Research On Vehicle-bridge Coupling Vibration Of Externally Prestressed Steel-concrete Composite Continuous Beams

The externally prestressed steel-concrete composite beam as a new type of composite structure has the advantages of light weight,superior performance,convenient construction and economy and so on,which has been widely applied in city overpass bridge.But its vehicle-bridge coupling vibration problem is not especially deeply analyzed enough.Therefore,it has great practical and theoretical significance to study the related issues of vehicle-bridge coupling vibration of externally prestressed steel-concrete composite beams.The main tasks and conclusions are as follows:Taking the Baihuting overpass for engineering background,the calculation model had been established through FEA software.Reliability was verified according to the model frequency based on environmental vibration testing,the different parameters of section,span,external cable and so on,which influence the characteristics of the vibration of composite beam were analysed.The results show that the steel-box web height and bridge span of composite beam contribute a lot to the natural frequency,the influence of prestress on the nature frequency of the beams will not exceed 10%.Only consider the cable layout,the double line,single line,straight line and curve layout effect on frequency of simply supported composite beams increase in turn.the stiffness ratio of external cable and rigidity have more obvious impact on frequency than the initial prestress.To prevent the syntony between the beam and its external tendons,the free length of the external cable without lateral support can not be too long,not be longer than 20m,or else some dampers or other absorber should be used.In light of biaxial vehicle model with 7 degrees of freedom,the analysis program of vehicle-bridge coupling is compiled by APDL language in ANSYS.The paper considers the influence on the dynamic responses and impact factor,which caused by road roughness,vehicle velocity,weight,vehicle stiffness,bridge damping and span.With the increase of bridge span and the deterioration of bridge roughness,structural dynamic response and impact factor will rise significantly,with the increment of vehicle weight,the impact coefficient in the midpoint of the bridge span increase first and then decrease,the influence of bridge damping and vehicle stiffness is smallAnalysed the Impact factors of full span control sections with vehicle-bridge coupling vibration,compared with the different standards of domestic and international,only consider the impact factor of the frequency or the span of old bridge the bridge is not safe.Finally,the response law analyzed on vehicle-bridge coupling vibration of externally prestressed steel-concrete composite continuous beam,it can support some new ideas and suggestions on the parameter design for this type of bridge.Meanwhile,the direction of further work on this topic of its vehicle-bridge coupling vibration problem is briefly discussed.