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Search results for: prestressed concrete structures
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Monitoring of metal structures with the dynamic methods
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Unusual structures of Mg2F5- superhalogen anion
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Modal diagnostics of civil engineering structures.
PublicationKsiążka dotyczy zastosowania analizy modalnej do diagnostyki konstrukcji budowlanych.
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Geodesic monitoring of tower and mast structures
PublicationW artykule przedstawiono obciążenia jakim są poddawane konstrukcje wieżowe i masztowe. Opisano zakres oraz wymagania dotyczące pomiarów geodezyjnych przeprowadzanych w czasie eksploatacji konstrukcji smukłych. Wskazano metody pomiaru oraz zaprezentowano niektóre sposoby pomiaru w praktyce. Zamieszczono wyniki pomiarów przemieszczeń elektrowni wiatrowej o mocy 2 MW i wysokości elementu wsporczego 80 m oraz zaprezentowano pomiary...
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Selected problems of stability of steel structures.
PublicationW pracy przedstawiono wyniki badań dotyczących stateczności wybranych konstrukcji stalowych. Prezentowane rozważania są oparte na klasycznych założeniach teorii prętów cienkościennych o nieodkształcalnym przekroju poprzecznym. Wyznaczono pierwszą wariację sił krytycznych pręta cienkościennego o bisymetrycznym otwartym przekroju poprzecznym uwzględniając następujące zmienne projektowe: ⎯wymiary przekroju poprzecznego, ⎯ charakterystyki...
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Geosynthetics tests in hydrotechnical structures design
PublicationW celu właściwego stosowania w konstrukcjach budowlanych (w tym również hydrotechnicznych)geosyntetyków - zarówno przepuszczalnych (geotekstylia i wyroby pokrewne) jak i nieprzepuszaczalnych (geomembrany i kompozyty uszczelniające), bardzo ważne jest wcześniejsze poddawanie go odpowiednim badaniom, których procedura musi być ściśle powiązana z późniejszym przeznaczeniem geomateriału i uwzględniać warunki, w jakich materiał będzie...
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Simulation and identification of damage in bar structures.
PublicationPraca zawiera opis i testy 3 procedur badawczych dotyczących lokalizacjizniszczeń w konstrukcjach. Procedury bazują na danych modalnych jakie obiektgeneruje podczas swoich drgań tzn. częstościach własnych i postaciach drgań Badane są zmiany podatności układu, zmiany krzywizn postaci drgań i wrażli-wość częstości na założone zniszczenia. Odpowiednie procedury wiążące się ztymi trzema metodami są przestestowane na przykładzie wspornika...
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Development of quay structures for container harbour .
PublicationPrace poświęcono nowym rozwiązaniom konstrukcyjnym nabrzeży przeznaczonym do przeładunku kontenerów. Zwrócono przy tym głównie uwagę na spełnienie warunków stateczności w przypadku występowania dużych prędkości strumieni zaśrubowych wywołanych napędami statków podczas ich manewrowania.
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Strengthening of structures by shock transmission units.
PublicationCelem niniejszego artykułu jest analiza możliwości zastosowania tzw. przenośników drgań do wzmacniania konstrukcji budowlanych (w tym mostowych) narażonych na oddziaływania dynamiczne takie jak: wiatr, siły hamowania pojazdów czy trzęsienia ziemi.
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Topological modifications for performance improvement and size reduction of wideband antenna structures
PublicationCompact antennas belong to the key components of modern communication systems. Their miniaturization is often achieved by introducing appropriate topological changes such as simple ground plane slots or tapered feeds. More sophisticated modifications are rarely considered in the literature because they normally lead to significant increase of the number of tunable parameters, which makes the antenna design process more challenging....
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Advanced Control Structures of Turbo Generator System of Nuclear Power Plant
PublicationIn the paper a synthesis of advanced control structures of turbine and synchronous generator for nuclear power plant working under changing operating conditions (supplied power level) is presented. It is based on the nonlinear models of the steam turbine and synchronous generator cooperating with the power system. Considered control structure consists of multi-regional fuzzy control systems with local linear controllers, including...
