Řada stavební. 2020, roč. 20 / Civil Engineering Series. 2020, vol. 20
Permanent URI for this collectionhttp://hdl.handle.net/10084/139129
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Item type: Item , Geogrid Reinforced Subbase under the Impact of Mining Subsidence(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Kałuźa, Mateusz; Kotasiński, MiroslawInfluence of geosynthetic localization in subbase was examined considering its effectiveness and mining influences. Large-scale apparatus was used to simulate horizontal unloosing strains εr. A coefficient of lateral earth pressure Kε determined on horizontal and vertical stresses was used to compare effectiveness of geosynthetic in different height of subbase. Results for unreinforced and reinforced subbase were compared. Implementation of geosynthetic reinforcement allowed to withstand higher values of horizontal unloosing strains εr.Item type: Item , A Crack Approaching the Edge of the Aggregate(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Vyhlídal, Michal; Klusák, JanIn this work, the influence of a crack approaching the edge of the amphibolite inclusion on fracture behaviour of cement composite is investigated. Specimens of the nominal dimensions 40 × 40 × 160 mm with polygonal amphibolite inclusion of 8 × 8 × 40 mm were provided with an initial central edge notch with a depth 12 mm, which was made by diamond blade saw. To determine the influence of polygonal cavity on fracture behaviour, fracture tests were conducted via three-point bending. The aim of this work is to analyse the behaviour of such specimen by means of finite element method (FEM) principles in Ansys, Inc. software. For this reason, a simplified 2D model was created for plane strain conditions. The crack propagation assessment was based on generalized fracture mechanics approaches using a criterion of an average value of tangential stress determined in dependence on the polar angle coordinate θ. The results of numerical analysis indicate that the debonding in the close vicinity of the bottom edge of the inclusion occurred. In other words, imperfect compaction of the fresh mixture and a smooth surface of the aggregate leaded to the formation of poor interface with lower mechanical-fracture parameters. Further, cutting of the initial notch by a diamond saw blade results in a precrack length greater than expected.Item type: Item , Numerical Method for Saint -Venant Torsion Problem with Arbitrary Cross-Sections(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Tran, Dang-Bao; Navrátil, Jaroslav; Čermák, MartinA numerical method solving the Saint-Venant torsion problem with arbitrary cross-sections was derived by Gruttmann in 1999. The numerical method is validated by analyzing two examples with two mesh types: uniform and non-uniform; excellent accuracy was obtained compared to analytical solutions. Further, the comparison between three elements: LINQUAD, QUAD8NOD, and QUAD9NOD to choose the appropriate element for the numerical method was performed. The conclusion drawn is that our numerical method with QUAD8NOD and QUAD9NOD elements is suitable for Saint-Venant torsion problem.Item type: Item , Hierarchical Modelling of Uncertainty in NDT Tests of Historic Steel Bridges(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Sýkora, Miroslav; Mlčoch, Jan; Ryjáček, PavelSustainable development can be supported by extending the service lives of existing road and railway bridges. Preservation and upgrade should be based on improved surveys, monitoring, reliability assessment, and strengthening methods. In the case of metallic materials, hardness methods (NDT) calibrated by a few tensile tests (DT) were shown to be associated with reasonable measurement uncertainty. This contribution discusses the current practice in assessment based on NDT results and introduces the hierarchical modelling of the measurement uncertainty in hardness tests. Preliminary results suggest that the variability of ultimate strength can hardly be estimated on the basis of NDTs only. It seems that the systematic component of measurement uncertainty has a lower coefficient of variation (3%) than the random component (8%); the variability of the latter may thus often exceed the variability of the ultimate strength of a homogeneous material.Item type: Item , Alkali-Activated Slag Mortars Containing Alternative Activator: Long-Term Mechanical Fracture Parameters(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Šimonová, Hana; Kucharczyková, Barbara; Bílek, Vlastimil; Kocáb, DaliborThis paper deals with the determination of longterm mechanical fracture properties of alkali-activated slag (AAS) mortars with the alternative activator. Waste sludge from the production of waterglass was used as a sole alkaline activator for ground granulated blast furnace slag. Two types of sand were used to prepare two different mortar sets: standardized siliceous CEN sand consisting of three fractions according to EN 196-1 and natural sand with a nominal grain size up to 4 mm. The results of the elastic, fracture and strength parameters for both sets of AAS mortars determined within the time interval of 3 to 650 days of ageing are summarized in the paper. The obtained results show a different trend in the development of the material properties of AAS mortars compared to the ordinary cement-based mortars which should be taken into the account in the material specification for practical application. It seems that the hardening process influencing the mechanical fracture characteristics is more progressive after the age of 28 days.Item type: Item , Submission and Limitations of Civil Engineering Tasks using ANSYS Tool in National Supercomputer Center IT4Innovations(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Neuwirthová, Zdeňka; Čajka, RadimThis article deals with a problem of soilstructure interaction on a simplified model using the commercial software Ansys on the Anselm supercomputer in the National Supercomputing Center IT4Innovations in the