Rigid Pavement Structures Research Articles

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 ν = 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 ν = 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.

Laboratory Assessment to Correlate Strength Parameter from Physical Properties of Subgrade

Abstract Subgrade soil is an essential component for design of both flexible and rigid pavement structures. Laboratory assessment of California Bearing Ratio beneficial for design of flexible pavement, Coefficient of subgrade reaction K-Value required for design of rigid pavement, raft footing and unconfined compressive strength (UCS) is useful for determination of shear strength parameter of subgrade are time consuming and demand significant effort but mandatory. This study considers the use of multiple variable regression analysis (MLR) to predict the California Bearing Ratio (CBR), Coefficient of subgrade reaction K-Value, unconfined compressive strength, Dynamic Cone Penetration (DCP) from maximum dry density (MDD) and optimum moisture content (OMC) of subgrade. This paper presents the empirical correlations developed from multiple variable regression analysis from test results obtained from experimental investigation of soil sample taken from different locations of Gujarat region. The formulations are validated using other sets of tests data. The developed empirical correlations maybe useful in quick determination of strength parameters of subgrade from physical properties.

Modeling of Airport Rigid Pavement Structure Made of RCC and Recycled Cement Concrete for Complex Configuration of Landing Gears

This paper presents the results of the research undertaken by the authors in the frame of the postdoctoral program 4D-POSTDOC. After a short introduction on the actual status of structural design of airport pavements including geometrical and loading characteristics of complex loading gears, the modeling and the structural design of airport rigid pavements, constructed with conventional and various recycled materials, using the finite element method, is described. The main objective of this research program was to elaborate a design method which, beside the complex landing gear including six footprint tires, all specific parameters related with the recycled materials and with conventional and reinforce rolled compacted concrete (RCC) technologies are included. Finally, practical design diagrams for structural design of the concrete slabs, including their specific correlation function, used for the construction of the Airbus-A380 runway are presented.

Análisis de sensibilidad de las variables de diseño de un pavimento rígido y su incidencia en la deflexión

990/5000 The sensitivity analysis of each of the variables that influence the design of a rigid pavement structure is presented, from the point of view of pavement mechanics, and the incidence of these on the deflection of the structural model. The variables analyzed were the following: the applied load, the thickness of the slab, the load radius, the modulus of elasticity of the concrete, the Poisson's ratio of the concrete and the reaction module of the support or foundation assembly of the slab. Through the sensitivity analysis it is possible to define the most sensitive variables or those that affect to a greater or lesser degree the deflection of the structure, and thus be able to have tools that allow pavement design engineers to be certain of the variables that must be modified to ensure that the structural model meets deflection requirements at the edge, corner, and interior of the concrete slab.

Response of Rigid Pavements due to Vehicle-Road Interaction

The dynamic response of a pavement structure, subject to a moving vehicle load, is investigated on a unified analytic framework. The time-dependent deflection and its derived dynamic quantities for a slab structure are obtained by linking together the characteristics of a road profile, a moving vehicle, and a slab on a viscoelastic foundation. Examples are presented to illustrate the analytic results derived from the established framework. The model may be applied to understand quantitatively the dynamic deflection and dynamic strains within a rigid pavement structure. It is found that the surface roughness effect on the dynamic response of a slab structure plays an important role for the serviceable life span of a pavement structure and may be taken into account in pavement design. The model may be calibrated to estimate the k-value for the evaluation of the subgrade support to a pavement as it ages.

Regression Model for Resilient Modulus of Subgrade Soils

Subgrade soil is an important part in both flexible and rigid pavement structures. AASHTO recommends the use of bulk stress and deviatoric stress models to characterize granular and cohesive soils, respectively. However, these models oversimplify the fundamental behavior of subgrade soils. Being proposed is the use of an octahedral stress-state model to characterize the resilient modulus of different soils. Eight different soils representing major soil types in Louisiana were selected to validate the model and to calibrate the model parameters. Additional analysis was then performed to develop correlations between the model parameters and other soil properties. Three types of correlation were produced: ( a) model parameter with soil properties, ( b) model parameters with California bearing ratio, and ( c) model parameters with unconfined compressive strength. Statistical analysis indicated that the correlation between model parameter and soil properties yielded the best results.

Performance Evaluation of Backcalculation Algorithms Through Three-Dimensional Finite-Element Modeling of Pavement Structures

Currently, the only means of assessing the performance of a backcalculation algorithm is to compare its results with the values obtained through laboratory measurements of core samples. Discrepancies are attributed to the inability of replicating in laboratory tests the same consolidation and stress conditions encountered in the field. In this paper, an explicit three-dimensional (3D) finite-element model (FEM) is used to back-calculate the layer moduli of rigid, flexible, and composite pavement structures. The modeling approach accounts for the dynamic nature of the falling weight deflectometer (FWD) load, friction at pavement-layer interfaces, and the 3D geometrical characteristics of the pavement structure. The FWD-measured and FEM-generated deflection basins are matched by adjusting the values of layer moduli used in the FEM. The backcalculated moduli using 3D FEM are compared with the results obtained from three backcalculation programs: MODCOMP, MODULUS, and EVERCALC. The results indicate that the three programs have an excellent capability of predicting the FEM-generated subgrade modulus values for flexible, composite, and rigid pavements provided that a correction factor is used. A correction factor for backcalculated subgrade modulus is estimated for each program and pavement type. The mechanistically evaluated correction factors were found to be in close agreement with the experience-based values recommended for flexible and rigid pavements in the American Association of State Highway Officials pavement design guide.