26,549 research outputs found
Enhanced N-V interaction domains for the design of CLT shear wall based on coupled connections models
No full textThe present paper proposes some enhanced models, with different levels of accuracy, for the design of monolithic CLT shear wall based on the definition of reliable N-V interaction domain. The basic assumptions and the novelty aspects of the proposed models are presented. In particular, the adoption of an elastic-perfectly-plastic constitutive law for the timber instead of an elasto-brittle one and the accounting for the coupled axial-shear behavior of the connection elements to derive N-V interaction domains are critically discussed. Moreover, two different methods are adopted for the linearization procedure of the connection load-displacement response. Four of the proposed models are design oriented, two representing a lower bound (more suitable for practitioners), and two representing an upper bound. One more model is developed, which is research oriented and based on hybrid force-displacement approach. The reliability of the different models is investigated by means of numerical analyses exploiting the ultimate failure condition of the materials both in terms of strength and displacement capacity. Finally, the N-V domains for some CLT shear walls are presented and the impact of the different basic assumptions on the results are discussed in comparison with both experimental and numerical literature results
Evolution of earthquake-resistant proprietary clt connections: a multi-parametric numerical analysis to assess the effect on building seismic response.
No full textCharacterisation of the rigid diaphragm conditions for cross laminated timber floors
No full textThis paper presents a comprehensive numerical study aimed at defining the conditions for which Cross-Laminated Timber (CLT) floor diaphragms of platform-type CLT buildings can be assumed rigid in linear seismic analyses. Numerical analyses are conducted on a regular CLT archetype within a framework of parametric analyses, in which different geometrical and mechanical parameters including the stiffness of the floor panel-to-panel connections, the stiffness of the floor-to-wall connections, the floor span, the distance between two consecutive shear-walls, the lateral stiffness of the shear-walls, and the number of storeys are varied. The conditions to ensure a rigid diaphragm behaviour are derived by calculating the discrepancies in terms of floor displacements, distribution of lateral forces in the shear-walls, and fundamental vibration period of the structure, between numerical models where the floor is modelled with its actual deformability and as rigid. The discrepancies are compared with threshold values given in Eurocode 8 and used to derive the conditions for which CLT floor diaphragms can be assumed rigid. The study reveals that the behaviour of the floor tends toward the rigid diaphragm condition by increasing the stiffness of the floor panel-to-panel connections and the number of storeys, and by decreasing the stiffness of the floor-to-wall connections, the ratio between the distance between two consecutive shear-walls and the floor span, and the stiffness of the shear-walls. Specific threshold values ensuring a rigid diaphragm behaviour are determined for the properties of the system, delivering the geometrical and mechanical conditions for rigid CLT floor diaphragms
Innovative experimental setup for N-V coupled tests on masonry panels: concept and predictive numerical simulations
No full textA masonry pier subjected to shear can fail according to a rocking, sliding or diagonal cracking failure mode,
depending on the element geometry, the acting tangential and normal stresses, the boundary conditions,
and the masonry mechanical parameters [Magenes and Calvi, 1997; Calderini et al., 2009; Ferretti et al.,
2019a]. With the objective of studying the shear behavior of masonry, several experimental setups were
proposed, in past researches, for the execution of in-plane shear tests on masonry panels [van Vliet, 2004].