VSB-Technical University of Ostrava. For a purpose of large-scale modelling tasks by supercomputer knowing program limitations are required as well as the area and scope of the selected solution. Therefore, a numerical model was created with increasing size, and therefore degrees of freedom until a maximum size of the task was determined because any larger task can´t be computed. The maximum size of the task and solution times obtained by the supercomputer was compared to the maximum size and computation times received by a standard computer workstation.Item type: Item , Mechanical and Durability Parameters of the Concrete Bridges under Service in the Czech Republic(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Lehner, Petr; Horňáková, Marie; Konečný, PetrRC bridges are the typical structures exposed to the combined effect of carbonation, chloride ingress, and mechanical load. Due to this, the structures are susceptible to corrosion, which influences the load-carrying capacity and safety. An important part of the preparation for performance-based design is an analysis of the durability of existing structures to improve the reliability of available numerical tools. In this study, the correlations between compressive strength, chloride content, pH, exposure time, and risk factor were analysed. All were evaluated based on the in-situ measurements performed on regular inspections of 14 motorway bridges under service in the Czech Republic.Item type: Item , Seismic Analysis of the Soil-Structure Interaction Considering the Local Site Effects(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Králik, Juraj; Králik, Juraj jr.The paper presents the results of analysis of the soil-structure interaction effects considering the local site effects. The influences of the local site effects – masses, stiffness and thickness of the layered subsoil - can significantly modify the stresses and deflections of the structural system. Two important characteristics that distinguish the dynamic soil-structure interaction system from other general dynamic structural systems are the unbounded nature and the plastic strains of the soil medium. Generally, the influence of the layered subsoil will be considered to define of the seismic loads and the stiffness and damping of the complex system soil-basestructure behaviour.Item type: Item , Mesh Size Influence of the Concrete Slab FE Model Exposed to Impact Load for Various Material Models(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Jindra, Daniel; Hradil, Petr; Kala, Jiří; Král, PetrNumerical approach using the FEM has been used to model the behaviour of the reinforced concrete specimen subjected to the pressure blast wave. The concrete structure is a slab freely supported around the perimeter by a steel plate and a concrete base. A simplified 3D blast model has been used, which involves the pure Lagrangian approach of FEM. The analyses have been conducted using explicit solver. 3 different non-linear material models of concrete have been used to capture the concrete behaviour: CSCM (Continuous surface cap model), Schwer Murray continuous surface cap model, and JHC (Johnson-Holmquist-Cook) material model. Influences of various mesh sizes on the final results (crack patterns, vertical deflection, strain-time dependence) are being monitored, compared with physical experiment data and discussed.Item type: Item , Conceptual Interventions into the Ferme Ornee Chateau Kacina near Kutna Hora(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Palánová, KláraThe empire style chateau Kačina near Kutná Hora is being used as a museum of agriculture and thus is not a very attractive tourist destination. The manager of the estate approached the students of Architecture and engineering, from the civil engineering Faculty at VŠBTU in Ostrava, to create conceptual designs of intervention into the ornamental estate, or Ferme ornée which preserve the significant historical context of the premises. The paper presents the process of approaching a solution to the assignment and attaches relevant outputs.Item type: Item , Influence of Vibrational Impacts on the Bell Towers and the Problem of Safety(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Smirnova, Elena; Larin, DenisDue to reconstruction and restoration of the original guise of the landmarked buildings the investigators are facing the problems of assessing possible adverse consequences of such sorts of work in the recent years. The most problematic are the works requiring dismantling of the bearing and fencing structures built into original scheme. This article gives consideration to the ways of solving a problem of ensuring safety of buildings and structures in use provided their operating conditions have changed (e.g. the assessment of possible consequences of bells installation on the steeples of St. Isaac's Cathedral is presented). The measurements of vibrations with simultaneous assessment of robustness and bearing capability of the brickwork have shown that the vibrational impact of chimes of heavy bells cannot adversely affect the bearing structures of the bell towers. However, there is always a risk of such adverse effect on the structure of the bell tower and stability of soils at its base. A danger emerges not because of significant settlements, but rather due to irregularity owing to inhomogeneity of soil. The obtained assessments of settlements show that they cannot be ignored and it is reasonable to perform an annual leveling check of settlements of foundation or base of the bell tower It is offered, therefore, to carry out investigation before the beginning of reconstruction using the structure model, which makes it possible to give consideration to the impact of «new» loads to exclude any possible emergency situation at the objects being reconstructed.Item type: Item , Fully Stochastic Nonlinear Analysis of Slender Reinforced Concrete Column(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Šmejkal, Filip; Pukl, Radomír; Červenka, JanThe following