DYNAMIC BEHAVIOUR of RIGID CONCRETE PAVEMENTS UNDER DYNAMIC TRAFFIC LOADS
This paper examines the dynamic behaviour of rigid concrete pavements under dynamic traffic loads, which includes the determination of the forces in the concrete plate and in the steel connecting devices at the joints, consisting of dowels and tie bars. For this purpose the rectangular plate is modelled as an elastic homogeneous orthotropic plate supported by a continuous Pasternak foundation, with boundary supports provided by the steel dowels and tie bars, providing elastic vertical support and rotational restraint. The free vibration problem is solved using two transcedental equations, obtained from the solution of two auxiliary Levy's type problems, known as the Modified Bolotin Method. The transcedental equations have infinite number of roots, of which the real roots are the wave numbers, while the integer part of the wave numbers represents the mode numbers. The mode shape is represented as a product of eigenfunctions, which are further used in the dynamic response analysis. The dynamic moving traffic load is expressed as a concentrated load of harmonically varying magnitude, moving on the plate in an arbitrary direction with a constant velocity. The homogeneous solution of the problem is obtained by a method of seperation of variables, in such a way that superposition yields a solution satisfying the boundary conditions. The general solution of the response of the plate to the dynamic moving load in integral form is obtained from the specific properties of the Dirac-delta function, so that it can be further integrated to obtain the various plate response equations during the time interval the load is moving within the plate boundaries, as well as after the load has left the plate. All of the equations are then used to analyse deflections and forces in the concrete plate, including forces in the load transferring steel devices at the joints between consecutive plates. A numerical example is given illustrating the dynamic behaviour of a rigid concrete pavement under a dynamic traffic load.