196,105 research outputs found
A 3D two-scale multiplane cohesive-zone model for mixed-mode fracture with finite dilation
No full textA 3D multi-scale cohesive-zone model (CZM) combining friction and finite dilation by a multi-plane approach (M-CZM), based on the concept of Representative Multiplane Element (RME), is developed within the mechanics of generalized continua for the analysis of mixed-mode fracture. The proposed M-CZM formulation captures the increase of measured fracture energy in mode II as a natural effect of multi-scale coupling between cohesion, friction and interlocking, employing a reduced set of micromechanical parameters characterized by a well-defined micromechanical interpretation. This permits to devise clear calibration and identification procedures for 3D fracture problems. Upon assessing the retrieval, by a regular 5-plane RME, of a quasi-isotropic response for fracture resistance and for dilation, the M-CZM is employed in FEM simulations of Double-Cantilever Beam (DCB) tests to obtain predictions of mixed mode I–II and mixed mode I–III fracture resistance. The DCB analyses show the key role of the characteristic height of asperities in determining the macroscopic fracture resistance in both mixed mode I–II and I–III interactions. Numerical results also show the independence of the mode-I fracture resistance on the geometry of the beam section and a marked dependence of the measured mixed-mode fracture resistance on the section aspect ratio
A 3D microstructured cohesive–frictional interface model and its rational calibration for the analysis of masonry panels
No full textA 3D microstructured composite Interphase Formulation (IF) based on a Multiplane Cohesive-Zone Model (M-CZM) is proposed for describing the behavior of quasi-brittle joints. The IF is devised so as to reproduce an initial linear elastic behavior, corresponding to the elastic parameters of a thin layer of finite thickness and stiffness, followed by a post-elastic response of the joint featuring progressive crack formation and onset of frictional and dilating responses. All nonlinear features of the joint response are determined by a zero-thickness multiplane-CZM accounting for the development of a microstructured crack inside the joint. The paper proposes a consistent and reproducible calibration procedure of the model parameters for its employment in the simplified micro-modeling of masonry joints. A numerical-experimental assessment of the predicted flexural response of masonry wallettes is presented, employing as a source for material parameters the data available from the experimental campaign of van der Pluijm and coworkers on the meso-scale response of units and mortar joints. The data from the structural bending tests on masonry wallets of the same campaign are used next to assess the simulated structural response following a blind-like approach, i.e., avoiding fine tuning of the mesoscale model parameters on the basis of experimental structural data on masonry wallettes. The numerical-experimental comparison appears to be satisfactory
Albarella future – zero carbon emission
No full textClimate warming is setting requirements on research also in the agronomic and forest fields. The soil and vegetation are available as carbon sinks. Ecosystems under high exploitation lost part of their carbon. It is possible to recover this carbon from the air with natural processes and to return it to the land. Besides, global warming requires a change in mentality that moves into the replacement of fossil fuels with other energy sources. In this perspective, the island of Albarella, with its environment and economic activities, represents an attractive miniature model of the planet Earth. For this design, we estimated (Vensim simulation) the emissions and storage of CO2 equivalent of the whole island. Then, with the idea of acting on natural ecosystems to make them more active in carbon storage, we analyzed two vegetation series from the forest to the sea, one located in the nearby natural reserve of Porto Caleri, and one on the island of Albarella. The investigation concerns the soil carbon storage and the quality and quantity of populations of arthropods, bacteria, and fungi as well. The biodiversity of artificial environments resulted in higher than that of natural habitats, opening a debate. Acting in different ways on the substitution of fuels, we obtained scenarios with decreasing emissions, from consumerist without substitution of fuels, realistic with 15% of replacement by solar energy, and sustainable with zero use of fossil energy and all the island electricity produced through photovoltaic panels
A Glossary of Zooarchaeological Methods
