Pub Date : 2023-09-27DOI: 10.14311/app.2023.41.0058
Martin Rak, Tereza Tmejová, Tomáš Bilík, David Jelínek, Albert Bradáč
This article focuses on the issue of portable traffic signs and their visibility using different light sources such as halogen, Xenon, or LED. The measured values of luminance and retroreflection for each object are used to distinguish the individual results. The results show the differences between the various light sources on the visibility of the measured objects. Furthermore, from these results it is possible to evaluate portable traffic signs regarding degradation due to mechanical wear or aging.
{"title":"The influence of modern headlamps on the recognition of portable traffic signs and warning triangles","authors":"Martin Rak, Tereza Tmejová, Tomáš Bilík, David Jelínek, Albert Bradáč","doi":"10.14311/app.2023.41.0058","DOIUrl":"https://doi.org/10.14311/app.2023.41.0058","url":null,"abstract":"This article focuses on the issue of portable traffic signs and their visibility using different light sources such as halogen, Xenon, or LED. The measured values of luminance and retroreflection for each object are used to distinguish the individual results. The results show the differences between the various light sources on the visibility of the measured objects. Furthermore, from these results it is possible to evaluate portable traffic signs regarding degradation due to mechanical wear or aging.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135587296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-27DOI: 10.14311/app.2023.41.0028
Kristýna Navrátilová, David Lehet, Eva Hajčiarová
The paper deals with the possibilities of implementing dynamic tariff regulation of on-street parking spaces in the capital city of Prague. Achieving optimal results is conditioned by the implementation of advanced technologies, but at the same time, the dynamic tariff regulation must follow the applicable legislation and, above all, be accepted by drivers. For this reason, the paper briefly discusses the technical and legislative possibilities of implementation, and most attention is paid to the conducted survey of user needs. The survey investigates the impact of parking prices on drivers’ motivation to park their vehicles in the area.
{"title":"Survey of user needs and the impact of parking prices on drivers’ motivation to use parking spaces in the capital city of Prague","authors":"Kristýna Navrátilová, David Lehet, Eva Hajčiarová","doi":"10.14311/app.2023.41.0028","DOIUrl":"https://doi.org/10.14311/app.2023.41.0028","url":null,"abstract":"The paper deals with the possibilities of implementing dynamic tariff regulation of on-street parking spaces in the capital city of Prague. Achieving optimal results is conditioned by the implementation of advanced technologies, but at the same time, the dynamic tariff regulation must follow the applicable legislation and, above all, be accepted by drivers. For this reason, the paper briefly discusses the technical and legislative possibilities of implementation, and most attention is paid to the conducted survey of user needs. The survey investigates the impact of parking prices on drivers’ motivation to park their vehicles in the area.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135587303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0088
H. Sekavová, Z. Prošek, P. Tesárek
One of the ways to use the treated gypsum waste is in gypsum mixtures for the production of gypsum blocks. Gypsum blocks can be used in standard interior as well as exterior applications and are made of gypsum, water, PP microfibres and are lightened with foam, which is created from a foaming additive and water. Above all, the amount of foam significantly influences the bulk density of the resulting material, and the bulk density then has a major influence on the mechanical and thermal properties. The use of PP microfibres had a positive effect on the overall stability of the foamed structure, which resulted in an increase in compressive strength while maintaining good thermal insulation properties.
{"title":"Dependence of mechanical and thermal properties on the composition of lightweight gypsum composites","authors":"H. Sekavová, Z. Prošek, P. Tesárek","doi":"10.14311/app.2023.40.0088","DOIUrl":"https://doi.org/10.14311/app.2023.40.0088","url":null,"abstract":"One of the ways to use the treated gypsum waste is in gypsum mixtures for the production of gypsum blocks. Gypsum blocks can be used in standard interior as well as exterior applications and are made of gypsum, water, PP microfibres and are lightened with foam, which is created from a foaming additive and water. Above all, the amount of foam significantly influences the bulk density of the resulting material, and the bulk density then has a major influence on the mechanical and thermal properties. The use of PP microfibres had a positive effect on the overall stability of the foamed structure, which resulted in an increase in compressive strength while maintaining good thermal insulation properties.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"2006 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72660691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0061
Martin Lebeda, P. Kabele
Simulations of tunnel excavations have to take into account the natural occurrence of joints and faults in the surrounding rock mass, which dominantly control its mechanical response. In this paper, we present work in progress toward 3D finite element analysis of excavation using equivalent rock-mass properties derived from stochastically generated discrete fracture networks (DFNs). The equivalent stiffness is determined by volume averaging. Presently, we solve the problem linearly for an incremental change of the stress state. The fracture’s stiffness is assumed to depend on the initial normal stress acting in direction normal to it. However, within the solved incremental step, we assume the fracture’s stiffness to be constant. This assumption is acceptable for small stress changes. Since the fractures represented in the DFN model have preferred directions, the equivalent stiffness is anisotropic.
