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

在人类产生的所有动力中，如行走、跑步、跳跃、弹跳/摆动和摇摆，当考虑到人行天桥、地板、看台和其他由这些活动动态激发的装配式结构的性能时，人类行走和跑步产生的动力是最不为人所知和最复杂的。这是因为它们在本质上是随机的，难以预测，而且在实践中更难使用，因为它们的行为不仅随时间而且随空间而变化。给设计师的关于行走和跑步引起的动态负载的本质的指导，往好了说是基本和简单的，往坏了说是不准确的。由于行人群体或人群，没有关于装载性质的正式指导，这种缺乏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（未进入公共领域的）昂贵的工业或实验设施由于行人负荷而不适合使用的例子。与普遍的看法和目前的编纂相反，走路/跑步的力量并不是完全周期性的，而是（正如最近的提议者所证明的那样）是窄带随机现象，在个体之间和同一个人之间都有相当大的差异。在结构设计和扩展中使用这种力来与一个以上的行人一起使用，确实需要实验和分析处理，类似于用于其他类型的动态激发土木工程结构的随机力，如风、波浪或地震。这种对移动的人类引起的动力的统计和概率处理目前只作为一个概念存在于少数研究论文中（包括提案人写的论文）。因此，收集大量的步行/跑步时变荷载记录，建立一个可行的数据库，并将其直接用于各种形式的基于概率的现实结构动力计算，为推进整个领域的振动适用性评估提供了及时的机会，该领域包括地板和人行天桥等运动人体占据和动态激励的结构。在提出的方法中有两个关键的新颖之处：(1)对于跑步机上的受限运动在多大程度上可以代表正常行走，存在不同的观点，因此我们将通过测量人体或身体的运动来使用“自由场”测量三分量连续行走/跑步力，并与跑步机上的标准直接测量力进行比较。(2)我们有办法利用已经建立的步行/跑步力时变轨迹测量数据库来建立这些力的随机模型，然后将它们应用于模拟现实结构的动态响应。我们也有很多实际的机会来应用和完善模型，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.