The variability of these setups, mainly related to the boundary conditions, the presence of a vertical load,
and the way of application of the horizontal load to the samples, highlights the need to correctly design such
systems to reproduce the desired shear failure [Ferretti et al., 2019b]
Administration of dexamethasone per os in finishing bulls. II. Effects on blood parameters used as indicators of animal welfare
No full textA set of hormonal, haematological and biochemical parameters was used to evaluate the physiological response and welfare status of 14 finishing Marchigiana bulls treated for 49 days with a low daily dosage (0.75 mg/head per day) of dexamethasone per os. Compared to the Control group, dexamethasone decreased cortisol concentrations (42.3 v. 5.7nmol/l; s.e.d. = 4.17; P < 0.001), and led to the reversal of the leukocyte formula in the animals treated (P < 0.05). Total serum proteins (70.2 v. 73.9 g/l; s.e.d. = 1.55; P < 0.05), in particular beta(1) globulins (7.5 v. 9.1 g/l; s.ed. = 0.24; P < 0.01) and fibrinogen (199 v. 258 mg/dl; s.e.d. = 32.70, P < 0.05), increased as a consequence of treatment. Prolonged dexamethasone administration led the bulls to an apparently chronic stress condition. Moreover, the study indicated various blood parameters that might be used by health officials as effective tools in identifying beef cattle suspected of being illegally treated with dexamethasone
Critical newborn assistence in intensive care units: model and simulation
No full textHigh risk newborns mortality has been dramatically reduced by recent progress in perinatal care. Related cares are organised by local regions in assistance structures classified according to three hospital levels; third level structures supply neonatal intensive and sub-intensive care. A simulation model describing critical newborns movements among birth centres and third level hospitals has been built and implemented, with the scope of checking regional third level neonatal care capacity and possibly suggesting suitable adaptations. The model has been usefully applied to Veneto region in Italy
Prima segnalazione di malattia nodulare branchiale nella trota fario (Salmo trutta L.)
No full textPRIMA SEGNALAZIONE DI MALATTIA NODULARE BRANCHIALE NELLA TROTA FARIO (SALMO TRUTTA L.)
Introduzione
La malattia nodulare branchiale (NGD) rappresenta uno dei maggiori problemi sanitari negli allevamenti italiani di trota iridea (Oncorhynchus mykiss). Episodi di NGD sono stati descritti in passato in salmerini alpini (Salvelinus alpinus) e salmoni reali (Oncorhynchus tshawytscha) allevati in acqua dolce. A marzo 2017, durante un monitoraggio di NGD in trote iridee nella Provincia di Trento, sono stati osservati i primi casi di malattia nodulare branchiale nella trota fario.
Metodologia
Le trote fario infette provenivano da due allevamenti dove erano contemporaneamente presenti episodi di NGD nelle trote iridee. I pesci, di taglia compresa tra i 20-25g (vasca 1) e 40-45 g (vasca 2), venivano allevati in vasche a fondo naturale alimentate con acqua di pozzo e sorgente. La temperatura dell’acqua variava da 5,5 a 7,2 °C nella vasca 1 e da 8,9 a 11,2°C nella vasca 2.
Da ogni vasca sono stati prelevati mensilmente 25 pesci a marzo, aprile e maggio 2017 per un totale di 150 soggetti. Le trote sono state sottoposte ad esami necroscopici ed analisi microscopiche. Le branchie sono state sezionate e fissate in formalina tamponata al 10% per l’esame istologico. In seguito i campioni sono stati processati, inclusi in paraffina, sezionati a 4 μm e colorati con soluzione di Giemsa.
Risultati
Le trote fario osservate in vasca non mostravano né grave sintomatologia respiratoria né alte mortalità tipiche di NGD nelle trote iridee. In 53 pesci su 150 sono state osservate branchie dall’aspetto rigonfio e pallido con presenza di noduli biancastri lungo gli apici dei filamenti.
Microscopicamente le branchie colpite mostravano reazioni proliferative a carico dei filamenti con fusione delle lamelle, specialmente nelle porzioni distali. Le lesioni descritte, sia a livello macroscopico che microscopico, erano tipiche delle infezioni da NGD.
L’esame microscopico ha permesso di osservare trofozoiti di amebe (di diametro di circa 15 x 20 μm) lungo la superficie dei filamenti iperplastici.
Le analisi istologiche hanno evidenziato iperplasia ed ipertrofia dell’epitelio branchiale e delle cellule mucipare, necrosi e presenza di amebe lungo la superficie dei filamenti in 32 trote su 150 campionate.
Discussione
Nonostante l’assenza di gravi sintomatologie respiratorie e di alte mortalità, le alterazioni proliferative delle branchie associate alla presenza di amebe hanno mostrato come anche la trota fario possa essere interessata dalla malattia nodulare branchiale. Ulteriori studi appaiono necessari per chiarire gli aspetti eziopatogenetici della NGD in questa specie ed il suo coinvolgimento nella diffusione della patologia nelle troticolture italiane
Occurrence of nodular gill disease in farmed brown trout (Salmo trutta L.)