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Advanced Control Structures of Turbo Generator System of Nuclear Power Plant
PublicationIn the paper a synthesis of advanced control structures of turbine and synchronous generator for nuclear power plant working under changing operating conditions (supplied power level) is presented. It is based on the nonlinear models of the steam turbine and synchronous generator cooperating with the power system. Considered control structure consists of multi-regional fuzzy control systems with local linear controllers, including...
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On Reduced-Cost Design-Oriented Constrained Surrogate Modeling of Antenna Structures
PublicationDesign of contemporary antenna structures heavily relies on full-wave electromagnetic (EM) simulation models. Such models are essential to ensure reliability of evaluating antenna characteristics, yet, they are computationally expensive and therefore unsuitable for handling tasks that require multiple analyses, e.g., parametric optimization. The cost issue can be alleviated by using fast surrogate models. Conventional data-driven...
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Uniform corrosion monitoring of carbon steel in concrete
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Impregnation vibro-pressed concrete pavement bricks.
PublicationW materiałach przedstawiono wyniki badań uzyskanych podczas prób impregnacji wibroprasowanych elementów betonowych. Celem badań było określenie odpowiedniego składu kompozycji impregnacyjnej, aby uzyskać najlepszy efekt zabezpieczenia powierzchni betonu przed wnikaniem cieczy organicznych np. oleju mineralnego.
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Concrete-domain reasoning techniques in knowledge cartography
PublicationWiele zjawisk w świecie rzeczywistym opisujemy korzystając z liczb i symboli. W ramach naszej pracy jako punkt wyjścia traktujemy podejście kartograficzne opracowane na potrzeby wnioskowania z ontologii opartych na logice opisowej i pozwalające na efektywne przetwarzanie baz wiedzy zwierających dużą liczbę osobników. Niniejszy artykuł przedstawia rozszerzenie podejścia kartograficznego pozwalające na wnioskowanie z wartości symbolicznych,...
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Damage Detection of Steel-Concrete Composite Beam
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Uniform corrosion monitoring of carbon steel in concrete.
PublicationW przypadku korozji prętów zbrojeniowych w żelbecie zaobserwowane zostały obszary wzmożonego zaatakowania. Pomiar prądowego i napięciowego szumu elektrochemicznego umożliwia wyznaczenie szybkości korozji ogólnej a zmiany parametrów statystycznych przebiegów szumowych umożliwiają detekcję występowania przestrzennych rejonów intensyfikacji korozji. Przedstawione rezultaty, oparte na wykorzystaniu odpowiedniego układu zastępczego,...
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Minimal transverse reinforcement of reinforced concrete members
PublicationW pierwszej części pracy omówiono zagadnienia dotyczące minimalnego zbrojenia na ścinanie elementów żelbetowych w kontekście norm europejskich oraz pozaeuropejskich. W drugiej części pracy dokonano analizy wyników badań eksperymentalnych dotyczących nośności elementów bez zbrojenia poprzecznego, które stanowią podstawę do weryfikacji zaleceń normowych w zakresie minimalnego zbrojenia na ścinanie.
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A two-scale (FEM-DEM) approach for concrete
PublicationArtykuł omawia dwu-skalowe podejście do betonu przy wykorzystaniu modelu Mes i DEM. Metodę elementów skończonych zastosowano na poziomie makro. Na poziomie mikro zastosowano metodę elementów dyskretnych. Macierz sztywności wyznaczono na podstawie tensora naprężeń wyznaczonego w skali mikro. Wyniki numeryczne dwusalowe porównano z wynikami dyskretnymi dla całego obszaru.
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A coupled continuous-discontinuous approach to concrete elements.
PublicationArtykuł omawia zastosowanie metody elementów skończonych do opisu procesu pękania elementów betonowych z równoczesnym uwzględnieniem lokalizacji odkształceń i rys. Obliczenia wykonano dla elementów poddanych zginaniu. Wyniki porównano z doświadczeniami.
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Modelling of behavior of plain concrete using DEM
PublicationW artykule pokazano rozwój różnych zjawisk mikrostrukturalnych na poziomie kruszywa w betonie podczas jednoosiowego ściskania i rozciągania.. Obliczenia wykonano stosując metodę DEM. Wyniki na poziomie globalnym porównano doświadczalnymi. Szczególna uwagę zwrócono na propagację rys i szerokość lokalizacji odkształceń.
