The paper presents results of field tests performed in Poland on innovative pavement structures. The test section was divided into four parts of the same layer thickness, but with different bituminous mixes, i.e. asphalt concrete, high modulus asphalt concrete, composite mixture and anti-fatigue mixture. This allowed direct comparison of different technologies. Tests sections were subjected to accelerated loading test with use of the Heavy Vehicle Simulator (HVS). The HVS tests were accompanied by the field tests and laboratory tests.
No abstract is provided for this article.
No abstract is provided for this article.
The fatigue life of an asphalt mix is defined as the number of load repetitions at which the crack initiation phase ends and macro cracks start to grow (crack propagation/failure phase). The problem is how to determine in an objective way this number of repetitions. Three different definitions for the fatigue life were applied and compared to each other using three different Polish asphalt mixes. Twelve beams of SBS-modified asphalt mix (mix A), 12 beams of the HiMA mix (mix B) and 14 beams of an ordinary Polish asphalt mix (mix C) were tested in a four-point bending (4PB) device in controlled deflection (strain) mode at 10 Hz and 10°C. During fatigue development, three different phases typically may be indicated (plus so-called transition zone). Based on the locations of the fatigue life (obtained on the basis of three different definitions) with respect to the characteristic fatigue phases a proposal for a new fatigue life definition was made. The location of this fatigue life definition will always fall in the transition zone between the fatigue initiation phase and the failure phase. The main advantage of this definition is that it can be used in automatic processing of fatigue data.
The authors focused on buckling resistance assessment of steel-I-section perfect beam-columns of the cross-section class 1 and 2, not susceptible to LT-buckling and subjected to compression and one directional bending about the section principal axes y–y or z–z. These assumptions lead to the case of elements considered as only sensitive to the flexural failure including second order in-plane bending and compression. The stability behaviour of elements subjected to different bending configurations and different static schemes was investigated through comprehensive numerical study with use of the finite element method. Geometrically and materially nonlinear analyses GMNA in case of perfect beam-columns and GMNIA fo the imperfect ones were carried out in reference to shell and beam element models. Static equilibrium paths accounting for pre- and post-limit behaviour were determined with use of the incremental-iterative algorithm taking into consideration displacement-control parameters. An analytical formulation for a quick verification of the perfect I-section beam-column resistance is proposed. Finally, the global effect of imperfections is also investigated using GMNIA. The verification method developed for perfect elements is extrapolated for imperfect beam-columns. The good agreement of the proposed analytical formulation is shown through an extensive comparison with more than 3500 results of finite element numerical simulations conducted with use of ABAQUS/Standard program.
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This paper presents the results of a research study and analysis conducted to determine the degree of anisotropy of asphalt concrete in terms of its initial elastic properties. The analysis of asphalt concrete was focused on determining the effective constrained stiffness modulus in three mutually perpendicular directions based on the finite element method. The internal structure of the asphalt concrete was divided into the mortar phase and the mineral aggregate phase. Static creep tests using the Bending Beam Rheometer were conducted for the mortar phase to fit the rheological model. The aggregate arrangement and orientation were analysed using an image analytical technique for the mineral phase. The Finite Element Method (FEM) meshes were prepared based on grey images with an assumption of plane strain in 2D formulation. Using the FEM model, the tension/compression tests using selected characteristic directions were conducted, and the effective constrained stiffness moduli were estimated. This study showed a dominant horizontal direction for all coarse aggregates resulting from the normal force of the road roller and paving machines during laying and compaction on a road site. Depending on the values of the mortar's mechanical parameters and the load direction, the effective stiffness modulus might differ by ±20%. Based on the FEM analysis, this result was proven and commented on through an effective directional modulus evaluation and a presentation of internal stress distribution. Depending on the shape and orientation of the aggregates, it was possible to observe local "stress bridging" (transferring stresses from aggregate to aggregate when contacting). Moreover, the rheological properties of the mortar were considered by assuming two limiting situations (instantaneous and relaxed moduli), determining the bands of all possible solutions. In the performed FEM analysis, the influence of the Poisson ratio was also considered. The analysed asphalt concrete tends to be isotropic when the Poisson's mortar ratio is close to the value of 0.5, which agrees with the physical expectations. The obtained results are limited to particular asphalt concrete and should not be extrapolated to other asphalt mixture types without prior analysis.
