The Vibration Control On Middle Span Pedestrian Suspension Bridge

In some mountainous valleys across valleys in C hina,or in some cities crossing the river,the suspension bridges are often constructed.For the suspension bridge with larger span or soften stiffness,its vibration control under wind loading and crowd loading has attracted attentions of bridge engineering researchers.However,for some mid-span pedestrian suspension bridges,the dynamic characteristics of the suspension bridge have their own features.The transverse bending and torsional-coupled vibration are more tend to occur under crowd loading excitation,which will reduce the comfort of people crossing the bridge.Therefore,for such medium-span suspension bridge,its dynamic response and vibration control under crowd loading need to be systematically studied.This paper first introduced and summarized the limitations of the existing studies on the type of crowd load and the relative norms of footbridge design at home and abroad such as the vertical and horizontal acceleration of pedestrians.Based on the background of a medium-span pedestrian suspension bridge in the northeast of C hina,the self-vibration features of the structure and the lateral dynamic response of the structure under various crowd loading modes are systematically studied,and the comfort of the pedestrian is evaluated..In order to reduce the difficulties of design and facilitate the construction,the stability cables are introduced on both sides of the main girder of the truss to play the role of strengthening the transverse whole of the deck.Firstly,the tensile force of the wire rope between the stabilizing cable and the truss is determined,and the te nsion and linear type of the transverse stabilizing cable are determined by the form-finding analysis.Then,geometrical stiffness matrix is modified to accurately consider its contribution to the lateral stiffness of the bridge deck.At last,the dynamic analysis under the transverse excitation of crowd loading was carried out,which was compared with the structural response without stabilizing cable.In order to further reduce the transverse response of the bridge under the crowd loading excitation,a Tuned Mass Damper(TMD)system was introduced to reduce the vibration.Based on TMD classical theory,according to the analysis result of the self-vibration force of the bridge,the relevant design parameters such as mass,rigidity and damping of TMD were determined,and the dynamic time history analysis under the same crowd loading mode was carried out,The dynamic response is compared with the original structure and the dynamic response with the stabilized cable.