Dynamic Characteristics Study Of Under-supported Concrete-filled Steel Tube Tied Arch Bridge

As a new bridge structure,the concrete-filled steel tubular(CFST)arch bridge have developed quickly in recent years.It is elegant appearance,novel structure,and the construction is simple and rapid.In view of CFST arch bridge belongs to new type,there is no specific design specifications,seismic theoretical study has just started and the design of the system has not been completed.This article based on the arch bridge dynamics principles and methods,use the finite element software ANSYS analysis CFST arch bridge's self-vibration characteristics and seismic response,as follows:(1) For a real project,select a reasonable type of unit,establish more accurate finite element model,its vibration characteristics were analyzed.CFST arch bridge modal vibration modes are more complex.There are three vibrations include the transverse vibration,vertical vibration and torsional vibration of the bridge.The bridge structure of the first-order symmetric mode shape for the arch-plane transverse vibration,the arch-plane stiffness is greater than transverse stiffness.(2) Discussed structural parameters of the main changes in the structure of the impact of the vibration characteristics,such as the cross-up(the number,location and form) arrangement,the arch rise-to-span ratio,wide-span.a) horizontal support have a great impact on the stiffness of the structure;increase the number of cross-support arch is good for enhancing the lateral rigidity and torsional rigidity;transverse support arrangement of the structure of relatively uniform vibration mode corresponds to a larger self-vibration frequency;a reasonable cross-up forms can be applied to engineering practice.b) the natural frequency of CFST arch birdge are increased when the rise-to-span ratio reduced,indicates rise-to-span is obviously affect transverse stiffness.C) in the arch section of the same form and horizontal linkages,the wide-span ratio changes within a certain scope,the Department of arch rib and deck width of the torsional rigidity with the increase of cross-ratio significantly decreased.(3) Select and enter the adjusted EL-Centro wave,Tianjin,Lanzhou artificial waves,two of the standard and two-way bridge(horizontal and vertical) of the seismic response analysis. showed the spectrum characteristics have a great influence on the horizontal displacement, the largest internal forces appeared near the arch foot,cross-section for the control at the arch foot,lateral arch displacement increase with the earthquake acceleration changes in a linear approximation.