Dynamic Assessment Of Pedestrian Bridge By Model Updating

Some certain assumptions and approximations on the structure geometry, material and boundary conditions often have to be made when attempt to build a finite element model. The conclusion of a finite element model without treatment may differ from that of actual structure or experiment results. By identifying or updating the parameters of finite element model, finite element model updating aims to make the results of finite element analysis be close to that of actual structure as much as possible. Use the Rainbow Bridge in Baimahu Park in Changde City as the background, discussions and analysis have been made on aspects like finite element modeling for special structure bridge, vibration test and modal parameter identification under ambient excitations, dynamic finite element model updating based on the sensitivity and optimization method. Finally, human-induce vibration analysis for the pedestrian bridge is performed using the updated model and comparison on the dynamic response of the finite element model of the before and after updating is made.The main researches and conclusions contain:1. The proper finite element model for this special-shaped structure has been created, theory modal analysis indicates that the Rainbow Bridge has dynamic characteristics of both the continuous curved beam bridge and the cable stayed bridge; and also points out the importance of taking shear deformation into consideration when dealing with closed thin wall box section beam with a large aspect ratio. And then a simplified and correct modeling method which can simulate beam with the upper characteristics has been found.2. On-site environmental vibration test was performed, the experiment modal analysis and parameter identification were accomplished with Peak-Picking and data-driven stochastic subspace identification separately. The results illustrate the ambient vibration testing is a convenient, fast and cheap measurement and can be applied to identify parameters of bridges with a large stiffness and high frequency.3. Using the results of theory and experiment modal analysis, the dynamic finite element model of Rainbow Bridge was updated based on sensitivity and optimization methods. Finally the finite element model having better agreement with experiment model was created. Analyze and discuss the selection of the updating parameters of bridge finite element model.4. Based on the updated finite element model, Using forced and random vibration theory to analyze the human-induced vibration of Rainbow Bridge separately, the result shows that the dynamic performance of Rainbow Bridge can fulfill its operational requirements. And also conclude that the acceleration response may not increase along with the number of pedestrians on account of the offset effects of each other. Thus, prove it is a conservative way to consider the pedestrians load effect by multiply the maximum acceleration of a single person load with (?)...