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Recent Research and Design Developments in Steel and Composite Steel-concrete Structures in USA
& F2 z) J5 F# d, m2 {% W) Y The paper will conclude with a look toward the future of structural steel research.
: _2 R8 @3 R! q! I! f0 P8 M- y 1. Research on steel bridges" `7 o6 K. q& a2 M$ R. {
The American Association of State Transportation and Highway Officials (AASTHO) is the authority that promulgates design standards for bridges in the US. In 1994 it has issued a new design specification which is a Limit States Design standard that is based on the principles of reliability theory. A great deal of work went into the development of this code in the past decade, especially on calibration and on the probabilistic evaluation of the previous specification. The code is now being implemented in the design office, together with the introduction of the Systeme Internationale units. Many questions remain open about the new method of design, and there are many new projects that deal with the reliability studies of the bridge as a system. One such current project is a study to develop probabilistic models, load factors, and rational load-combination rules for the combined effects of live-load and wind; live-load and earthquake; live-load, wind and ship collision; and ship collision, wind, and scour. There are also many field measurements of bridge behavior, using modern tools of inspection and monitoring such as acoustic emission techniques and other means of non-destructive evaluation. Such fieldwork necessitates parallel studies in the laboratory, and the evolution of ever more sophisticated high-technology data transmission methods.! r7 S: }1 N: h* {' B$ q4 D0 F
近期美国在钢结构和钢筋混凝土结构研究和设计方面的发展& j5 ~& r: x6 C) j* L$ @
这篇文章将总结对钢结构的研究展望.
7 \! b" u& Z0 Z4 e3 } 1.钢结构桥梁的研究
- J# _" O& ]8 ?, X9 P$ a 美国国家运输和公路官员协会(AASTH0)是为美国桥梁发布设计标准的权威。1994年它发行了一个新的设计规范，这是一个限定性规范，它是以可靠性理论为基础而建立的。在过去10年中的大量工作促 使了该规范的发展，尤其是在对原有规范的校准和概率性评估方面。连同国际单位制的引入，目前该规范已经应用于各个设计事务所。这种新的设计方法还存在许多问题，对桥梁擎体系统的可靠性研究还有很多新的课题。一个目前的课题就是研究并发展概率模型、荷载系数以及合理的荷载组合法则，以处理活载和风载；活载和地震；活载、风和船只碰撞；船只碰撞、风和冲刷作用这些共同作用对桥的影响。此外，还通过利用现代监控工具，例如声传播技术和其他非破坏性测试方法，对桥体进行现场测量。这些现场工作不仅需要并行的试验室研究相配合，还需要快速发展高科技数据传输方法。 | 
