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1

Shear strengthening of deficient RC deep beams using NSM FRP system: Experimental and numerical investigation

Abadel Aref

Materials Science Poland

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2024

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Vol. 42, No. 1

140--157

EN

It is essential to retrofit deep beams with shear inadequacies because these beams, although they have the same shear and flexural reinforcements as ordinary beams, are more susceptible to shear failure. Hence, it is of great significance to overcome the shear weaknesses in deep beams. This research paper aims to experimentally examine the effectiveness of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) for retrofitting reinforced concrete (RC) deep beams subjected to shear forces. The study involved three different types of specimens. The first specimen was constructed with concrete throughout its span and included shear stirrups. The second specimen was divided into two halves, with one half lacking shear reinforcements and the other half having them. The third specimen had steel web reinforcement in one half of the span, while the other half was strengthened using NSM CFRP U-wrap strips and externally bonded horizontal CFRP strips. The proposed strengthening method significantly increased the shear strength of the deep beams, surpassing that provided by steel web reinforcement alone. Furthermore, the NSM CFRP strengthened specimen exhibited a change in failure mode from shear to flexural failure. In comparison to the control beam without stirrups, the beams strengthened with NSM CFRP U-wrap strips demonstrated an impressive 82% improvement in shear strength, while the beam with shear reinforcement showed a 23 % enhancement in load capacity. The proposed strengthened scheme is capable of enhancing the structural performance and load-carrying capacity effectively. A finite element model was generated utilizing ABAQUS software to simulate the behavior of the tested deep beams and verified against the experimental outcomes. The numerical models successfully predicted the behavior of the RC deep beams strengthened with NSM CFRP when compared to the experimental data.

2

Numerical modeling of RDE

Folusiak Michal, Swiderski Karol, Wolanski Piotr

Transactions on Aerospace Research

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2020

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Nr 4 (261)

13--47

EN

The idea of using the phenomenon of rotating detonation to propulsion has its roots in fifties of the last century in works of Adamson et al. and Nicholls et al. at the University of Michigan. The idea was recently reinvented and experimental research and numerical simulations on the Rotating Detonation Engine (RDE) are carried in numerous institutions worldwide, in Poland at Warsaw University of Technology (WUT) since 2004. Over the period 2010-2014 WUT and Institute of Aviation (IOA) jointly implemented the project under the Innovative Economy Operational Programme entitled ‘Turbine engine with detonation combustion chamber’. The goal of the project was to replace the combustion chamber of turboshaft engine GTD-350 with the annular detonation chamber. This paper is focused on investigation of the influence of a geometry and flow conditions on the structure and propagation stability of the rotating detonation wave. Presented results are in majority an outcome of the aforementioned programme, in particular authors’ works on the development of the in-house code REFLOPS USG and its application to simulation of the rotating detonation propagation in the RDE.

PL

Pomysł wykorzystania zjawiska wirującej detonacji do napędu był po raz pierwszy rozważany w latach pięćdziesiątych ubiegłego wieku przez zespoły badawcze Adamsona i Nichollsa na Uniwersytecie Michigan. Badania nad silnikiem z detonacyjną komorą spalania zostały wznowione po blisko 40 latach i dziś prace prowadzone są w wielu jednostkach naukowych na świecie, a w Polsce na Politechnice Warszawskiej od 2004 roku. W latach 2010-2014 Instytut Lotnictwa oraz Politechnika Warszawska wspólnie realizowały projekt w ramach Programu Operacyjnego Innowacyjna Gospodarka ‘Silnik Turbinowy z detonacyjną komorą spalania’. Projekt zakłada zastąpienie komory spalania turbowałowego silnika GTD-350 pierścieniową komorą detonacyjną. Artykuł skupia się na badaniach numerycznych wpływu geometrii oraz parametrów przepływu na strukturę i stabilność propagacji wirującej detonacji. Przedstawione wyniki są w większości wynikiem prac autorów nad rozwojem kodu REFLOPS USG w czasie trwania projektu i koncentruje się na rozwoju i implementacji wysokowydajnych metod symulacji silnika z detonacyjną komorą spalania oraz ich zastosowaniu w symulacjach numerycznych propagacji wirującej fali detonacyjnej w silniku RDE.

3

Numerical, experimental and fuzzy logic applications for investigation of crack location and crack depth estimation in a free-free aluminum beam

Behera S. K., Parhi D. R., Das H. C.

