Modelling of Airport Rigid Pavement for Complex Configuration of Landing Gears and for a Large Spectrum of Cement Concrete

The purpose of this paper is to develop new design diagrams in order to complete the actual Romanian standard. This addendum is justified by the fact that the current design diagrams are elaborated for a single value of the E - dynamic elasticity modulus (in Romanian standard E = 30000 MPa) and of the Poisson ratio (in Romanian standard nu = 0.15). Therefore the diagrams from the Romanian standard NP034-99 do not permit the design for other types of concrete cement with improved characteristics with elasticity modulus E >= 30000 until E = 50000 MPa or of the Rolled Compacted Concrete (RCC) with Poisson ratio nu = 0.25 or of the other concrete types as cement concretes with recycled aggregates or steel fibre reinforced concrete. The first part of the paper presents the stress design methodology based on the finite element software and on the parameters which interfere in the design calculation. In addition to the diagrams from the Romanian standard which apply only to an external load up to a four wheel bogie, the diagrams with loads with six wheel bogie are introduced. Further are shown the differences between the stress calculated with single values from the actual Romanian standard and the stress calculated with the exact values of the considered parameters [E dynamic elasticity modulus and the Poisson ratio]. The study relies on the specific load of modern aircrafts (like Airbus - A380, Boeing - B777) that have six footprints tire in the landing gear structure. In the end, the article brings forward a graphic comparison analysis between the diagrams of the Romanian current standard and the ones conducted in the present study by using FEM (Finite Element Method). Furthermore, a design case study exemplifies the method used to obtain the slab thickness for an airport rigid pavement structure using an external load from a complex landing gear with six footprints tire.