25 research outputs found
Nonlinear analysis of the bridge nr. 2-2043-15, E4 Kristineberg, Stockholm
Příspěvek představuje výstavbu a nelineární analýzu mechanické odezvy mostu č. 2-2043-15
E4 Kristineberg ve Stockholmu. Simulované výsledky jsou srovnány s hodnotami naměřenými při
zatěžovací zkoušce a jsou identifikována místa se zvýšeným rizikem poškození, vyžadující
monitorování během užívání stavby.The paper is focused on the construction and nonlinear analysis of the bridge 2-2043-15 E4
Kristineberg in Stockholm. Simulated results are compared with load tests. Locations with higher risk
of damage are pointed out – these places should monitored during the life cycle of the bridge
Database of fracture-mechanical concrete parameters and its implementation into software FReET
Příspěvek přibližuje tvorbu databáze lomově-mechanických parametrů betonů vybraných
pevnostních tříd a její implementaci do pravděpodobnostního softwaru FReET. Podklad databáze
představují výsledky dříve provedených lomových zkoušek trámců se zářezem, na jejichž realizaci se
podílely širší týmy pracovníků Ústavu stavební mechaniky a Ústavu stavebního zkušebnictví fakulty
stavební VUT v Brně. Implementovaná databáze bude využita pro potřeby pravděpodobnostních
výpočtů betonových konstrukcí.The paper presents the database of fracture-mechanical parameters of selected concrete
strength classes and its implementation into probabilistic software FReET. A basis for the database
were the results of earlier performed fracture tests of notched beams, which were realized in close
cooperation of research teams from Institute of Structural Mechanics and Institute of Testing, Faculty
of Civil Engineering, Brno University of Technology. The implemented database will be used for
the reliability calculations in mentioned software
Reliability modelling of real response of concrete structures
Předkládaná práce nahlíží beton – významný materiál při realizaci dopravní infrastruktury – jako kvazikřehký materiál s nezanedbatelnou variabilitou mechanických parametrů. Studuje aspekty (např. vliv charakteristické délky kompozitu na korektní provedení štípacího testu) a možnosti určení lomově-mechanických parametrů betonu, přičemž některé získané výsledky představuje v prakticky uplatnitelné podobě (např. databáze softwaru FReET). Na vybraných aplikacích představuje možnosti spolehlivostního modelování reálné odezvy betonových konstrukcí.Dopravní fakulta Jana Perner
Analysis of influence of cylidrical specimen's proportions on fracture parameters from wedge splitting test
Uplatnění lomových parametrů při vývoji speciálních vláknových kompozitů
Přehledový příspěvek nastiňuje využití stanovených lomově-mechanických parametrů
při řešení dílčích problémů vývoje vláknokompozitů (hledání vhodného složení vláknokopozitu s elektrovodivou příměsí, kvantifikace vlivu výrobní technologie – extruze a vlivu degradace kompozitu) realizovaného ve spolupráci s Výzkumným ústavem stavebních hmot především při řešení projektu FT-TA3/027 – Multifunkční kompozity mimořádných vlastností na bázi anorganických nanosložek (2006–2010), příp. CIVAK – Centrum integrovaného výzkumu anorganických kompozitů (2006–2011). V závěru je představen přístup ke komplexnímu posouzení
konstrukcí/konstrukčníh prvků z cementových kompozitů a tým zabývající se na STM FAST VUT
v Brně dlouhodobě lomovou mechanikou kvazikřehkých kompozitů a je otevřena možnost budoucí spolupráce s pracovišti Dopravní fakulty Jana Pernera
Numerical analysis of influence of own weight of wedge splitting specimen on contraint level at crack tip
Stochastic assessment of concrete core strength in fire exposed specimens simulating non-engineered RC structures in Turkey
The spatial variability of concrete compressive strength over the specific region is simulated by the stochastic approach. The compressive strength of cores taken from fire-exposed beams simulating non-engineered structures in Turkey is obtained. Therefore, improper mix-design and low strength concrete are targeted. Then, the uneven distribution of the concrete compressive strength along the fire exposed specimens is handled by the random fields approach. Thus, the adverse effect of the fire is not only established by the compressive test results but also the scatter in the core results is estimated by the stochastic method. The stochastic model accounting for the scatter in the core results is generated from the given distribution and mean cylindrical compressive strength values. The concrete compressive strength is not distributed evenly but established stronger and weaker regions over the specimen in the stochastic models. The statistical samples are generated by the Monte Carlo-type stratified sampling method, which is Latin Hypercube Sampling (LHS). A total of 500 random samples closely