静偏应力和置换率等因素对水泥土桩复合体累积塑性应变的影响。研究结果表明：循环荷载下水泥土桩复合体累积塑性显著小于软土,且应变随围压、动应力比及静偏应力的增大而增大,随置换率的增大而减小;静偏应力的增加会导致复合单元体临界动应力比的减小。基于试验结果,建立了水泥土桩复合体长期沉降计算方法。结合现代有轨电车算例,分析交通荷载作用下软土路基以及经水泥土桩法处理后的路基长期沉降结果。计算结果表明,采用水泥土桩法可有效减小软土路基长期沉降。     

Time-domain simulation of wave-induced nonlinear motions and loads and its applications in ship design

A nonlinear time-domain formulation for ship motions and wave loads and a nonlinear long-term statistics method are presented and applied to the S175 container ship. The general agreement between model tests and numerical results is very satisfactory. The calculated long-term vertical sagging and hogging moments amidships are comparable to those given by DNV rules. The approach described in this paper can be used as a way of more accurately evaluating extreme wave loads and other nonlinear responses in ship design.     

桥梁裂缝宽度监测方法

桥梁典型裂缝的发展尤其是宽度的发展能够直观地反应桥梁的技术状况。通过对某高速公路两座桥梁典型裂缝宽度的长期监测,介绍了目前桥梁裂缝宽度的主要监测方法、每种方法的适用条件和优缺点。同时,对部分新兴的监测方法做了相关的分析与研究,得出了目前适用于桥梁裂缝宽度监测的优选方法,工程实例应用证明这种方法简单、有效且实用。     

基于灰色系统的桥梁长期变形预测研究

针对大跨径预应力混凝土箱梁桥长期变形影响因素众多,影响机理不明确,计算理论不完善的现状,基于灰色预测理论,以虎门大桥辅航道桥的实测挠度数据为基础,建立桥梁长期变形预测系统,计算结果表明:只要对原始数据作合理的处理,预测系统计算得出的数据精度完全能够满足工程需求,这为桥梁长期变形控制提供了一种依据.