This paper presents the results of a round robin test (RRT) on binder fatigue, with data received from 11 participating laboratories. Most data were obtained with a Dynamic Shear Rheometer (DSR) equipment, one laboratory used a tension-compressiontest. In a first stage, the RRT consisted of three binders, two unmodified binders and onepolymer modified binder. These three binders had almost the same stiffness level at the testing conditions, 10°C and 10 Hz. Fatigue tests were conducted at three strain levels, and each strain level was measured in three repeats. For each test it was asked to follow the small strain stiffness during an equilibration time of 30 minutes. A second stage of this RRT including two more binders is foreseen. The same three binders were also tested in two and in four point bending mix fatigue tests. The analysis was separated into two parts, in a first part the repeatability and reproducibility of the small strain equilibrium stiffness was evaluated and in a second part the fatigue data were analyzed. Small strain stiffness data showed that the repeatability and reproducibility of G* is still not very high, and possible reasons are under evaluation. The analysis of the fatigue data showed that the overall reproducibility was not good. But when all participants that did in some way not follow the preparation procedure or that had problems with recording, were excluded, it was found that for 6 of the participating laboratories the fatigue properties gave good repeatability and reproducibility levels, for the two unmodified binders in this study. Each laboratory could distinguish the better fatigue life of the polymer modified binder compared to the unmodified binders as was also confirmed by mixture tests. This shows that the binder behavior plays an important role in the fatigue behavior of the mix, and that a binder test should be able to evaluate this role. The binder fatigue test can be used as a surrogate test for mixture fatigue, implying considerable time savings in sample preparation, however the testing of the binders is still time consuming.
No abstract is provided for this article.
The subject of this paper is the structural analysis of a concrete airfield pavement with doweled joints after curling focusing on the doweled joints behaviour. The paper presents some examples of such pavement structures and dowel bar installation. Attention is paid to the effects of curling of slabs due to the temperature gradient across the slab thickness. It can result in the development of cracks at edges and corners of the slabs. A global structural analysis was carried out for a concrete airfield pavement exposed to extreme loading after curling. Aircraft wheel loading was considered in the analysis. The calculations of the doweled joints were parameterized based on the slab thickness and dowel diameter. The finite element method analysis was carried out using the ABAQUS/Standard software package.
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No abstract is provided for this article.
No abstract is provided for this article.
No abstract is provided for this article.
Tall buildings are nowadays erected with top spires which serve to increase the building height or to locate on it a symbolic detail identifying the building function. Moreover, the unoccupied upper floors of highrise buildings are frequently designated only for storing hardware, playing the function of observation decks or accommodating mass dampers that counteract the induced sway associated with building response to wind or earthquake. This paper is concerned with a case study of the nonuniform cylindrical spire placed on the building roof floor that had created structural problems after its erection, in relation to the cross wind vibrations. The authors were involved in an expertise aiming in identifying possible reasons of wind induced vibrations of a non-prismatic spire. A number of FEM simulations with data taken from observations made available during the site visits were conducted. Their results are presented in this paper. The numerical results are compared with analytical calculations according to Eurocode's procedures and some conclusions related to engineering practice are drawn.
The article describes the impact of modeling the plasticity constitutive relationship on the buckling of a short section of a perforated thin-walled steel bar with an open cross-section (modeled as a perforated shell) subjected to compression, being one of the elements of a high-storage system. Numerical calculations were performed in the ABAQUS/Standard program with application of the elasto-plasticity theory of large deformations with additive decomposition of the logarithmic strain tensor and taking into account the nonlinear isotropic or kinematic strain hardening models. The isotropic nature of the material was considered and the plastic flow law associated with the Huber-Mises plasticity condition was assumed. In the elasticity range, linear characteristics of the material was assumed, while in the plasticity range, the shape of the uniaxial strain hardening curve was described as piecewise linear approximation of plastic strain-stress graphs obtained from uniaxial tensile tests. The 24 sets of material data obtained on the basis of experimental tests were analyzed and the influence of differences in the values of material parameters were described (in tests carried out on samples cut from the modeled bars, large differences were found in the values of material parameters and the shape of uniaxial tension graphs). Also the accuracy of strain hardening modeling (the number of sections assumed in the model piecewise linear) on the calculated bearing capacity force value was considered and evaluated.
