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- 저자 : Rogowsky, David M. (검색결과 5 건)
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Splitting of reinforced concrete panels under concentrated loads
Foster, Stephen J.,Rogowsky, David M. Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.6
It is well understood that concentrated forces applied in the plane of a beam or panel (such as a wall or slab) lead to splitting forces developing within a disturbed region forming beyond the bearing zone. In a linearly elastic material the length of the disturbed region is approximately equal to the depth of the member. In concrete structures, however, the length of the disturbed region is a function of the orthotropic properties of the concrete-steel composite. In the detailing of steel reinforcement within the disturbed regions two limit states must be satisfied; strength and serviceability (in this case the serviceability requirement being acceptable crack widths). If the design requires large redistribution of stresses, the member may perform poorly at service and/or overload. In this paper the results of a plane stress finite element investigation of concentrated loads on reinforced concrete panels are presented. Two cases are examined (i) panels loaded concentrically, and (ii) panels loaded eccentrically. The numerical investigation suggests that the bursting force distribution is substantially different from that calculated using elastic design methods currently used in some codes of practice. The optimum solution for a uniformly reinforced bursting region was found to be with the reinforcement distributed from approximately 0.2 times the effective depth of the member ($0.2D_e$) to between $1.2D_e$ and $1.6D_e$. Strut and tie models based on the finite element analyses are proposed herein.
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Krzysztof Rogowski 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.5
The purpose of this study is the analysis of flow around a one-bladed Darrieus-type wind turbine using computational fluid dynamics (CFD). The rotor geometry consists of a NACA 0015 airfoil with chord length of 0.15 m. Numerical simulations are performed using ANSYS Fluent, employing laminar model and two turbulence models: SST k-ω and RNG k-ε. The obtained numerical results of unsteady aerodynamic blade loads are compared with available experimental results from literature. Computed aerodynamic characteristics of normal and tangential forces comply with the experiment results. The RNG k-ε turbulence model has a good accuracy in determining aerodynamic blade loads for the upwind and downwind parts of the rotor. The laminar model and the SST k-ω turbulence model slightly overestimate the tangential aerodynamic blade loads at the downwind part of the rotor. An averaged wind turbine velocity profile computed at one rotor radius downstream of the rotor has a Gaussian shape. The steady-state airfoil characteristics are computed for the Reynolds number comparable to the Reynolds number of a moving blade employing the SST k-ω and RNG k-ε turbulence models and using the same computational grid as for unsteady simulations of the rotor.
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Bolesław Szadkowski,Jacek Rogowski,Waldemar Maniukiewicz,Emmanuel Beyou,Anna Marzec 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.105 No.-
We present a strategy that leads to the formation of high-performance hybrid pigments made from naturalanthraquinone chromophores (alizarin, purpurin) and mineral supports (palygorskite (PAL), sepiolite(SEP), and hydroxyapatite (HAP)). Thanks to the mineral filler form features and the synergy between theorganic and inorganic components, the as-prepared hybrid pigments showed excellent thermal andchemical stability. The natural pigments exhibited strong pH-sensing activity, changing their color uponexposure to HCl and/or NH3 vapors. The PAL-based pigments were found to be the most effective pH indicators,showing pronounced color changes after 10 min of exposure to HCl (DE for PAL/A was 7.4). ToFSIMS,13C NMR and XPS techniques revealed interactions between the organic dyes and metal ions presentin the minerals. XPS spectroscopy was also used to examine the alterations in the structure of thehybrid colorants following exposure to acid vapors. The proposed pH sensors were successfully appliedto elastomer and thermoplastic elastomer matrices. The purpurin-based hybrid pigments exhibited significantlyreduced migration from the polymer (about six times lower concentration in ethanol after14 days). The results of this study pave a new way for the design, development, and application ofadvanced hybrid colorants with pH-sensing activity and improved stability.
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Anna Marzec,Bolesław Szadkowski,Jacek Rogowski,Waldemar Maniukiewicz,Marcin Kozanecki,Dariusz Moszy nski,Marian Zaborski 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.70 No.-
In this paper a novel, simple method for synthesis of lake pigments based on 1,2-dihydroxyanthra-quinone dye and LDH carbonates was proposed. LDHs were modified with 1,2-dihydroxyanthraquinone,transforming the soluble dye into a new kind of hybrid lake. In result, the solvent resistance andphotostability of the chromophore were improved, which may be attributed to strong dye–LDHinteractions. TOF-SIMS technique was used for thefirst time to confirm the role of C14H7O4Mg+ andC14H6O5Al ions in the formation of the hybrids. Alizarin lakes have been recognized as a new class ofcolorants which demonstrated good color characteristics and chemical stability.
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Brykala, Marcin,Walczak, Rafal,Wawszczak, Danuta,Kilim, Stanislaw,Rogowski, Marcin,Strugalska-Gola, Elzbieta,Olczak, Tadeusz,Smolinski, Tomasz,Szuta, Marcin Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.1
A modern approach to nuclear energy involves reprocessing like transmutations of spent nuclear fuel products to reduce their radiotoxicity and time needed for their storage. For this purpose, they are immobilized in inert matrices made of zirconia and can be "burned" in fast neutron reactor or Accelerator Driven System. These matrices in spherical form can be obtained by sol-gel process. The paper presents a method of microspheres fabrication based on the combined Complex Sol-Gel Process and double extraction process consisting in the preparation of zirconium-ascorbate sol and simultaneous extraction of water and nitrates. The procedure allows obtaining gel microspheres with a diameter of 50 ㎛, which after heat treatment are processed into the final product. The synthesis of zirconia microspheres with Yttrium by internal gelation process is well known for over a decade now. However, the explanation and characterization of synthesis of such material by extraction of water process is rarely found. Parameters such as: pH, viscosity, shape, sphericity and crystal structure have been determined for synthesized products and semi-products. In addition, preliminary research consisting in irradiation of the obtained materials in fast and thermal neutron flux was carried out. The obtained results are presented and described in this work.
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