Search results for "stiffne"
showing 10 items of 533 documents
Out-of-plane behaviour of unreinforced masonry infill walls: Review of the experimental studies and analysis of the influencing parameters
2021
Abstract Over the last 50 years, research has mainly focused on characterizing the In-Plane behaviour of unreinforced masonry infill walls. Recently, the focus of research has been addressed to understanding Out-of-Plane behaviour, also from the experimental point of view. However, in the experimental campaigns, there is high variability in the geometrical and mechanical properties of URM infill walls and also in the application of Out-of-Plane loads. Therefore, it is important to outline and critically evaluate the major findings obtained by experimental studies and identify research gaps to better understand the differences and the affinity of apparently equivalent tests. In this paper, t…
Liver stiffness measurement by transient elastography predicts early recovery from acute hepatitis
2010
We read with interest the lead article by Castera and Pinzani,1 particularly the comment regarding the role of transient elastography (TE) in the context of acute hepatitis (AH). The assumption that liver stiffness is determined exclusively by hepatic fibrosis has been challenged by evidence that patients with AH can have high values of liver stiffness measurement (LSM) by TE.2 AH is a suitable model for studying the kinetics of LSM, since inflammation and necrosis increase rapidly and sometimes massively, but may revert with equal speed. We evaluated 92 consecutive patients (mean age 41.8±16.3 years, 71.7% males) with symptomatic AH to assess how LSM was influenced by aetiology, and whethe…
Immune-inflammatory markers and arterial stiffness indexes in subjects with acute ischemic stroke with and without metabolic syndrome.
2014
Objective: The aim of our study was to evaluate the associations between arterial stiffness indexes and immune-inflammatory markers in subjects with acute ischemic stroke with and without metabolic syndrome. Materials/Methods: We enrolled 130 patients with acute ischemic stroke and metabolic syndrome, 127 patients with acute ischemic stroke without metabolic syndrome and 120 control subjects without acute stroke. Applanation tonometry was used to record the augmentation index (Aix) and pulse wave velocity (PWV). We also evaluated plasma levels of C-reactive protein (CRP), Interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), Interleukin-6 (IL-6) and Interleukin-10 (IL-10), E-selec…
Comparison of Histochemical Staining Methods and Correlation with Transient Elastography in Acute Hepatitis.
2014
<b><i>Objective:</i></b> To compare Masson's trichrome (MT), Sirius red (SR) and orcein staining in acute hepatitis (AH) and to correlate them with<b> </b>transient elastography (TE),<b> </b>a noninvasive method to assess hepatic fibrosis. <b><i>Methods:</i></b> We evaluated liver stiffness by TE in a cohort of 34 consecutive patients and assessed MT-, SR- and orcein-stained biopsies using the METAVIR scoring system and digital image analysis (DIA). <b><i>Results:</i></b> MT and SR both showed severe fibrosis (stage III-IV, DIA = 12.7%). Orcein showed absent or mild fibrosis (stage 0-II, DIA = 4.…
Local ex-vivo evaluation of the biomechanical properties of the ascending aortic aneurysms
2019
Introduction Currently, surgical recommendations for aneurysm of the ascending aorta (AsAA) are based on the maximum diameter of the ascending aorta, but this factor is not reliable. Understanding the biomechanical properties of the aorta could lead to improve the prediction of the development of an AsAA. The aim of this study is to obtain the local patient specific elastic modulus distribution of the AsAA from a biaxial tensile test. Methods Pathologic ascending aortic tissue samples (n = 10) were obtained from patients undergoing elective surgical repair of AsAA ( Table 1 ). All the aortic wall samples were partitioned related to medial, posterior, lateral, and anterior quadrants. Each As…
Liver stiffness, a non-invasive marker of liver disease: a core study group report
2010
The ability to evaluate liver stiffness non-invasively in clinical practice by measuring transient elastography using FibroScan® has resulted in considerable interest and enthusiasm. A core study group, organized by the Italian Association for the Study of the Liver, has assessed the usefulness of FibroScan® in the diagnosis and management of liver disease in clinical practice. The group concluded that FibroScan® is a valuable, non-invasive technique and have developed a consensus report form for registering transient elastography results. In this article, we report the findings of the study group.
Roughening of a propagating planar crack front
2000
A numerical model of the front of a planar crack propagating between two connected elastic plates is investigated. The plates are modeled as square lattices of elastic beams. The plates are connected by similar but breakable beams with a randomly varying stiffness. The crack is driven by pulling both plates at one end in Mode I at a constant rate. We find $\ensuremath{\zeta}=1/3, z=4/3,$ and $\ensuremath{\beta}=1/4$ for the roughness, dynamical, and growth exponents, respectively, that describe the front behavior. This is similar to continuum limit analyses based on a perturbative stress-intensity treatment of the front [H. Gao and J. R. Rice, J. Appl. Mech. 56, 828 (1989)]. We discuss the …
Fractional mechanical model for the dynamics of non-local continuum
2009
In this chapter, fractional calculus has been used to account for long-range interactions between material particles. Cohesive forces have been assumed decaying with inverse power law of the absolute distance that yields, as limiting case, an ordinary, fractional differential equation. It is shown that the proposed mathematical formulation is related to a discrete, point-spring model that includes non-local interactions by non-adjacent particles with linear springs with distance-decaying stiffness. Boundary conditions associated to the model coalesce with the well-known kinematic and static constraints and they do not run into divergent behavior. Dynamic analysis has been conducted and both…
The multiple slope discontinuity beam element for nonlinear analysis of RC framed structures
2018
The seismic nonlinear response of reinforced concrete structures permits to identify critical zones of an existing structure and to better plan its rehabilitation process. It is obtained by performing finite element analysis using numerical models classifiable into two categories: lumped plasticity models and distributed plasticity models. The present work is devoted to the implementation, in a finite element environment, of an elastoplastic Euler–Bernoulli beam element showing possible slope discontinuities at any position along the beam span, in the framework of a modified lumped plasticity. The differential equation of an Euler–Bernoulli beam element under static loads in presence of mul…
Structural damage detection using auto correlation functions of vibration response under sinusoidal excitation
2015
Structural damage detection using time domain vibration responses has attracted more and more researchers in recent years because of its simplicity in calculation and no requirement of a finite element model. This paper proposes a new approach to locate the damage using the auto correlation function of vibration response signals under sinusoidal excitation from different measurement points of the structure, based on which a vector named Auto Correlation Function at Maximum Point Value Vector (AMV) is formulated. A sensitivity analysis of the normalized AMV with respect to the local stiffness shows that under several specific frequency excitations, the normalized AMV has a sharp change aroun…