Study On Comfort Assessment And Vibration Reduction Control For A Landscape Footbridge Composed Of An Inclined Arch And A Curved Beam

With the application of lightweight and high-strength materials and the increasing demand of bridge aesthetics,modern pedestrian bridges are gradually developing in the direction of large span and light flexibility and complex structural stresses.At the same time,it also leads to a series of problems such as low fundamental frequency,low damping,and close structural frequency to pedestrian step frequency which affects pedestrian comfort.As a typical representative of new footbridges,composed of an inclined arch and a curved beam(FIACB),which is a combination of inclined single cable-faced arch ribs and curved beams,has been widely used in urban footbridge construction in recent years.The design and construction of FIACB should not only consider how to integrate with the surrounding cityscape,but also whether it can carry and guide the pedestrians.Due to its novel and unique shape,the structure of FIACB is very complex in terms of stresses and spatial effects,which makes the accurate assessment of pedestrian comfort a major problem in the design and construction process.A lot of research has been carried out at home and abroad on the comfort of footbridges,but no research on the comfort and vibration control methods of FIACB has been reported publicly.This paper takes the first FIACB spanning both sides of the Pearl River as the research background,and conducts a systematic study on its comfort and proposes corresponding vibration damping control methods,which effectively improves the pedestrian comfort of the bridge.The main work of this paper is as follows.(1)The commonly used pedestrian bridge human-induced vibration calculation theory,comfort evaluation method and vibration control method are summarized and sorted out.The pedestrian load model of footbridge is introduced,the mechanism of human-induced vibration is analyzed,the comfort evaluation criteria are clarified,and the domestic and international codes for footbridge comfort design are compared,and the differences,advantages and disadvantages between the codes are pointed out.(2)The comfort assessment method of FIACB is proposed.The refined finite element model of the FIACB is established,its dynamic characteristics such as self-oscillation frequency and vibration pattern are analyzed,the vertical and lateral comfort indexes of the bridge given by domestic and foreign pedestrian bridge design codes are compared,the influence of pedestrian mass,the value of pedestrian load reduction factor and structural damping ratio on the comfort of the FIACB is discussed,and the suggested values of the comfort analysis parameters of the FIACB are given.The recommended values of the parameters for the comfort analysis of the FIACB are given.(3)The method of human-induced vibration control for FIACB is proposed.Based on the damping principle and parameter design method of TMD and MTMD system,the effects of TMD mass ratio,MTMD neutron TMD quantity and TMD spatial distribution on the humaninduced vibration response characteristics of the FIACB are analyzed,and the optimal damping control design scheme is given from the perspectives of economy,practicality and site adaptability,which effectively improves the comfort index of the bridge and provides a reference study for the design of pedestrian comfort of similar bridges.The optimal vibration reduction control scheme is given from the perspective of economy,practicality and site adaptation.