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Creep of oak dowel: various loading and environmental conditions
Hasníková, Hana; Kunecký, Jiří; Hataj, M.
2022 - English
For research of timber joints, the crucial role in force distribution inside the joint is played by distribution and variability of stiffness of the dowels. Not only the instant stiffness, but the one that we can encounter after some longer period. Also, this value and its statistical distribution is influenced by many other factors, however, humidity and temperature are in timber (oak) dowels of utmost importance. In the work results of a creep experiment made using a special testing rig is presented. It has been found, that biggest changes in creep behavior are in case if very humid conditions are present, and, also, that cycling the temperature in high humidity conditions can produce about 104% of the original instantaneous displacement. The result is not surprising, however, new insights are made thanks to relatively high number of samples and ability to produce some statistics. Another outcome is relation of dowel stiffness in time to the level of applied stress, which is quantified in the article.
Keywords:
oak dowel; creep; humidity
Available at various institutes of the ASCR
Creep of oak dowel: various loading and environmental conditions
For research of timber joints, the crucial role in force distribution inside the joint is played by distribution and variability of stiffness of the dowels. Not only the instant stiffness, but the one ...
Chemical and microstructural analysis of plaster samples from the Mayrau mine, Kladno – Vinařice
Slížková, Zuzana; Frankeová, Dita; Vondráčková, Michaela; Bauerová, Pavla; Náhunková, Pavla
2022 - Czech
An analysis of historical plasters was carried out using thermal analysis and SEM-EDS analysis. The binders and aggregates of mortars and their surface treatments were characterized. The survey results were used for the design of the repair mortars. V rámci stavebně-technického průzkumu byl proveden rozbor vzorků historických omítek s využitím termické analýzy a SEM‐EDS analýzy. Byla provedena charakterizace plniva a složek pojiva malt a jejich povrchových úprav. Výsledky průzkumných prací byly použity jako podklad pro návrh rekonstrukce objektu.
Keywords:
TGA; SEM/EDS; binder characterization
Available at various institutes of the ASCR
Chemical and microstructural analysis of plaster samples from the Mayrau mine, Kladno – Vinařice
An analysis of historical plasters was carried out using thermal analysis and SEM-EDS analysis. The binders and aggregates of mortars and their surface treatments were characterized. The survey ...
Proceedings of the SHATIS 2022 – 6th International conference on structural health assessment of timber structures
Kunecký, Jiří; Hasníková, Hana
2022 - English
Structural health assessment of timber structures associates various procedures in order to evaluate the safety and serviceability of structures. Also, it helps to assure or extend the predicted service life of structures. Service life sustainability can be promoted by the incorporation of monitoring systems or by providing tools and methods that deliver accurate reports about the structural condition. Conservation and assessment of timber structures is based on a multidisciplinary approach. The conference topics cover the wide spectrum, from wood properties, through performance of joints and timber design, to modern monitoring and digital technologies. As the topics include both existing and historical timber structures, the need for reliable non destructive testing methods is part of the approach as well.
Keywords:
timber structures; monitoring and survey; design
Available at various institutes of the ASCR
Proceedings of the SHATIS 2022 – 6th International conference on structural health assessment of timber structures
Structural health assessment of timber structures associates various procedures in order to evaluate the safety and serviceability of structures. Also, it helps to assure or extend the predicted ...
Charpy tests of load measuring pins from ČSN 19 312 material
Šperl, Martin; Gajdoš, Lubomír; Bejdl, Jan
2022 - Czech
Charpy tests of load measuring pins from ČSN 19312 steel were carried out at the temperature 20 °C, 0 °C, -20 °C, and\n-40 °C with the aim to verify that Charpy notch toughness of the pins keeps its average magnitude even at -40 °C. The results showed that the steel did not exhibit a typical S-type transit curve in the temperature range 20 °C ÷ -40 °C due to which the Charpy notch toughness at -40 °C practically did not differ from that at higher temperatures. Charpyho zkoušky zátěžových měřicích trnů z oceli ČSN 19312 byly provedeny při teplotě 20 °C, 0 °C, -20 °C, popř.\n-40 °C s cílem ověřit, že Charpyho vrubová houževnatost kolíků si zachovává svou průměrnou hodnotu i při -40 °C. Výsledky ukázaly, že ocel nevykazuje typickou tranzitní křivku typu S v teplotním rozsahu 20 °C ÷ -40 °C, díky čemuž se vrubová houževnatost podle Charpyho při -40 °C prakticky nelišila od vrubové houževnatosti při vyšších teplotách.
Keywords:
load-measuring pins; impact test; Charpy method; low temperature
Available at various institutes of the ASCR
Charpy tests of load measuring pins from ČSN 19 312 material
Charpy tests of load measuring pins from ČSN 19312 steel were carried out at the temperature 20 °C, 0 °C, -20 °C, and\n-40 °C with the aim to verify that Charpy notch toughness of the pins keeps its ...
