CH of masonry materials via meshless meso-modeling

In the present study a multi-scale computational strategy for the analysis of masonry structures is presented. The structural macroscopic behaviour is obtained making use of the Computational Homogenization (CH) technique based on the solution of the boundary value problem (BVP) of a detailed Unit Cell (UC) chosen at the meso-scale and representative of the heterogeneous material. The smallest UC is composed by a brick and half of its surrounding joints, the former assumed to behave elastically while the latter considered with an elastoplastic softening response. The governing equations at the macroscopic level are formulated in the framework of finite element method while the Meshless Method (MM) is adopted to solve the BVP at the mesoscopic level. The work focuses on the BVP solution. The consistent tangent stiffness matrix at a macroscopic quadrature point is evaluated on the base of BVP results for the UC together with a localisation procedure. Validation of the MM procedure at the meso-scale level is demonstrated by numerical examples that show the results of the BVP for the simple cases of normal and shear loading of the UC

A FE-Meshless Multiscale Approach for Masonry Materials

AbstractA FE-Meshless multiscale computational strategy for the analysis of running bond masonry is presented. The Meshless Method (MM) is adopted to solve the boundary value problem (BVP) at the mesoscopic level. The representative unit cell is composed by the aggregate and the surrounding joints, the former assumed to behave elastically while the latter are simulated as non-associated elastic-plastic zero-thickness interfaces with a softening response. Macroscopic localization of plastic bands is obtained performing a spectral analysis of the tangent stiffness matrix. Localized plastic bands are embedded into the quadrature points area of the macroscopic finite elements

The FE-Meshless multiscale approach applied to masonry structures

Heterogeneous structures have an overall response that is strongly dependent on the inelastic events developing at the local level. In these structures, the most relevant kinematical and mechanical phenomena take place at a scale which is small if compared to the dimensions of the entire structure. In literature, a mesoscopic and a macroscopic scales of interest are distinguished, directly linked to as many theoretical approaches. The mesoscopic approach [1] considers materials and their interfaces individually, but many difficulties arise in the mesh creation and a fine discretization of the structure is needed, which leads to prohibitive computational costs. The macroscopic approach considers the structure as constituted by a fictitious homogeneous and continuous material. The multiscale techniques belong to the second approach and couple different scales of interest by means of apposite transition laws capable to exchange informations between different consecutive scales [2]. This work relates with the multiscale first order computational homogenization technique applied to masonry structures. A unit cell (UC) is assumed constituted by an elastic bulk volume surrounded by weak joints, which are simulated by zero-thickness elasto-plastic interface models. At a single time step, the FE solution of the fictitious homogenized structure provides strains at all quadrature points. The corresponding macrostress field associated to the strain is obtained by solving a Boundary Value Problem (BVP) of the UC at the mesoscale level. The solution of the BVP is approached by means of a meshless strategy [3] instead of a classical finite element procedure, that is usually time-consuming. By imposing Taylor-Voigt type boundary conditions on the UC, the macroscopic stress is evaluated averaging the UC boundary tractions, according to the Hill-Mandel principle. Localization is faced at both the quadrature point level and at the element level. At the quadrature point level plastic bands are localized applying a continuous-discontinuous bifurcation theory [4] based on the spectral analysis of the acoustic tensor associated to the stiffness matrix. At the element level inelastic response is obtained smearing the plastic zones at the quadrature points over the element area, considering the localized and not localized fraction areas. The proposed model has been implemented on a research oriented finite element analysis pro- gram to run 2D simulations in plane-stress conditions for heterogeneous periodic structures. Quali- tatively good results are obtained in comparison with numerical data available in literature

FE·Meshless multiscale modeling of heterogeneous periodic materials

The computational mutiscale modeling of periodic heterogeneous materials, characterized by the assembly of units and joints, represents a compromise between the inaccuracy resulting from the macro modeling approach and the computational effort of the meso modeling. Assuming that the heterogeneities are orders of magnitude smaller than the structure dimensions, according to the multiscale approach, the macroscopic stresses and strains around a certain point can be found by averaging the stresses and the strains in a small representative part of the microstructure or a representative volume element (RVE) attributed to that point. A first-order two-scale scheme has been used to model heterogeneous polymers [1] or masonry panels [2]. The macroscopic strain is evaluated at each integration point and then is transferred to the RVE at the mesoscale as essential boundary conditions (macro-meso scale transition). As a result of the mesoscopic equilibrium problem, the RVE stress field is available and, by averaging it, the macroscopic stress is obtained (meso-macro scale transition). Thus, a new homogeneous material is created without using complex closed form constitutive relation for the representation of its behavior. As the model is based on the use of two scales, two different numerical approaches are employed: the finite element method at the macroscopic level and the meshless approach [3] at the mesoscopic one. The meshless method involves the construction of an approximated function of the displacements field, based on the values obtained in correspondence to several nodes, arbitrarily chosen in the domain and with specific domains of influence. The moving least square approximation is adopted for the construction of this function. In the present work the RVE is composed by the aggregate and the surrounding adhesive joints, which are simulated by zerothickness interface models. The non linear behavior of the heterogeneous material results from the inelastic deformation mechanisms occurring at the interfaces, while the units behaves elastically. The interface laws are formulated in the framework of elastoplasticity in order to simulate the softening response which occurs along the decohesion process in presence of shear and tensile tractions. The elastoplastic model is developed in a thermodynamically context and for plane stress applications. Numerical examples show the main features of the multiscale model and the novelties introduced

