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• Error quantification of the phase-field model in Westergaard's problem. • Assessment of different pre-crack definition approaches. • Verification of strain energy splits using an exact solution as a benchmark problem. • Application to mode I and mixed-mode loading conditions. One challenge in verifying strain energy splits in phase field fracture models is the lack of reference problems with exact solutions in mixed-mode loading that could serve as benchmark problems. In this work, different strain energy splits used in the variational phase field model have been applied to the classical Westergaard's problem. In contrast to other benchmark problems used in the literature, the proposed problem not only includes the singular term as a boundary condition but also implicitly considers all terms. To the authors' knowledge, this is the first time in the literature that this reference problem has been used to rigorously verify the accuracy of different energy splits of the phase field model. Several critical factors such as the pre-crack definition, mesh size, mixed mode ratio and the length scale parameter have been analysed. A good correlation between the numerical estimations and the analytical predictions was found for some pre-crack definition approaches under mode I. However, we demonstrated that the compatible regularisation length scale and mesh size are significantly lower under mode II loading (i.e., when the crack kinks) than under mode I. [ABSTRACT FROM AUTHOR]

In the Gran Chaco, one of the most biodiverse, yet imperiled, arid biomes in the world, open-to-air concrete water canals may threaten wildlife via drowning and habitat fragmentation, although these effects are usually overlooked. We performed field surveys and local people interviews along 250 km of canals in the Gran Chaco ecoregion of Argentina during austral spring and summer (six months). We documented 207 drowned individuals of 35 wildlife species, but more realistic estimations could increase this number to the thousands. Six species of conservation concern drowned in the canal, and eight of the drowned species have decreasing population trends. Drownings in some mammal species decreased with time without any mitigation measures implemented at the canal yet, suggesting an ongoing, large-scale population reduction due to this high mortality rate. Since mitigation measures applied in other regions were not effective to stop drowning and population isolation, these infrastructures should be avoided in arid environments worldwide. • We surveyed an open-to-air water canal in the arid Great Chaco ecoregion in Argentina. • More than 200 individuals of 35 wildlife species drowned in this infrastructure. • This includes six species of conservation concern, the Giant anteater being the most affected. • The decrease in the number of drownings with time suggests a large-scale defaunation. • We recommend intubating the canal to avoid drownings and habitat fragmentation. [ABSTRACT FROM AUTHOR]

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Obesity has been described as a protective factor in cardiovascular and other diseases being expressed as 'obesity paradox'. However, the impact of obesity on clinical outcomes including mortality in COVID-19 has been poorly systematically investigated until now. We aimed to compare clinical outcomes among COVID-19 patients divided into three groups according to the body mass index (BMI). We retrospectively collected data up to May 31st, 2020. 3635 patients were divided into three groups of BMI (<25 kg/m2; n = 1110, 25−30 kg/m2; n = 1464, and >30 kg/m2; n = 1061). Demographic, in-hospital complications, and predictors for mortality, respiratory insufficiency, and sepsis were analyzed. The rate of respiratory insufficiency was more recorded in BMI 25−30 kg/m2 as compared to BMI < 25 kg/m2 (22.8% vs. 41.8%; p < 0.001), and in BMI > 30 kg/m2 than BMI < 25 kg/m2, respectively (22.8% vs. 35.4%; p < 0.001). Sepsis was more observed in BMI 25−30 kg/m2 and BMI > 30 kg/m2 as compared to BMI < 25 kg/m2, respectively (25.1% vs. 42.5%; p = 0.02) and (25.1% vs. 32.5%; p = 0.006). The mortality rate was higher in BMI 25−30 kg/m2 and BMI > 30 kg/m2 as compared to BMI < 25 kg/m2, respectively (27.2% vs. 39.2%; p = 0.31) (27.2% vs. 33.5%; p = 0.004). In the Cox multivariate analysis for mortality, BMI < 25 kg/m2 and BMI > 30 kg/m2 did not impact the mortality rate (HR 1.15, 95% CI: 0.889−1.508; p = 0.27) (HR 1.15, 95% CI: 0.893−1.479; p = 0.27). In multivariate logistic regression analyses for respiratory insufficiency and sepsis, BMI < 25 kg/m2 is determined as an independent predictor for reduction of respiratory insufficiency (OR 0.73, 95% CI: 0.538−1.004; p = 0.05). HOPE COVID-19-Registry revealed no evidence of obesity paradox in patients with COVID-19. However, Obesity was associated with a higher rate of respiratory insufficiency and sepsis but was not determined as an independent predictor for a high mortality. [ABSTRACT FROM AUTHOR]

• 3.8 kg/m2 urban vs. 2.2 kg/m2 conventional agriculture, exceeding expectations. • Crop diversification boosts food security and dietary diversity in urban systems. • Urban agri-food systems cut 27–37% of global greenhouse gas emissions effectively. • Sustainable practices curb pollution and plastic waste in urban farming. • Colombia needs adaptable prototypes for food security and sovereignty. The ongoing climate crisis, coupled with contemporary factors, starkly underscores the global vulnerability of food systems and the pressing need for adaptive approaches. Urban agriculture emerges as a multifaceted remedy for production, sustainability, and communal well-being. This study probes the role of small-scale organic urban agriculture in driving sustainable urban development through a focused case study. Essential markers of sustainable agro-production effectiveness take center stage. The research scrutinizes yield and productivity within a rooftop agri-food framework spanning eleven months. A collective of 336 vegetables were reaped, yielding an impressive 82.1% relative yield. Standout performers, including lettuce, arugula, and mizuna, achieved a relative yield of 4.1 kg/m2, comfortably situated within the 2.1–16 kg/m2 spectrum. This yield potential remains sensitive to intricate agronomic and environmental variables. The innovative potential extends to conferring food autonomy upon 11,553 families via 432 projects within Bogota. In conclusion, this research highlights the importance of small-scale organic urban agriculture as a viable approach to sustainable development in urban areas. The results contribute to the existing knowledge on yield and productivity indicators in sustainable agro-production systems, providing valuable insights for policymakers, urban planners, and public and private organizations. [ABSTRACT FROM AUTHOR]

