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An Analysis of the Structure and Thermal Conductivity of Hollow Microsphere Filled Syntactic Foams

Abstract

The influence of types and parameters of hollow microspheres in the composition of syntactic foams on their structure and coefficient of thermal conductivity has been studied. By using structural and thermal analysis it has been found that the volume concentration and the size of the ceramic and glass hollow microspheres have a strong impact on the density and thermophysical properties of the thin syntactic foams coatings. It has been shown that the best heat insulating properties belong to syntactic foam with composition of 60 vol. % ceramic microspheres with particle size of 1 - 40 μm (k = 0.029 W/m·K, R = 0.008 (m2·K)/W) and with composition of 80 vol. % glass hollow microspheres with particle size of 9 - 25 μm (k = 0.087 W/m·K, R = 0.008 (m2·K)/W). The results demonstrate that application of syntactic foams as thin insulating coatings is appropriate and they are an energy efficient material with number of benefits compare with the common thermal insulators.

Open access
The Centenary of Professor Arpád Tesár

Abstract

On 1st February 2019 is celebrated the birthday centenary of great Slovak scientist and engineer - professor Arpád Tesár (1919 - 1989). His name is connected with many bridges, engineering structures and scientific works being appreciated by the technical community worldwide.

Open access
Comparison of 2D Grid Simulations for Flow Past Cylinder at High Reynolds Numbers

Abstract

The paper focuses on the verification of the suitability of the SST k - ω model on the flow past a circular cylinder in 2D for a high Reynolds number. The study compares the results of drag and lifts coefficients with respect to different types of meshes and time steps. The mean velocity field in the wake region behind the cylinder is evaluated and compared to experimental data available from literature. The numerical simulations are solved using CFD codes in the ANSYS Fluent software and use the finite volume method.

Open access
Freezing of the Subballast Layers of the Railway Formation – High Embankment and Double Track

Abstract

In the paper, a numerical modelling experiment is presented in order to detect the temperature transition through the individual layers of the railway formation during the winter period that is their undesirable freezing. In the experiment, the temperature behaviour and the zero isotherm (0 °C) are investigated. We want to prove that the temperatures are also affected by the volume of mass in the railway formation. The modelling of new experiment has been carried out done on a low and also high embankment of single and double track railway, where the volume of material in the core of the formation is almost doubled. The experiment demonstrated that the greater is the mass of the subballast layers, the higher is the resistance to freezing due to the accumulated heat in the pre-winter period.

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The Late Gothic Portal in Trebišov Pauline Order Church, Architecture and Geometry

Abstract

Gothic architecture is one of the oldest surviving architecture in Slovakia. The Church of Pauline Order in Trebišov has many building phases; its entrance stone portal belongs to the later phase dated about the second half of the 15th century. Paper focuses on an architectural features and geometry of this portal. Portal has clearly a geometrical construction that is compared to another late gothic portal from church in Handlová. Conclusion suggests, that ratio of the entire portal dimensions is close to 4 : 3, proportions of jamb and opening widths are 1 : 4 : 1 part of the overall portal width and there highly probably existed some simple method of determining position of pointed arch arches.

Open access
The Meshfree Localized Petrov-Galerkin Approach in Slope Stability Analysis

Abstract

The article focuses on the use of the meshfree numerical method in the field of slope stability computations. There are many meshfree implementations of numerical methods. The article shows the results obtained using the meshfree localized Petrov-Galerkin method (MLPG) – localized weak-form of the equilibrium equations with an often used elastoplastic material model based on Mohr-Coulomb (MC) yield criterion. The most important aspect of MLPG is that the discretization process uses a set of nodes instead of elements. Node position within the computational domain is not restricted by any prescribed relationship. The shape functions are constructed using just the set of nodes present in the simple shaped domain of influence. The benchmark slope stability numerical model was performed using the developed meshfree computer code and compared with conventional finite element (FEM) and limit equilibrium (LEM) codes. The results showed the ability of the implemented theoretical preliminaries to solve the geotechnical stability problems.

Open access
On the Eccentrically Loaded Socket Footings With Cut - Off Pyramid Shaped Socket

Abstract

In this work considerations concerning eccentrically loaded socket footing with cut-off pyramid shaped socket were presented. As an object of study sloped footing with 1.40 m height, corresponding to the maximum frost depth has been adopted. Knowing that in practice there are no perfect pure axial loads, load applied on the eccentricity has been taken into considerations. Eccentric loads result in footing rotation in the direction of eccentricity and acting load, hence one footing end is imbedding into the ground, whereas second end tries to rise up. To observe that phenomenon, elastic type of support under the foundation was introduced corresponding to the naturally humid sand with medium compaction. Presented in this paper considerations of innovative connection technology between footing and column were based on performed numerical studies. Advantages and disadvantages of presented footing in comparison to normal socket footings solutions were widely discussed. Numerical analyses were performed with the utilization Finite Element Method based SolidWorks software.

Open access
Performance of Fiber Optical Sensors in the Structure of Concrete Dams to Deal with the Impact Actions (Case Study: Seimare Dam)

Abstract

Due to the fact that dams are considered one of the strategic infrastructures of a country, it is very important to protect it against destructive acts. Accordingly, sensors were used at various points to record structural responses to the dam. Based on the questionnaires completed by experts, accuracy had the score of 3.8 so it was considered as the most important feature of the sensors and the optical fiber sensor with a mean score of 3.93 was selected as the best sensor type among the available ones. For this project, a questionnaire was prepared based on Likert scale and SPSS method was used in TOPSIS software. Then, Seimare concrete double curvature arch dam was simulated in ABAQUS 2017 software and the proper positioning of the sensors for optimum performance was determined based on Finite Element Method analysis and according to structural control criteria such as tension, displacement, strain, velocity and so one.

Open access
Presenting a Suitable Quick Construction Pattern Using Prefabricated Components in Critical Conditions

Abstract

Every year, many people in the world lose their homes due to natural disasters such as earthquakes, floods and so on. In critical situations, the use of prefabricated parts in the buildings has many technical and economic advantages. Hence, today, this technology is widely used in the industrialized societies. The purpose of this research is to provide an appropriate model for speeding up the process of constructing buildings using prefabricated parts in critical conditions. To do this, Analytic Network Process (ANP) approach has been used to select the best option for speeding up construction projects using prefabricated parts and in critical situations. In this study, the intended criteria are quality, time, cost, and strength. The options that we should compare and the best option among them, according to the criteria mentioned, are Lightweight Steel Frame (LSF) parts, steel parts and concrete parts. In order to find this prioritization, the viewpoints of civil engineers and construction experts have been used. It should also be noted that for the ANP method, the Super Decisions software has been used.

Open access
Propagation of Surface Waves in Asphalt Pavements Generated by Different Load Impulse of Falling Weight Deflectometer

Abstract

The propagation of waves generated by load impulse of two FWD types was assessed using test outputs in the form of time history data. The calculated travel time of wave between the receiver in the centre of load and others receivers showed the contradiction with the theory as for the receivers up to 600 (900) mm from the centre of load. Therefore, data collected by the sensors positioned at the distance of 1200 and 1500 mm were used.

The influence of load magnitude on the waves propagation was investigated via the different load force with approximately the same load time and vice versa. Expectations relating to the travel time of waves, depending on the differences of load impulse, were not met. The shorter travel time of waves was detected in the case of the lower frequencies. The use of load impulse magnitude as a possible explanation was not successful because opposite tendencies in travel time were noticed.

Open access