Research On The Impact Coefficient Of Continuous Beam-Concrete Filled Steel Tube Arch Combination Highway Bridge

In recent years,continuous beam-concrete filled steel tubular arch composite highway bridge construction has developed rapidly,this bridge has beautiful appearance and strong spanning ability.Because this type of bridge has many components,more complex stress,and is a flexible structure,it is also worth discussing whether the code impact coefficient is suitable for this structure.The existing research generally believes that the bridge impact coefficient is related to the external excitation and structural characteristics,such as bridge deck roughness,vehicle,bridge damping ratio and stiffness.At present,scholars at home and abroad have little research on the bridges impact coefficient,and most of them are limited to study the main beam.In order to further study the dynamic characteristics,this paper takes a three span continuous beam-concrete filled steel tubular arch composite highway bridge as the research background,uses Ansys to establish the beam-arch composite bridge element model and the three-axis half-car model,uses Matlab to generate four different bridge deck unevenness sample values,according to the contact constraint method,considering various factors such as vehicle-bridge coupling response,bridge deck unevenness,etc.,analyzes the composite highway bridge impact coefficient.The main contents and conclusions are as follows:(1)Summarizes the current research status of vehicle-bridge coupling theory and bridge impact coefficient,discusses the bridge,vehicle and bridge deck roughness in vehicle-bridge coupling analysis modeling characteristics and their influence on impact coefficient.According to the impact coefficient calculation method in national design specifications,divided into the span and fundamental frequency discusses the different design specifications.It is clear that the fundamental frequency can directly reflect the bridge dynamic characteristics compared with the span.On this basis,the main research contents and methods are combed.(2)Building bridge model and vehicle model,the vehicle fleet is determined according to the deflection equivalent method.The analysis shows:the vertical deflection response caused by the longitudinal four vehicles is close to the design load.The vehiclebridge coupling analysis and bridge deck roughness input by contact constraint method.The bridge modal analysis shows that the arch rib stiffness is weaker than the main beam.Select the vertical bending frequency,according to the standard method to calculate the bridge impact coefficient is 0.05.(3)Discusses the different external excitations impact coefficient,studied for bridge deck roughness,vehicle speed,vehicle number and vehicle spacing.The analysis shows:the bridge deck roughness has a great influence on the bridge impact coefficientWhen the bridge deck roughness level is above B,the impact coefficient is greater than the current specification calculated value.The different components impact coefficients,the same component different positions and the same position different responses are different.The suspender axial force impact coefficient is relatively large.The deflection impact coefficient and bending moment impact coefficient are greater than the axial force impact coefficient.(4)Discusses the different structural characteristics impact coefficient,analyzed for the structural stiffness ratio,the cross-sectional area of the suspender and the damping ratio.The analysis shows:the beam-arch stiffness ratio has a great influence on the impact coefficient;the influence of bridge damping ratio on the impact coefficient is small,which can be ignored under certain circumstances.The bridge impact coefficient increases first and then decreases with the increase of suspender cross-sectional area.(5)Discusses the least square method theory is applied to give the main beam and arch impact coefficient regression formula with the deck roughness and vehicle speed,and the measured value of real bridge impact coefficient is verified.The analysis shows:The impact coefficient-bridge deck roughness and vehicle speed binary quadratic regression formula considers bridge and vehicle factors,which is more consistent with the actual situation.On the basis of bridge deck roughness and vehicle speed,the similar bridges impact coefficient can be quickly estimated by regression formula.