Optimal Design of Wire-and-Arc Additively Manufactured I-Beams for Prescribed Deflection

Alloys fabricated by wire-and-arc additive manufacturing (WAAM) exhibit a peculiar anisotropy in their elastic response. As shown by recent numerical investigations concerning the optimal design of WAAM-produced structural components, the printing direction remarkably affects the stiffness of the optimal layouts, as well as their shape. So far, single-plate specimens have been investigated. In this contribution, the optimal design of WAAM-produced I-beams is addressed assuming that a web plate and two flat flanges are printed and subsequently welded to assemble the structural component. A formulation of displacement-constrained topology optimization is implemented to design minimum weight specimens resorting to a simplified two-dimensional model of the I-beam. Comparisons are provided addressing solutions achieved by performing topology optimization with (i) conventional isotropic stainless steel and with (ii) WAAM-produced orthotropic stainless steel at prescribed printing orientations. Lightweight solutions arise whose specific shape depends on the selected material and the adopted printing direction

Wire-and-Arc Additive Manufacturing for lattice steel structures: overview of the experimental characterization on dot-by-dot rods

With the advent of a new arc-based additive manufacturing (AM) process, referred to as Wire-and-Arc Additive Manufacturing (WAAM), the scale of the metal printed parts increased up to several meters, thus becoming suitable for large-scale applications in marine, aerospace and construction sectors. However, specific considerations in terms of geometrical and mechanical properties ought to be made in order to effectively use the printed outcomes for structural engineering purposes. The introduction of the novel printing strategy referred to as “dot-by-dot”, consisting in successive drops of molten metal, enabled the use of WAAM to realize complex lattice structures, made by continuous grids of WAAM rods. Nevertheless, their proper design requires an accurate evaluation of the influence of the non-negligible inherent geometrical irregularities on the mechanical response of the rods. Hence, extensive experimental work is needed in order to evaluate the mechanical response of “dot-by-dot” WAAM rods with geometrical imperfections. The present study focuses on the mechanical characterization of dot-by-dot WAAM-produced 304L stainless steel intersected rods, constituting the basic units of grid and lattice structures. The mechanical response of the specimens is assessed through tensile experimental tests conducted on two-ways planar nodes obtained from the intersection of two rods with different angles, hereafter also refereed to as crossed rods. The experimental results are then compared with tensile tests on single rods, to quantify the influence of the intersection angle in the structural response of the lattice structures

Large-Scale 3D Printing for Construction Application by Means of Robotic Arm and Gantry 3D Printer: A Review

Additive manufacturing technologies are becoming more popular in various industries, including the construction industry. Currently, construction 3D printing is sufficiently well studied from an academic point of view, leading towards the transition from experimental to mass large-scale construction. Most questions arise about the applicability of construction 3D printers for printing entire buildings and structures. This paper provides an overview of the different types of construction 3D printing technologies currently in use, and their fundamental differences, as well as some significant data on the advantages of using these advanced technologies in construction. A description of the requirements for composite printing is also provided, with possible issues that may arise when switching from lab-scale construction printing to mass large-scale printing. All printers using additive manufacturing technologies for construction are divided into three types: robotic arm printers, portal-type printers, and gantry 3D printers. It is noted that gantry printers are more suitable for large-scale printing since some of their configurations have the ability to construct buildings that are practically unlimited in size. In addition, all printers are not capable of printing with concrete containing a coarse aggregate, which is a necessary requirement in terms of the strength and economic feasibility of 3D printing material for large-scale applications

An environmental sustainability roadmap for partially substituting agricultural waste for sand in cement blocks

Agricultural waste can be used in cement block production for a number of reasons, including its environmental, economic, and labor benefits. This study examines the mechanical, durability, and cost-effectiveness characteristics of cement blocks. A cement block made from agriculture waste promotes sustainable construction practices, since waste agriculture is often dumped in landfills and regarded as a waste material. Carbon dioxide (CO2) emissions produced by the construction sector, either from the firing of clay bricks or from the production of cement, contribute significantly to global warming. In many developing countries, air pollution from agricultural activities is primarily accounted for the emissions from agricultural machinery and openly burning agro-waste. Farming is one of the leading causes of water and soil pollution. Hence, adopting agricultural waste into cement production would significantly reduce the environmental impact of concrete structures. The goal of this research is to determine whether agricultural waste products, such as vermiculite, pistachio shells, sugarcane bagasse, and coconut husks, can be used to substitute sand in concrete blocks. The water absorption capacity of waste materials, density, flexural strength, fire resistance, and compressive strength of waste materials as admixtures in concrete were evaluated using experimental tests. In most cases, the concrete blocks made from agricultural waste were strong enough to satisfy ASTM standards. The specimens containing coconut husks and pistachio shells, among others, were found to be fairly strong and durable, even when isolating them from water

An environmental sustainability roadmap for partially substituting agricultural waste for sand in cement blocks

Agricultural waste can be used in cement block production for a number of reasons, including its environmental, economic, and labor benefits. This study examines the mechanical, durability, and cost-effectiveness characteristics of cement blocks. A cement block made from agriculture waste promotes sustainable construction practices, since waste agriculture is often dumped in landfills and regarded as a waste material. Carbon dioxide (CO2) emissions produced by the construction sector, either from the firing of clay bricks or from the production of cement, contribute significantly to global warming. In many developing countries, air pollution from agricultural activities is primarily accounted for the emissions from agricultural machinery and openly burning agro-waste. Farming is one of the leading causes of water and soil pollution. Hence, adopting agricultural waste into cement production would significantly reduce the environmental impact of concrete structures. The goal of this research is to determine whether agricultural waste products, such as vermiculite, pistachio shells, sugarcane bagasse, and coconut husks, can be used to substitute sand in concrete blocks. The water absorption capacity of waste materials, density, flexural strength, fire resistance, and compressive strength of waste materials as admixtures in concrete were evaluated using experimental tests. In most cases, the concrete blocks made from agricultural waste were strong enough to satisfy ASTM standards. The specimens containing coconut husks and pistachio shells, among others, were found to be fairly strong and durable, even when isolating them from water

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

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

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

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

Comparison of earthquake-related consequences through loss analysis of different braced frame structural systems

Il presente elaborato di tesi tratta la valutazione di differenti sistemi di controventatura, sia dal punto di vista di risposta ad un evento sismico che in termini di perdite economiche legate al danneggiamento delle varie componenti. Tra di esse è presentata anche una nuova tipologia strutturale, ideata per ridurre il comportamento “soft-story” e “weak-story”, tipico delle strutture controventate convenzionali. In questo caso, è integrata alla struttura una trave reticolare metallica, che funge da supporto verticale ed è progettata per rimanere in campo elastico. Tale sostegno garantisce una distribuzione più uniforme degli sforzi lungo l’intera altezza della struttura, anziché concentrarli in un unico piano. La ricerca tratta lo studio della fattibilità economica di questa nuova tecnologia, rispetto alle precedenti soluzioni di controventatura adottate, confrontando le perdite economiche delle diverse soluzioni, applicate ad un unico prototipo di edificio collocato a Berkeley, CA. L’analisi sismica tiene in considerazione di tre diversi livelli di intensità, riferiti a un periodo di ritorno di 50 anni, corrispondente alla vita dell’edificio: questi sono caratterizzati dalla probabilità di ricorrenza, rispettivamente del 2%, 10% e 50% ogni 50 anni. L’ambito di ricerca presentato è estremamente innovativo e di primario interesse per lo sviluppo di uno studio sulla resilienza, che può essere adattato anche in un modello di urbanizzazione futura