RESONANCE, TACOMA NARROWS BRIDGE FAILURE, AND UNDERGRADUATE PHYSICS TEXTBOOKS
RESONANCE, TACOMA NARROWS BRIDGE FAILURE, AND UNDERGRADUATE PHYSICS TEXTBOOKS
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DOI：
10.1119/1.16590
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发表时间：
1991-02-01
影响因子：
0.9
通讯作者：
SCANLAN, RH
中科院分区：
文献类型：
--
作者：
BILLAH, KY;SCANLAN, RH
1940年戏剧性的塔科马海峡大桥灾难至今仍在公众的视线中。值得注意的是，在许多本科物理教科书中，这场灾难是作为机械振荡器的基本强迫共振的例子提出的，风提供了与自然结构频率相匹配的外部周期频率。这种过于简单的解释在许多文本中已经存在了很长一段时间，并一直持续到今天，在一些新的和更新的文本中甚至有更详细的介绍。另一方面，工程师在过去的半个世纪里一直在研究这种现象，他们目前的理解与大多数物理学教科书中表达的观点有着根本的不同。在这篇文章中，工程师的观点被提交给物理界，以明确存在实质性分歧的地方。首先指出，强迫共振的一个误导性的识别产生的概念，即周期性的自然涡脱落的风在结构上的破坏性的外部激励的来源。然后，它表明，最终失败的桥梁实际上是有关的空气动力诱导的条件下的自激或“负阻尼”的扭转自由度。所涉及的气动弹性现象是一种相互作用的现象，其中产生的风力与结构运动密切相关。本文强调，从物理和数学上讲，强迫共振和自激是根本不同的现象。最后，本文对塔科马海峡现象进行了定量评估，该现象与桥梁本身在其最后时刻的记录行动以及20世纪50年代研究的完整动态缩放模型完全一致。
The dramatic Tacoma Narrows bridge disaster of 1940 is still very much in the public eye today. Notably, in many undergraduate physics texts the disaster is presented as an example of elementary forced resonance of a mechanical oscillator, with the wind providing an external periodic frequency that matched the natural structural frequency. This oversimplified explanation has existed in numerous texts for a long time and continues to this day, with even more detailed presentation in some new and updated texts. Engineers, on the other hand, have studied the phenomenon over the past half-century, and their current understanding differs fundamentally from the viewpoint expressed in most physics texts. In the present article the engineers' viewpoint is presented to the physics community to make it clear where substantial disagreement exists. First it is pointed out that one misleading identification of forced resonance arises from the notion that the periodic natural vortex shedding of the wind over the structure was the source of the damaging external excitation. It is then demonstrated that the ultimate failure of the bridge was in fact related to an aerodynamically induced condition of self-excitation or "negative damping" in a torsional degree of freedom. The aeroelastic phenomenon involved was an interactive one in which developed wind forces were strongly linked to structural motion. This paper emphasizes the fact that, physically as well as mathematically, forced resonance and self-excitation are fundamentally different phenomena. The paper closes with a quantitative assessment of the Tacoma Narrows phenomenon that is in full agreement with the documented action of both the bridge itself in its final moments and a full, dynamically scaled model of it studied in the 1950s.