Multi-scale techniques for mansonry structures

The aim of this work is, hence, to adopt the computational homogenization techniques to obtain the global response of masonry structures. Since the experimental global response curves, obtained in typical shear tests on masonry panels, show stiffness and resistance degradation, damage is the fundamental ingredients which must be taken into account in such problems. Moreover, as it is well known, due to the aforementioned softening behavior, regularization techniques are required in order to avoid spurious mesh dependencies when a numerical solution is sought in the framework of finite element method. The first step of this work is the adoption of the standard first order computational homogenization, where Cauchy continuum is used both at the macro and micro-level. This approach is well known in literature and several authors applied it to different engineering problems. An example of the adoption of regularization techniques in the context of multi-scale approaches is found in Massart (2003). Hence a regularization based on the imposition of the macroscopical length scale at the micro-level, in the framework of the fracture energy regularization, is proposed. However, as previously stated, many authors have pointed out the inner limits of first order computational homogenization. Such a formulation, in fact, may be adopted only if 1)the microstructure is very small with respect to the characteristic size at the macro-scale; 2)the absolute size of the constituents does not affect the mechanical properties of the homogenized medium and in presence of low macroscopic gradients of stresses and strains. As a consequence no localization phenomena typically exhibited by masonry can be analyzed. For masonry structures, instead, microstructural typical sizes are comparable with the macro-structural sizes; shape, size and arrangement of the constituents strongly affect the mechanical global response and high deformation gradients typically appear. An enriched formulation is then proposed in order to overcome these problems, based on the adoption of a Cosserat medium at the macro-level and a Cauchy medium at the micro-level. The theoretical and computational schemes remain the same as before but for the fact that the two media present different variables. In particular in the Cosserat medium additional strain and stress variables appear, with respect to the Cauchy continuum, as a consequence of the independent rotational degree of freedom assigned to every material point. Thus, a more sophisticated kinematic map, containing higher order polynomial expansions, is needed to state proper bridging conditions between the two levels. The innovative contribution of this work concerns the adoption of an enhanced multi-scale computational homogenization technique for studying the masonry response, together with the employment of damage models for the constituents description. Thus, by exploiting the inner regularization properties of the Cosserat continuum at the macro-level and by adopting a classical fracture energy regularization at the micro-level, localization phenomena, typically exhibited by masonry structures, are analyzed. Since this material shows a typical strain softening behavior, an ad hoc regularization technique has been developed at both levels in order to obtain objective numerical responses. To the knowledge of the author, no previous examples of Cosserat-Cauchy computational homogenization techniques, taking into account localization effects, have been presented. A possible objection to the use of a fully-coupled multi-scale technique could be related to the high computational efforts required, but here the use of parallel computing brings them down. In this context, these procedures strike a good balance between the achievement of detailed information at the scale of the constituents and the requirement of holding the computational costs down

Influence of the Spatial Variability of Joints Characteristics on the Elastic Properties of Masonry

Brick masonry is a multicomponent composite material, characterized by a marked inhomogeneity, a highly anisotropic behavior arising from the complex interactions between joints and bricks, and a considerable spatial variability of material properties, particularly relevant in the case of historical masonries. The focus of this paper is on the interdependence between the spatial variability of mechanical properties of joints and the overall homogenized response of a given volume element of masonry. It is assumed that mechanical properties of bed joints may vary according to a fixed probability distribution and correlation function and the mechanical response of the volume element is investigated in terms of the overall elastic stiffness. As confirmed by preliminary results, the spatial variability of the mechanical properties may affect the overall response of a masonry wall

Quantitative determinations and imaging in different structures of buried human bones from the XVIII-XIXth centuries by energy dispersive X-ray fluorescence - Postmortem evaluation

In this work, a non-commercial triaxial geometry energy dispersive X-ray Fluorescence (EDXRF) setup and a benchtop mu-XRF system were used to identify postmortem contamination in buried bones. For two of the individuals, unusually high concentrations of Cu and Pb, but also Zn (in one individual) were observed. The pigments of the burial shroud coverings have been identified as the source of contamination.Accurate and precise quantitative results were obtained by nondestructive process using fundamental parameters method taking into account the matrix absorption effects.A total of 30 bones from 13 individuals, buried between the mid-XVlllth to early XIXth centuries, were analyzed to study the elemental composition and elemental distribution. The bones were collected from a church in Almada (Portugal), called Ermida do Espirito Santo, located near the Tagus River and at the sea neighbourhood.The triaxial geometry setup was used to quantify Ca, Fe, Cu, Zn, Br, Sr and Pb of powder pressed bone pellets (n=9 for each bone). Cluster analysis was performed considering the elemental concentrations for the different bones. There was a clear association between some bones regarding Fe, Cu, Zn, Br and Pb content but not a categorization between cortical and trabecular bones. The elemental distribution of Cu, Zn and Pb were assessed by the benchtop p.-analysis, the M4 Tornado, based on a polycapillary system which provides multi-elemental 2D maps. The results showed that contamination was mostly on the surface of the bone confirming that it was related to the burial shroud covering the individuals

