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A system approach to medieval ruins management
Novotný, Jakub; Bláha, Jiří
2019 - English
The aim of this paper is to briefly discuss the complexity of monument care and the young heritage science disciplines on the example of historical ruins management. There is an empirical reflection on problems connected with historical ruins management presented as an introduction. The following part then presents a possible methodological interconnection of a systems approach and cultural heritage management. The next part of the paper first introduces the RUINS project in general and then one of its methodological outputs—rules and model forms for ruins. Based on practical experience, the paper concludes that the more general methodological basis and foundation of cultural heritage sites management may be general systems theory and a systems approach.
Keywords:
historical ruins; heritage science; systems approach; RUINS project
Fulltext is available at external website.
A system approach to medieval ruins management
The aim of this paper is to briefly discuss the complexity of monument care and the young heritage science disciplines on the example of historical ruins management. There is an empirical reflection ...
Možnosti využití 4D výpočetní tomografie v lomových testech
Kumpová, Ivana; Fíla, Tomáš; Koudelka, Petr; Rozsypalová, I.; Keršner, Z.; Kytýř, Daniel; Vopálenský, Michal; Vavřík, Daniel; Vyhlídal, M.; Drdácký, Miloš
2019 - Czech
Příspěvek prezentuje studium vnitřní struktury a lomových vlastností vybraných kvazikřehkých stavebních materiálů vystavených teplotním změnám a možnosti uplatnění metody kombinující ohybové lomové testy a časově závislou výpočetní tomografii (4D CT). Zkušební tělesa byla podrobena účinkům vysokých teplot a následně testována čtyřbodovým ohybem během 4D CT. Byly tak získány 3D obrazové informace v různých fázích zatížení a porušování materiálu. Rovněž bylo provedeno komparativní měření pevnosti v tlaku. Tyto výsledky jsou v dobré shodě. The paper presents the study of the internal structure and fracture properties of selected quasi-brittle building materials subjected to temperature changes and the possibility of applying the method combining bending fracture tests and time-dependent computed tomography (4D CT). The tested specimens were subjected to hightemperature effects and subsequently tested by a four-point bending during 4D CT. Thus, 3D image information was obtained in different phases of loading and material damage. Comparative compression strength measurements were also performed. These results are in good agreement
Keywords:
fracture process zone; spatial crack distribution; quasi-brittle material; X-Ray computed tomography; four-point bending test
Fulltext is available at external website.
Možnosti využití 4D výpočetní tomografie v lomových testech
Příspěvek prezentuje studium vnitřní struktury a lomových vlastností vybraných kvazikřehkých stavebních materiálů vystavených teplotním změnám a možnosti uplatnění metody kombinující ohybové lomové ...
Proposal for loading tests of bridges - simulation and laboratory experiments
Bayer, Jan; Urushadze, Shota; Černý, Miloš
2018 - English
A new dynamic load testing of bridges is proposed and theoretically investigated. A transient analysis of passing vehicle over a bridge in ANSYS and an analytical program in MATLAB for the transient solution of piecewise linear mechanical structures were developed to assess the effects of the proposed dynamic load on a bridge model. According to the first laboratory experiments, it seems that the proposed travelling impulse load could surpass some of the shortcomings and limitations of the currently applied methods of bridge testing. The investigation is a part of a project aimed at drive-by identification of dynamic properties of bridges and further experimental and analytical research will follow.
Keywords:
dynamic loading tests; transient analysis; vibrations; vehicle-bridge interaction
Fulltext is available at external website.
Proposal for loading tests of bridges - simulation and laboratory experiments
A new dynamic load testing of bridges is proposed and theoretically investigated. A transient analysis of passing vehicle over a bridge in ANSYS and an analytical program in MATLAB for the transient ...
