A nonlinear macroelement formulation for the seismic analysis of masonry buildings

A macroelement is presented for the nonlinear dynamic analysis of masonry structures under seismic actions. The macroelement, developed in the framework of the equivalent frame model, has a force-based formulation and accounts for flexural and shear failure mechanisms, by means of two flexural hinges at the ends and a shear link, respectively. The flexural hinges are formulated according to the Bouc-Wen model to describe the progressive development of cracks and the hysteresis loops under load reversals. The shear link, in addition to the aforementioned effects, accounts for the strength/stiffness decay and is formulated adopting the Bouc-Wen-Baber-Noori model. Numerical comparisons with experimental tests on masonry piers are presented, showing the suitability of the presented macroelement

A micro-macro homogenization for modeling the masonry out-of-plane response

This study introduces a finite element model based on a two-scale beam-to-beam homogenization procedure for the analysis of masonry structural members undergoing prevailing axial and bending stress states. The model is developed considering the periodic repetition of bricks and mortar joints in regular stack bond arrangement and assuming a linear elastic behavior for the former and a nonlinear response for the latter. At the microscopic heterogeneous scale, the behavior of a Unit Cell (UC) made of a single brick and mortar layer is described through an equivalent Timoshenko beam representation, where a nonlocal damage formulation with friction plasticity governs the mortar nonlinear constitutive relationship. Basing on a semi-analytical approach, the microscopic quantities are, then, homogenized to define an equivalent beam model at the macroscopic scale. The proposed finite element model is implemented in standard numerical codes to investigate the response of typical one-dimensional (1D) masonry elements. This study shows the numerical simulation of two experimental tests: a rectangular wallette under out-of-plane bending and a circular arch under vertical forces. The results obtained for the proposed model are compared with those resulting from micromechanical approaches and the experimental outcomes

Mangosteen Extract Shows a Potent Insulin Sensitizing Effect in Obese Female Patients: A Prospective Randomized Controlled Pilot Study.

There is a widely acknowledged association between insulin resistance and obesity/type 2 diabetes (T2DM), and insulin sensitizing treatments have proved effective in preventing diabetes and inducing weight loss. Obesity and T2DM are also associated with increased inflammation. Mangosteen is a tropical tree, whose fruits—known for their antioxidant properties—have been recently suggested having a possible further role in the treatment of obesity and T2DM. The objective of this pilot study has been to evaluate safety and efficacy of treatment with mangosteen extract on insulin resistance, weight management, and inflammatory status in obese female patients with insulin resistance. Twenty-two patients were randomized 1:1 to behavioral therapy alone or behavioral therapy and mangosteen and 20 completed the 26-week study. The mangosteen group reported a significant improvement in insulin sensitivity (homeostatic model assessment-insulin resistance, HOMA-IR −53.22% vs. −15.23%, p = 0.004), and no side effect attributable to treatment was reported. Given the positive preliminary results we report and the excellent safety profile, we suggest a possible supplementary role of mangosteen extracts in the treatment of obesity, insulin resistance, and inflammation

Nonhuman gamblers: lessons from rodents, primates, and robots

The search for neuronal and psychological underpinnings of pathological gambling in humans would benefit from investigating related phenomena also outside of our species. In this paper, we present a survey of studies in three widely different populations of agents, namely rodents, non-human primates, and robots. Each of these populations offers valuable and complementary insights on the topic, as the literature demonstrates. In addition, we highlight the deep and complex connections between relevant results across these different areas of research (i.e., cognitive and computational neuroscience, neuroethology, cognitive primatology, neuropsychiatry, evolutionary robotics), to make the case for a greater degree of methodological integration in future studies on pathological gambling

An orthotropic macromechanical model with damage for the analysis of masonry structures

The in-plane response of masonry walls is analyzed by using a novel macromechanical damage model. This is able to capture the directional mechanical properties characterizing regular masonry textures by adopting an orthotropic description of the elastic and inelastic behavior. A damage matrix, defined in terms of damage independent scalar variables, is introduced in the constitutive law to describe and distinguish the stiffness degradation due to tensile, compressive and shear states along masonry natural axes, fixed as the parallel and normal direction to bed joints. The model is implemented in a finite element procedure, where the mesh-dependency drawback is overcome by adopting a classical nonlocal integral approach. Comparisons of numerical and experimental results are performed to test the model capability of describing influence of the orientation of applied stresses with respect to bed joints direction. Moreover, a numerical study is conducted with reference to different masonry textures with the aim of evaluating the effect of bricks and mortar relative arrangement on the elastic properties of the homogenized material. Finally, the response of a large scale masonry wall subjected to seismic loads is studied and the obtained pushover curve is compared with those collected from existing literature models