Time-integrated luminosity recorded by the BABAR detector at the PEP-II e+e- collider

This article is the Preprint version of the final published artcile which can be accessed at the link below.We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-→e+e- and (for the ϒ(4S) only) e+e-→μ+μ- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e+e-→e+e- and e+e-→μ+μ-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the ϒ(3S) and ϒ(2S) resonances, an additional uncertainty arises due to ϒ→e+e-X background. For data collected off the ϒ resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the ϒ(4S), 0.58% (0.72%) for the ϒ(3S), and 0.68% (0.88%) for the ϒ(2S).This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat à l’Energie Atomique and Institut National de Physique Nucléaire et de Physiquedes Particules (France), the Bundesministerium für Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e Innovación (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation (USA)

Am J Prev Med

CC999999/Intramural CDC HHS/United States2017-02-19T00:00:00Z26456878PMC531651

The Influence of Age and Sex on Genetic Associations with Adult Body Size and Shape : A Large-Scale Genome-Wide Interaction Study

Genome-wide association studies (GWAS) have identified more than 100 genetic variants contributing to BMI, a measure of body size, or waist-to-hip ratio (adjusted for BMI, WHRadjBMI), a measure of body shape. Body size and shape change as people grow older and these changes differ substantially between men and women. To systematically screen for age-and/or sex-specific effects of genetic variants on BMI and WHRadjBMI, we performed meta-analyses of 114 studies (up to 320,485 individuals of European descent) with genome-wide chip and/or Metabochip data by the Genetic Investigation of Anthropometric Traits (GIANT) Consortium. Each study tested the association of up to similar to 2.8M SNPs with BMI and WHRadjBMI in four strata (men 50y, women 50y) and summary statistics were combined in stratum-specific meta-analyses. We then screened for variants that showed age-specific effects (G x AGE), sex-specific effects (G x SEX) or age-specific effects that differed between men and women (G x AGE x SEX). For BMI, we identified 15 loci (11 previously established for main effects, four novel) that showed significant (FDR= 50y). No sex-dependent effects were identified for BMI. For WHRadjBMI, we identified 44 loci (27 previously established for main effects, 17 novel) with sex-specific effects, of which 28 showed larger effects in women than in men, five showed larger effects in men than in women, and 11 showed opposite effects between sexes. No age-dependent effects were identified for WHRadjBMI. This is the first genome-wide interaction meta-analysis to report convincing evidence of age-dependent genetic effects on BMI. In addition, we confirm the sex-specificity of genetic effects on WHRadjBMI. These results may providefurther insights into the biology that underlies weight change with age or the sexually dimorphism of body shape.Peer reviewe

A micromechanical approach for the micropolar modeling of heterogeneous periodic media

Computational homogenization is adopted to assess the homogenized two-dimensional response of periodic composite materials where the typical microstructural dimension is not negligible with respect to the structural sizes. A micropolar homogenization is, therefore, considered coupling a Cosserat medium at the macro-level with a Cauchy medium at the micro-level, where a repetitive Unit Cell (UC) is selected. A third order polynomial map is used to apply deformation modes on the repetitive UC consistent with the macro-level strain components. Hence, the perturbation displacement field arising in the heterogeneous medium is characterized. Thus, a newly defined micromechanical approach, based on the decomposition of the perturbation fields in terms of functions which depend on the macroscopic strain components, is adopted. Then, to estimate the effective micropolar constitutive response, the well known identification procedure based on the Hill-Mandel macro-homogeneity condition is exploited. Numerical examples for a specific composite with cubic symmetry are shown. The influence of the selection of the UC is analyzed and some critical issues are outlined

Analisi multi-scala dei pannelli in muratura basata su formulazioni agli elementi finiti miste

A first order multi-scale model for regular masonry based on a periodic homogenization technique is presented. In particular, a two-field mixed finite element formulation is proposed for the solution of the boundary value problem at the macroscopic level, aiming at improving the accuracy of the macroscopic field evaluation. Some applications on simple 2D structures are shown both in the field of linear elastic and elastic-plastic behavior