Forced movement of a ball in spherical cavity under kinematic excitation
Náprstek, Jiří; Fischer, Cyril
2018 - English
In the paper the response of a heavy ball rolling inside a semi-spherical cavity under horizontal kinematic excitation is investigated. The system with six degrees of freedom with three non-holonomic constraints is considered. The contact between the ball and the cavity surface is supposed to be perfect without any sliding. The mathematical model using the Appel-Gibbs function of acceleration energy is developed and discussed. The most important post-critical regimes are outlined and qualitatively evaluated on the frequency axis. Numerical experiments have been performed when excitation frequency is slowly swept up and down. Results obtained by means of semi-analytical investigation and numerical simulation are evaluated and physically interpreted. Some applications in civil engineering as a tuned mass damper used on slender structures is outlined. Strengths and weaknesses of solution method are evaluated.
Keywords:
nonlinear dynamics; non-holonomic systems; Appell-Gibbs formulation; singular states; tuned mass damper
Fulltext is available at external website.
Forced movement of a ball in spherical cavity under kinematic excitation
In the paper the response of a heavy ball rolling inside a semi-spherical cavity under horizontal kinematic excitation is investigated. The system with six degrees of freedom with three non-holonomic ...
Accuracy and numerical efficiency of approximate method for complex eigensolution of structure with specialized damping device
Hračov, Stanislav
2018 - English
The paper provides a detailed parametric analysis of the recently proposed approximate method for complex eigensolution of non-classically damped structures. This method is based on a combination of perturbation and incremental approaches and is applicable to the classically damped structures equipped with a specialized passive damping device. The numerical efficiency in terms of the required calculation times and the accuracy is demonstrated on a model of an existing structure for various combination of computational parameters. Wide numerical simulations revealed the selection of real eigenmodes of undamped system used in the approximate eigensolution as the most important parameter affecting the final accuracy.
Keywords:
non-classical damping; complex eigensolution; perturbation method; passive damper
Fulltext is available at external website.
Accuracy and numerical efficiency of approximate method for complex eigensolution of structure with specialized damping device
The paper provides a detailed parametric analysis of the recently proposed approximate method for complex eigensolution of non-classically damped structures. This method is based on a combination of ...
Crystallization force of sodium chloride
Koudelková, Veronika; Wolf, Benjamin
2018 - English
Soluble salts are one of the most deteriorating factor causing damage of historical building materials due to generation of crystallization pressure inside pore space. Direct measurement of crystallization force is quite challenging, hence we developed at our institute a novel device able to detect the force of growing crystal. The device is based on the monitoring of force developed with upper microscopic glass on the growing crystal to maintain constant position. The crystal could generate force because of the existence of thin liquid layer of solution between both surfaces come into contact. The driving force for the subsequent growth of crystal against obstacle is supersaturation, which is mainly induced by evaporation of the salt solution. In this experiment, the crystal of sodium chloride generated force 16.8 mN and the corresponding crystallization pressure was equal to the value 0.48 MPa.
Keywords:
crystallization force; sodium chloride; salt deterioration
Fulltext is available at external website.
Crystallization force of sodium chloride
Soluble salts are one of the most deteriorating factor causing damage of historical building materials due to generation of crystallization pressure inside pore space. Direct measurement of ...
Analysis of Baroque sculpture based on X-ray fluorescence imaging and X-ray\ncomputed tomography data fusion
Vavřík, Daniel; Kumpová, Ivana; Vopálenský, Michal; Lauterkranc, J.
2017 - English
It is advantageous to combine information about geometry and the inner structure of historical artifacts with information about the elemental composition of decorative layers, typically covering historical wooden sculptures. X-ray computed tomography describing artifact structure is quite common and easy. Standard X-ray fluorescence (XRF) analysis of decorative layers is typically done for several selected spots of the artifact’s surface utilizing single pad detector. XRF imaging fully describing the surface’s elemental composition is commonly done for flat objects, while time consuming XRF tomography is applied to relatively small objects. It will be shown in this work that an effective fusion combination of XRF imaging and X-ray tomography describing the whole object can be realized even when using a limited number of XRF images.
Keywords:
X-ray computed tomography; X-ray flourescence imaging; cultural heritage; data fusion
Fulltext is available at external website.
Analysis of Baroque sculpture based on X-ray fluorescence imaging and X-ray\ncomputed tomography data fusion
It is advantageous to combine information about geometry and the inner structure of historical artifacts with information about the elemental composition of decorative layers, typically covering ...