{"title":"Analysis of tunnel excavation based on linear DFN-FEM modelling","authors":"Martin Lebeda, P. Kabele","doi":"10.14311/app.2023.40.0061","DOIUrl":"https://doi.org/10.14311/app.2023.40.0061","url":null,"abstract":"Simulations of tunnel excavations have to take into account the natural occurrence of joints and faults in the surrounding rock mass, which dominantly control its mechanical response. In this paper, we present work in progress toward 3D finite element analysis of excavation using equivalent rock-mass properties derived from stochastically generated discrete fracture networks (DFNs). The equivalent stiffness is determined by volume averaging. Presently, we solve the problem linearly for an incremental change of the stress state. The fracture’s stiffness is assumed to depend on the initial normal stress acting in direction normal to it. However, within the solved incremental step, we assume the fracture’s stiffness to be constant. This assumption is acceptable for small stress changes. Since the fractures represented in the DFN model have preferred directions, the equivalent stiffness is anisotropic.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86004495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0008
Miroslav Čáp, M. Polak, T. Plachý, M. Talich, Jan Havrlant, Lubomír Soukup, F. Antoš
Recent advances in radar systems have led to the development of radar interferometry (RI) methods for contactless vibration monitoring of large-scale structures, i.e. bridges, water tower reservoirs, and factory chimneys. Interferometric radars are devices capable to measure with 200 Hz sampling frequency and relative movement precision of 0.1 mm up to 0.01 mm. The major part of this paper describes an in-situ footbridge experiment near Hradec Králové. Radar interferometry devices were deployed along with ordinary techniques compounded by accelerometers, wiring, and acquisition station. Experiment was focused on the evaluation of basic dynamic structural properties such as natural frequencies and mode shapes. A lot of attention was also given to the result comparison of these measurement methods. Test results have confirmed the applicability of RI for bridge vibration monitoring.
{"title":"The footbridge Jesípek – application of radar interferometry for dynamic response evaluation","authors":"Miroslav Čáp, M. Polak, T. Plachý, M. Talich, Jan Havrlant, Lubomír Soukup, F. Antoš","doi":"10.14311/app.2023.40.0008","DOIUrl":"https://doi.org/10.14311/app.2023.40.0008","url":null,"abstract":"Recent advances in radar systems have led to the development of radar interferometry (RI) methods for contactless vibration monitoring of large-scale structures, i.e. bridges, water tower reservoirs, and factory chimneys. Interferometric radars are devices capable to measure with 200 Hz sampling frequency and relative movement precision of 0.1 mm up to 0.01 mm. The major part of this paper describes an in-situ footbridge experiment near Hradec Králové. Radar interferometry devices were deployed along with ordinary techniques compounded by accelerometers, wiring, and acquisition station. Experiment was focused on the evaluation of basic dynamic structural properties such as natural frequencies and mode shapes. A lot of attention was also given to the result comparison of these measurement methods. Test results have confirmed the applicability of RI for bridge vibration monitoring.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"112 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87669751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0039
Petra Kálalová, M. Polak, V. Stančík
Experimental analyses of civil engineering structures have been carried out for decades. While in the past, mainly static load tests of new structures were performed, a few severe accidents with fatal results caused a lot of emphasis to be given to monitoring existing structures recently. The need for continuous or periodical evaluation of static or dynamic behaviour of structures in operation led to a good progress in the development of modern methods for experimental analysis. The paper deals with one of the modern methods of experimental analysis – the DIC method. Possible application of the DIC method was verified by an experimental analysis of a railway truss bridge in Rataje nad Sázavou. The experiment was divided into two stages. During the experiment, deflections of the bridge measured by LVDT sensors and the DIC method were compared. Technological problems of the DIC method were found in the first stage. One of the problems was related to stability of the camera tripod. A solution was proposed and verified during the second stage.