article presents nonlinear resistance assessment of a slender reinforced concrete column using commercial FEM software ATENA. Furthermore, three different approaches are used to determine design value of resistance. Firstly, the most commonly used method of partial safety factors is described. Secondly, method ECoV (estimate of coefficient of variation) is presented, which is one of the possible options used in fib Model Code to asses design resistance of structures using nonlinear analysis. Eventually, a fully probabilistic analysis is performed using commercial software package SARA.Item type: Item , Reliability of Industrial Chimneys Affected by Vertical Reinforcement Corrosion(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Mlčoch, Jan; Sýkora, MiroslavReliability of a reinforced concrete chimney is analysed considering probabilistic models for the effects of wind loads and the principles provided in Eurocodes. Corrosion of reinforcement due to carbonation is considered. Obtained reliability indices are compared with the target levels indicated in the EN and ISO standards. Sensitivity analysis identifies the parameters that have a significant impact on structural reliability, namely wind velocity and time-invariant wind pressure parameters. The values of these parameters can be updated based on measurements and a more economic design can be achieved.Item type: Item , Comparison of S-N Curves for Concrete in EN 1992-2 and fib Model Code 2010(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Krejsa, Jan; Sýkora, MiroslavThe paper is focused on the comparison of Wöhler’s curves for concrete in accordance with fib Model Code 2010 and EN 1992-2. It discusses the great difference for bridge fatigue assessment between Model Code 2010 and EN 1992 observed in previous studies. Respective S-N curves were compared with the experimental data for concrete C20. Evaluation is performed for concrete exposed to compression only. Wöhler’s curve in fib Model Code 2010 is more complex and can better fit experimental data than the Eurocode model.Item type: Item , Nonlinear Analysis of the Extreme Wind Fragility of the Reactor Hall Frame(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Králik, Juraj; Králik, Juraj jr.This paper describe the methodology and the results of the safety analysis of the Nuclear Power Plant structures under impact of the extreme climatic loads. In the case of the Nuclear Power Plant structures, the design criteria are stronger. The requirements of the international agency IAEA and NRC standards are based on the probability of mean return period equal to one per 104 years. The fragility curve of the extreme wind was determined on the base of the nonlinear probability analysis of the steel hale frame considering material and geometric nonlinearity using ANSYS software. The failure mode of the NPP structures is expressed by High Confidence of Load Probability of Failure (HCLPF).Item type: Item , Strength Tests of Concrete Specimen Exposed to an Aggressive Environments(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Hegedüsová, Iveta; Kotrasová, KamilaThe paper presents the results of static tests of the concrete beams exposed to the aggressive environment in the agricultural building. The long-term effect of an aggressive environment was expected. The aim of analysis was to evaluate the condition of the ceiling panels. Static tests have provided information on the possible modulus of elasticity and the classes of concrete used to make the beams. The concrete beams with higher structure porosity and lower bulk density showed lower strength values and lower modulus of elasticity values. The knowledge gained from the analysis of beams will be used for comparison with the results obtained from the ceiling panels.Item type: Item , Hardwood - Softwood Combination in Glued Laminated Timber Cross-Section(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Balász, Ivan; Pešek, Ondřej; Bukovská, PavlaGlued laminated timber (glulam), as one of the types of engineered wood products, is in our conditions most often made of coniferous, specifically spruce wood. In order to find optimal usage of material, some new configurations of cross-sections are being suggested. An advanced solution of glulam cross-section could be represented by cross-section formed from combination of hardwood (from deciduous trees) and softwood (from conifers). This paper deals with a possibility of combination of outer lamellas from a hardwood and inner lamellas from a softwood in glulam cross-section. The solution is focused on members suitable for a use in a skeleton frame. Attention is paid to two types of structural members: beam and column. Results of theoretical study are presented which arise from an analytical calculation and from a numerical modelling. For comparison, the calculations were carried out for a reference cross-section consisting of softwood lamellas only. By comparing the combined and reference crosssections, it can be stated that the use of the combined cross-section can save material for both the compression member (column) and the member subjected to bending moment (beam, girder). The combined cross-section appears to be more advantageous than the reference crosssection, especially in cases of smaller beam depth.Item type: Item , The Pure Bending Task in Case of Composite Rod Based on Four-Element Model(Vysoká škola báňská - Technická univerzita Ostrava, 2020) Abesadze, BidzinaIn the presented paper is stated distribution of deformations and stresses development at external constant force moment in the rod with taking into account geometric characteristic as well as the time factor based on the four-element model. The values of the curvature and rotation angle are estimated. The values of deflection of rod with dependence on its coordinate and time are determined. The behavior and distribution of arisen in the cross-section of rod stresses at constant deformation (the case of relaxation) depended on the time is also determined.