No full textIntroduction
Nodular gill disease (NGD) represents one of the most serious pathology affecting freshwater farmed rainbow trout (Oncorhynchus mykiss) in Italy. This disease has also been observed in arctic char (Salvelinus alpinus) and Chinook salmon (Oncorhynchus tshawytscha) cultured in freshwater environment. The first case of branchitis associated with amoebic infection is detected in farmed brown trout (Salmo trutta L.) in March 2017, during an investigation of NGD in rainbow trout in the province of Trento (Northern Italy).
Methodology
In a NGD affected rainbow trout farming an outbreak of low mortality occurred in brown trout in one earth tank supplied by spring water with temperature of 6°C. The average weight of the fish was 20-25g. Twenty five fish from the affected tank were collected for necropsy, microscopical and parasitological analysis. Gills were dissected and fixed in 10% neutral buffered formalin solution for histological examination. The samples were dehydrated, embedded in paraffin wax, sectioned (4 μm) and stained with Hematoxylin Eosin and Giemsa solution.
Results
The fish did not exhibit the typical respiratory symptoms described in NGD of the rainbow trout. The gill tissue appeared pale and swollen at the necropsy with whitish nodules in 9 out of 25 sampled trout. Microscopically numerous Gyrodactylus spp. were observed on the skin. The affected gills showed a proliferative reaction of some filaments, especially in the distal part. These lesions were typical of NGD infection. The microscopic examination of gill tissue revealed the presence of amoebic organisms (approximately 15 x 20 μm). The histology showed multi-focal epithelial hyperplasia of the gills causing lamellar fusion, mucous cells hypertrophy, cellular necrosis and presence of limited number of amoebae along the surface of the affected filaments in 6 out of 25 collected gills.
Discussion
Despite absence of respiratory symptoms and high mortality rate, gill proliferative lesions associated with amoebae shows that brown trout may be affected by nodular gill disease. Studies are in progress to clarify pathogenesis, biological and environmental determinants of NGD in brown trout and to define the involvement of this species in the spread of the disease in Italian trout farms
Cyclic response of CLT Post-Tensioned Walls: Experimental and numerical investigation
No full textThis paper presents the main outcomes of full-scale cyclic tests on CLT post-tensioned walls. Investigated systems were constituted by rocking dissipative timber walls, whose main features were the re-centering of walls, low damage in case of seismic actions, additional hysteretic dissipation, and easy replacement of dampers. Referring to previous experimental campaign on LVL and CLT structures available in literature, the proposed post-tensioned CLT wall system was conceived employing an innovative and replaceable damping system and realizing all the technological details in order to minimize local and global damages due to horizontal cyclic loading. Two kinds of post-tensioned systems were tested: single wall and double walls with different set-up configurations and patterns of the dampers. Specifically, two different levels of initial post-tensioning force were applied and different patterns of damper system were experimentally investigated in order to define the energy dissipation contribution provided by the individual damper types installed. These different configurations were investigated by using the same CLT wall system which, despite having been subjected to repeated cyclic tests, showed limited residual damage and therefore fulfilled the low-damage requirement. In order to properly design the experimental set-up, an advanced Finite Element nonlinear numerical model was developed in the OpenSEES framework and then calibrated on the local response of the individual components of the system. Model calibration is presented and the comparison with the experimental results is critically discussed both in terms of local and global response of the PT-wall systems. The proposed model well captured the hysteretic behaviour of the wall system highlighting the reliability of the modelling strategy
Post-tensioned low damage CLT walls with replaceable hysteretic devices - Concept, experimental and numerical characterization
No full textThis paper deals with the conception, the experimental and numerical characterization of an innovative post-tensioned CLT wall system equipped with external and replaceable hysteretic devices. The cyclic behavior of the post-tensioned walls was firstly investigated at the mechanical laboratory of CIRI-EC of University of Bologna by means of experimental tests on single component of the structural system and on the full-scale post-tensioned CLT walls prototypes. Results from experimental tests demonstrate the capability of the conceived post-tensioned wall systems to withstand significant drift without damage on the main timber and steel components. A good dissipative capacity of the wall configurations equipped with dissipaters was also observed. A nonlinear Finite Element model capable of reproducing the wall system hysteretic behavior was developed in the OpenSees framework. Implemented FE numerical model demonstrated a good capability of reproducing the experimental response
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