Řada stavební. 2023, roč. 23 / Civil Engineering Series. 2023, vol. 23

Permanent URI for this collectionhttp://hdl.handle.net/10084/152426

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Now showing 1 - 17 out of 17 results

Damage Identification Using Artificial Neural Network-Aided Aimed Multilevel Sampling Method
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Šplíchal, Bohumil; Lehký, David
Structural health monitoring is extremely important for sustaining and preserving the service life of civil structures. Research to identify the dam- age can detect, locate, quantify and, where appropri- ate, predict potential structural damage. This paper is about damage identified by non-destructive vibration- based experiments, which uses the difference between modal frequencies and deflection of an initial and dam- aged structure. The main objective of this paper is to present a hybrid method for structural damage identi- fication combining artificial neural network and aimed multilevel sampling method. The combination of these approaches yields a more efficient damage identifica- tion in terms of time and accuracy of damage localiza- tion and damage extent determination.
Experimental Analysis of Actual Behaviour of Fiber Cement Boards
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Pilgr, Milan; Karmazínová, Marcela; Melcher, Jindřich
The paper is focused on analysis of limit states and actual behaviour of the great size fibre cement boards that are produced without autoclaving. In this paper the basic information on the testing of the fibre cement boards is summarized, but its main goal is the utilization of acquired specification and data for the elaboration of backgrounds for direct determining of the defined load carrying capacity of boards for basic cases of loading, span and support conditions. The elaborated solutions and results follow the contemporary approach of the structural design method and reliability verification based on the concept of limit state design using the partial safety factors.
Recent Advances in Polynomial Chaos Expansion: Theory, Applications and Software
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Novák, Lukáš; Novák, Drahomír
he paper is focused on recent advances in uncertainty quantification using polynomial chaos expansion (PCE). PCE is a well-known technique for approximation of costly mathematical models with ran- dom inputs – surrogate model. Although PCE is a widely used technique and it has several advantages over various surrogate models, it has still several lim- itations and research gaps. This paper reviews some of the recent theoretical developments in PCE. Specif- ically a new active learning method optimizing the ex- perimental design and an extension of analytical sta- tistical analysis using PCE will be reviewed. These two topics represent crucial tools for efficient applications: active learning leads generally to a significantly more efficient construction of PCE and improved statistical analysis allows for analytical estimation of higher sta- tistical moments directly from PCE coefficients. Higher statistical moments can be further used for the iden- tification of probability distribution and estimation of design quantiles, which is a crucial task for the proba- bilistic analysis of structures. Selected applications of the theoretical methods are briefly presented in a con- text of civil engineering as well as some preliminary results of further research. A part of the paper also presents UQPy package containing state-of-the-art im- plementation of the PCE theory.
Effect of Climatic Conditions on Carbonation of Concrete Structures
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Mlčoch, Jan; Holický, Milan; Sýkora, Miroslav
Carbonation-induced corrosion is a degradation processes, which causes significant economic losses to the operators of an aging large, reinforced concrete (RC) structures such as cooling towers. Due to large variability of basic variables, the probabilistic approach is suitable to describe carbonation ingress. In this study, the probabilistic model is developed for service life assessments of large RC structures exposed to environmental effects. For existing structures, carbonation ingress in normally described using carbonation depth data from in-situ surveys. The shape of a time-dependent carbonation depth curve, essential for long-term predictions, is expressed through the weather function which accounts for the effect of environmental exposure of the structure. This study indicates how a probabilistic model of carbonation ingress can be established; numerical illustration is focused on existing cooling towers located in the Czech Republic. It appears that when long-term observations of carbonation depth are unavailable, the shape of a time-dependent carbonation depth curve can be determined on the basis meteorological data.
Dynamic Analysis of Block Concrete Foundation
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Melcer, Jozef; Valášková, Veronika; Vlček, Jozef
The paper is dedicated to the assessment of the dynamic response of a block concrete foundation to dynamic effect of an external force. The basic dynamic characteristic of the system is analysed. The state of resonance and introduction of the resonance curves are assessed. Description of the possibilities of numerical solution of the foundation response to dynamic loading and analysis of the behaviour of the foundation under different conditions are presented.
Dual Discrete and Continuous Meso-scale Modelling of Concrete
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Mašek, Jan; Miarka, Petr
The present paper is devoted to the development of a software equipment that allows to model composite materials by both discrete and continuous modelling approaches. The aim is to create a geometrical and topological representation of a discrete lattice particle model as well as its 1:1 twin counterpart as modelled by a continuum FEM model. Both representations capture the heterogeneous composite structure at the meso-level. The presented results illustrate the ongoing initial phase of the efforts of the team in advanced modelling of damage propagation within concrete.
