Analysis Of Seismic Response For High-pier And Long-span Continuous Rigid-framed Bridge

In recent years, with the development of bridge engineering, the bridge span becomes longer, the height of bridge pier becomes higher, framework becomes more and more flexible, which presents many new problems in the studies on the seismic design of long-span bridge. The continual rigid frame bridge is also developing towards the high pier and long span, and tending to use high strength materials and thin wall structure in construction. Taking the Longtanhe Bridge on the Yichang to Enshi section of Hurong Speedway in Hubei Province as the engineering background, the seismic performance is studied in this thesis. The main research work is summarized as follows:First, this thesis introduces the seismic design theory, the state and the problem of seismic research of long-span bridge. The software used in this thesis is the Large Finite Element Analyze Software ANSYS. The dynamic analysis function of ANSYS and different methods time-history analysis of earthquake in the advanced analysis program ANSYS are reviewed. By using the element of BEAM3, the bridge is divided into 275 units in accordance with section properties. The calculation model of Longtanhe Bridge (left line) is built up.Second, the dynamic properties of Longtanhe Bridge is analyzed. Its natural frequencies and mode properties are calculated. Based on this, The earthquake response is analyzed using the elastic response spectrum method, and the internal forces of the earthquake response are obtained.Third, it programs in language APDL of ANSYS, and calculates the time-history response of Longtanhe Bridge. The effect on the earthquake response of the bridge is compared due to different seismic excitations, such as El-Centro Wave, Qianan Wave and Taft Wave. It is shown that the main response values of the control sections are the largest due to the El-Centro Wave excitation. Then the effect on the earthquake response of the bridge due to the vertical earthquake is considered with the El-Centro Wave input. In order to investigate the effect apparently clearly, two analyzing cases are performed. Case 1 is longitudinal excitation , case 2 is longitudinal and vertical excitation at the same time.Last, the influence of the travelling-wave effect on the seismic response of the bridge is calculated. The results are compared with the result of uniform excitation. It is shown that travelling-wave effect causes different degree variations of the longitudinal horizontal displacement,bending moment and shear force at the top or the bottom of the pier, but the effect on the axial force at the top or the bottom of the pier is not obvious.