Long term monitoring of cracks in masonry of the Fürstenberk Palace in Prague
Drdácký, Miloš; Zíma, Pavel
2022 - Czech
Results of long-term monitoring of the behavior of cracks in the masonry of a Baroque palace exposed to the cyclical effects of temperature and humidity. Determining the rate of permanent change in crack width to predict future behavior. Výsledky dlouhodobého sledování chování trhlin ve zdivu barokního paláce vystaveného cyklickým účinkům teploty a vlhkosti. Určení rychlosti trvalé změny šířky trhliny pro predikci budoucího chování.
Keywords:
monitoring; cracks; historic masonry; weather cycle loading; rate of the crack growth
Available at various institutes of the ASCR
Long term monitoring of cracks in masonry of the Fürstenberk Palace in Prague
Results of long-term monitoring of the behavior of cracks in the masonry of a Baroque palace exposed to the cyclical effects of temperature and humidity. Determining the rate of permanent change in ...
Dynamic loading test of the footbridge for pedestrians and cyclists over the Berounka river in Prague - Radotin
Hračov, Stanislav; Urushadze, Shota
2022 - Czech
The report describes the procedure and results of the dynamic loading test carried out at footbridge in Prague - Radotín. The determined modal properties of the real structure are compared with the results of the theoretical modal analysis of its numerical model. The levels of the vibrations of the deck originated from pedestrians and runners are assessed with respect to their comfort and health. Zpráva popisuje postup provedení a výsledky dynamické zatěžovací zkoušky lávky pro pěší v Praze Radotíně. Zjištěné modální vlastnosti skutečné konstrukce jsou porovnány s výsledky teoretické modální analýzy jejího numerického modelu. Úroveň vibrací mostovky lávky od přechodů chodců a běžců je poté posouzena s ohledem na jejich pohodlí a zdraví.
Keywords:
footbridge; dynamic loading test; pedestrian load; vibration comfort criteria
Available at various institutes of the ASCR
Dynamic loading test of the footbridge for pedestrians and cyclists over the Berounka river in Prague - Radotin
The report describes the procedure and results of the dynamic loading test carried out at footbridge in Prague - Radotín. The determined modal properties of the real structure are compared with the ...
Report on survey of salinity of masonries under 3rd courtyard at Prague Castle
Slížková, Zuzana; Náhunková, Pavla
2022 - Czech
In 2022, the characterization of the chemical composition and amount of salt efflorescence on archaeological constructions under Prague Castle was supplemented by two new locations (at the site of the foundations of the Chapel of St. Bartholomew and near the northern wall of zone III). In the results, carbonate minerals were not detected as in previous years (except for calcite in small quantities). Sodium sulfate was again the majority component in the efflorescences. Using thermal analysis, the presence of sodium sulfate in the form of mirabilite was confirmed in the samples taken in February. The high contamination of marlstone with nitrates and chlorides in today's crown of the chapel's masonry of St. Bartholomew and increased sulfate contamination in the plinth section was detected. Conversely, no risk values of water-soluble ions were detected in the mortar or the black bricks of the perimeter wall. V roce 2022 bylo doplněno mapování chemického složení a množství výkvětů solí na archeologických stavebních konstrukcích pod Pražským hradem o dvě nové lokality (v místě základů kaple zv. sv. Bartoloměje a v okolí obvodové severní zdi zóny III). Ve výsledcích nebyly detekovány uhličitanové minerály jako v minulých letech (kromě kalcitu v malém množství). Ve výkvětech byl opět majoritní složkou síran sodný. Pomocí termické analýzy byla potvrzena přítomnost síranu sodného s navázanou krystalovou vodou v jeho struktuře (mirabilit) ve vzorcích odebraných v únoru. Z výluhů stavebního materiálů je patrná vysoká kontaminace opuky dusičnany a chloridy v dnešní koruně zdiva kaple tz. sv. Bartoloměje a zvýšená kontaminace sírany v soklové partii. Naopak v maltě a ani černých cihlách obvodové zdi nebyly zjištěny rizikové hodnoty vodorozpustných iontů.
Keywords:
characterization; sodium sulfate; mortars
Available at various institutes of the ASCR
Report on survey of salinity of masonries under 3rd courtyard at Prague Castle
In 2022, the characterization of the chemical composition and amount of salt efflorescence on archaeological constructions under Prague Castle was supplemented by two new locations (at the site of the ...
Microscopic analysis of materials sampled from the Mánes bridge in Prague
Frankeová, Dita; Bauerová, Pavla; Slížková, Zuzana
2022 - Czech
A microscopic analysis of historical concrete samples was performed within the construction-technical survey framework using a scanning electron microscope and SEM-EDS analysis. Characterization of mortar components, concrete degradation degree determination, and chemical corrosion products identification. The results of the survey work were used as a basis for the reconstruction project. V rámci stavebně-technického průzkumu byl proveden mikroskopický rozbor vzorků historického betonu s využitím skenovacího elektronového mikroskopu a SEM‐EDS analýzy. Byla provedena charakterizace plniva a složek pojiva malt, určení stupně degradace betonu a identifikace produktů chemické koroze. Výsledky průzkumných prací byly použity jako podklad pro návrh rekonstrukce objektu.