Stress Concentration Factor on a Corrosion Pit
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Malíková, Lucie; Benešová, Anna; Al Khazali, Mohammad Sami; Křivý, Vít; Seitl, Stanislav
Phenomenon of corrosion in structural materials is very important, because they very often yield to aggressive environment. Moreover, not inconsiderable effect of fatigue damage via cyclic loading of such engineering structures should be considered as well. Thus, the influence of a corrosion pit (of a circular segment shape) on the stress distribution in a rectangular specimen subjected to remote tensile stress range has been investigated via finite element method. Particularly the stress concentration factor has been calculated for various sizes of the corrosion pit and the results obtained have been discussed.
Fuzzy Analytical Hierarchy Damage Assessment In Old Reinforced Concrete Buildings: Case Study
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Lallam, Mostefa; Mammeri, Abdelhamid
This study uses a fuzzy analytical hierarchy method to help people make decisions about how to plan maintenance for older reinforced concrete buildings (ORCB). Visual inspections, in addition to a variety of criteria and sub-criteria, will be used to accomplish the goal of classifying the level of deterioration that has occurred to the administrative building that serves the city of El Malah. The historical context of the building, environmental circumstances, structural capability, and professional participation are the key aspects that were evaluated in this study. After that, these components are broken down further into a number of other sub-factors. The calculation of weights (Wi) using Buckley's fuzzy geometric mean approach is what determines the relevance of each component and sub-factor individually. After that, scores from experts are allotted to each criterion and sub-criterion, and these ratings are then used to compute the comprehensive score (CS), which represents the ORCB's level of deterioration. The EMS-98 rating system is used to assign an overall rating to reinforced concrete structures based on the overall ratings. In general, this methodology offers a way that is both organised and objective to evaluate the deteriorating condition of ORCBs. As a result, it enables informed decision-making in the process of planning maintenance.
Uncertainty Quantification of Existing Bridge using Polynomial Chaos Expansion
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Křížek, Michael; Novák, Lukáš
This paper is focused on uncertainty quan- tification (UQ) of an existing bridge structure repre- sented by non-linear finite element model (NLFEM). The 3D model was created according to the original drawings and recent inspections of the bridge. In order to reflect the realistic mechanical behavior, the mathe- matical model is based on non-linear fracture mechan- ics and the calculation consists of the three construction stages. The single calculation of the NLFEM is very costly and thus even the elementary task of stochastic analysis – the propagation of uncertainties through a mathematical model – is not feasible by Monte Carlo- type approach. Thus, UQ is performed via efficient surrogate modeling technique – Polynomial Chaos Ex- pansion (PCE). PCE is a well-known technique for approximation of the costly mathematical models with random inputs, reflecting their distributions and offer- ing fast and accurate post-processing including statis- tical and sensitivity analysis. Once the PCE was con- structed, it was possible to analyze all quantities of in- terest (QoIs) and analytically estimate Sobol indices as well as the first four statistical moments. Sobol indices directly measure the influence of the input variability to a variability of QoIs. Statistical moments were used for reconstruction of the probability distributions of QoIs, which will be further used for semi-probabilistic assess- ment. Moreover, once the PCE is available it could be possible to use it for further standard probabilistic or reliability analysis as a computationally efficient ap- proximation of the original mathematical model.
Fragility Analysis of the Reactor Steel Shaft Door Due to Accidental Extreme Overpressure
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Králik, Juraj; Bočkaj, Jozef
This paper describes the probabilistic nonlinear analysis of the hermetic steel door of the reactor shaft failure due to extreme pressure and temperature. The probabilistic assessment of NPP structures for Probabilistic Safety Analysis (PSA2) level 2 of VVER 440/213 in the case of the technology accidents is presented. The scenario of the hard accident in nuclear power plant (NPP) and the methodology of the calculation of the fragility curve of the failure overpressure using the probabilistic safety assessment PSA 2 level is presented. The nonlinear deterministic and probabilistic analysis based on the response surface method (RSM) were considered.
The Influence Of Different Notches On Fatigue Lifetime Of Round Bar Specimens Made Of HDPE
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Kozáková, Kamila; Trávníček, Lukáš; Klusák, Jan; Poduška, Jan; Hutař, Pavel
The presented paper introduces an approach for fatigue lifetime predictions of notched round bar specimens made of HDPE. This approach uses axial stress distribution calculated from finite element anal- ysis and experimental fatigue data. The fatigue results obtained experimentally on the round bar specimens with “v” notch with radius R = 0.4 mm and extremely sharp notch are used for a determination of averaging distance. The averaging distance is applied to speci- men with different notch radius for determination of its fatigue lifetime. The fatigue lifetime prediction of a specimen with notch radius R = 0.1 mm is performed. These fatigue lifetime predictions are compared to ex- perimental fatigue data.