predicts the scatter in the compressive strength at each temperature level with a range of 25 & ndash;700 degrees C. The variability at different geometrical positions on the fire-exposed beam specimens with low strength concrete is characterized as well. Overall, the experimentally observed uncertainties arising from uneven distribution of concrete compressive strength over the fire-exposed beams simulating non-engineered structures in Turkey are accurately reproduced by the random fields approach. (c) 2021 Elsevier Ltd. All rights reserved.The spatial variability of concrete compressive strength over the specific region is simulated by the stochastic approach. The compressive strength of cores taken from fire-exposed beams simulating non-engineered structures in Turkey is obtained. Therefore, improper mix-design and low strength concrete are targeted. Then, the uneven distribution of the concrete compressive strength along the fire exposed specimens is handled by the random fields approach. Thus, the adverse effect of the fire is not only established by the compressive test results but also the scatter in the core results is estimated by the stochastic method. The stochastic model accounting for the scatter in the core results is generated from the given distribution and mean cylindrical compressive strength values. The concrete compressive strength is not distributed evenly but established stronger and weaker regions over the specimen in the stochastic models. The statistical samples are generated by the Monte Carlo-type stratified sampling method, which is Latin Hypercube Sampling (LHS). A total of 500 random samples closely predicts the scatter in the compressive strength at each temperature level with a range of 25 & ndash;700 degrees C. The variability at different geometrical positions on the fire-exposed beam specimens with low strength concrete is characterized as well. Overall, the experimentally observed uncertainties arising from uneven distribution of concrete compressive strength over the fire-exposed beams simulating non-engineered structures in Turkey are accurately reproduced by the random fields approach. (c) 2021 Elsevier Ltd. All rights reserved
Fracture Analysis of Cube- and Cylinder-Shaped WST Specimens Made of Cementitious Composites with Various Characteristic Length
A refined description of the crack tip stress field in wedge-splitting specimens – a two-parameter fracture mechanics approach
The paper is focused on a detailed numerical analysis of the stress field in specimens used for the wedge splitting
test (WST) which is an alternative to the classical fracture tests (bending, tensile) within the fracture mechanics of
quasi-brittle building materials, particularly cementitious composites. The near-crack-tip stress field in the WST
specimen is described by means of constraint-based two-parameter fracturemechanics in the paper. Different levels
of constraint in the vicinity of the crack tip during fracture process through the specimen ligament are characterized
by means of the T -stress. Two basic shapes ofWST specimen – the cube-shaped and the cylinder-shaped one – are
investigated and the determined near-crack-tip stress field parameters are compared to those of compact tension
(CT) specimens according to the ASTM standard for classical and round geometry. Particular attention is paid
to the effect of the compressive component of the loading force (complementing the splitting force) acting on
the loaded side of the specimen and its reaction from the opposite part of the specimen on the stress field in the
cracked body. Several variants of boundary conditions on the bottom side of the specimen used for this kind of
testing procedure are also considered. The problem is solved numerically by means of the finite element method
and results are compared with data taken from the literature
The influence of the shape of a saw-cut notch in quasi-brittle 3PB specimens on the critical applied force
Values of fracture parameters of quasi-brittle building materials are usually determined from results of tests performed on notched testing specimens. The contribution deals with the influence of various shapes of tips of notches prepared by a diamond saw in three point bending (3PB) specimens. The influence of the notch tip shape on the applied force corresponding to a failure initiation at the notch tip and also on the critical applied force appropriate to the maximal load-bearing capacity of the specimen is studied. Calculations are performed in two finite element method (FEM) systems (ATENA, ANSYS) based on two different approaches to fracture description (Cohesive crack models and LEFM, respectively). The numerical results obtained by both FEM systems are compared. The influence of notch shapes and width is quantified