Adhesive debonding detection of FRP reinforcement by the ultrasonic non-destructive technique

Fiber reinforced polymer (FRP) composite systems are extensively used for repairing and reinforc- ing structurally inefficient concrete structures. The performance of an FRP rehabilitation system is highly influenced by its integrity. In particular, the presence of defects, e.g. voids, inclusions, debonds, improper cure and delaminations, caused by an inaccurately manufacture and installation, may affect the capability of the rehabilitated structure. For this reason, non-destructive (ND) meth- ods could be used to assess the quality of the reinforcement [1,2]. In this work an ultrasonic ND technique for detecting delamination defects in FRP reinforcement is presented. The technique couples the Akaike information criterion (AIC), used as automatic starting time signal detection [3] and the equivalent time-lenght (ETL) of the signal, used as indicator of the energy distribution of the signal with respect to the beginning of the signal [4]. When a perfect bonding between FRP and concrete substrate exists, the acoustical impedance mismatch is small, as both the FRP and the underlying material are dense solids, so the energy is almost transmitted to the concrete. On the other hand, when the adherence between FRP and concrete is compromised by the presence of a thin air gap, the acoustical impedance mismatch is bigger and a great amount of energy is reflected back. The results show that the energetic indicator ETL is particularly sensitive to the quality of the bonding of the FRP-concrete substrate. The proposed technique has been tested in pitch-catch mode on FRP reinforcements bonded to concrete substrates, both in vitro, using samples with imposed well-known defects, and in situ, on reinforced concrete beams included in a floor slab

Assessment of bonding defects in FRP reinforced structures via ultrasonic technique

Fiber reinforced polymer (FRP) composite systems are widely used for the rehabilitation of concrete structures such as building that need to resist to seismic loads, bridges that have to carry heavier traffic loads. The technique consists in bonding the composite plate to the concrete surface element in order to increase the flexural capacity. A proper attachment of the FRP plate to the concrete surface is necessary for the efficiency of the load transfer between the reinforcement and the substrate. In this work, the quality of composite bonding is characterized through ultrasonic testing. The proposed technique is relative to a time domain analysis of the ultrasonic signals and couples the Akaike Information Criterion (AIC), used as automatic onset signal detection, and the Equivalent Time-Length (ETL), used as an indicator of the quantity of energy propagating through the bonding. It has been tested both numerically and experimentally, in vitro, using samples with imposed well- known defects

Beta-Blocker Use in Older Hospitalized Patients Affected by Heart Failure and Chronic Obstructive Pulmonary Disease: An Italian Survey From the REPOSI Register

Beta (β)-blockers (BB) are useful in reducing morbidity and mortality in patients with heart failure (HF) and concomitant chronic obstructive pulmonary disease (COPD). Nevertheless, the use of BBs could induce bronchoconstriction due to β2-blockade. For this reason, both the ESC and GOLD guidelines strongly suggest the use of selective β1-BB in patients with HF and COPD. However, low adherence to guidelines was observed in multiple clinical settings. The aim of the study was to investigate the BBs use in older patients affected by HF and COPD, recorded in the REPOSI register. Of 942 patients affected by HF, 47.1% were treated with BBs. The use of BBs was significantly lower in patients with HF and COPD than in patients affected by HF alone, both at admission and at discharge (admission, 36.9% vs. 51.3%; discharge, 38.0% vs. 51.7%). In addition, no further BB users were found at discharge. The probability to being treated with a BB was significantly lower in patients with HF also affected by COPD (adj. OR, 95% CI: 0.50, 0.37-0.67), while the diagnosis of COPD was not associated with the choice of selective β1-BB (adj. OR, 95% CI: 1.33, 0.76-2.34). Despite clear recommendations by clinical guidelines, a significant underuse of BBs was also observed after hospital discharge. In COPD affected patients, physicians unreasonably reject BBs use, rather than choosing a β1-BB. The expected improvement of the BB prescriptions after hospitalization was not observed. A multidisciplinary approach among hospital physicians, general practitioners, and pharmacologists should be carried out for better drug management and adherence to guideline recommendations

