The Pedestrian Loads Of Large Span Steel Box Girder Footbridge Dynamic Response Analysis And TMD Vibration Control

With the rapid development of social economy, urban pedestrian overpass constantly to the direction of large-span, gentle and beautiful, lead to the natural frequency and damping of the footbridge is falling, the first order vertical natural frequencies are often in a pedestrian load frequency within the range of 1.5 ~ 3.2 Hz, produce- bridge resonance, light pedestrians discomfort and psychological panic, or may cause structural damage, and even damage, so in view of the large span footbridge in pedestrian loads for vibration analysis and vibration control research has important practical significance. In this paper, a 64 m long span steel box girder pedestrian bridge as the research object, using Midas civil and SAP2000 finite element modeling in the first place, through the contrast analysis to verify the rationality of the finite element model; Then based on the Midas civil numerical model has been verified, comparative study of different specification pedestrian load mode of dynamic response of large span footbridge to law, and further discusses the large span footbridge in dynamic response under different pedestrian load excitation; Finally for people- bridge resonance produced beyond specification limit of acceleration, the introduction of TMD(Tuned Mass Damper) vibration control technology to carry out the vibration control analysis of large span footbridge. In this paper, the main research work and conclusions obtained are as follows:1. In view of the large span footbridge first-order vertical frequency in pedestrian stride frequency range is easy to cause people bridge resonance phenomenon, taking a 64 m long span steel box girder footbridge as the background, design the four in pedestrian footbridge stride frequency range(the first vertical frequency of 1.796 Hz, 2.164 Hz, 2.653 Hz, 3.016Hz). The large general finite element Midas civil and SAP2000 software build finite element model of the four footbridge, respectively, based on the modal analysis results validate the correctness of the model, the research results show that the two kinds of software to calculate the period, vibration mode has the very good inosculation, cycle maximum error is 5.05%(model 4, 6) mode, prove Midas civil finite element model is feasible.2. Under the effect of different specification pedestrian load model(international standards organization ISO10137 Bro, British standard BS 5400, Sweden specification 2004 specification), Germany standard EN03 and China, comparative study the rule of four kinds of the dynamic response of a pedestrian bridge, the results show that, in contrast, in ISO10137 specification given pedestrian load model under the action of the acceleration and displacement response of the largest, strict recommendations for some comfort requirements of engineering structures can be used the load model; In China, Britain and Sweden specification given by the pedestrian load incentive mode, the dynamic response of the pedestrian bridge decreases with the increase of the first order vertical frequency of the structure; In Germany specification given inspired pedestrian load model, the pedestrian bridge dynamic response along with the rising of the first order frequency of vertical structure, present the phenomenon of the increase with the decrease of the first, and when the load excitation in the 2.3 ~ 2.5 Hz frequency range, the specification is not applicable.3. In random, the beat, walking and jumping pedestrian loads in a row, in view of the four large span footbridge model carried out under different load excitation frequency of 52 cases of dynamic response analysis, comparative study of different parameters under the condition of large span footbridge law of displacement and acceleration response, the results show that when the pedestrian excitation frequency and vertical natural frequency of vibration is relatively close to the pedestrian bridge, pedestrian bridge, the vertical dynamic response peak, produce- bridge resonance; Vertical vibration response and the pedestrian footbridge stride length proportion relation, and depends on the vertical natural frequency of vibration and pedestrian footbridge stride length is uniform; Dynamic response of large span footbridge across, and with close distance and bearing and gradually reduce; Pedestrian load excitation, the footbridge peak acceleration response is often more than specification limit, especially people- bridge resonance case, and displacement responses are smaller, regardless of whether resonance can satisfy the requirements of specification limits.4. The introduction of TMD and MTMD(Multi- Tuned Mass Damper) vibration control technology, under different load pedestrian excitation of 4 kinds of large span footbridge structure vibration control analysis of 12 working conditions, the results show that the TMD damping control technology can effectively improve the pedestrian footbridge under the load excitation of the dynamic response, greatly improve the comfort of the pedestrian bridge; Although TMD damping technology can effectively control the pedestrian bridge pedestrian load excitation response, but the MTMD on the pedestrian bridge dynamic response of the control effect is superior, not only on the control effect has a better stability, but also in the wider range of frequency domain are good vibration damping effect(that is, the wider vibration control frequency band), to avoid when pedestrians stride length away from the structure of vertical natural frequency of vibration TMD damping technology possible negative damping effect phenomenon.