生物力学与结构动力学有机结合的大跨人行桥振动计算理论与方法

The trend in the construction of footbridges is towards long span, greater lightness and flexibility, which, from perspective of structural dynamics, is noted as closely spaced mode shapes, low natural frequency, light modal mass and damping. As a result, the issue of pedestrian induced footbridge vibrations is more concerned than ever. In this project, study is performed on analysis method of combining biomechanics with structural dynamics, by using which a dynamical model of human walking over ground is constructed after a closely analysis of human walking process over ground. Subsequently, a walking load expression is derived from the model. Furthermore, a time domain based analysis method is proposed of multi-mode participated footbridge vibration under pedestrian walking load, in which the walking load over ground is used as forced vibration sources and walking process over bridge is fully considered. with the alternative application of biomechanics and structural dynamics, human walking process over vibration deck is explored extensively, which is followed by study on principle of human walking load evolution process. And the method of evaluating the effect of interaction between pedestrian and bridge is proposed as well. By doing so, an analytical model dealing with the interaction effect is fitted out. To quantify the overall effect of interaction between pedestrian and bridge, a forced vibration experiment was carried out in laboratory. By comparison with test results, the analytical model is further approved to accurately calculate the interaction effect exerted by a pedestrian. On the basis above, a modification methodology is introduced to consider the effect of human-bridge interaction on footbridge response calculated with forced vibration theory. On the basis, focus is moved to the interaction effect on footbridge response. What's more, a modification method is proposed to consider this effect, which leads to a more systematic and practical method on the analysis of pedestrian induced footbridge vibration.

人行桥建设呈现出大跨轻柔化的发展趋势。其动力特性表现为模态分布密集、固有频率低、模态质量轻和结构阻尼小。人行桥人致振动问题因此而日益突出。本项目首先运用生物力学与结构动力学有机结合的方法，分析地面行人步行过程，建立地面行人动力学模型，导出行人在地面行走时的动荷载表达式（称为行人自然步行力）。以行人自然步行力荷载为激振力，依据结构强迫振动理论模拟桥面行人的迈进过程，建立人行桥振动多模态响应计算的时域分析法。综合运用生物力学及结构动力学，结合地面行人动力学模型，研究行人在振动环境下的步行动作特征及步行力演化规律，建立行人落脚点的平衡控制理论和人-桥相互作用理论计算模型。开展人-桥相互作用强迫振动试验，结合试验结果对原有理论模型进一步修正完善。以此为基础，重点研究相互作用效应对人行桥振动响应的影响，建立相应的响应修正方法，形成系统实用的大跨人行桥振动计算理论与方法。

随着现代城市及旅游业的高速发展，人行桥在实现道路人车分流、方便居民日常出行、注入景区新活力等方面，发挥了越来越重要的作用。人行桥的建设数量、规模因此而出现逐年攀升的趋势。这些新建人行桥呈现出以下几个特点：其一，多以钢材为主要建筑材料，呈现出结构跨度大、质量轻、频率低、阻尼小等特点；其二，桥面行人通行量大，行人动荷载效应突出，极易激发大幅的桥梁结构振动，轻则降低人行桥的使用品质，造成不良的社会舆论，严重情况下还可能引发诸如踩踏事故等此类的次生灾害。因此，本项目针对大跨轻质人行桥的结构振动问题展开研究，具有一定的理论意义与较强的工程实用价值。.项目从引发人行桥结构振动的源头出发，主要研究了以下几个方面的问题：一）结合生物力学与结构动力学，建立行人动力学模型，研究了行人自然行走状态下的步行力计算理论与方法；二）基于行人动力学模型，从行人动平衡调控理论出发，研究了人-桥相互作用的力学机理、整体动力效应以及作用效应的评价方法等；三）针对模态密集型低频大跨人行的特点，基于强迫振动理论，研究了考虑人-桥相互作用效应的人行桥人致振动响应计算的简便方法。.项目研究结果表明：一）基于生物力学与结构力学建立的行人动力学模型，将步行力的获取方法由试验测定拓宽到理论分析；二）人-桥相互作用效应可通过附加质量与附加阻尼的形式考虑，其中，附加阻尼随着振幅的增加而减小，且始终表现为正阻尼，也就是说，人行桥人致振动振幅越大，结构整体有效阻尼越小，越容易引发更大幅度的振动；三）本项目提出的人行桥人致振动响应实用计算方法与部分人行桥现场试验测试结果吻合良好，但也存在简化计算方法计算结果远小于实测结果的情形，出现偏差的原因目前还在努力探索中。.本项目从学科交叉的角度，综合运用生物力学与结构力学，建立了行人动力学模型，研究了人-桥相互作用效应，提出了大跨人行桥人致振动响计算的简化计算理论与方法，研究结果丰富了人行桥人致振动计算理论，有助于改进、提高现有人行桥计算理论的准确性，为人行桥动力设计计算提供了有益参考，研究具有较好的理论意义与工程实用价值。