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Modelling the effect of composition on the tensile properties of concrete
PublicationRozdział omawia wyniki analizy mezoskopowej procesu pękania w betonie podczas zginania. Obliczenia wykonano na poziomie mezo wykorzystując model degradacji sztywności z nielokalnym osłabieniem. Zbadano wpływ właściwości kruszywa, stref przejściowych, nacięcia oraz długości charakterystycznej mikrostruktury na zachowanie sie betonu. Zaproponowano 2 metody określenia reprezentatywnego elementu objętościowego w betonie.
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Continuous and discontinuous modeling of cracks in concrete elements
PublicationW artykule przedstawiono różne sposoby modelowania rys w elementach betonowych w warunkach mieszanego sposobu obciążenia przy zastosowaniu modeli ciągłych i nieciągłych. Symulacje wykonano przy zastosowaniu 3 różnych modeli ciągłych: modelu sprężysto-plastycznego, modelu w ramach mechaniki zniszczeniowej i modelu rys rozmytych z rysami obracającymi się oraz 1 modelu nieciągłego przy zastosowaniu stref kontaktu..
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Investigation of low-temperature cracking in newly constructed high-modulus asphalt concrete base course of a motorway pavement
PublicationThe paper presents the issue of low-temperature transverse cracks which have developed in newly constructed base courses made of high-modulus asphalt concrete mix (HMAC). Numerous transverse cracks developed in the analysed HMAC base during the winter season before the pavement was actually completed, both at the transverse joint locations and in the areas between them. This had not happened so far on such a scale during road construction...
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Size effect at aggregate level in microCT scans and DEM simulation – Splitting tensile test of concrete
PublicationThe paper describes an experimental and numerical study of size effect on concrete cylindrical specimens in splitting tensile test. Own experimental campaign was performed on specimens with 5 various diameters from D = 74, 105, 150, 192 and 250 mm with hardboard loading strips (distributed load according to standard methods) scaled proportionally to the specimen diameter. The crack opening-control system was applied to obtain the...
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An Efficient PEEC-Based Method for Full-Wave Analysis of Microstrip Structures
PublicationThis article introduces an efficient method for the equivalent circuit characterization and full-wave analysis of microstrip structures, leveraging the full-wave partial element equivalent circuit (PEEC). In particular, the multilayered Green's function is evaluated using the discrete complex-image method (DCIM) and employed to establish the mixed potential integral equations. The proposed strategy considers time delays for the...
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Crystal structures of aminotransferases Aro8 and Aro9 from Candida albicans and structural insights into their properties
PublicationAminotransferases catalyze reversibly the transamination reaction by a ping-pong bi-bi mechanism with pyridoxal 5′-phosphate (PLP) as a cofactor. Various aminotransferases acting on a range of substrates have been reported. Aromatic transaminases are able to catalyze the transamination reaction with both aromatic and acidic substrates. Two aminotransferases from C. albicans, Aro8p and Aro9p, have been identified recently, exhibiting...
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Accelerated Re-Design of Antenna Structures Using Sensitivity-Based Inverse Surrogates
PublicationThe paper proposes a novel framework for accelerated re-design (dimension scaling) of antenna structures using inverse surrogates. The major contribution of the work is a sensitivity-based model identification procedure, which permits a significant reduction of the number of reference designs required to render the surrogate. Rigorous formulation of the approach is supplemented by its comprehensive numerical validation using a...
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Particle Shape Effect on Macroscopic Behaviour of Underground Structures: Numerical and Experimental Study
PublicationAbstract: The mechanical performance of underground flexible structures such as buried pipes or culverts made of plastics depend not only on the properties of the structure, but also on the material surrounding it. Flexible drains can deflect by 30% with the joints staying tight, or even invert. Large deformations of the structure are difficult to model in the framework of Finite Element Method, but straightforward in Discrete...
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Pareto Ranking Bisection Algorithm for Expedited Multi-Objective Optimization of Antenna Structures
PublicationThe purpose of this letter is introduction of a novel methodology for expedited multi-objective design of antenna structures. The key component of the presented approach is fast identification of the initial representation of the Pareto front (i.e., a set of design representing the best possible trade-offs between conflicting objectives) using a Pareto-ranking bisection algorithm. The algorithm finds a discrete set of Pareto-optimal...
