La Stima dei Moduli Elastici delle Murature Secondo le Norme Tecniche: il Confronto con la Sperimentazione

Nel presente lavoro viene proposto uno studio sperimentale per la caratterizzazione meccanica di diverse tipologie di muratura. Vengono in particolare valutati i moduli elastici longitudinali e tangenziali che come è noto condizionano la risposta di sistemi murari sotto carichi laterali. I valori sperimentali sono confrontati con quelli stimabili per mezzo dei modelli proposti dalle normative tecniche italiana (DM 14/01/2008) e europea (Eurocodice 6). Lo studio prende spunto dalla questio posta dalla norma americana (MSJC 2008) che, pur proponendo l’uso di tali modelli, riconosce la poca sperimentazione eseguita a supporto della loro validazione. La campagna sperimentale ha incluso prove di compressione sui componenti (malte e blocchi), prove di compressione diagonale e prove di compressione ordinaria (in direzione ortogonale ai letti di malta) su porzioni di muratura. I risultati conseguiti hanno consentito la valutazione diretta dei moduli elastici e successivamente di ottenere le grandezze meccaniche necessarie per l’utilizzo dei succitati modelli normativi

Real-life effects of dupilumab in patients with severe type 2 asthma, according to atopic trait and presence of chronic rhinosinusitis with nasal polyps

BackgroundThe efficacy of dupilumab as biological treatment of severe asthma and chronic rhinosinusitis with nasal polyps (CRSwNP) depends on its ability to inhibit the pathophysiologic mechanisms involved in type 2 inflammation.ObjectiveTo assess in a large sample of subjects with severe asthma, the therapeutic impact of dupilumab in real-life, with regard to positive or negative skin prick test (SPT) and CRSwNP presence or absence.MethodsClinical, functional, and laboratory parameters were measured at baseline and 24 weeks after the first dupilumab administration. Moreover, a comparative evaluation was carried out in relation to the presence or absence of SPT positivity and CRSwNP.ResultsAmong the 127 recruited patients with severe asthma, 90 had positive SPT, while 78 reported CRSwNP. Compared with the 6 months preceding the first dupilumab injection, asthma exacerbations decreased from 4.0 (2.0-5.0) to 0.0 (0.0-0.0) (p < 0.0001), as well as the daily prednisone intake fell from 12.50 mg (0.00-25.00) to 0.00 mg (0.00-0.00) (p < 0.0001). In the same period, asthma control test (ACT) score increased from 14 (10-18) to 22 (20-24) (p < 0.0001), and sino-nasal outcome test (SNOT-22) score dropped from 55.84 ± 20.32 to 19.76 ± 12.76 (p < 0.0001). Moreover, we observed relevant increases in forced expiratory volume in one second (FEV1) from the baseline value of 2.13 L (1.62-2.81) to 2.39 L (1.89-3.06) (p < 0.0001). Fractional exhaled nitric oxide (FeNO) values decreased from 27.0 ppb (18.0-37.5) to 13.0 ppb (5.0-20.0) (p < 0.0001). These improvements were quite similar in subgroups of patients characterized by SPT negativity or positivity, and CRSwNP absence or presence. No statistically significant correlations were detected between serum IgE levels, baseline blood eosinophils or FeNO levels and dupilumab-induced changes, with the exception of FEV1 increase, which was shown to be positively correlated with FeNO values (r = 0.3147; p < 0.01).ConclusionOur results consolidate the strategic position of dupilumab in its role as an excellent therapeutic option currently available within the context of modern biological treatments of severe asthma and CRSwNP, frequently driven by type 2 airway inflammation

Mechanical properties of steel fibre reinforced lightweight concrete with pumice stone or expanded clay aggregates

This paper presents basic information on the mechanical properties of steel fibre-reinforced lightweight concrete, manufactured using pumice stone or expanded clay aggregates. Results are presented for standard compressive tests and indirect tensile tests (splitting tests on cylinder specimens and flexure tests on prismatic beams using a three-point loading arrangement) under monotonically increasing or cyclically varying loads. The influence of steel fibres and aggregate types on modulus of elasticity, compressive and tensile strength and post-peak behaviour is evaluated. Test results show that compressive strength does not change for pumice stone aggregates, while an increase is observed for expanded clay; tensile strength and fracture toughness are significantly improved for both pumice stone and expanded clay. The results also show that with both expanded clay and pumice stone lightweight aggregates a suitable content of fibres allows one to obtain performances comparable with those expected from normal weight concrete, the important advantage of lower structural weight being maintained

