Concretes with dispersed reinforcement are increasingly used in structural engineering. The basic source of knowledge on their application and design are the Model-Code 2010 guidelines. These guidelines, however, apply mainly to steel rebar reinforcement and are not fully sufficient in the analysis of the load-bearing capacity of elements made of concrete with dispersed reinforcement. Therefore, scientific research in this field is carried out continuously. The main goal of our work is to provide experimental data for the calibration of constitutive models of the cracking mechanics of concrete with reinforcement in the form of steel and polypropylene fibers. This article shows the possibility of using the digital image correlation system (DIC) to achieve this goal. The method of sample preparation and the method of conducting the tests were modeled on the recommendations contained in the PN-EN 14651: 2007 standard. The tests were carried out on prismatic elements with a notch loaded in a three-point bending setup. The results of standard strength tests are presented in the form of column graphs and tables. As an extension, the results of calculations of energy dissipated in fracture process are given. Moreover, the experimentally obtained graphs of the relationship between the force, displacement and crack opening were presented, which were supplemented with the images of crack development obtained with the use of DIC. The development of the crack net is characterized not only qualitatively but also quantitatively as a function of deflection or crack mouth opening displacement. Conclusions concerning the adopted research methodology and the tested materials are presented at the end of the article.
In the presented paper the local instabilities occurring in compression test of perforated thin-walled bars of low slenderness are observed using digital image correlation system ARAMIS. The tested samples slenderness is so low, that from theoretical point of view we are dealing with compression tests of some perforated shells. The samples are made from typical low carbon steel, which has to be treated as elasto-plastic material. Because of that, the final geometry of the sample (after unloading) is also analysed giving a good data for calibration of the theory of elasto-plasticity for large deformations. In analysed cases the total strain values are not exceptionally large, while local rotation (and permanent deformations) have significant values.
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Compressive capacity of the thin-walled steel columns, corroded uniformly over their entire side surface length is analysed in this paper. The thin-walled profile steel columns are often used for bridges, rail and road building constructions. Loss of the profile mass that appears due to corrosion growth reduces the cross-sectional area and influences column compressive capacity. Computational models of the structure are assumed based on the observation of existing corroded columns. The theory of thin-walled profiles is taken for the analysis. Models simulating the walls weakening due to corrosion growth are considered on the example of three thin-walled steel profiles: semi-closed channel section, two semi-closed channel section connected by webs and HKS profiles. Different patterns and degrees of corrosion growth were considered and, as a result, changes of the profile cross-sectional geometry were observed. Theoretical considerations of thin-walled compressed corroded steel columns stability are illustrated by bearing capacity calculations. Geometric cross-sectional characteristics are determined and the system of stability equations is solved. The calculation results are presented in the form of graphs illustrating the effects caused by the geometry change due to corrosion defects. The reduction of column compressive strength in each of the considered case is observed. Moreover a variation of the buckling mode from flexural one into warping is noticed in one of the analysed items. It has been found that more dangerous corrosion growth pattern appears when asymmetric loss of the profile wall thickness arises. That may change the form of buckling from flexural one into warping.
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