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

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

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

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