Impact Coefficient Calculation Methodology For Simply Supported T-beam Bridge

In “General Code for Design of Highway Bridges and Culverts (JTG D60,-2004)” theimpact coefficient is only to consider the structureal of natural frequency,it does not considerthe vehicle’s dynamic performance and deck unevenness. The traditional method of impactcoefficient calculation only consider the dynamic response of the bridge structure when thevehicle moves to the mid-span location, it can not consider the delay of the maximumdynamic response at the same time,it can not take into account the impact of vehicle on theother locations for the test section.The vehicle load is not just one but more than one "point"load acting on the bridge, the impact coefficient should reflect multiple dynamic load.Therefore, the study for the impact coefficient for the bridge is of great significance andpractical value.As part of the National Natural Science Foundation of China (No.51008028), the existingimpact factor of three methods (the traditional method, test method and specification method)are compared. For a simply supported beam bridge, the paper use of ANSYS APDL languageprogram, the bridge structure dynamic response, the deflection and moment curve of thebridge structure are obtained. For the shortcomings of traditional and experimental test ofimpact coefficient calculation method, the two amendment methods are proposed, the firstamendment is to take the maximum dynamic response time curve to calculate the vehicle’simpact coefficient of the bridge structure. The second amendment is to take all the time curve" peak"(local minimum dynamic response value), or "trough"(local maximum dynamicresponse value) to calculate the vehicle’s dynamic effects on the bridge structure, and localimpact coefficient is to be weighted. By comparative analysis of different calculationmethods, the second amendment method of calculating impact coefficient is recommerded.Finally,the simply supported T-beam bridge in a highway is taken as the example, using ninedegrees of freedom of three-axis space vehicle model, different vehicle speed, bridge deckunevenness, vehicle loading factors are considered to study the simply supported T-beamimpact coefficient distribution law, and impact coefficient formula based on the deckcalculation is presented.The proposed calculation method can provide a reference for performance evaluation ofthe old bridge structure, and also provide a reference for the calculation of a specificationimpact coefficient.