Research On Dynamic Performance Of Steel-concrete Composite Girder Bridges Under Moving Vehicle Loads

The steel-concrete composite girder bridge has excellent mechanical properties,which can combine the tensile properties of steel and the compressive properties of concrete.Because of its light weight,large stiffness,good comprehensive benefits and many other performance advantages,it has been currently widely used in bridge construction all over the world.However,the researches on steel-composite beam bridges in China generally focus on static analysis,while the researches on their dynamic analysis are relatively rare at present.The bridge is frequently affected by vehicle loads during operation.With the increasing traffic volume,the impact of vehicle dynamic effect on the bridge is more and more significant.This paper studies the steel-concrete composite beam bridge under the load of a moving vehicle,and deduces the analytical solution of the natural vibration frequency of the simply supported beam bridge with one end simply supported and one end consolidated is derived.I also establish finite elements with different connection levels for the example bridge model,to study the quick calculation method of natural frequency of continuous composite beam bridge.I analyze the dynamic performance changes of the bridge under the action of simple harmonic load,1/4 vehicle model,1/2 vehicle model and vehicle model.And starting from the simple supported beam bridge and the continuous beam bridge,the parameters of the dynamic performance of the steel-concrete composite beam bridge are analyzed.Based on different boundary conditions,this paper deduces the analytic solution of natural vibration frequency considering slip of steel-mixed composite beam bridge,and establishes a finite element model for verification.The analytical solution is very close to the finite element solution in the low order,and the result is reliable.A fast calculation method of the natural frequency of the continuous composite beam bridge with equal span and constant section is found.The natural frequencies of all orders of equal span continuous composite girder bridge under various interface shear stiffness and span numbers can be quickly obtained through the calculation in this paper,with the first-order natural frequency of composite beam bridge with simple support at both ends,and simple support at one end and consolidation at the other end.In order to analyze the influence of the moving vehicle load on the dynamic response of the steel-composite beam bridge,this paper simplifies the moving vehicle load and studies the dynamic performance sensitivity of the bridge under various parameter variations.Then,the vehicle model and the simple supported beam bridge model are further established.Considering road roughness,the coupling vibration analysis of vehicles and bridges is carried out,and five parameters,namely bridge frequency,vehicle frequency,driving speed,vehi cle lateral position and bridge deck roughness,are analyzed respectively.The impact coefficient is taken as the index to study the variation law of its dynamic performance.In this paper,the continuous composite beam bridge model and the vehicle model are established to study the influence of deck roughness and driving speed on the dynamic performance of continuous composite beam bridge.It is found that for the concrete slab and steel girder,the impact coefficient at the middle span > the impact coefficient at the negative moment of pier top > the impact coefficient at the side span;for the shear connector,the conclusion is just the opposite,the impact coefficient at the side span > the impact coefficient at the negative moment of pier top > the impact coefficient at the middle span.In addition,the dynamic effect of steel-concrete composite continuous girder bridge is greater than that of steel-concrete composite simply supported girder bridge.