The article presents the results of a research study aimed at determining the optimum amount of 0/1 mm rubber powder additive for cement-sand mortars (CSM) used in asphalt-cement concretes (ACC), to meet the requirements for mineral-cement-emulsion mixtures (MCEM) due to the lack of regulations concerning these concretes. The study includes test results for indirect tensile strength (ITS) and stiffness modulus (IT-CY method) at 5°C, performed after 7 and 28 days of curing. The regression curves for ITS and IT-CY values in relation to rubber powder content after 7 days were well described by exponential functions, whereas the results after 28 days were best fitted by linear functions. It has been observed that compliance with ITS limit requirements excludes CSR mortars that meet IT-CY requirements, and vice versa. In order to clearly define the requirements for mortar mixtures, minimum and maximum ITS and IT-CY values were proposed so that the samples would meet both requirements simultaneously. Supplementary tests were also carried out to assess water resistance.
The development of measurement methods, and in particular digital image correlation (DIC) systems, which are designed to measure of entire displacements and deformations fields, opens up new areas of research. In general, the materials constitutive relations are formulated in such a way that material parameters could be determined with relatively simple experimental tests carried out on samples with uniform (approximately) stress and strain fields. Then it is possible to apply them to complex boundary value problems formulated e.g. in the small or large deformation theories. The application of DIC allows to verify the accuracy of their predictions by comparing the results of the experiment with solutions to boundary value problems obtained using the finite element method (FEM).
No abstract is provided for this article.
Assessment of the flexural buckling resistance of bisymmetrical I-section beam-columns using FEM is widely discussed in the paper with regard to their imperfect model. The concept of equivalent geometric imperfections is applied in compliance with the so-called Eurocode’s general method. Various imperfection profiles are considered. The global effect of imperfections on the real compression members behaviour is illustrated by the comparison of imperfect beam-columns resistance and the resistance of their perfect counterparts. Numerous FEM simulations with regard to the stability behaviour of laterally and torsionally restrained steel structural elements of hot-rolled wide flange HEB section subjected to both compression and bending about the major or minor principal axes were performed. Geometrically and materially nonlinear analyses, GMNA for perfect structural elements and GMNIA for imperfect ones, preceded by LBA for the initial curvature evaluation of imperfect member configuration prior to loading were carried out. Numerical modelling and simulations were conducted with use of ABAQUS/Standard program. FEM results are compared with those obtained using the Eurocode’s interaction criteria of Method 1 and 2. Concluding remarks with regard to a necessity of equivalent imperfection profiles inclusion in modelling of the in-plane resistance of compression members are presented.
No abstract is provided for this article.
The top-down cracking of asphalt concrete pavements caused by thermal factors are very common in Poland. Cracking can occur as a result of a single intensive event (severe temperature drop) or as a result of cyclic long-term less severe events (thermal fatigue). In both cases precise constitutive modeling of materials is a key issue for rational prediction of the pavement behavior. As a starting point the Thermal Stress Restrained Specimen Test (TSRST) in which the shrinkage proceeds due to temperature reduction is analyzed and compared with experiment results for chosen mix. The TSRST is modeled using the finite element method in a frame of thermo-mechanics with the so-called weak coupling between thermal and mechanical effects. Mechanical properties are taken into account by the constitutive relations of elasticity, visco-elasticity and continuum cracking models. Among the continuum cracking models special place is devoted to cohesive zone model which is a new development in fracture mechanics. Cohesive zone model in many works is presented as the only solution for rational modeling of TSRST and this notion is also addressed herein.
