Research On Comfort Evaluation And Vibration Control Of Steel Box Girder Pedestrian Bridge Across The Railway Line

With the implementation of China’s "12th5-year plan", the national railway networkconstruction has entered a new historical period of rapid development. During this period, asa result of new railway and speeding it up and its electrification, the construction of a bridgeacross the railway line are increasing. With the expansion of the steel applications, simplysupported steel bridge has become the most commonly used structure type as the flyover andits vibration comfort is the crux as well as the aproria in the design of railway stations, alsothe ability to meet the specifications for vibration comfort requirements becomes the keyflyover in the design process. In this paper, with the actual project, and the application offinite element software SAP2000, the static analysis, modal analysis, dynamic responseanalysis, the comfort rating and vibration control forpedestrain bridge are carried out. Theresearch content and the main conclusion are as follows:1.Using the software SAP2000, the integra medel for Xitieshan station passengerfootbridge across the line is created. After static analysis and modal analysis, the bridgeforces, deflection, stress ratio, natural frequency and other parameters, meet the specificationsrequirements well.2.With the bridge dynamic response analysis, the bridge acceleration, velocity anddisplacement time history dynamic response curve are obtained; and we can see the closer thepedestrian bridge cadence to the natural frequency, the greater the dynamic response of thepeak value.3.Combined with annoyance rate and acceleration of the curve, after vertical, lateral andtransverse comfort evaluation for two bridges with beam height of1650mm and1250mmrespectively, it turns out that vertical annoyance rate is much greater than the lateral, and itsannoyance rate is61.16%and63.62%.4.By compareing the "Raising beamheight" and "creation of tuned mass dampers" twokinds of vibration control measures, it could be found that the latter damping effect is morepronounced, itsvalue is only36.5%of the former, vertical annoyance rate declined by55.39 percentage points.On basis of this article,it can be recommended that the dynamic checking for footbridgewith30meters’ span should be carried out, the span of50metres or more, the dampingmeasures should also be considered; proposed based on the equivalent vertical accelerationcomfort evaluation and annoyance rate based on the evaluation criteria; comparing the twocommon vibration control measures, the addition of the damper damping effect is superior. Inthis arctical, some references for footbridge comfort evaluations and vibration control areprovided reflecting its practical value.