This research is devoted to a finite element method (FEM) numerical simulation of the bond-slip between epoxy coated plain steel bars and concrete and the ductile capacity of the mechanical process of extracting the steel bars. In this case the cured epoxy coating is assumed to be mid-layer, located between the steel bar and the concrete. This layer leads to a change of the ductile capacity of the bond and to some differences in the nonlinear bond-slip relation in comparison with the bond-slip relation in the case of non-insulated steel bars. The aim of the research is the generation of an adequate numerical model for extracting the bond-slip relation. For that purpose, a more realistic concrete material model is assumed in the proposed computational model, by means of development of dispersion micro cracks. The pull-out force is compared with the force recorded in an experiment.The ductile capacity of the bond is also analyzed and discussed in detail. The analysis is performed by the FEM.
The paper summarizes and discusses the approaches to the nonlinear SDOF free vibration behaviour to be analyzed and included in force vibration models. In brief, the general structure of the equation of motion, given in a Fourier like series form, is demonstrated. Bi-linear and multi-linear methods are compared with the so-called method of the harmonic balance from theoretical point of view. Such a method can be applied in the case of preliminary known, or predicted, total mass displacements. By a numerical example the results obtained through the discussed methods are verified by a FEM model.
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