Applied Mechanics and Materials Vol. 769

Abstract: In the design of multi-storey frame structures, there is a question of a proper evaluation of the stiffness of reinforced concrete frame joints. This problem is very important especially in the case of structures subjected to seismic load, where the forces act repeatedly. Concrete is able to carry the compression stresses and partially the shear stresses. The tension stresses can reach only low level. The maximum tension stresses (tension strength) obtained from simple tension test of the concrete are not the same as the maximum tension stresses in the reinforced concrete. The shear stiffness is the matter of the width of the concrete cracks. To improve the knowledge in this field, the experimental verification of the reinforced concrete frame joint had been arranged.

Abstract: An impoundment is an engineering construction used for the safe deposition of unexploitable waste from industrial and mining facilities. In terms of the legislative requirements of the Slovak Republic, a Measurements Project must be developed for each impoundment. In this document the prerequisites for the safe operation of an impoundment, the limit and critical values of the monitored phenomena and the facts influencing the safety of the impoundment and the area endangered by such a site are also defined. The safety and stability of an impoundment are verified according to a Measurements Project by considering stability at regular time intervals. This contribution presents, in the form of a parametric study, a stability analysis of a lime sludge impoundment. The stability analysis provides an example of the utilization of an information database of the results of the regular monitoring of the geotechnical properties of the materials forming the impoundment ́s body and the surrounding rock mass.

Abstract: Analysis of the rules for calculation of the reduction factor for plate buckling of internal and outstand elements defined by Eq. (4.2) and Eq. (4.3) given in Annex E of EN 1993-1-5. Proposals for improvements of the rules, which were already accepted in Working Groups WG EN 1993-1-3 and WG EN 1993-1-5 for the next generation of Eurocodes.

Abstract: Paper deals with the assessment of the fire safety of composite steel and concrete column as the selected structural element of 30 storey building. The effects of the fire are considered in accordance with the standard EN 1994-1-2. The probability of the column collapse is calculated. The deterministic and probability analysis of the fire resistance of the composite column is considered. The MC simulation is realized for 10⁶ samples of the input data. The sensitivity analysis of the various input parameters shows the significant influence of the action effect and material uncertainties.

Abstract: In the time of exploitation of building structures frequently situations do occur, in which due to failures they are exposed to much higher loads than originally predicted. The subject matter of the performed investigations and a numerical analysis are models of four narrow reinforced concrete slabs with the dimensions 7140×500×190 mm. The paper presents the results of the numerical analysis, the aim of which was to reflect and to provide detailed information about phenomena occurring in the course of laboratory tests. Numerical models were constructed according to the system ANSYS, applying volumetric elements SOLID65 and bars LINK8. In order to determine the relation σ-ε of steel an isotropic model of strengthening in the system ANSYS was used, constructed by Misses. The behaviour of concrete was represented by the material model Concrete. The parameters applied in the material models had been obtained in laboratory tests of the material. The paper quotes the results of calculations compared with the results obtained in laboratory tests.

Abstract: One of the fundamental elements applied in reinforced concrete structures are beams. Depending on the proportion of the dimensions and the way of imposing the load, two fundamental mechanisms of destruction are to be distinguished (brittle destruction caused by shearing the supporting zones or flexural destruction in the zone of the span). The present paper provides the results of the analysis of four reinforced concrete beams with the dimensions 4000×400×200 mm, reinforced with steel of varying ductility. The aim of this analysis was to reflect and to provide more detailed information about the phenomena observed in the course of laboratory investigations. The numerical models were constructed in compliance with the system ANSYS, applying volumetric elements Solid 65 and bars Link 8. In order to determine the relation σ-ε of the steel an isotropic model of strengthening according to Misses was implemented in the system ANSYS. The behaviour of concrete was represented making use of the material model Concrete. The parameters applied in the material models were obtained basing on laboratory tests of materials. The results of calculations have been quoted in the paper, as well as their comparison with the results of investigations carried out in the laboratory.

Abstract: The paper presents preliminary results of theoretical and experimental analysis of the resistance of construction panels at compressive loading. Panels, made on the base of polystyrene foam in combination with thin-walled cold-formed elements, should be used as a load-bearing wall panels for simple and small structures. Investigated panels, with dimensions 1.0x2.5x0.15 m, are formed by six thin-walled elements of U-profile with a thickness of 0.8 mm, which are stabilized by glued polystyrene board EPS 100 S, 150 mm thick. Sufficient number of strain gages and inductive sensors were used for the experimental measurement of strains and deflections. Strain gauges and inductive sensors were both-sided suitably located on each tested panel. Spatial calculation model was created within software SCIA and ANSYS. Geometrically nonlinear analysis was used for the numerical solution. Based on the numerical and experimental results, the efficiency of polystyrene boards on the stability of used thin-walled steel elements was determined.

Abstract: Presented paper offers simplified equations for evaluation of residual stresses. Residual stresses are very important for evaluation of properties of steel thin-walled structures. They play a crucial role in definition of ultimate load and stiffness properties. Generally the residual stresses must be in equilibrium. In the case of statically determinate beam structures residual stresses do not have influence for natural frequency. But in case of plate structures situation is different. Relationship between residual stresses and natural frequency can be used as the base for preparation of non-destructive method for the investigation of residual stresses in thin-walled structures.

Abstract: The article describes the study of turbulent characteristics in the enclosed chamber of a rectangular corss-section nozzle using numerical calculations. Suitable Ansys Fluent software models were selected based on the measurements results comparison in an aerodynamic tunnel as the fluid exits the nozzle. Special attention is paid to profile velocity near the peripheral wall of the observed enclosed chamber in order to confirm the optimal shape of the contraction and thus take steps towards a high quality velocity field.

Abstract: This article is focused on the comparison of mathematical models, which are usable for description of damping in the linear proportional systems with single and multi degrees of freedom (SDOF and MDOF). The viscous and hysteretic models have been applied on the SDOF system. The hysteretic damping, Rayleigh's and Caughey's damping matrices have been mentioned and considered for modeling of damping in systems with more than one degree of freedom. The wellknown Rayleigh's model is proportional to the mass and stiffness matrices. Caughey's model is more general than Rayleigh's. This model is able to prescribe an arbitrary number of damping ratios, but on the other hand using odd number of members in Caughey's series should not be allowed due to the negative values of damping ratios in higher modes, which brings self exciting effect. The hysteretic model is defined only in the frequency domain therefore the frequency response functions of each model have been compared.