Applied Mechanics and Materials Vol. 837

Abstract: Mathematical modeling of boundary value problems in linear theory of viscoelasticity. Definitions and basic principles in the mathematical modeling theory. Constitutive functional and its transformation into a form of Stieltjes integral. Application of theory of algebraic sets and corresponding subsets. Riesz theorem of representation and its application for derivation of constitutive equations. Integral operator forms of stress-strain relationships for a solid-phase continuous media.

Abstract: An objective reliability analysis of structural members made of advanced cementitious composites must be based on good knowledge of stochastic properties of individual mechanical fracture parameters of utilized material models. The article presents a comprehensive approach to the design and assessment of precast structural elements including: The series of fracture tests of the two concrete mixtures with various ages in two configurations (three point bending and wedge splitting test, subsequent identification of material parameters using effective crack model, work of fracture method and artificial neural networks, execution of destructive tests of scaled structural members and creation of deterministic models of these tests using collected data. In subsequent phases of the project reliability analysis of tested beams will be carried out in order to obtain stochastic parameters of structural response of prestressed elements to shear load. The obtained data will be used to calibrate the analytical equation describing the response of element exposed to both normal and shear forces. The entire process will be concluded by reliability-based optimization of manufactured components.

Abstract: The paper deals with design of model and verification of a pile loaded by pressure. The pile is embedded in the layered ground mass. Its model has been created using the ANSYS software system. The obtained results have been compared with results of the pile loading test performed during the construction of a multifunctional building. In the conclusion the results have been presented in graphs.

Abstract: The corrosion of reinforcement is one of the predominant reasons for loss of reliability of reinforced concrete structures. This has an impact on safety, serviceability and durability of the structure. The corrosion of steel in concrete reduces the cross sectional area of the reinforcement and decreases the bond between reinforcement and concrete. Corrosion products have a higher volume than steel, which produces internal stresses that lead to the cracking and spalling of the concrete cover. Additionally, corrosion of steel changes the mechanical properties of reinforcement. In this paper, the relationship between crack widths and bond strength between reinforcement and concrete was investigated.

Abstract: The paper presents results of numerical investigation of fracture behaviour of initially notched beams made of foamed concrete. Extended Finite Element Method (XFEM) was used to simulate the damage and fracture process of the beams subjected to three-point bending. Subsequently, the numerical models were validated by a series of static loading tests. Numerical models simulate correctly the fracture behaviour of beams observed during testing. XFEM method and computer simulation technologies allow for reliable approximation of load–bearing capacity and damage mechanisms of beams made of foamed concrete, which provides some foundations for realistic structural applications.

Abstract: In this article we verified the methodology of experimental measurements on plexiglass plate. We compared the natural frequencies of plate. The experiment was done under laboratory conditions using a portable dynamic measuring apparatus. We compared the experimental results with the results from software ANSYS based on finite element method.

Abstract: In this contribution, we employ non-stationary filtered Gaussian processes as an enrichment of a periodic mean value in order to approximate crowd loads on grandstands. Our work generalizes previous considerations where the superposition of a mean value and a stationary filtered Gaussian noise was used, and helps therefore to better predict the response of a structure mainly in the transition stages. We specify general theory of stochastic differential equations within the context of grandstands by recalling particular moment equations, and demonstrate its benefits or drawbacks on two simple examples. Overall performance is measured in terms of the second moment evolutions in time and in terms of the total up-crossings of the system's response compared to previously developed stationary approximation and Monte Carlo simulation. Throughout, only an active part of a crowd is considered.

Abstract: The aim of the paper is focused on the analysis of the mechanical properties of the concrete specimens with plasticizer at three point bending test by the signal analysis of the acoustic emission signal. The evaluations were compared the measurement and the results obtained with theoretical presumptions. The Joint Time Frequency Analysis applied on measurement data and its evaluation is described. It is well known that the Acoustic Emission Method is a very sensitive method to determine active cracks into structure. However, evaluation of acoustic emission signals is very difficult. A non-traditional method was used to signal analysis of burst acoustic emission signals recorded during three point bending test.

Abstract: The external wind pressure coefficients are based on the measurements on the structures without free-end flow near the top of vertical structures. The end-effect factor takes into account reduction of the pressures due to specific flow around the top of atypical building. The article is based on the experimental measurements in BLWT tunnel in Bratislava on the model of building with cross section of the quarter circle. The model was tested in two spaces - in steady and turbulent wind flow, by changing of wind direction and wind velocity. The end-effect factor depending on the wind direction is shown in the graphs.

Abstract: Turbulence is a flow regime characterized by chaotic property changes. Randomness, fluctuations, vorticity and large Reynolds number (Re) are the basic characteristics of turbulent flows. In this contribution is Computer Fluid Dynamic simulation of air-flow over an obstacle in shape of “quarter-circular” object compared to the data from previous work. This comparison is focused on mean values of pressure in 16 selected points at different elevations. k-ω turbulence model performed well (convergence, time, CPU) and the overall error is 13.61 %.