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Particle Shape Effect on Macroscopic Behaviour of Underground Structures: Numerical and Experimental Study
PublicationThe mechanical performance of underground flexible structures such as buried pipes or culverts made of plastics depend not only on the properties of the structure, but also the material surrounding it. Flexible drains can deflect by 30% with the joints staying tight, or even invert. Large deformations of the structure are difficult to model in the framework of Finite Element Method, but straightforward in Discrete Element Methods....
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Chitin and derivative chitosan-based structures — Preparation strategies aided by deep eutectic solvents: A review
PublicationThe high molecular weight of chitin, as a biopolymer, challenges its extraction due to its insolubility in the solvents. Also, chitosan, as the N-deacetylated form of chitin, can be employed as a primary material for different industries. The low mechanical stability and poor plasticity of chitosan films, as a result of incompatible interaction between chitosan and the used solvent, have limited its industrialization. Deep eutectic...
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SFEM Analysis of Beams with Scaled Lengths including Spatially Varying and Cross-Correlated Concrete Properties
PublicationThis paper presents the results obtained for plain concrete beams under four-point bending with spatially varying material properties. Beams of increasing length but constant depth were analyzed using the stochastic finite element method. Spatial fluctuation of a uniaxial tensile strength, fracture energy and elastic modulus was defined within cross-correlated random fields. The symmetrical Gauss probability distribution function...
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Recent Advances in Performance-Driven Surrogate Modeling of High-Frequency Structures
PublicationDesign of high‐frequency structures, including microwave and antenna components, heavily relies on full‐wave electromagnetic (EM) simulation models. Their reliability comes at a price of a considerable computational cost. This may lead to practical issues whenever numerous EM analyses are to be executed, e.g., in the case of parametric optimization. The difficulties entailed by massive simulations may be mitigated by the use of...
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Application of Shape Memory Alloys in Retrofitting of Masonry and Heritage Structures Based on Their Vulnerability Revealed in the Bam 2003 Earthquake
PublicationFor decades, one of the most critical considerations of civil engineers has been the construction of structures that can sufficiently resist earthquakes. However, in many parts of the globe, ancient and contemporary buildings were constructed without regard for engineering; thus, there is a rising necessity to adapt existing structures to avoid accidents and preserve historical artefacts. There are various techniques for retrofitting...
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Numerical Analysis of Steady Gradually Varied Flow in Open Channel Networks with Hydraulic Structures
PublicationIn this paper, a method for numerical analysis of steady gradually varied fl ow in channel networks with hydraulic structures is considered. For this purpose, a boundary problem for the system of ordinary differential equations consisting of energy equation and mass conservation equations is formulated. The boundary problem is solved using fi nite difference technique which leads to the system of non-linear algebraic equations....
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High-Efficacy Global Optimization of Antenna Structures by Means of Simplex-Based Predictors
PublicationDesign of modern antenna systems has become highly dependent on computational tools, especially full-wave electromagnetic (EM) simulation models. EM analysis is capable of yielding accurate representation of antenna characteristics at the expense of considerable evaluation time. Consequently, execution of simulation-driven design procedures (optimization, statistical analysis, multi-criterial design) is severely hindered by the...
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The Revitalization Processes of the Port Structures in Gdynia and Gdansk on the Background of Contemporary Port Changes
PublicationTransformations of the port facilities against the modernization of the port structures are present in many city-port centers since more than 50 years. The modernization taking place in the ports located in Gdynia-Gdansk mainly concerns communication availability and adapted to the multimodal technology of transport and transshipment. Developing specialized tech-terminals serving a specific type of load, causes development of the...
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Influence of pitting corrosion on fatigue and corrosion fatigue of ship structures. Part I: pitting corrosion of ship structures.
PublicationThe paper is a literature survey focused on pitting corrosion and its influence on fatigue of ship and offshore steels. Mechanisms of short- and long-term pitting corrosion in marine environment have been described including pit nucleation and growth phases. Some models of pit growth versus time of exposure have been presented. Some factors which influence the pit growth have been discussed briefly.
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Performance-driven yield optimization of high-frequency structures by kriging surrogates
PublicationUncertainty quantification is an important aspect of engineering design, as manufacturing toler-ances may affect the characteristics of the structure. Therefore, quantification of these effects is in-dispensable for adequate assessment of the design quality. Toward this end, statistical analysis is performed, for reliability reasons, using full-wave electromagnetic (EM) simulations. Still, the computational expenditures associated...