In this paper, the influence of the heterogeneity in the predicted crack initiation lifetime under fretting fatigue conditions is analysed for a regular and a random distribution of micro-voids. A critical plane analysis with two multiaxial damage criteria is performed to assess the crack initiation lifetime. The predicted initiation lifetime in the heterogeneous material is compared with the results obtained in the homogeneous case. The numerical results show that the heterogeneity has a noticeable influence on the predicted initiation lifetime. Furthermore, the numerical model suggests that a crack may firstly initiate at the upper edge of the micro-voids located close to the contact edge, leading to a mean reduction of the predicted crack initiation lifetime. However, in some cases, the introduction of micro-voids reduces the stress intensity at the contact edge and thus decreasing the predicted crack initiation lifetime. • Effect of heterogeneity on fretting fatigue crack initiation. • Numerical analysis using Finite Element Method. • Regular and random distribution of micro-voids. • Critical plane analysis using multiaxial damage criteria. [ABSTRACT FROM AUTHOR]

Highlights • The effect of different phase angles under biaxial fatigue loads is analysed. • Crack paths are predicted via orientation criteria for nonproportional loading. • The use of XFEM facilitates parametrical crack growth simulations. • Important differences are observed depending on the orientation criteria. • The minimum range of kII criterion agrees well with experimental evidences. Abstract In the present research work, a numerical crack growth analysis using linear elastic fracture mechanics is carried out paying attention to the crack paths that grow in the central part of cruciform specimens under biaxial fatigue loads. The crack propagation in this type of specimens has been studied using the extended finite element method (XFEM). The objective is to analyse the effect of different phase angles under biaxial fatigue loads and to assess the different orientation criteria for nonproportional loading, benefiting from the advantages of XFEM. The crack path and the stress intensity factor range of a crack either aligned or inclined to the load directions have been investigated using different crack orientation criteria. Symmetrical branching is predicted for an initial crack inclined at 45° with phase angle of loading equal to 90° and 180°. Numerical results are in good agreement with the experimental observations found in the literature, although the study reveals important differences in the crack path predictions depending on the orientation criteria. [ABSTRACT FROM AUTHOR]

Abstract In fatigue problems, an accurate estimation of the propagation direction is important for life prediction. We identify the most relevant factors that affect the crack orientation during the propagation stage of fretting fatigue cracks, arising from complete contacts. Contrary to what initially expected, parameters such as normal load, cyclic bulk load, etc. do not have a noticeable influence on the orientation. However the relative Young's moduli of indenter/specimen materials, the indenter width and the surface coefficient of friction are the most influencing factors. Analyses are performed through the extended finite element method (X-FEM) and an orientation criterion for non-proportional loading proposed by the authors. Experimental fretting fatigue tests confirm the predicted trends. An explanation of this behaviour is also given. Highlights • Factors that have the greatest influence on crack deflection are identified. • These are the relative stiffness of indenter/specimen and the indenter width. • The COF between indenter and specimen has also a large influence. • Analyses are performed using XFEM and the minimum variation of shear stress. • Experimental tests validate the results. A mechanical explanation is given. [ABSTRACT FROM AUTHOR]

Highlights • Variation of material properties could lead to a reduction in the pedestrian comfort. • Boards unions produce an important reduction in the response standard deviation. • Finger joint unions produce a change in the structural effective properties. • Stochastic analysis allows us to extend the range of the response. • New design guidelines provide a rational assessment that accounts the uncertainties. Abstract The dynamic study of a short span timber footbridge with uncertain mechanical properties under the action of a deterministic walking load model which represents one individual is presented. The aim of the work is to quantify the influence of the uncertain material properties in the natural and forced vibration problems of a short span timber footbridge. These structural systems made of timber are increasingly employed due to the high stiffness/weight ratio that this material exhibits. This feature can lead to lightweight structural systems in which the acceleration levels can exceed the human comfort limits. The assumed sources of uncertainties of this structural model are the Modulus of Elasticity (MOE) and the mass density. Also, the geometrical design of the boards that compose the laminated timber beams supporting the floor involves variability of the distances between finger joints. Probability Density Functions (PDFs) of the timber properties are formulated from the Principle of Maximum Entropy (PME). The finger joints distance generates the lengthwise variability of the MOE and the mass density in each board of the laminated beams. The PDFs of the natural frequencies of the structure, the mode shapes and the structural response are numerically obtained through the Finite Element Method (FEM) and statistic tools. In order to carry out this analysis, plate and laminated beam elements derived from the First Order Shear Deformation Theory (FSDT) are employed. The variation of the effective stiffness and mass along the elements due to the union of boards with different properties produces an important reduction of the standard deviation of the natural frequencies. The conditions in which the stochastic properties of the structure lead to unacceptable acceleration levels are studied. In some scenarios, the variation of the material properties can lead to unacceptable serviceability performances of the structure and a reduction in the pedestrian comfort, according to the codes in force. However, new design guidelines replace the line limits by comfort regions which are also discussed here. [ABSTRACT FROM AUTHOR]