Wyniki wyszukiwania - BazTech

1

Połączenia w prefabrykowanych drewnianych budynkach szkieletowych

Roszczyc Rafał, Szczesiak Tomasz

Materiały Budowlane

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2023

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nr 3

61--63

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Nieliniowe modele zniszczenia belek drewnianych przy zginaniu

Rapp Piotr

Przegląd Budowlany

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2020

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R. 91, nr 11

43--47

PL

W artykule przywołano dwa znane nieliniowe modele zniszczenia belek drewnianych przy zginaniu. Jeden z nich to model Suensona, w którym naprężenia ściskające w przekroju aproksymuje się za pomocą paraboli, a naprężenia rozciągające mają rozkład liniowy. Drugi to model Thunella, w którym rozkład naprężeń w całym przekroju belki aproksymuje się za pomocą linii łamanej złożonej z odcinków prostych. Na tle tych modeli przedstawiono model, w którym naprężenia w strefie ściskanej aproksymuje się za pomocą wielomianu 4 stopnia. W ramach tych modeli sformułowano związki między wytrzymałościami doraźnymi drewna bez wad na ściskanie, rozciąganie i zginanie oraz oszacowano moment zginający w belce w chwili zniszczenia. Na przykładach wykazano, że model Thunella oraz zaproponowany model nieliniowy 4 stopnia dobrze pasują do danych doświadczalnych i mogą być stosowane w obliczeniach praktycznych.

EN

The article refers to two known nonlinear models of failure of wooden beams in bending. One of them is the Suenson model, in which the compressive stresses in the cross-section are approximated by a parabola, and the tensile stresses have a linear distribution. The second is the Thunell model, in which the stress distribution in the entire cross-section of the beam is approximated by a line composed of straight segments. Against the background of these models, a model has been presented in which the stresses in the compressed zone are approximated by a polynomial function of degree 4. Within these models, it is possible to formulate the relationship between the compression, tensile and bending ultimate strengths of clear wood. It is also possible to estimate the bending moment in the beam at the moment of failure. The examples show that the Thunell model and the proposed nonlinear model of degree 4 fit well with the experimental data and can be used in practical calculations.

3

Stability of anchored retaining walls under seismic loading conditions to obtain minimal anchor lengths using the improved failure model

Benamara Fatima Zohra, Rouaiguia Ammar, Bencheikh Messaouda

Civil and Environmental Engineering Reports

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2020

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Vol. 30, no. 3

214--233

EN

Anchored retaining walls are structures designed to support different loading applied in static and dynamic cases. The purpose of this work is to design and study the stability of an anchored retaining wall loaded with different seismic actions to obtain minimal anchor lengths. Mononobe-Okabe theory has been applied for the evaluation of seismic earth pressures developed behind the anchored wall. Checking the dynamic stability of anchored retaining walls is usually done using the classic Kranz model. To take into consideration the effects of the internal forces developed during failure, we have proposed a new model, based on the Kranz model, which will be used as the Kranz model to find the critical angle failure performed iteratively until the required horizontal anchor length is reached for a minimum safety factor. The results of this study confirm that the effect of the seismic load on the design of an anchored retaining wall, and its stability, has a considerable influence on the estimation of anchor lengths. To validate the modifications made to the new model, a numerical analysis was carried out using the Plaxis 2D software. The interpretation of the obtained results may provide more detailed explanation on the effect of seismic intensities for the design of anchored retaining walls.

4

Damage initiation of laminated FRP composite plates under impact

Chakrabarti A., Ashraf Iqbal M., Agrawal P.

International Journal of Applied Mechanics and Engineering

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2009

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Vol. 14, no 3

659-682

EN

The behaviour of composite laminates is not yet well understood under various impact loadings. Matrix cracking and delamination are the most common damage mechanisms in laminated fiber reinforced composite structures under impact. These damages are very difficult to detect by inspection from outside but they may cause a serious decrease in material strength and stiffness at the time of production, maintenance and due to small particle crashing to composite body. In this study, an efficient Finite Element Analysis model is developed in order to simulate initiation of damage in laminated composite plates under transverse impact loading considering different failure mechanisms. Hashin's failure model is incorporated into ABAQUS/Explicit for the present purpose. The influence of impactor velocity, thickness of plates and different stacking sequences is investigated for the initiation of damage in laminated composite plates under impact loading. Many new useful results are presented to show the variation of contact force, displacement, energy and stress resultants with time.

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Contribution to the simulation of textile reinforced plastics under crash and impact loads

Hufenbach W., Andrich M., Gude M., Langkamp A.

Kompozyty

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2004

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R. 4, nr 9

47-51

EN

Novel textile reinforced composites have outstanding specific mechanical properties and superb energy absorption capabilities, which makes them excellent candidates for impact and crash resistant elements. Despite their distinguished properties, textile reinforced composites have not experienced a broad application yet, mainly due to the lack of realistic failure models, that account for the complex mechanisms involved in the dynamic failure of such materials. In developing appropriate simulation and failure models for textile composites under dynamic loading, basic experimental investigations are required to understand the complex structural and failure mechanisms. The performed experiments provide the necessary knowledge to develop adapted material models, which take into account the textile reinforcement structure and serve for the simulation of the impact and crash behaviour with the help of numerical programs.

PL

Nowe kompozyty ze wzmocnieniem tekstylnym posiadają znakomite właściwości mechaniczne oraz doskonale zdolności absorpcji energii, dlatego są one predestynowane do zastosowań w elementach i konstrukcjach obciążonych udarowo. Kompozyty tekstylne nie są do tej pory w pełni wykorzystane w praktyce z powodu braku realistycznych modeli zniszczenia, wyjaśniających złożone mechanizmy pękania przy szybko narastających obciążeniach. Do opracowania modeli umożliwiających symulację niszczenia kompozytów tekstylnych niezbędne jest przeprowadzenie szczegółowych badań eksperymentalnych w celu zrozumienia przebiegu pękania. Eksperymenty wykonane w ILK dostarczyły danych służących dopasowaniu modelu materiału, uwzględniającego tekstylną strukturę wzmocnienia przy bardzo dużych prędkościach obciążenia.