土木工程结构的试验分析已经进行了几十年。过去主要是对新建结构进行静载试验，但近年来由于发生了一些严重的致命事故，人们开始重视对既有结构的监测。对运行中的结构的静力或动力特性进行连续或定期评估的需要，使现代实验分析方法的发展取得了良好的进展。本文介绍了一种现代实验分析方法——DIC法。通过对raaje nad Sázavou铁路桁架桥的试验分析，验证了DIC方法的可能应用。实验分为两个阶段。在实验中，比较了LVDT传感器测量的桥体挠度和DIC法测量的桥体挠度。在第一阶段发现了DIC方法存在的技术问题。其中一个问题与相机三脚架的稳定性有关。在第二阶段提出了解决方案并进行了验证。
{"title":"Experimental analysis of the railway truss bridge using modern methods","authors":"Petra Kálalová, M. Polak, V. Stančík","doi":"10.14311/app.2023.40.0039","DOIUrl":"https://doi.org/10.14311/app.2023.40.0039","url":null,"abstract":"Experimental analyses of civil engineering structures have been carried out for decades. While in the past, mainly static load tests of new structures were performed, a few severe accidents with fatal results caused a lot of emphasis to be given to monitoring existing structures recently. The need for continuous or periodical evaluation of static or dynamic behaviour of structures in operation led to a good progress in the development of modern methods for experimental analysis. The paper deals with one of the modern methods of experimental analysis – the DIC method. Possible application of the DIC method was verified by an experimental analysis of a railway truss bridge in Rataje nad Sázavou. The experiment was divided into two stages. During the experiment, deflections of the bridge measured by LVDT sensors and the DIC method were compared. Technological problems of the DIC method were found in the first stage. One of the problems was related to stability of the camera tripod. A solution was proposed and verified during the second stage.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89427534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0015
J. Chalupová, J. Němeček, V. Hybášek, V. Pommer, J. Němeček
Porosity is an important part of cement paste microstructure, which significantly influences the mechanical properties (especially durability and strength) of cement-based materials. Electrochemical impedance spectroscopy (EIS) is a non-destructive method used to measure the pore system utilizing a range of frequencies of electric current, which is fed to the cement paste by stainless steel electrodes. The pore volume is obtained from the pore resistance and the matrix capacitance measured by EIS. This paper deals with the evaluation of porosity based on resistance values from EIS on a sample of pure CEM I 42.5R Portland cement paste at 3 different hydration times (age 7, 14, 28 days).
孔隙率是水泥浆体微观结构的重要组成部分，对水泥基材料的力学性能(尤其是耐久性和强度)有重要影响。电化学阻抗谱(EIS)是一种非破坏性的方法，它利用一系列频率的电流来测量孔隙系统，这些电流由不锈钢电极馈送到水泥浆体中。孔隙体积由EIS测量的孔隙电阻和基质电容得到。本文基于EIS对纯CEM I 42.5R波特兰水泥浆样在3个不同水化时间(龄期7、14、28天)的阻力值进行孔隙度评估。
{"title":"Measurement and evaluation of cement paste porosity by electrochemical impedance spectroscopy","authors":"J. Chalupová, J. Němeček, V. Hybášek, V. Pommer, J. Němeček","doi":"10.14311/app.2023.40.0015","DOIUrl":"https://doi.org/10.14311/app.2023.40.0015","url":null,"abstract":"Porosity is an important part of cement paste microstructure, which significantly influences the mechanical properties (especially durability and strength) of cement-based materials. Electrochemical impedance spectroscopy (EIS) is a non-destructive method used to measure the pore system utilizing a range of frequencies of electric current, which is fed to the cement paste by stainless steel electrodes. The pore volume is obtained from the pore resistance and the matrix capacitance measured by EIS. This paper deals with the evaluation of porosity based on resistance values from EIS on a sample of pure CEM I 42.5R Portland cement paste at 3 different hydration times (age 7, 14, 28 days).","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91011924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0083
L. Řehounek, A. Jíra
Two variants of implant-supported overdentures (IODs) were investigated by quantitative computed tomography-assisted finite element method (QCT-FEA) on a patient-specific CTreconstructed model of human maxilla. The analyzed variants are bar-supported (splinted) and unsupported (unsplinted) implant assemblies. The loading was done by a 800 N force slanted by 30° in the buccolingual direction. The results of the analyses show favorable stress distributions for the bar-supported variant.