Three-dimensional characterization of polymer foams using X-ray dark-field imaging
Senck, S.; Plank, B.; Gusenbauer, C.; Salaberger, D.; Vavřík, Daniel; Santer, W.; Kastner, J.
2017 - English
Due to the low cost, the ease of processing, and excellent material properties, polymer foams are used in various applications, e.g. packaging, building and construction, furnitures and bedding, and the automotive and aerospace sector. The mechanical response of polymer foams is primarily influenced by density and morphology. While foam density can be determined with high precision, cell morphology is more difficult to determine since the size distribution of foam cells differs in three dimensions. However, using conventional methods, e.g. optical light microscopy or scanning electron microscopy, it is very difficult to obtain three-dimensional information and to differentiate between the strut system and cell walls. An alternative for the three-dimensional characterization of foam morphology is micro-computed tomography (XCT). But even non-destructive techniques like XCT are not able to characterize anisotropic foams if the thickness of single struts and cell walls is below the physcial resolution of the respective XCT system. In this contribution we therefore investigate different polymeric foam samples using a Talbot-Lau grating interferometer XCT (TLGI-XCT) system. We show that the obtained darkfield contrast images show a high contrast and a strong signal at struts and cell walls, facilitating the segmentation of foam cells in various examples.
Keywords:
foam; micro-computed tomography; Talbot-Lau grating interferometer XCT; dark-field imaging
Fulltext is available at external website.
Three-dimensional characterization of polymer foams using X-ray dark-field imaging
Due to the low cost, the ease of processing, and excellent material properties, polymer foams are used in various applications, e.g. packaging, building and construction, furnitures and bedding, and ...
Analytical approach of slender structure vibration due to random component of the wind velocity
Náprstek, Jiří; Hračov, Stanislav
2017 - English
Along wind random vibration of slender structures represents one of the most important aeroelastic effects resulting from wind - structure interaction. The theoretical model being based on one-dimensional elements with continuously distributed mass and stiffness has been introduced in this paper. The system has been considered to be linear self-adjoint with strongly non-proportional linear damping due to both material of the structure and presence of vibration dampers. The additive random excitation continuously distributed in time and space is Gaussian, therefore the response is Gaussian as well. Consequently, mathematical mean value and correlation function are satisfactory for the full description of the generalized solution of the respective PDE in the stochastic meaning. The general results have been obtained mostly in the form of analytical formulae for important cases of input spectral densities. A numerical example dealing with real structure is presented.
Keywords:
random vibrations; slender structures; wind load; non-proportional damping; distributed-parameter systems
Fulltext is available at external website.
Analytical approach of slender structure vibration due to random component of the wind velocity
Along wind random vibration of slender structures represents one of the most important aeroelastic effects resulting from wind - structure interaction. The theoretical model being based on ...
Optimization of acquisition parameters in radiography and tomography
Vopálenský, Michal; Vavřík, Daniel; Kumpová, Ivana
2017 - English
Contrast in radiographic images is one of the most important parameters both in radiography and tomography. This paper investigates the possibility of adjusting the radiographic parameters, in particular the accelerating voltage of the X-ray tube, in order to maximize the difference in the detected intensity in response to the change in the thickness of the investigated object. Simplified model is used that allows finding the optimal operating point for the given material and thickness without an apriory knowledge about the X-ray spectra, detector response and the material composition. It is shown that in case of small changes of thickness, the optimum is met when the detected intensity behind the object of certain thickness is at approx. 37 % of the full range (i.e., of the value that would be measured under the same conditions in the absence of the object). In spite of simplifications made, the theoretical model shows a very good correspondence with the experimental data. A brief consideration is made on the case of a general difference in thicknesses.
Keywords:
X-ray computed tomography; X-ray radiography; X-ray optimization; image processing; contrast
Fulltext is available at external website.
Optimization of acquisition parameters in radiography and tomography
Contrast in radiographic images is one of the most important parameters both in radiography and tomography. This paper investigates the possibility of adjusting the radiographic parameters, in ...
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