Comfort Evaluation And Vibration Control Of Long-span Special-shaped Steel Box Girder Bridge

As an important way of modern transportation,various footbridges have been built in many cities and tourist attractions.It not only makes it easier for going out,but beautifies the urban environment.With the development of society,all kinds of light materials with high strength and durability are gradually used during the construction of footbridge,the structure of footbridge is becoming more and more complex.Footbridge tends to vibrate in an excessive manner for the sake of its structure and pedestrian load,thus discomforting pedestrian.For now,in term of domestic norms,the current comfort evaluation and vibration control system on footbridge are not perfect.Therefore,this study focuses on the comfort evaluation and vibration control of footbridge,by means of the analysis of a typical large-span steel box girder bridge.(1)Analysis and comparison have been made to study the pedestrian load mode,including frequency standards and response standards,as well as the comfort issues of footbridge in norms at home and abroad.Walking load model has been selected for computing,and the Evaluation of norms from various countries has been made,and selected four classic step frequency step of the foot curve and simplified crowd model.(2)Comfort evaluation of long span special-shaped steel box girder bridge based on frequency method.Both the analysis of dynamic characteristics and practical test have been carried out for the Large-span steel box girder bridge,to determining the lower fundamental frequency mode of vibration of the bridge.The comfort of the bridge is evaluated based on the code of different countries on the basis of avoiding the sensitive frequency method,to determine whether the dynamic response of the bridge under pedestrian load is required.(3)Comfort evaluation of long span special-shaped steel box girder bridge based on response method.According to the step frequency in different circumstances,many walking conditions are drafted based on forced vibration theory.The dynamic response of the large-span steel box girder bridge under various walking loads has been calculated.The loading test under walking load has been carried out in practice.The corresponding vibration response under different conditions can be calculated,thereby exploring the accuracy of calculation results.Moreover,based on the acceleration indicator,the comfort evaluation is made during the service life.As a result,the vibration response cannot satisfy the requirements of comfort,and vibration control should be introduced.(4)On the basis of dynamic characteristics,theoretical calculation results and experimental data of pedestrian walking loading,the tuned mass damper(TMD)has been designed and vibration control of the bridge has been implemented under the formation most easily aroused by walking load.The control effect of TMD under different circumstances are analyzed and evaluated.Due to the vibration control by means of TMD,the comfort issues of bridge are improved,and it meets the requirements of comfort during its service.