Dynamic And Seismic Response Analysis Of Three-span PC Partly Cable-stayed Bridge

Partly cable-stayed bridge is a new bridge structure. By now, the static performance of this new style bridge system was studied deeply and widely. But, dynamic behaviors were seldom studied. When it comes to system dynamic analysis, it was none. Therefore, studying on dynamic characteristics and seismic response performances for partly cable-stayed bridge, and making proposition and reference to the earthquake resistance design are a pressing work. This paper based on a tow-pylon-three-span PC partly cable-stayed bride, dynamic properties and seismic response properties of this new bridge system were studied.Data about partly cable-stayed bridge were collected and analyzed firstly, and the range of every parameter's value was decided. Then, nine parameters were selected for dynamic analysis. These parameters include the coupling mode between girder and pier, the length of non-stayed cable segment, the space between adjoin stay cables, the style of cable plan, the ratio between height of tower and length of main span, section rigidity of tower, side to main span ratio, the ratio between height of girder and length of main span, and the total section area of cables. After dynamic analysis, the concept of influence degree of pylons and cables was induced to reflect the influence of cables and pylons on the dynamic behaviors. By compared with traditional cable-stayed bridge and continuous beam bridge (rigid frame bridge), the dynamic characteristics of partly cable-stayed bridge were presented. The study results indicated that dynamic characteristics of partly cable-stayed bridge, with girder fixing with the towers and separating from the piers, were more like characteristics of continuous beam bridge than ordinary cable-stayed bridge. Pylons and cables mainly impact on in-of-plane bending of partly cable-stayed bridge, and the dynamic influence degree of pylons and cables was less than 15%.Based on dynamic analysis, parameters include the coupling mode between girder and pier, the ratio between girder and pier, side to main span ratio, the ratio between height of pylon and length of main span were analyzed to find out the characteristics of seismic response. The concept of influence degree of pylons and cables is put forward to reflect the influence of cables and pylons on the seismic response. Study results indicated that seismic response of partly cable-stayed bridge is very sensitive to parameters. Specialized seismic response analysis and anti-seismic design are necessary for every partly cable-stayed bridge.The conclusions of this paper are valuable reference for further understanding of the dynamic properties of partly cable-stayed bridge. Some suggestions for anti-seismic design are presented in the paper too.