Vibrations in Physical Systems

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2018

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Vol. 29

art. no. 2018019

EN

A beam structure under natural vibration in presence of crack undergoes a sharp change in its dynamic characteristics. In the present study the changes in two important modal vibration parameters like mode shapes and natural frequencies have been extensively studied for crack diagnosis in presence and absence of crack. Numerical and experimental investigations have been carried out using an aluminium Free-Free beam structure with and without crack. The crack presence is indicative of a decrease in local flexibility at crack location and a variation in mode shapes and natural frequencies are noticed. These variations in modal parameters have been used as the tools for crack diagnosis. In the present paper, efforts are made to analyse the presence of a crack using the application of fuzzy logic methodology. Here relative natural frequencies preferably first three are derived from experimental and theoretical investigations are utilised as input data to the fuzzy controller with Gaussian membership functions to obtain crack position and crack depth as output data. The resulted output data from fuzzy logic and the result from corresponding experimental and numerical analysis have been compared.The deviation of result of fuzzy logic from numerical and experimental results have been found to be within a limit of 3%.

4

Numerical modelling of ejector operating with isobutane

Śmierciew K., Butrymowicz D., Gagan J., Pietrowicz S.

Zeszyty Energetyczne

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2017

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T. 4

51--62

EN

The rapid growth of various applications of the ejection refrigeration systems could be observed recently. Because of possibility of the application of solar or waste energy to supply the motive energy they can be thought as a real alternative to compression devices in air-conditioning technologies. Ejection system can effectively compete with absorption system under temperature of the motive heat source lower than 80°C. The paper deals with CFD numerical simulation along with experimental investigations carried out on a specially constructed prototype/stand for the case of isobutane as a working fluid under motive vapour temperature below 75°C. The numerical and experimental results of entrainment ratio were compared. A good accuracy between numerical and experimental results was observed. The divergent of the results are lower than 20% for tested series. The exemplary pressure and velocity field were presented. Also it was shown that predicted by numerical simulation pressure distribution at ejector wall fits well with experimental pressure distribution.

5

The thermodynamic analysis of the Szewalski hierarchic vapour cycle cooperating with a system of waste heat recovery

Ziółkowski P., Kowalczyk T., Hernet J., Kornet S.

Transactions of the Institute of Fluid-Flow Machinery

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2015

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nr 129

51--75

EN

In this paper, thermodynamic analysis of the Szewalski hierarchic vapour cycle cooperating with a system of waste heat recovery from exhaust gases are presented. According to that purpose, the CFM (computation flow mechanics) approach has been used correctly. In this paper, traditional steam cycle, the bottoming organic Rankine cycle (ORC) and a system of waste heat recovery with use of water with temperature 90 ◦C have been analyzed. The Szewalski binary vapour cycle is providing steam as the working fluid in the high temperature part of the cycle, while another fluid – organic working fluid – as the working substance substituting conventional steam over the temperature range represented by the low pressure steam expansion. The steam cycle for reference conditions, the Szewalski binary vapour cycle, and the Szewalski hierarchic vapour cycle cooperating with a system of waste heat recovery have been comprised. Four working fluids in the low temperature part of binary cycle such as ammonia, propane, isobutene and ethanol have also been investigated. Moreover, the Szewalski cycle is a good resolution for proper using heat flux received from the exhaust gases heat regeneration system.

6

Improvement of the internal combustion engine cam-tappet pair characteristics using numerical step-by-step cam design method

Vasilyev A., Bakhracheva J.

Journal of KONES

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2009

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Vol. 16, No. 1

517-522

EN

In this paper the numerical step-by-step method of cam profile design is presented. The results of its using for internal combustion engine valve gear are submitted. Its basis is a principle of step-by-step formation of the tappet movement law taking into account restrictions, which permit to refuse of before hand, accepted cam profile description. Thus instead of the analytical law of tappet movement the numerical representation is used, and the algorithm of positive and negative acceleration forming provides maximum cam efficiency, depending on the tappet displacement diagram completeness and connected to it valve timing. A longside with formation of the tappet movement law definition of the necessary data for manufacturing and the control of the corresponding cam profile using various kinematic schemes is stipulated. This method allows to profile of maximum efficiency cams in view of many restrictions on parameters, connected to valve gear serviceability and reliability: contact stress in cam-tappet pair, pressure angle, coverage factor of the valve springs effort, radius of cam profile curvature, oil film thickness in the cam-tappet pair and the restrictions on the higher order of derivative from the tappet displacement on the cam turn angle. Efficiency ofa considered method has been confirmed at profiling cams for lines of tractor and automobile engines.

7

Numerical investigation of turbulent flow and heat transfer in channel with ribs

Myllerup L., Larsen P.

Archives of Thermodynamics

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2000

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Vol. 21, nr 3-4

17-24

EN

The performance of three different low-Reynolds number turbulence models has been explored for the benchmark test of fully developed (periodic) flow in aribbed plane channel. Results are presented for two values of the Reynolds number (based on mean velocity and hydraulic diameter), Re=37,200 and Re=12,600, for which experimental data are available for the flow field and heat transfer, respectively. Comparison with experimental data includes the Nusselt number distribution along ribbed surface and profiles of mean velocity.