{"title":"Bar-supported and unsupported dental implants: a QCT-FEA study in human maxilla","authors":"L. Řehounek, A. Jíra","doi":"10.14311/app.2023.40.0083","DOIUrl":"https://doi.org/10.14311/app.2023.40.0083","url":null,"abstract":"Two variants of implant-supported overdentures (IODs) were investigated by quantitative computed tomography-assisted finite element method (QCT-FEA) on a patient-specific CTreconstructed model of human maxilla. The analyzed variants are bar-supported (splinted) and unsupported (unsplinted) implant assemblies. The loading was done by a 800 N force slanted by 30° in the buccolingual direction. The results of the analyses show favorable stress distributions for the bar-supported variant.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"103 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77226457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0098
Klára Vašířová, J. Fládr
The aim of the research is to verify the effect of lithium water glass on the durability and reduction of concrete absorption. For this purpose, the absorption test was made and the influence of the impregnation agent on durability when the test specimens are exposed to cyclic freezing and thawing was verified. Finally, the permeability of the test specimens was measured before and after impregnation. On the basis of the tests carried out, the effect of the impregnation agent was determined by comparing impregnated test specimens with reference specimens.
{"title":"The influence of lithium water glass on the durability of concrete","authors":"Klára Vašířová, J. Fládr","doi":"10.14311/app.2023.40.0098","DOIUrl":"https://doi.org/10.14311/app.2023.40.0098","url":null,"abstract":"The aim of the research is to verify the effect of lithium water glass on the durability and reduction of concrete absorption. For this purpose, the absorption test was made and the influence of the impregnation agent on durability when the test specimens are exposed to cyclic freezing and thawing was verified. Finally, the permeability of the test specimens was measured before and after impregnation. On the basis of the tests carried out, the effect of the impregnation agent was determined by comparing impregnated test specimens with reference specimens.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"86 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85840969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.14311/app.2023.40.0076
Veronika Pavelcová, T. Janda
This paper is concerned with the process of determining the material parameters of advanced constitutive models for clays. Provided results are applicable already in the early stages of geotechnical survey when no detailed data from laboratory tests of soils expected at construction site are known. A worldwide database of laboratory tests obtained during four year operation of web calibration application ExCalibre was used for this purpose. This application allows automatic calibration of three advanced constitutive soil models based on detailed data from triaxial and edometric tests. The paper describes the process of determining the confidence intervals of each material parameter of modified Cam-clay and hypoplastic clay models for low (CL) and high (CH) plasticity clay according to unified soil classification system (USCS) and tabulates their typical ranges. The purpose of presented work was to contribute to the use of advanced constitutive models among practical engineers.
{"title":"Extracting general knowledge of model parameters for clays out of numerous laboratory tests","authors":"Veronika Pavelcová, T. Janda","doi":"10.14311/app.2023.40.0076","DOIUrl":"https://doi.org/10.14311/app.2023.40.0076","url":null,"abstract":"This paper is concerned with the process of determining the material parameters of advanced constitutive models for clays. Provided results are applicable already in the early stages of geotechnical survey when no detailed data from laboratory tests of soils expected at construction site are known. A worldwide database of laboratory tests obtained during four year operation of web calibration application ExCalibre was used for this purpose. This application allows automatic calibration of three advanced constitutive soil models based on detailed data from triaxial and edometric tests. The paper describes the process of determining the confidence intervals of each material parameter of modified Cam-clay and hypoplastic clay models for low (CL) and high (CH) plasticity clay according to unified soil classification system (USCS) and tabulates their typical ranges. The purpose of presented work was to contribute to the use of advanced constitutive models among practical engineers.","PeriodicalId":7150,"journal":{"name":"Acta Polytechnica CTU Proceedings","volume":"222 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76730213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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