Multidisciplinary approach to aeroelastic studies of long-span bridges

This paper focuses on the design of long-span suspension bridges under aeroelastic constraints. Such challenging structures need to be protected against wind-induced instabilities as flutter. The authors envision that a set of scientific disciplines not currently used in bridge engineering may help along the design process and constitute a useful tool. First, the formulation of sensitivity analysis of flutter speed is described, indicating how this technique can be a guide for engineers making changes in the prototype; two examples of important bridges, as the Great Belt and Messina Strait, are used to demonstrate the capability of this approach. Then, the idea of producing computer animations to represent the aeroelastic deformation of bridges simulating virtual boundary layer wind tunnel testing is presented showing pictures of the Tacoma Narrows and Messina Bridges. Finally, the advantages of introducing distributed computing to make easier to implement the previously mentioned techniques are demonstrated. The authors have previously published papers related with sensitivity analysis in bridges or computer animations of the aeroelastic behaviour of suspension bridges. However, this is the first time that their comprehensive multidisciplinary approach is presented.     

基于图形工作站的塔台管制模拟器的设计与实现

通过对空中交通管制程序，陆空通话模式，机场管理方式等的分析综合，提出并拟定了基于图形工作站实现塔台管制模拟器的总体方案。在此基础上，研究了在图形工作站上基于Unix/X Windows系统利用Motif/OpenGL编程的基本技术，并采用计算机图像生成技术较好地模拟了机场周围的三维视景系统，有效逼真地表现了飞机运动的动态行为过程，实完成了塔台管制模拟器的基本功能。     

具有信息分析功能的防火墙系统研究

1 引言随着Internet/Intranet在我国的普及与飞速发展,网络安全技术已经成为我们国家走向信息化的重要前提条件。为了保护机关及企事业内部的重要信息资源,免受外来非法访问与破坏,同时阻止内部人员对外部非法站点的访问,采用防火墙技术是行之有效的办法,但是传统的防火墙技术只能根据网络包的源和目的地址来判断该网络包的安全性,而对包的内容不进行处理;传统的包过滤防火墙处于IP层,对用户来讲仍然不够透明,而且不能对其他协议的网络包如     

三峡工程覃家沱特大桥的设计与施工

覃家沱特大桥是一座多功能的特大重载桥，桥型为三跨连续刚构，主梁１３０ｍ，主要设计荷载为汽１３５级挂６６０级，设计荷载相当于双线路路荷载，与目前国内同类经线铁路桥相比主跨度居国内第一，大桥上部结构箱梁采用单箱双室截面，设置纵，横，竖三向预应力；下部结构主墩为单壁实体墩，主墩及桥台基础均为灌注桩，在结构设计及重载挂篮悬臂施工技术等方面具有特点，对桥梁工程的设计与施工具有借鉴价值。     

桥区参数对Ni-Cr薄膜换能元发火性能的影响

依据GJB/z 377A-94感度试验川兰利法,对设计制作的不同桥区参数的Ni-Cr薄膜换能元进行了发火感度测试.结果显示:当桥区尺寸、形状一定时,随着桥膜厚度的增加,换能元的发火电压减小,当桥膜的厚度增加到0.9μm,换能元发火电压又有增加的趋势;当桥膜厚度、桥区形状一定时,随着桥区宽度减小,发火电压降低,但当桥区宽度小于0.10mm时,发火电压反而上升;当桥膜厚度、桥区宽度一定时,桥区长度越长,发火电压越高,而且不同桥区形状对换能元发火感度有明显的影响.     

Full-Scale Test of Continuity Diaphragms in Skewed Concrete Bridge Girders

Continuity diaphragms used in prestressed girder bridges on skewed bents have caused difficulties in detailing and construction. The results of the field verification for the effectiveness of continuity diaphragms for skewed, continuous, and prestressed concrete girder bridges are presented. The current design concept and bridge parameters that were considered include skew angle and the ratio of beam spacing to span (aspect ratio). A prestressed concrete bridge with continuity diaphragms and a skewed angle of 48° was selected for full-scale test by a team of engineers from Louisiana Department of Transportation and Development and the Federal Highway Administration. The live load tests performed with a comprehensive instrumentation plan provided a fundamental understanding of the load transfer mechanism through these diaphragms. The findings indicated that the effects of the continuity diaphragms were negligible and they can be eliminated. The superstructure of the bridge could be designed with link slab. Thus, the bridge deck would provide the continuity over the support, improve the riding quality, enhance the structural redundancy, and reduce the expansion joint installation and maintenance costs.     

Pipe Heating System with Underground Water Tank for Snow Thawing and Ice Prevention on Roads and Bridge Decks

In order to prevent traffic accidents on snow-covered bridge decks, the writers developed a new pipe heating system that uses only groundwater stored in a large underground tank. The underground tank provides geothermal energy, i.e., groundwater of constant temperature, through heating pipes embedded in concrete pavements with no electric heater or fuel boiler. The pipe heating system was constructed at approximately 50% of the cost of comparable systems. In addition, there is a reduction of 10% in operating costs compared with the previous system. The present paper outlines its design and construction and provides fundamental data for the developed system. The piped heating system has kept the road conditions safe during the winter season by always removing the snow and ice from the heated road and bridge sections earlier than the surrounding roads. According to long-term temperature measurements, this system has prevented the road temperature from decreasing below 0°C, even through nighttime and morning periods. This report presents the system as an economical and effective solution for snow thawing and ice prevention.     

分步拼装在900 t级架桥机钢结构安装工程中的应用

针对架桥机钢结构在工厂内无法整体试装的现状,依据理论分析,提出分步拼装方案,并预先考虑架桥机钢结构工地安装可能出现的问题,通过分步拼装过程对关键构件、关键工序加以控制,从而达到满意的工地安装效果。     

武汉二七长江大桥防雷与接地设计

介绍武汉二七长江大桥的直击雷防护、侧击雷防护措施和电涌保护器的设置．以及接地设计、接地电阻的检测、施工要求等。重点介绍大桥利用基础桩基内外边缘的结构钢筋（包括钢护筒）作为接地板的做法。     

Structural health monitoring of innovative bridge decks

For more than a century, important civil engineering structures such as bridges, high-rise buildings, dams and marine platforms have contained iron or steel as the reinforcement for concrete or wood. The useful lives of such structures have often been severely limited by the corrosion of this ferrous component. Much thought has been given in recent years to constructing structures that are lighter, stronger and non-corrosive. These innovative structures are new and for these to be accepted by the engineering community monitoring is mandatory. ISIS Canada has been developing such structures and monitoring them. In this paper, innovative bridge decks that have been implemented are described.