Evaluation of the lateral-torsional buckling resistance of bisymmetrical I-section beams using finite element method was widely discussed in the paper. Numerous FEM simulations with regard to the stability behavior of steel structural elements subjected to bending about the major principal axis were performed. The use of different finite element modeling techniques and their influence on obtained results were presented by the authors. The ultimate state of both perfect and imperfect elements was assessed. Considerations were concerned with hot-rolled wide flange HEB and narrow flange IPE section beams. Idealization of boundary conditions of FEM models complies with the assumptions used in the analytical formulation of stability problems of thin-walled beams. Geometrically and materially nonlinear analyses GMNA and GMNIA preceded by LBA analyses were carried out. Numerical simulations were conducted with use of ABAQUS/ Standard program.
The paper presents an analysis of a flexible road pavement with a concrete pipeline running along the road axis, just under the pavement. The subgrade of such a pavement cannot be regarded as homogenous and the design cannot be limited to merely the selection of a catalogue pavement structure or to the direct application of the mechanistic-empirical method. Additional analyses are necessary in order to evaluate whether the proposed road design will provide proper protection for the underground structures located in the subgrade. The problem is considered as three-dimensional and the analyses are carried out using the finite element method. The proposed design variants are evaluated and the solution recommended for considered case is indicated. Moreover, the results of parametric analyses of the selected variant, carried out to determine the influence of the backfill parameters on the deformation of the geosynthetic reinforcement in the road foundation and on the tensile stresses in the concrete pipe, are presented.
In this paper, we analyse various minimization algorithms applied to the problem of determining elasto-plastic material parameters using an inverse analysis and digital image correlation (DIC) system. As the DIC system, ARAMIS is used, while for the finite element solution of boundary value problems, Abaqus software is applied. Different minimization algorithms, implemented in the SciPy Python library, were initially juxtaposed, compared and evaluated based on benchmark functions. Next the proper evaluation of the algorithms was performed to determine the material parameters for isotropic metal plasticity with the Huber-Mises yield criterion and isotropic or combined kinematic-isotropic plastic hardening models. For all researchers utilizing back calculation methods based on a DIC measuring system, such analysis results may be interesting. It was concluded that among the local minimization methods, derivative free optimization algorithms, especially the Powell algorithm, perform the most efficiently.
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The paper deals with determination of flexural resistance buckling curves for welded I-section steel members made of high strength steel (S 690). In the paper the previously proposed BF analytical model is used for approximation of FEM results obtained using moderately large deformation shell theory and ABAQUS/Standard software. Final formulation of flexural resistance buckling curves is possible through the use of the Merchant-Rankine-Murzewski approach adopted extensively in the authors’ previous papers. For nonlinear optimization, which is needed for analytical model parameters determination, the Wolfram Mathematica package is used. Obtained results for S 690 steel are presented against the results for S 355 steel.
In this paper, a simple method is proposed to estimate capacity of multilayered road structure including the degradation of the elastic and plastic properties of the constituent materials. In the study boundary value problem modeling interaction of wheels with road surface layer in the frame of large deformation theory for elastic-plastic materials was formulated. Plastic properties of the material were described by the flow rule un-associated with yield condition. The Coulomb-Mohr yield condition was assumed and the potential for plasticity is its smooth approximation. In addition, in constitutive modeling the dependence of the Young’s modulus and cohesion of the material from the number of cycles is taken into account. This paper presents qualitative findings in relation to mechanical behavior of the road structure, i.e., for example, the development of plastic zones with increasing load for un-degraded and degraded materials. In addition, a parametric study of the influence of the degradation ratio of the elasticity and plasticity properties for road structure failure mechanism (limit load value) was made.
The paper deals with the processing of the data of the four point bending tests carried out for determination of material properties. The tests are interpreted throughout the Bernoulli's beam theory with neglecting dynamical influences at the start of the test. Presented interpretation is done mainly for problems dealing with determination of visco-elastic, thixotropy and fatigue properties of road bituminous materials.
The paper presents results of field tests performed in Poland on innovative pavement structures. The test section was divided into four parts of the same layer thickness, but with different bituminous mixes, i.e. asphalt concrete, high modulus asphalt concrete, composite mixture and anti-fatigue mixture. This allowed direct comparison of different technologies. Tests sections were subjected to accelerated loading test with use of the Heavy Vehicle Simulator (HVS). The HVS tests were accompanied by the field tests and laboratory tests.
No abstract is provided for this article.
No abstract is provided for this article.
