The Research On Traffic Comfort Index And Vibration Comfort Control Of Special-shaped Steel Arch Footbridges

The profiled steel arch bridge belongs to a more flexible bridge’s system. So the basic frequency of the structure is difficult to meet 3Hz which the current standard requires. And it may increase human induced vibration response and cause the problem of traffic comfort. In practice, it is very difficult to meet the fundamental requirements of 3Hz by adjusting the structural system or the stiffness for the similar bridge. Even if it meets the fundamental requirements, it can also reduce the advantage of this type of bridge or cost increases a lot. Therefore, it has a certain practical significance and engineering application value to carry out the research of the traffic comfort and vibration control for special-shaped steel arch footbridges and to explore whether similar bridge must meet the requirements of the fundamental frequency of 3Hz. This paper selects two profiled steel arch footbridges in Wenling as the research background.Firstly, put forward the traffic comfort evaluation system and method in this paper and verify its feasibility. And then use the traffic comfort evaluation system and method in this paper to evaluate comfort of the engineering background. At the end of this paper, design the vibration reduction of the two profiled steel arch footbridges. The main research works and conclusions are as follows:Firstly, put forward the traffic comfort evaluation system which is suggested in this paper and use the existing software-Midas Civil/2013 torealize the numerical calculation method of complex footbridge’s vibration response. Use the traffic comfort evaluation system and method which are proposed in this paper to evaluate comforts of Ligong first bridge and Xitieshan railway station passengers’ overline bridge which are in the literatures. And the results of the comfort evaluation in this paper are aligned with the results of the comfort evaluation which use the method of literature study. It could verify the traffic comfort evaluation system and method which are proposed in this paper are feasible. And it could provide a reference for design calculation and conceptual design of the same type of bridges.Secondly, use the finite element software — Midas Civil2013,SAP2000 V15 and ANSYS to take analysis of the dynamic characteristics and comparison of the two profiled steel arch footbridges in Wenling. And use the traffic comfort evaluation system and method which are proposed in this paper to evaluate traffic comforts of the two profiled steel arch footbridges. The results:(1) Even if the structural basic frequency is less than 3Hz of the standard requirements, The traffic comfort can also be satisfied for normal people.(2) Although the two order natural frequency of Jinping Park pedestrian bridge2 f ?3.6895 Hz has already greater than 3Hz of the standard requirement, it may also occur the problem of human induced vibration comfort in the dense crowd effect. It explains that the limit of the safe self vibration frequency which is regulated in Chineseoverpass standard is questionable;Thirdly, systematically summarize the dynamic characteristics of the pedestrian bridge with damping system. Focus on analysis of the control principles and design methods of tuned mass damper(TMD). And then optimize the design parameters of TMD;Fourthly, use the tuned mass dampers installed in the two profiled steel arch footbridges to design damping. Though contrast footbridges’ human induced vibration acceleration between setting the TMD damping devices and no TMD damping devices, get the max results of the Wengao footbridge’s damping ratio is 96.8% and the Jinping Park footbridge’s damping ratio can reach 55.6%. So it is reasonable that setting TMD can have a good damping effect.