Flexural response of external R.C. beam-column joints externally strengthened with steel cages

An experimental and theoretical research referred to the flexural behavior of external R.C. joints strengthened with steel cages constituted by steel angles and battens is presented. The subassemblage (beam, column and joint) was subjected to a constant vertical load acting on the column and to a monotonically increasing lateral force applied at the tip of the beam. The control specimen is without strengthening system and it was designed with weak column and strong beam and overstrength in the joint region. Strengthening cases here studied refer to steel caging in the column and both in the beam and in the column. Cyclic response in term of load-displacement curves, crack patterns and observation of failure mode types were the main results of the experimental results. Results highlight the effectiveness of the external steel cages as strengthening system, which increases the flexural strength and allows one to move the failure mode from the column to the beam. A simplified analytical model is proposed that can be used for pushover analysis and is able to reproduce the flexural behavior of external beam-column joints under monotonic loading. The model includes shear-to-moment interaction for beams and columns and confinement effects induced by external steel cages. The model is based on the determination of elastic-plastic behavior of the beam and of the columns, the latter being obtained from knowledge of the ultimate moment associated with the design axial force and deduced through a simplified moment-axial force domain. The joint was modeled with a strut and tie model in which concrete crushing and yielding of stirrups are the only limit states considered. Finally, a comparison between experimental load-deflection curves and analytical prediction is made showing good agreement

Stainless steel grids for confinement of clay brick masonry columns

This work presents the results of an experimental investigation on the behavior of 21 solid clay brick columns internally strengthened by stainless steel grids placed in the horizontal joints of mortar. This reinforcing technique can be applied as a constructive technique for new construction or as a retrofitting technique for existing structures (old structures to be reconstructed by original constructive method and internal reinforcement). Monotonic compressive loading tests were carried out under concentric and eccentric load. The effects of different numbers of steel grids and eccentricity of the external load were examined. Also, a detailed characterization of the constituent materials was made experimentally. The compression tests show the effectiveness of the proposed strengthening technique, which proves to be able to produce the increases in strength and energy required to collapse brick columns under both concentric and eccentric loads. To provide an analysis method for practical applications, an analytical expression is proposed that gives the strength value of confined brick columns by considering that the biaxial strength domain of the bricks is modified due to the tensile contribution offered by the presence of steel grids. Moreover, moment-axial force domains, derived using the plane cross section theory, are calibrated on the basis of the compressive strength values experimentally detected

Simplified analytical model for moment–axial force domain in the presence of shear in R.C. members externally strengthened with steel cages

Equations for a hand calculation of moment–axial force domain in the presence of shear for R.C. beam/column externally strengthened with steel angles and strips are developed. The analytical derivation is made assuming, for axial load and flexure, the equivalent stress-block parameters for internal forces, considering the confinement effects induced in the concrete core by external cages both in the cases of strips or angles yielding. Limit states due to bond failure, concrete crushing and yielding of steel angles and strips in flexure and in shear, including moment-to-shear interaction, are considered. The proposed model gives results in a good agreement with available experimental data and it allows a hand control of the influence of the main parameters governing the problem (angle and strip geometry and mechanical properties of constituent materials)

Advanced Strategies and Materials for Reinforcing Normal and Disturbed Regions in Brick Masonry Columns

This work presents the results of an experimental investigation on the behavior of 42 solid clay brick masonry columns internally strengthened by fiber-reinforced polymer (FRP) fabrics or stainless steel grids placed in horizontal mortar joints. In some cases, every course, and in other cases, alternate courses were reinforced with steel grids, carbon, and basalt FRP fabrics. Monotonic compressive loading tests were carried out under concentric and eccentric loads. Eccentric tests were carried out by loading the specimens on a reduced area with respect to the entire cross section, producing a disturbed region (D-region). A detailed characterization of the constituent materials was made experimentally. The compression tests show the effectiveness of the proposed strengthening techniques to produce increases in strength and the energy required for collapse of brick columns under concentric loads. Under eccentric loads, the reduction in the load-carrying capacity owing to the reduced loaded area is attenuated by the presence of the transverse reinforcements. An analytical expression is proposed that gives the strength of clay brick masonry columns considering that the biaxial strength domain of the bricks is modified because of the tensile contribution provided by the presence of transverse reinforcements. Moreover, a strut-and-tie model was utilized to calculate the load-carrying capacity in the D-region and was verified against experimental data, with good agreement