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Monitoring the fracture process of concrete during splitting using integrated ultrasonic coda wave interferometry, digital image correlation and X-ray micro-computed tomography
PublicationThe paper deals with the continuous-time monitoring of mechanical degradation in concrete cubes under splitting. A series of experiments performed with integrated coda wave interferometry (CWI) and digital image correlation (DIC), supported with X-ray micro-computed tomography (micro-CT) is reported. DIC and micro-CT techniques were used to characterize the fracture process in detail. CWI method was proved to be effective in the...
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Coordination polymers and molecular structures among complexes of mercury(II) halides with selected 1-benzoylthioureas
PublicationSix new 1-benzoyl-3-phenylthiourea and 1-benzoyl-3-(2-methylphenyl)thiourea complexes of mercury( II) were obtained in the reactions of the ligands with HgX2 in methanol (X = Cl, Br, I). Their structures, determined by single-crystal X-ray diffraction analysis, exhibit different stoichiometries and molecular organization. Coordination centers adopt more or less distorted tetrahedral geometry (five structures) or distorted trigonal...
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Mathematical Modelling of a Seismic Isolation System to Protect Structures During Damaging Earthquakes
PublicationThe present study aims to determine the effectiveness of a nonlinear mathematical model in simulating complex mechanical behaviour of a seismic isolation system to protect structures during strong and damaging earthquakes. In order to construct the Polymeric Bearings considered in this research, a specially prepared flexible polyurethane elastomer with increased damping properties has been used. The usefulness of the proposed mathematical...
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Simplified Map-based Selection of Optimal Spindle Speeds When Milling Complex Structures
PublicationIn the paper a method for selecting optimal spindle speeds for complex structures during milling operations is presented. It is based on the selection of the spindle speed in accordance with a simple equation resulting from the minimisation of vibration energy, which leads to the minimisation of the work of cut-ting forces presented in previous elaborations by the authors [1]. Optimal spindle speeds are obtained for many points...
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EM-Driven Multi-Objective Optimization of Antenna Structures in Multi-Dimensional Design Spaces
PublicationFeasible multi-objective optimization of antenna structures is presented. An initial set of Pareto optimal solutions is found using a multi-objective evolutionary algorithm (MOEA) working with a fast surrogate antenna model obtained by kriging interpolation of coarse-discretization EM simulation data. To make the surrogate construction computationally feasible in multi-dimensional design space, the space subset containing non-dominated...
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A new time-frequency detection method of stray current field interferenceon metal structures.
PublicationA new detection method has been presented of stray current field interference on underground metal structures. The method employs short time Fourier transformation (STFT). This method of analysis allows determination of signal spectral power density changes (e.g., structure potential) in the function of time. In the paper results have been presented of total time–frequency analysis of a pipeline potential in a stray current field...
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Tubular House - Form Follows Technology, Concrete Shell Structure with Inner Thermal Insulation
PublicationThe aim of this paper is the theoretical analysis of the possibilities and limitations of using an unconventional technology and the original architectural form stemming from it – the building with external construction and internal insulation. In Central European climatic conditions, the traditional solution for the walls of heated buildings relies on using external thermal insulation. This stems from building physics: it prevents...
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The use of a two-phase Monte Carlo material model to reflect the dispersion of asphalt concrete fracture parameters
PublicationThe work covers comprehensive laboratory tests of semi-circular bending (SCB) of asphalt concrete samples. The results of two test series, including four and 32 SCB specimens, indicate a substantial scatter of force–deflection (F-d) histories. The numerical analysis is aimed to reflect the maximum breaking load and fracture energy of the samples, pointing out their random character. The original simulation-based fictitious Monte...
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Sub-national structures matter when evaluating physical activity promotion: Lessons from Germany
PublicationBackground Public policies are increasingly acknowledged as important part of promoting physical activity (PA). However, especially in states with sub-national administrative structures such as Germany, national and sub-national approaches differ considerably. In Germany, sport for all (SfA) promotion is mostly organized at sub-national level, which is usually not covered in national evaluations. Knowledge of these structures helps...