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.
The paper contains a review of hydraulically bound layers fatigue resistance criteria that are commonly applied in designing the road pavement structures. The effect of the mechanical parameters applied in the respective criteria on the obtained fatigue resistances is analysed with their different nature underscored. Most of the fatigue criteria define the fatigue life through parameters which are related to it only indirectly (such as the tensile strength, the ultimate tensile strain, etc.) instead of using the results of fatigue tests. The results obtained with different criteria are compared and correlated with the results obtained with the methodology used in preparation of “The Catalogue of Typical Flexible and Semi-rigid Pavements”, a Polish pavement design guide published in 2014. It is demonstrated that the differences between predictions generated with the different empirical fatigue models are noticeably greater in the case of lower traffic classes (service levels), converging for higher traffic classes.
No abstract is provided for this article.
The main goal of introducing the MSCR test was to estimate the rheological properties of pen grade and modified binders using the same measure. The conditions for this test were chosen at random (the length of creep and recovery period, the stress levels, as well as the test temperature). In most applications, the test temperature value was equal to 64 or even 70°Celsius. It is clear that for such high temperature values for softer binders the test interpretation is not always possible or burdened with a significant statistical error. Some time ago authors of this paper proposed a certain very similar test, but with different test parameters and with different interpretation of the test results. The test may be called a multiple shear creep long recovery (MSCLR) test and the main differences are the test temperature assumed as 10°Celsius and duration of creep and recovery period. In the first part of test, 10 cycles of creep-recovery periods are applied in the stress shearing mode on an asphalt binder sample. This part of the test ends with a long-term recovery period. The test is interpreted through the permanent deformation ratio determined on the basis of the maximum shearing strain observed during the test and the strain value after the long recovery period. In the paper the MSCR and MSCLR tests are conducted on highly-modified binders currently produced in Polish market. The obtained results are statistically analyzed, compared with each other and correlation functions between the results from MSCR and MSCLR tests are determined. Selected results are then presented in relation to results of modified and pen binders produced 8 years before (or some archival binders used for analysis in the paper [1]). Based on the analysis of the results, it is possible to observe some advantages of MSCLR test over MSCR test. One of them is a higher test sensitivity in distinguishing resistance to permanent deformations of individual binders and another one is the simplicity of interpretation of the test data.
W pracy przedstawiono analizę nośności stalowej
No abstract is provided for this article.
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.
No abstract is provided for this article.
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.
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.
When designing embankments on a soft ground improved with columns (rigid inclusions) and with a geosynthetically reinforced load transfer platform (LTP), the methods of determining strains in reinforcement reduce the spatial problem to a two-dimensional one, and analytical calculations are carried out for reinforcement strips in the directions along and across the embankment. In addition, the two-dimensional FEM models do not allow for a complete analysis of the behavior of the reinforcement material. The aim of this research was to analyze the work of the membrane in the 3D space modeling of the LTP reinforcement, depending on the interaction with the column, the shape of the column’s cap, the value of the Poisson’s ratio, the value of the stiffness of the elastic foundation (subgrade reaction k) modeling of the soft soil resistance between the columns and the load distribution over membranes that model the reinforcement. The membranes were modeled in the framework of the theory of large deformations using the finite element method and slender shell elements as three-dimensional objects. This modeling method allowed for the analysis of the behavior of the LTP reinforcement in various directions. The conducted analyses showed, among others, that in the absence of soil resistance between the columns, regardless of the shape of the cap (square, circle), the greatest strains are located near the edge of the cap in the diagonal direction between the columns.
No abstract is provided for this article.
Welding is the most important joining technique and offers the advantage of customizable plate thicknesses. On the other hand, welding causes residual stresses and deformations influencing the load carrying capacity. Their consideration in the design requires simple and fast models. Though welding simulation has contributed to accurately access to these values nowadays, their application to large components remains still in a less practicable range. Nevertheless, many studies emphasized the need to make corrections in recently available simplified models. Especially the influence of residual stresses seems somewhat overestimated in many cases if comparing conventional structural steel S355 and high-strength steel S690. In times of computer-aided design, an improved procedure to implement weld-inducted imperfections appears overdue. This will be presented in two parts. The first part illustrates the potential influence of post-welding imperfections exemplified for weak axis buckling in comparison with the general method in accordance with Eurocode 3. Residual stresses and initial crookedness were varied systematically in order to produce a scatter band of capacities. An approach to characterize the borders of these imperfections was untertaken before that. The excessive scattering of reduction factors for the load bearing capacity demonstrates the importance of these variables. Results were finally evaluated against advanced simulation models which will be further detailed in part two of this contribution.