No full textThis methodological glossary presents brief explanations of the main analytical methods employed by zooarchaeologists and makes reference to those chapters in the Handbook that provide examples of their applications. The aim is to provide non-expert readers with a basic understanding of how the evidence presented in this volume has been obtained. The limitations and biases of each type of analysis are also briefly outlined, as their acknowledgement represents an essential prerequisite to research on archaeological materials. The definitions always refer to zooarchaeological applications of the term, although many of them may be employed in other disciplines with similar or different meanings. Each term makes reference to the chapters where it is mentioned, with the exception of approaches that are invariably adopted (e.g. taxonomic identification, quantification)
Tackling climate change: The Albarella island example
No full textWe attempted to consider Albarella Island as a model for estimating the ability of humans and the capacity of the environment to react to climate change. On its 550 hectares, this island hosts management centers, 2800 private homes, several restaurants and hotels, shops, public and private swimming pools, a golf course, beaches, green areas equipped to satisfy the 2,000 stable inhabitants and more than 110,000 annual tourists. We collected data on the following variables: 1) net carbon storage of the semi-natural ecosystems; 2) diet of humans staying on the island; 3) currently used fossil energy; 4) electricity demand; 5) waste produced; 6) transport. A dynamic simulation model of the island’s CO2 equivalent (CO2eq) emissions proposes two scenarios that illustrate how these variables can change over the next 10 years if the management remains that of the present day, or switching to all photovoltaics, proposing new diets to inhabitants and tourists, and planting trees on half of the island’s lawns. In the second case, CO2eq emissions lowered to 1/4 of the current value, bringing them to the level of 50-60 years ago. Running the Albarella touristic activities with renewed technology and minimum emissions impact in 2032 produces 4.8 kty-1of CO2eq: 14.5% (0.7 kty-1 of CO2eq) of these emissions could be stored in the ecosystems of the island, 25% (1.2 kty-1) would be produced by the solar panels construction, functionning and recycling that would furnish all the necessary domestic and industrial energy, and 60.5% (2.9 kty-1) would correspond to the emissions to supply the island’s food needs
A 3D multiscale cohesive zone model for quasi-brittle materials accounting for friction, damage and interlocking
No full textA three-dimensional (3D) two-scale Cohesive Zone Model (CZM), which is based on a multiplane approach and couples damage with friction and interlocking, is presented for analysing crack propagation in quasi-brittle materials along structural interfaces where formation of cracks is expected. The main idea of the 3D multiplane formulation herein exploited is to describe the asperities of the interface in the form of periodic patterns of inclined planes, denominated Representative Interface Elements (RIE). The interaction within each plane of the RIE is governed by the interface formulation proposed by Alfano and Sacco in earlier work. After reporting details of the formulation and of its algorithmic implementation, the sensitivity of the macroscopic mechanical response to the specific selection of the RIE is analysed and reported with a general numerical assessment of the 3D interface mechanical response to monotonic and cyclic loading histories. A fundamental issue addressed in this paper is the identification of optimal RIE patterns with a minimum number of planes capable of providing isotropic in-plane behaviour in response to confined slip tests
A 3D two-scale multiplane cohesive-zone model for mixed-mode fracture with finite dilation
No full textZooarchaeology in the twenty- first century: where we come from, where we are now, and where we are going
No full textAfter more than a century of growth, zooarchaeology has started fulfilling its full potential. The recognition of the centrality of zooarchaeological investigations in archaeology represents the most important, and hopefully enduring, development. Zooarchaeology remains, however, ultimately inter-disciplinary and cannot be pigeonholed within either Science or Humanities. Zooarchaeologists use a multitude of approaches, and contribute to all aspects of investigations of past human life, ranging from social structure, to economy, diet, ecology, ideology, and religion. The discipline has developed a set of well-established methods, whose widespread use enhances data comparability. It is, however, important that the research strategies and approaches of zooarchaeologists remain dynamic and open to constant scrutiny. Zooarchaeology is today highly international, enjoying a healthy level of open communication. There is, however, the need to reach out to areas where the discipline is still underdeveloped, as those will generate new stimuli as well as research opportunities
A 3D microstructured cohesive–frictional interface model and its rational calibration for the analysis of masonry panels
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