A 3D mixed frame element with multi-axial coupling for thin-walled structures with damage

A 3D mixed beam finite element is presented, modeling the warping of the cross-sections as an independent kinematic field. The beam formulation is derived on the basis of the Hu-Washizu variational principle, expressed as function of four independent fields: the standard displacements, strains and stresses and the additional warping displacement. This is interpolated along the beam axis and on the cross-section, by placing on it a regular grid of interpolation points and adopting Lagrange polynomials. The warping degrees of freedom defined at the cross-section interpolation points are condensed, thus preserving the element matrix and vector sizes. A fiber discretization of the cross-sections is adopted. The constitutive relationship at the midpoint of each fiber is based on an isotropic damage model for brittle-like materials, distinguishing between the damage variables in tension and in compression to properly describe the unilateral effect. An efficient algorithm is formulated for the element state determination, based on a consistent linearization of the governing equations. A simple numerical application on a cantilever beam with torsion in the linear elastic range is presented and two torsion tests on plain concrete beams are performed, by comparing the numerical results with the experimental outcomes

Are chimpanzees really so poor at understanding imperative pointing? Some new data and an alternative view of canine and ape social cognition

There is considerable interest in comparative research on different species’ abilities to respond to human communicative cues such as gaze and pointing. It has been reported that some canines perform significantly better than monkeys and apes on tasks requiring the comprehension of either declarative or imperative pointing and these differences have been attributed to domestication in dogs. Here we tested a sample of chimpanzees on a task requiring comprehension of an imperative request and show that, though there are considerable individual differences, the performance by the apes rival those reported in pet dogs. We suggest that small differences in methodology can have a pronounced influence on performance on these types of tasks. We further suggest that basic differences in subject sampling, subject recruitment and rearing experiences have resulted in a skewed representation of canine abilities compared to those of monkeys and apes

Dynamic characterization of a system with degradation: A masonry wall

Characterization of the dynamic behavior of linear systems is exhaustively described with a single frequency response curve (frc). For nonlinear systems, which tend to depend on load amplitude, at least one frc for each excitation intensity is required to detect the main characteristics of the dynamic response. Nonlinear systems, more commonly dealt with in the literature, are invariant with respect to the deformation history and, thus, frcs obtained with increasing and decreasing driving frequency coincide, apart from the frequency range with coexistent solutions. This is not so for many real systems which suffer from their past, often exhibiting degradation of their mechanical properties. Here the focus is on the effects of damage on the dynamic signature of systems. The response of a masonry wall, representative of systems with a degrading restoring force, is analyzed under harmonic excitation. A refined finite element model is used to represent the typical degradation that occurs in masonry and its reliability is proved by comparing numerical results and experimental outcomes from shaking table tests. Particular attention is paid to the wall frcs, emphasizing the influence of the deformation history on the curves characteristics and their role in the dynamic characterization of a system with degradation

Advanced Fiber Beam Finite Element Model for Neural Network Training in Vibration-Based Bridge Monitoring

Recent advancements in civil infrastructure monitoring have witnessed the increasingly high-performance sensor technologies and data-driven algorithms, opening up new possibilities for assessing structural conditions. In recent years, there has been a growing interest in leveraging the potential of Artificial Intelligence for civil infrastructure monitoring. One promising approach is the use of computational models to train and test data-driven algorithms aiming to tackle damage detection problems. To enhance the effectiveness of such procedures based on simulated data, this study proposes a high-performance beam finite element model for training a neural network model able to predict the dynamic response of the structure and for generating various damage scenarios. Compared to 2D and 3D finite element models, the advanced fiber beam model offers superior computational efficiency while accurately capturing the nonlinear behavior of structural elements. Specifically, a force-based beam finite element based on a damage-plasticity model is implemented to describe damage and degradation of materials in reinforced concrete girders. Through the simulation of the dynamic structural response under withe noise excitation, a neural network model representing the structure in the undamaged conditions is obtained. The prediction error of such network model is investigated as a suitable measure for the definition of a damage indicator able to detect the presence of damage (concrete cracks and reinforcement yielding). The integration of an advanced fiber beam model, accurate constitutive law and neural network models shows promising potential in the monitoring of existing bridges