Keywords:
microscopic analysis; historical concrete; SEM-EDS
Available at various institutes of the ASCR
Microscopic analysis of materials sampled from the Mánes bridge in Prague
A microscopic analysis of historical concrete samples was performed within the construction-technical survey framework using a scanning electron microscope and SEM-EDS analysis. Characterization of ...
Determination of reference parameters for evaluating the strengthening of degraded sandstone masonry of the Cathedral of St. Vit at Prague Castle
Válek, Jan; Kozlovcev, Petr; Fialová, Anna; Slížková, Zuzana; Kotková, Kristýna; Svoboda, Milan; Koudelková, Veronika
2022 - Czech
Sandstone materials exposed to weather conditions degrade naturally, consequently consolidation of these materials is often required. The aim of this research was to evaluate the impact of four commercials organosilicate consolidants on degraded sandstones, which were used during the neogothic rebuilding of st. Vithus Cathedral at the turn of the 19th to 20th century. The depth of penetration of consolidants into the sandstone porous system and the impact of consolidants on the physical properties of sandstones, namely on the hydrofobicity, water absorption and evaporation, were evaluated primarily. According to the test results, all four consolidants should be suitable for consolidation of sandstones mentioned above even though the results varied slightly between consolidants. For final chose of appropriate consolidant, it is necessary to consider the properties of the treated sandstoned and the technological conditions of the application given by the manufacturer. Pískovcové materiály vystavené povětrnostním podmínkám podléhají přirozené degradaci, v důsledku čehož je často nutné jejich zpevnění konsolidačními prostředky. Cílem tohoto výzkumu bylo ověření vlivu čtyř vybraných komerčně dostupných organokřemičitých konsolidantů na degradované pískovce, které byly použity při novogotické dostavbě katedrály sv. Víta z přelomu 19. a 20. století. Hodnocena byla především hloubka penetrace jednotlivých konsolidantů do porézního systému kamene pomocí mikroskopických metod a dále vliv konsolidantů na vybrané fyzikální vlastnosti kamene, především na jeho hydrofobicitu, nasákavost a rychlost vysychání. Ačkoliv se výsledky u jednotlivých konsolidantů mírně lišily, lze je všechny pro konsolidaci zmíněných pískovců doporučit. Při výběru konkrétního konsolidantu je nutné vzít v potaz především vlastnosti ošetřovaného kamene a technologické podmínky aplikace dané výrobcem.
Keywords:
consolidation of sandstone; organosilicates; penetration depth; water absorption
Available at various institutes of the ASCR
Determination of reference parameters for evaluating the strengthening of degraded sandstone masonry of the Cathedral of St. Vit at Prague Castle
Sandstone materials exposed to weather conditions degrade naturally, consequently consolidation of these materials is often required. The aim of this research was to evaluate the impact of four ...
Investigation of basic mechanical and fracture-mechanical properties of specimens cut from high pressure gas pipeline – locality L177/2 after a seven months exposition to moist hydrogen at the pressure 3 MPa
Gajdoš, Lubomír; Šperl, Martin; Šorm, Filip; Bejdl, Jan
2022 - Czech
Investigation of the effect of moist hydrogen pressurized to 3 MPa on mechanical and fracture properties of gas pipeline steel ČSN 13126, tensile specimens, Charpy specimens and CT specimens were kept loaded during the exposition in moist hydrogen, after a seven months exposition it was found that ductility of tensile specimens and fracture parameters Jin and J0,2 of CT specimens decreased whilst the parameter Jm was slightly increased. Vyšetření vlivu vlhkého vodíku stlačeného na tlak 3 MPa na mechanické a lomové vlastnosti plynovodní oceli ČSN 13126, tahové vzorky, Charpy vzorky i CT vzorky byly během expozice ve vlhkém vodíku trvale zatíženy, po sedmi měsících expozice byl zjištěn pokles tažnosti tahových vzorků, pokles lomových parametrů Jin a J0,2 a mírné zvýšení parametru Jm.
Keywords:
stress-strain diagram; Ramberg-Osgood dependence; impact strength; fracture toughness
Available at various institutes of the ASCR
Investigation of basic mechanical and fracture-mechanical properties of specimens cut from high pressure gas pipeline – locality L177/2 after a seven months exposition to moist hydrogen at the pressure 3 MPa
Investigation of the effect of moist hydrogen pressurized to 3 MPa on mechanical and fracture properties of gas pipeline steel ČSN 13126, tensile specimens, Charpy specimens and CT specimens were kept ...
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