The originality of this paper is in the presentation of the experimental results on tension splices in steel S690 with three or four bolts, positioned in the direction of loading. The tests were also numerically simulated to evaluate the stress and deformation state in the steel plates due to localized pressure of the bolts. It was shown that the distribution of forces between bolts may be non-uniform and as such it is not included in any of the Eurocode rules. The results were compared to the Eurocode bearing resistance formula and it was proven that the bearing resistance is not properly defined and it also does not properly limit the bolt-hole deformation. It was demonstrated that the unfavourable initial position of the bolts due to fabrication tolerances did not significantly affect the force distribution or the resistance. The new bearing resistance formula is also proposed in the paper. The new formula defines the bearing resistance in a more consistent way and can differ between failure modes. In comparison to tests it gives better results than Eurocode bearing resistance formula.
COBISS.SI-ID: 5173345
The aim of this paper is to present a general method for the automation of finite element formulations of large deformation frictional contact problems. Derivation of contact elements is complex due to the high sensitivity of the radius and the rate of convergence on smoothness of contact surface. Various approaches to the problem are compared and evaluated.
COBISS.SI-ID: 5103969
Thermal degradation of the TSSS PU B and TISS PU A coatings, both deposited on aluminium substrates, was studied by following, as close as possible, the methodology worked out within TASK 10 of the IEA's Solar and Heating Programme. Thermal load tests were performed in the temperature range from 170 to 200 °C at various time intervals (1, 6, 10, 15, 21 days). Degradation of the coatings was assessed using a variety of degradation indicators: changes of solar absorptance and thermal emittance determined from the hemispherical IR and VIS/NIR spectra, intensity changes of selected vibrational modes attributed to the polymeric backbone and ester and urethane linkages and combined with peel-off tests used as adhesion and cohesion indicators. The results revealed that the degradation of the polyurethane resin binder was attributable to the breaking of the urethane linkages, also shown from the AFM and XPS spectra measurements. For the TISS PU A coating, the life expectancy was estimated to be 22.77 years (activation energy (Ea)=163.2 kJ/mol, Teff=113.4 °C), while for the TSSS PU B coatings it was at least 25.96 years (activation energy (Ea)=96 kJ/mol, Teff=102 °C).
COBISS.SI-ID: 5509729