SYNCHRONISATION IN DYNAMIC LOADING DUE TO MULTIPLE PEDESTRIANS AND OCCUPANTS OF VIBRATION-SENSITIVE STRUCTURES

对于人行天桥、地面和体育场等振动敏感结构，由于人的行走、奔跑、跳跃或弹跳而产生的动载荷知之甚少，给设计带来了很大的挑战。行人天桥和体育馆往往是非常显眼的地标结构，对轻便优雅和低振动水平的要求相互冲突，以满足乘员/使用者的舒适性。设计失误招致重大宣传(千禧大桥)，成功招致赞誉(2012年奥运会赛车场)。迎接挑战需要科学合理的设计指导，而不是因为加载的不确定性而过于保守。因此，在一个在此类结构设计方面处于世界领先地位的国家，我们还需要在制定最先进的振动适用性设计指南方面发挥带头作用。尽管最近取得了重大进展，但由于对使用者和居住者协调的简单化假设，由于群体和人群的原因，在指导动态负荷方面仍然存在重大缺陷。我们对步行者、慢跑者和足球迷之间的同步是如何工作的了解非常有限(例如)，所以我们对完美的同步和完全协调的活动做出了非常简单的假设，这会导致最糟糕的保守设计。这个研究项目是研究平衡控制、感觉运动功能和运动定时的心理学家和结构工程师之间的合作，结构工程师研究人类动态加载和装配结构的性能，他们对同步有共同的兴趣。对于心理学家来说，他们关心的是音乐家、舞者和运动员(例如赛艇运动员)的表现，而对于工程师来说，他们关心的是由于人的移动而对建筑物施加的有效最大动载的性质。到目前为止，关于同步化的研究仅限于两个人；这些方法将被推广和开发，用于在一系列情况下扩大和发展规模越来越大的群体，以评估不同线索的相对重要性。这些线索将是对邻居的运动、脚步声或音乐的视觉感知，以及邻居和支架(例如摇晃的人行桥或弹性看台悬臂)的身体接触和运动。测量人体运动本身就是一个复杂的过程，因为直接测量，即使是在受控的实验室环境中来自单个行人的力，也需要昂贵的仪表盘跑步机。在实验室之外测量两个以上的人是一项主要的研究挑战，我们打算使用无线惯性传感器和基于闭路电视的运动捕获来管理，这项技术将在实验室有限的环境中为个人进行评估。这些不是简单的技术，但直接的经验、观察和讨论告诉我们，它们是在大规模环境中测量人体运动的前进方向。在工程师的推动下，这项研究的主要成果将是一种估计最大动态载荷和确定控制载荷场景的方法，从而导致更合理的指导和更具竞争力的设计。实验研究的最后部分涉及对样本结构进行良好控制的全面测试。对同步机制和因素的理解将是一个双产品，有利于更广泛的社区，在那里，人类对周期性活动的协调是重要的。

For vibration-sensitive structures such as footbridges, floors and stadia, dynamic loads due to humans walking, running, jumping or bouncing are poorly understood and present a major challenge for design. Footbridges and stadia are often highly visible landmark structures with conflicting requirements for lightweight elegance with low vibration levels for occupant/user comfort. Design mistakes attract significant publicity (Millennium Bridge) and successes attract accolades (2012 Olympic Velodrome). Meeting the challenge requires scientifically rational design guidance which is not overly conservative as a result of uncertainties in the loading. Hence in a country that leads the world for design of such structures we also need to lead in development of state of the art design guidance for vibration serviceability. Despite significant recent developments, there remain major deficiencies in guidance for dynamic loads due to groups and crowds of people owing to simplistic assumptions of coordination by users and occupants. We simply have very limited understanding about how synchronisation works among pedestrians, joggers and football fans (for example) so we make very simple assumptions about perfect synchronisation and totally coordinated activities that lead to worst case conservative design.This research project is a collaboration between psychologists researching balance control, sensory motor function and timing of movement, and structural engineers researching human dynamic loading on and performance of 'assembly structures' and who have common interests in synchronisation. For the psychologists, the interests concern performance of musicians, dancers and sportsmen (e.g. rowers) ,while for the engineers the concern is the nature of the effective maximum dynamic loading on a structure due to moving human occupants. Studies on synchronisation have to date been limited to two individuals; the methods will be extended and developed for groups of increasing size in a range of circumstances to assess the relative importance of different cues. Such cues would be visual perception of motion of neighbours, sound of footfalls or music and physical contact and motion both of neighbours and of the support (such as a wobbly footbridge or bouncy grandstand cantilever).Measurement of human motion that leads to derivation of synchronisation measures and aggregate dynamic loading is by itself a complex process since direct measurement, even of forces from a single pedestrian in a controlled laboratory environment, requires an expensive instrumented treadmill. Measurement of more than two people beyond the laboratory is a major research challenge that we intend to manage using wireless inertial sensors and CCTV-based motion capture, technology to be evaluated for individuals in the laboratory-limited environment. These are not simple technologies but direct experience, observation and discussions tell us they are the way forward to measuring human motion in large-scale environments.Being driven by engineers, the major outcome of the research will be a means to estimate the maximum dynamic loading and determine the governing loading scenario, leading to more rational guidance and competitive designs. The last part of the experimental research involves well controlled full scale tests on exemplar structures.Understanding of the mechanisms and factors on synchronisation will be a bi-product benefitting the wider communities where human coordination of periodic activities is important.