Markus Oeser

Studies on creep and recovery of rheological bodies based upon conventional and fractional formulations and their application on asphalt mixture

Traditionally, the time-dependent behaviour of bituminous mixtures has been modelled using linear visco-elastic theory described by creep and relaxation functions. Research, however, has shown that parameter identification for functions with linear time derivatives becomes problematic when the behaviour of asphalt mixtures needs to be matched for both the loading and unloading responses. The research introduced in this paper explored the possibility of using fractional creep functions for modelling. Furthermore, the possibility of using fractional creep functions for various rheological bodies to investigate the fractional time derivatives for strain is discussed. It is shown that, by means of these creep functions, the time-dependent deformation behaviour of bituminous material in terms of the retarded creep during loading and the relaxation behaviour during unloading may be described more realistically than by using time derivatives of integer order. The fractional creep functions allow for the development of non-linear viscous strain during the creep process and to better match the observed behaviour of asphalt mixtures, compared to the use of conventional linear models. This study specifically investigated the retardation and relaxation times in creep and recovery, and examined how these can be influenced by the choice of the fractional derivatives. The constitutive relationships developed in this paper are implemented in a non-linear computational model based on the finite element method. Modelling of the above-mentioned phenomena is presented and discussed with the help of numerical simulations and determination of model parameters with the help of actual test data.

Application of semi-analytical finite element method to evaluate asphalt pavement bearing capacity

Abstract Bearing capacity is a key index in pavement management systems in many countries, which reflects the essential material properties of asphalt pavements. Many stationary measuring methods have been undertaken in the past; current assessment of the bearing capacity tends towards fast and continuous measurements at traffic speed for a network analysis. The conventional evaluation using stationary loads do not represent real traffic loading condition; therefore the results will inevitably lead to discrepancies from reality. A specific computational program SAFEM based on semi-analytical finite element method is proposed to overcome the difficulty. The reliability and efficiency of the SAFEM is proved by verification with commercial FE software ABAQUS and field measurements. The variation tendency of the back-calculated bearing capacity has a quite good negative linear relation with the number of loading cycles in the experiment. The investigation shows this proposed assessment system is a feasible option for the fast and reliable analysis of the pavement bearing capacity at a network level for road administrations.

3D Constitutive Model for Asphalt Pavements

The deformation behaviour of asphalt is modelled in the present work with the aid of so-called rheological elements. A special element (HOOK-, KELVIN-, Newton-element) is assigned to each deformation contribution (elastic, visco-elastic, visco-plastic). Non-monotonic damage-healing processes are described phenomenologically and taken into consideration with the aid of a newly-developed damage-healing element. The rheological elements are dependent on free values; these permit the computation of deformation increases. Under the assumption of small deformations the contributions to the deformation increases are summated. This results in an elastoplastic material model. This material model exists in a differential form in one and three-dimensional configuration and is converted into an algorithm for implementation in a computational model.

Tire–Road Contact Stiffness

When a rubber block is squeezed against a nominal flat but rough surface, the rubber bottom surface will penetrate into the substrate roughness profile. The relation between penetration depth

Development of morphological properties of road surfacing aggregates during the polishing process

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SAFEM – Software With Graphical User Interface for Fast and Accurate Finite Element Analysis of Asphalt Pavements

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Hydraulic and mechanical properties of porous cement-stabilised materials for base courses of PICPs

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