【作者】 李平；

【导师】 刘德辅；

【作者基本信息】 中国海洋大学 ， 港口、海岸及近海工程， 2007， 博士

【摘要】 随着人行桥结构的发展,人致桥梁振动问题成为影响人行桥使用性能的主要问题之一。针对目前越来越多的大跨轻型人行桥出现的振动问题,本文对人行荷载、人致桥梁振动机理以及振动舒适度评价和采用TMD抑制人行桥振动等内容进行了研究。研究的主要成果有:(1)对MTMD抑制结构振动的机理进行了研究,推导了MTMD抑制结构振动的方程,分析了主系统在谐波、带宽白噪声激励下,MTMD的频率范围(Δγ)、MTMD阻尼、MTMD个数、模态质量比、主系统频率变化、荷载激励时间及带宽白噪声等对MTMD抑制振动效果的影响,推荐了MTMD抑制结构振动的合理参数。(2)系统回顾了关于人行荷载的已有研究成果,对各国学者提出的单人、人群激励荷载进行了比较分析,在此基础上对桥梁振动对行人的舒适影响进行了讨论。通过分析表明,国外主要是从舒适度方面对人行桥的振动进行研究,关注的是人行桥的振动加速度;而我国由于对人行桥的研究较少,仅是从桥梁自振频率方面对人行桥进行要求,存在较大不足,需进一步修改完善。(3)对人行桥振动计算理论进行了分析和比较,对各国规范计算公式进行了介绍和讨论,在此基础上,推导并建立了单人和人群过桥的运动方程,采用强迫振动分析方法,对于单人作用或随机人群步行作用的情况进行了分析。(4)本文以青岛市广饶路人行桥为工程背景,分析研究了:单人过桥,一组人过桥和人群过桥时桥梁的振动性能,并研究了提高桥梁刚度后桥梁振动特性的变化。结果表明:当fp/f接近于1时,发生共振,桥梁跨中的位移和加速度最大;一组人过桥和人群过桥时,由于人的步伐是随机的,虽然由于过桥人数的增加,桥梁的振动会增加,但不会按人数比例增加;当梁体刚度和自振频率提高后,人行荷载产生桥梁共振的速度也相应提高。该人行桥跨度大,其自振频率不能满足国内规范,其加速度也不能满足国外规范限值,会在使用过程中产生较大的振动问题。(5)本文通过建立TMD-桥梁-人行系统动力方程,对采用MTMD抑制青岛市广饶路人行桥的振动效果进行了分析,分析结果表明:采用12个TMD抑制该人行桥的振动是一种有效的措施,无论是单人、一组人和人群过桥,MTMD抑制振动效果非常明显。虽然采用MTMD并不能提高结构的自振频率,但采用MTMD后桥梁最大振动加速度不超过0.35m/s2,满足国外规范对人行桥振动限值的要求。更多还原

【Abstract】 With the development of footbridge structure, the human-induced vibration has become one of major problems affecting the use performance of footbridge. In regard of the vibration problems arising from more and more large-span light footbridges, in this paper, walking load, human-induced bridge vibration mechanism, vibration comfortability assessment, and footbridge vibration control by TMD has been investigated deeply. The major research results are as follows:(1) Vibration control mechanism of the structure by the MTMD was investigated and the motion equation of MTMD -structure system has been established. Forthermore, the effects of the MTMD frequency range(Δγ), MTMD damping, MTMD number, generalized mass ratio, frequency variation of the master system, excitation time, and band breadth of white Gaussian noise on the vibration control were discussed. Finally, the rational parameters for the MTMD were recommended.(2) Development of research on walking load has been reviewed, and the excitation load for single-person and crowd by the scholars of various countries has been compared. Based on these, the effects of bridge vibration on the pedestrian comfortability were discussed. The result shows that the overseas research on footbridge vibration mainly concern comfortability, which focuses on vibration acceleration of footbridge. But in China, because relative less research has been carried on the footbridge, only the free vibration frequency of footbridge was concerned.(3) The calculating theory for footbridge vibration has been discussed and the calculation formulas specified by various countries have been introduced. Fourthermore, the motion equations for single-person and crowd crossing the bridge have been established and the forced vibration analysis method was applied to seek the solution in time domain.(4) In this paper, the Qingdao Guangrao Road Footbridge was takes as an example, and the vibration performance when single person, a group of people or crowd crossing the bridge has been investigated. The results show that when fp/f approaches 1, the resonance occurs, the displacement and acceleration at the mid-span reach the maximum value.When a group of people or crowd crosses the bridge, even though with the increase of pedestrians the vibration of bridge will be intensified. However, because the steps are random, the vibration will not be intensified in the proportion with pedestrian number. If the stiffness of the bridge beam and the free-vibration frequency has been increased, the resonant speed caused by pedestrian walking load to bridge will accordingly be raisen. Because the footbridge span is very large, its free vibration frequency can not meet domestic regulations, and its acceleration will not meet the limit value specified by overseas regulations. Therefore, the footbridge will cause large vibration in use.(5) In this paper, the dynamic equation of the TMD-bridge-pedestrian system is established and the control vibration effect of MTMD for Qingdao Guangrao Road Footbridge is investigated. The analysis results show that the adoption of 12 TMDs to control footbridge vibration is an effective method, whatever it is a single person, a group of people or crowd, the effect of the vibration control of MTMD is very remarkable. Even though the adoption of MTMD can not improve the free vibration frequency of structure, after the adoption of MTMD, the maximum vibration acceleration of footbridge will not exceed 0.35m/s2, which meet the requirements of vibration limit value specified by overseas regulations.更多还原