Antidiabetic Drug Prescription Pattern in Hospitalized Older Patients with Diabetes

Objective: To describe the prescription pattern of antidiabetic and cardiovascular drugs in a cohort of hospitalized older patients with diabetes. Methods: Patients with diabetes aged 65 years or older hospitalized in internal medicine and/or geriatric wards throughout Italy and enrolled in the REPOSI (REgistro POliterapuie SIMI—Società Italiana di Medicina Interna) registry from 2010 to 2019 and discharged alive were included. Results: Among 1703 patients with diabetes, 1433 (84.2%) were on treatment with at least one antidiabetic drug at hospital admission, mainly prescribed as monotherapy with insulin (28.3%) or metformin (19.2%). The proportion of treated patients decreased at discharge (N = 1309, 76.9%), with a significant reduction over time. Among those prescribed, the proportion of those with insulin alone increased over time (p = 0.0066), while the proportion of those prescribed sulfonylureas decreased (p < 0.0001). Among patients receiving antidiabetic therapy at discharge, 1063 (81.2%) were also prescribed cardiovascular drugs, mainly with an antihypertensive drug alone or in combination (N = 777, 73.1%). Conclusion: The management of older patients with diabetes in a hospital setting is often sub-optimal, as shown by the increasing trend in insulin at discharge, even if an overall improvement has been highlighted by the prevalent decrease in sulfonylureas prescription

The “Diabetes Comorbidome”: A Different Way for Health Professionals to Approach the Comorbidity Burden of Diabetes

(1) Background: The disease burden related to diabetes is increasing greatly, particularly in older subjects. A more comprehensive approach towards the assessment and management of diabetes’ comorbidities is necessary. The aim of this study was to implement our previous data identifying and representing the prevalence of the comorbidities, their association with mortality, and the strength of their relationship in hospitalized elderly patients with diabetes, developing, at the same time, a new graphic representation model of the comorbidome called “Diabetes Comorbidome”. (2) Methods: Data were collected from the RePoSi register. Comorbidities, socio-demographic data, severity and comorbidity indexes (Cumulative Illness rating Scale CIRS-SI and CIRS-CI), and functional status (Barthel Index), were recorded. Mortality rates were assessed in hospital and 3 and 12 months after discharge. (3) Results: Of the 4714 hospitalized elderly patients, 1378 had diabetes. The comorbidities distribution showed that arterial hypertension (57.1%), ischemic heart disease (31.4%), chronic renal failure (28.8%), atrial fibrillation (25.6%), and COPD (22.7%), were the more frequent in subjects with diabetes. The graphic comorbidome showed that the strongest predictors of death at in hospital and at the 3-month follow-up were dementia and cancer. At the 1-year follow-up, cancer was the first comorbidity independently associated with mortality. (4) Conclusions: The “Diabetes Comorbidome” represents the perfect instrument for determining the prevalence of comorbidities and the strength of their relationship with risk of death, as well as the need for an effective treatment for improving clinical outcomes

Clinical features and outcomes of elderly hospitalised patients with chronic obstructive pulmonary disease, heart failure or both

Background and objective: Chronic obstructive pulmonary disease (COPD) and heart failure (HF) mutually increase the risk of being present in the same patient, especially if older. Whether or not this coexistence may be associated with a worse prognosis is debated. Therefore, employing data derived from the REPOSI register, we evaluated the clinical features and outcomes in a population of elderly patients admitted to internal medicine wards and having COPD, HF or COPD + HF. Methods: We measured socio-demographic and anthropometric characteristics, severity and prevalence of comorbidities, clinical and laboratory features during hospitalization, mood disorders, functional independence, drug prescriptions and discharge destination. The primary study outcome was the risk of death. Results: We considered 2,343 elderly hospitalized patients (median age 81 years), of whom 1,154 (49%) had COPD, 813 (35%) HF, and 376 (16%) COPD + HF. Patients with COPD + HF had different characteristics than those with COPD or HF, such as a higher prevalence of previous hospitalizations, comorbidities (especially chronic kidney disease), higher respiratory rate at admission and number of prescribed drugs. Patients with COPD + HF (hazard ratio HR 1.74, 95% confidence intervals CI 1.16-2.61) and patients with dementia (HR 1.75, 95% CI 1.06-2.90) had a higher risk of death at one year. The Kaplan-Meier curves showed a higher mortality risk in the group of patients with COPD + HF for all causes (p = 0.010), respiratory causes (p = 0.006), cardiovascular causes (p = 0.046) and respiratory plus cardiovascular causes (p = 0.009). Conclusion: In this real-life cohort of hospitalized elderly patients, the coexistence of COPD and HF significantly worsened prognosis at one year. This finding may help to better define the care needs of this population