Design Aspects of an Energy Piles
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Mohyla, Marek; Hrubešová, Eva; Mäkiranta, Anne
The paper deals with the issue of thermomechanical loading of the energy pile, which is also subjected to thermal stresses compared to a conventional pile, which is required to carry only static loads. In the context of the thermal volumetric changes of the energy pile, the stiffness of an upper structure, and a behaviour of the contact between the pile and the soil environment, we are presented with a problem that goes beyond standard design procedures. The issue is presented by a parametric study that evaluates the thermal load, the stiffness of the upper structure preventing thermal volumetric changes of the pile, but also the pile soil contact properties that have a major influence on the pile-soil friction and therefore the pile bearing capacity. The study was carried out using the Thermo-Pile software developed by the Soil Mechanics Laboratory of the University of Lausanne. This paper gives an overview of the differences in the design of energy piles and highlights the potential risks in their design.
Semi and Fully-probabilistic Nonlinear Analyses of Post-tensioned Concrete Bridge Made of KT-24 Girders
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Šplíchal, Bohumil; Lehký, David; Doležel, Jiří
This paper deals with the assessment of the design resistance of an existing railway bridge made of KT-24 precast post-tensioned concrete girders. The load-bearing capacity of the structure is determined us- ing probabilistic nonlinear analysis by the finite element method. Load-bearing capacity is determined for the ultimate and serviceability limit states. A fully proba- bilistic approach is compared to selected recommended semi-probabilistic methods, which can greatly reduce the number of nonlinear calculations needed to estimate the design value of resistance. Two stochastic mod- els are compared, reflecting the level of knowledge of actual material properties from the diagnostic survey. The results are compared and discussed with respect to accuracy and required computational time, which is a critical issue when performing a global nonlinear anal- ysis of a complex structure.
Experimental Temperature Monitoring in Mock-up of the Mass Concrete Foundation
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Ho, Nguyen-Trong; Tran, Mien Van; Čajka, Radim
This paper presents an experimental result to monitor temperature in mass concrete foundation slab through mock-up specimen in coordinate with various conditions of some suppliers. This result enables to control maximum temperature in mass concrete foundation along with measuring temperature difference in real construction. In addition, decreasing the thermal stress in concrete by use of cooling pipe system with the water volumes for each water temperature and cracking prediction due to thermal gradient in foundation concrete will be considered in further research. This result contributes to prove the relationship between external condition and inside temperature of mass concrete foundation.
On Development of Numerical Resistance Models of Thin-web Steel Girders
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Nadolski, Vitali; Marková, Jana; Podymako, Vladislav; Sýkora, Miroslav
Thin-web steel girders are attractive to be used because of their efficiency in bending. For such girders, the issue of ensuring local buckling becomes very relevant. Calculation formulas in most cases are complex and have a limited scope of application. The calculations based on numerical models make it possible to consider all the specifics of the designed element more universally. The article deals with the calculation of the buckling of the web girder under the combination of patch and shear loading by finite element modelling. Numerical models have been created, and a comparative analysis with experimental results has been carried out. The presented principles for constructing FE models (mesh size, material model, etc.) are recommended to follow when analysing the resistance and behaviour of beams with a thin web. Sensitivity analysis of the FE model with respect to the input parameters revealed the most important parameters (yield strength of steel, web thickness, geometry), the uncertainty of which needs to be taken into account when creating FE models. The convergence of the results supports the use of the finite element method in the design of steel beams for a qualitative and quantitative assessment of resistance. However, further development of unified principles for creating FE models and their verification on a larger amount of experimental data is required, as well as the determination of partial factors considering the variability and uncertainties in the obtained results and specified reliability level.
Real Possibilities of Numerical Modelling of Vehicle Responses
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Lajčáková, Gabriela; Melcer, Jozef
The presented article is devoted to the assessment of real possibilities of numerical modelling of interaction phenomena in the vehicle - road system. It analyses the observed phenomena in the time and frequency domain. Describes the possibilities of numerical modelling of road irregularities as a source of vehicle kinematic excitation. It presents a computational model of the vehicle and a method of numerical solution of its response. Describes the performed experiment and the used measuring technique. Numerically obtained results are evaluated based on the results of the in situ experiment. Makes conclusions for applications in engineering practice.
FEM Matrices for Problems of Free Vibrations and Buckling of a Truncated Cone Beam
(Vysoká škola báňská - Technická univerzita Ostrava, 2023) Chalecki, Marek
Proper use of materials is one of the most important criteria of a rational design and shaping of engineering constructions. It requires such dimensioning of each element of the construction which will ensure that the element is matched to its load – and this condition is fulfilled only for beams with variable cross section. Hence, it is essential to develop possibilities of calculations of beams with cross section varying along the beam longitudinal axis. This study provides relevant matrices (i.e. stiffness, mass and initial stress matrix) applied in the Finite Element Method for calculations of natural frequencies and buckling critical forces. The matrices have been derived for beams shaped as a truncated cone with a linear generatrix, supported in various ways. The results have been compared to those obtained for the stair-shaped beams approximating the conical ones; a good concordance of results has been stated.

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