HUMAN WALKING AND RUNNING FORCES: NOVEL EXPERIMENTAL CHARACTERISATION AND APPLICATION IN CIVIL ENGINEERING DYNAMICS

在所有由人类引起的动态力中，例如行走、跑步、跳跃、弹跳/摇摆和摇摆，当考虑诸如人行桥、地板、看台和由这些活动动态激励的其他组装结构的土木结构的性能时，由人类行走和跑步引起的动态力是最不了解的，并且处理起来最复杂。这是因为它们在本质上是随机的，很难预测，甚至更难在实践中使用，因为它们的动作不仅在时间上而且在空间上都在变化。由于行走和跑步而引起的动态载荷的性质，给设计师的指导充其量是基本的和简单的，最坏的情况是不准确的。由于行人成群或拥挤，没有关于装载性质的正式指导，缺乏这种理解的结果可能是经济上的灾难。伦敦千禧桥的例子只是冰山一角：有许多例子（未达到公共领域）的高度昂贵的工业或实验设施，由于行人负荷而不适合使用。与普遍的看法和目前的编纂相反，步行/跑步力不是完全周期性的，（如最近由提议者所证明的）是窄带随机现象，在个体之间以及对于同一个人具有相当大的变化。在结构设计和扩展中使用这种力以用于多个行人确实需要类似于用于动态激励土木工程结构的其他类型的随机力（例如风、波浪或地震）的实验和分析处理。这种统计和概率处理移动的人引起的动态力目前只存在于少数研究论文（包括tjose写的提案人）的概念。因此，收集大量的步行/跑步的时变载荷记录，建立一个可行的数据库，并直接使用它的各种形式的概率为基础的动态计算的现实生活中的结构提供了一个及时的机会，以推进整个领域的振动舒适性评估的占用和动态激励的人，如地板和人行天桥。在所提出的方法中有两个关键的新颖之处：（1）对于跑步机上的受约束运动可以代表正常行走的程度有不同的意见，因此除了跑步机上的力的标准直接测量之外，我们将通过测量人体或身体的运动来使用三分量连续行走/跑步力的“自由场”测量，并与之进行比较。(2)我们有办法使用这样建立的数据库的测量随时间变化的痕迹步行/跑步的力量，这些力量的随机模型，然后将它们应用到模拟现实生活中的结构的动态响应。我们也有很多实际的机会来应用和改进模型，以评估结构设计阶段的振动适用性。

Of all dynamic forces induced by humans, such as walking, running, jumping, bouncing/bobbing and swaying, the dynamic forces induced by human walking and running are the least understood and most complex to deal with when considering performance of civil structures such as footbridges, floors, grandstands and other assembly structures that are dynamically excited by these activities. This is because they are random in nature, difficult to predict and even more difficult to use in practice as their action changes not only in time but also in space.Guidance to designers on the nature of dynamic loads due to walking and running is at best rudimentary and simplistic and at worst inaccurate. There is no formal guidance on the nature of loading due to groups or crowds of pedestrians and the result of this lack of understanding may be financially disastrous. The example of the London Millennium Bridge is the tip of the iceberg: there are many examples (that do not reach the public domain) of highly expensive industrial or experimental facilities that are unfit for purpose due to pedestrian loading.Contrary to common belief and current codification, walking/running forces are not perfectly periodic but (as recently demonstrated by the proposers) are narrow-band random phenomena with considerable variation between individuals as well as for the same person. Use of such forces in structural design and extension to use with more than one pedestrian really requires experimental and analytical treatment similar to that used for other types of random forces that dynamically excite civil engineering structures, such as wind, waves or earthquakes. Such statistical and probabilistic treatment of moving human-induced dynamic forces currently exists only as a concept in a few research papers (including tjose written by the proposer). Hence gathering a large number of time-varying loading records of walking/running, establishing a viable database of them and using it directly for various forms of probability-based dynamic calculations of real-life structures presents a timely opportunity to advance the whole field of vibration serviceability assessment of structures occupied and dynamically excited by moving humans, such as floors and footbridges. There are two key novelties in the proposed approach: (1) There are varied opinions on the extent to which the constrained motion on a treadmill can represent normal walking, so we will use 'free field' measurement of three-component continuous walking/running forces by measuring movement of the human body or bodies in addition to and for comparison with standard direct measurement of forces on a treadmill.(2) We have the means to use the so established database of measured time-varying traces of walking/running forces to develop stochastic models of these forces and to then apply them to simulate dynamic response of real-life structures. We also have many practical opportunities to apply and refine the models to assess vibration serviceability at the stage of structural design.