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Praca pierwszego z autorow (S.J.) byla cześciowo finansowana z Grantu KBN Nr 7 T07A 04318 oraz Grantu Rektorskiego PW pt.: ”Modele konstytutywne hipersprezystych materialow gumopodobnych w ramach teorii duzych odksztalcen. Identyfikacja parametrow materialowych i implementacja numeryczna w systemie ABAQUS.” Prezentowane w pracy wyniki obliczen zostaly uzyskane z wykorzystaniem zasobow komputerowych Centralnego Ośrodka Informatyki Politechniki Warszawskiej.
Present Eurocode's approach to design of steel I-section beams is based on the analytical resistance evaluation yielding from the interaction resistance criteria established for beam-columns that cover two design situations: a) the flexural in-plane failure (second order biaxial bending and compression), and b) the flexural-torsional out-of-plane failure (second order spatial bending, warping torsion and compression). The Eurocode's unified resistance ultimate limit state criteria of I-sections are depended upon the technological aspects of steel section production via the buckling curve differentiation for the evaluation of reduction factors for buckling in compression and lateral-torsional buckling in bending about the major axis. This paper attempts to verify the Eurocode's buckling resistance criteria in case of welded I-section in mono-axial bending on the basis of finite element simulations and on the separate inclusion of material and geometrical imperfections. The finite element shell model is utilized and built within the ABAQUS software. The Eurocode's resistance criteria are verified by results of FEM simulations in case of moment gradient loading conditions. Concluding remarks in relation to analytical formulations presented in Eurocode 3 are drawn.
A theoretical model for an elastic anisotropic composite of road mixtures reinforced with grids together with its isotropic approximation is proposed. In the considered models, some elements of the mechanics of fibrous composite materials and optimisation theory are used. A composite model is an energy model; that is, constitutive relationships result from the differentiation of the stored energy function arising from two summed parts corresponding to the matrix and reinforcement grid energy via mixture theory. The obtained model is incorporated into the commercial finite element program ABAQUS via a user subroutine written in Fortran. The correctness of the proposed composite constitutive model has been tested by a numerical solution (with the application of a finite element program) of the structure, in which the matrix is modelled as a three-dimensional continuum region and the reinforcement as working in one dimension a set of truss elements. In addition, in the paper the proposition of approximation of the composite orthotropic model with an isotropic one is presented. The interpretation and application of this approximation are analysed. The energetically equivalent isotropic model for the layer with grid reinforcement can be directly used in standard programs used for designing road pavements with mechanistic methods.
Rozkład obciążenia zastępczego w analizie zbrojenia warstwy transmisyjnej nasypów na słabym podłożu wzmocnionym kolumnami ma wpływ na zachowanie membrany modelującej to zbrojenie. W zależności od modelu obliczeniowego powszechnie stosowane są rozkłady trójkątny, równomierny i odwrotny trójkątny. W pracy przeanalizowano zachowanie membrany pod wpływem 11 różnych rozkładów obciążenia. Dla wszystkich rozkładów wyznaczono krzywe ugięcia oraz wykresy sił rozciągających, odkształceń i kąta obrotu membrany dla zadania modelującego eksperyment w skali rzeczywistej. Przeprowadzono także analizę wpływu współczynnika sztywności k słabego podłoża między kolumnami oraz sztywności zbrojenia na zachowanie membrany. Stwierdzono, że przyjęcie jednego z rozkładów jako odpowiedni w każdej sytuacji projektowej nie zawsze jest uzasadnione. W pracy wykazano, że stosunek odporu gruntu do sztywności zbrojenia ma istotny wpływ na charakter funkcji i wartości ekstremalne sił wewnętrznych, odkształceń i ugięć. W wyniku przeprowadzonych analiz wykazano, że zwiększanie sztywności gruntu (parametr k) zmienia w sposób istotny charakter funkcji ugięcia, odkształcenia i siły normalnej w membranie, a zmiana ta zależy od rozkładu obciążenia zastępczego.
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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.
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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.
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Summary: Three asphalt binders were tested, two paving grade bitumens 35/50 and 50/70 and PMB 25/55-60. Basic characteristics were determined for all binders in three stages: original and after short-term and long-term ageing. The short-term ageing was performed using the RTFOT procedure, and the long-term ageing was performed using the PAV method. The shear stress Superpave fatigue tests, long-time-sweep, and LAS were conducted using a Dynamic Shear Rheometer (DSR) with parallel plates of 8 mm in diameter and a gap of 2 mm in a long-term PAV-aged state. The dataset includes: Basic characteristics of bituminous binder (R&B Temperatur, Penetration, Viscosity), CSV raw data: 01 - R&B and Pen.csv 02 - Dynamic Viscosity.csv FATIGUE parameters: Superpave fatigue factor G*·sin& after PAV: 03 - DSR PAV Superpave fatigue factor.csv Fatigue time-sweep test: 04.1 - 35_50_1 DSR PAV fatigue time-sweep test.csv 04.2 - 35_50_2 DSR PAV fatigue time-sweep test.csv 04.3 - 50_70_1 DSR PAV fatigue time-sweep test.csv 04.4 - 50_70_2 DSR PAV fatigue time-sweep test.csv 04.5 - PMB25_55-60_1 DSR PAV fatigue time-sweep test.csv 04.6 - PMB25_55-60_2 DSR PAV fatigue time-sweep test.csv Linear amplitude sweep (LAS): 05.1 LAS fatigue 35_50.zip 05.2 LAS fatigue 50_70.zip 05.3 LAS fatigue PMB 25_55-60.zip
