Ambient Vibration-based Seismic Response Analysis Of A Long-span Continuous Rigid-frame Bridge

Long-span continuous rigid-frame bridges become more and more popular in bridge engineering and are widely used in highway and railway engineering. But the unmatched condition is that the seismic responses of this type of bridges are very complex, and the seismic design, analysis and evaluation are still very difficult. The study on the seismic response analysis of long-span continuous rigid frame bridge is full of great significance both in the theoretical area and in the practical applications.In this thesis, ambient vibration-based seismic response analysis of a long-span continuous rigid frame bridge, namely Houzhu Bridge in Quanzhou City, was conducted. The main work are listed as follows:1. The field ambient vibration testing induced by wind and normal traffic was conducted, and modal parameter identification was performed to determine the dynamic characteristics of the bridge.2. The initial 3-D finite element model in which the pile-soil interaction was considered was established. The FE model was calibrated in terms of ambient vibration test results, and more precise FE model was obtained, which could represent the current service condition of the bridge correctly.3. Based on the calibrated FE model, the spectral analysis and the dynamic time-history analysis (under the coincident earthquake excitation and considering traveling wave effect.) were conducted.Several important conclusions are included:1. The fundamental dynamic characteristics of the Houzhu bridge were identified. The first model shape is longitudinal, the second model shape is transversal and the third model shape is vertical bending. Their fundamental frequencies in the three directions are 0.742Hz, 0.821 Hz and 1.222Hz respectively.2. The seismic response analysis indicated that the largest seismic response forces in piers occurred at the top and the bottom of the piers.3. Because of the rigid-fame configuration for continuous rigid frame bridges, the seismic response forces at the bottom of the piers and at the connections betweenboxed beam and pier cannot be ignored under the vertical earthquake. During the seismic response analysis for continuous rigid frame bridges, the vertical earthquake effects must be considered.4. For long-span bridges, the more rational method for seismic response analysis should be performed considering the traveling wave effect. Under the longitudinal seismic wave, the longitudinal displacements decrease initially, and then increase while the traveling wave speed increasing. The seismic response inner forces in the boxed girder are very sensitive to the time difference between the piers, the bigger of the time difference, the larger of the inner force.