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La resistenza a taglio di pannelli murari rappresenta un elemento fondamentale per la capacità sismica degli edifici in muratura. Pertanto, una corretta stima di tale resistenza è, senza, dubbio, di primaria importanza sia per la valutazione della vulnerabilità sismica degli edifici esistenti, sia per le nuove progettazioni. Allo stato attuale diverse sono le formulazioni proposte in letteratura o presenti nei codici normativi per la stima della resistenza a taglio, anche se spesso ricavate da differenti ipotesi sullo stato tensionale che si instaura all’interno del pannello o ottenute con diverse modalità di prova. In questo articolo è stato analizzato il problema della determinazione della resistenza a taglio di pannelli murari mediante prove di compressione diagonale, formulando un criterio di resistenza alternativo per l’interpretazione dei risultati sperimentali. In particolare è stata proposta una modifica al criterio di Drucker-Prager che, tipicamente espresso in tensioni principali, è stato rielaborato in termini di tensioni tangenziali. La superficie limite proposta, nel piano di Mohr, è descritta mediante due rette aventi differenti inclinazioni (coefficiente di attrito) nel quadrante delle compressioni ed in quello delle trazioni. I risultati teorici ottenuti sono stati poi validati confrontandoli con quelli di prove sperimentali presenti in letteratura scientifica, nonché comparati con le formulazioni attualmente presenti nei codici normativi.

Fiber-Reinforced Polymer (FRP) represents one of the most diffuse and effective strengthening technique for retrofitting columns in existing buildings when presenting insufficient mechanical properties. In fact, the confinement effect provided by wraps with high-tensile strength and stiffness induces significant enhancement of the mechanical behaviour. In this paper experimental results of axial compression tests on both un-confined and FRP-confined prismatic yellow tuff masonry columns are presented. In particular, two types of masonry arrangements, regular and irregular, were reproduced in order to investigate the effectiveness of the confinement on column typologies widely used in the past in Southern Italy and Mediterranean basin. The performed experimental tests allowed to obtain the constitutive axial and transversal stress-strain laws and to evaluate the improvement of the mechanical behaviour, in terms of strength and ductility, due to FRP confinement. The results have highlighted a significant difference in the shape of the constitutive law for confined masonry with respect to the one of confined concrete. Contrary to FRP confined concrete members, in the case of confined masonry members specific theoretical constitutive model has been not yet developed. To this aim, in this paper the various stress-strain laws developed for FRP-confined concrete elements has been applied to masonry elements too and a comparative analyses between experimental and theoretical results has been carried out.

Great part of the existing buildings in seismic areas and in particular in developing countries is represented by masonry buildings, diffused also in the major part of historical centres in Europe. Damages due to seismic events have evidenced the large demand of rehabilitation together with suitable assessment methods for these structures. When out of plane mechanism can be avoided, the contribution of in-plane shear resistance of the masonry walls is a key aspect to consider in the vulnerability analysis of the whole structure. Based on this last consideration, this paper presents an approach to the analysis of in-plane behaviour of masonry walls, involving a minimum energy strategy. The results of the numerical analyses presented are compared with those obtained by laboratory tests on brick masonry panels. © Patron Editore S.r.l. Gran parte del patrimonio edilizio esistente in zona sismica, soprattutto nei paesi in via di sviluppo, è costituito da edifici in muratura, largamente diffusi anche in tutti i centri storici europei. I collassi e i danni rilevati a seguito di eventi sismici hanno evidenziato la necessità di interventi e soprattutto di tecniche di analisi idonee. In un edificio in muratura ben progettato e realizzato, ove i meccanismi di collasso per azioni fuori piano possono essere esclusi, il comportamento nel piano delle pareti in muratura diventa un aspetto chiave da esaminare nelle valutazioni di vulnerabilità sismica. Partendo da quest'ultima considerazione, questo lavoro presenta un approccio per la l'analisi del comportamento nel piano di pareti murarie sottoposte a compressione e taglio. La procedura utilizzata considera la muratura come un materiale elastico non resistente a trazione, definisce pertanto una sagoma reagente contenuta nell'ambito del pannello murario soggetta a soli sforzi di compressione e risolve una procedura numerica la cui soluzione corrisponde al minimo dell'energia potenziale per il pannello. Vengono presentati confronti fra i risultati numerici e alcune prove sperimentali presenti in letteratura per diverse geometrie di pannello. © Patron Editore S.r.l.

This paper deals with the influence of the rolling shear deformation on the flexural behavior of CLT (Cross-Laminated Timber) panels. The morphological configuration of the panels, which consist of orthogonal overlapped layers of boards, led to a particular shear behavior when subjected to out-of-plane loadings: the low value of the shear modulus in orthogonal to grain direction (i.e., rolling shear modulus) gives rise to significant shear deformations in the transverse layers of boards, whose grains direction is perpendicular with respect to the tangential stresses direction. This produces increases of deflections and vibrations under service loads, creating discomfort for the users. Different analytical methods accounting for this phenomenon have been already developed and presented in literature. Comparative analyses among the results provided by some of these methods have been carried out in the present paper and the influence of the rolling shear deformations, with reference to different span-to-depth (L/H) ratios investigated. Moreover, the analytical results have also been compared with those obtained by more accurate 2D finite element models. The results show that, at the service limit states, the influence of the rolling shear can be significant when the aspect ratios became less than L/H = 30, and the phenomenon must be accurately considered in both deflection and stress analysis of CLT floors. Contrariwise, in the case of higher aspect ratios (slender panels), the deflections and stresses can be evaluated neglecting the rolling shear influence, assuming the layers of boards as fully-connected.

Objectives: To explore the rate, the determinants of success, and the hemodynamic impact of balloon postdilatation (BPD) of self-expanding transcatheter heart valves (SE-THVs). Background: BPD is commonly used to optimize valve expansion and reduce paravalvular leakage (PVL) after transcatheter aortic valve implantation (TAVI) without clearly knowing its hemodynamic benefits. Methods: Patients (n = 307) who received a SE-THV were stratified according to whether a BPD was performed or not. Patients who received BPD were stratified according to the severity of PVL remaining after BPD into two groups: Successful BPD (≤mild PVL + BPD) and Failed BPD (moderate-severe PVL + BPD). Results: BPD was performed in 121 patients (39.4%) and was successful in 106 patients (87.6% of attempts). A ratio of the postdilatation balloon diameter to the annulus diameter ≤0.95 was an independent predictor of BPD failure (OR: 10.72 [2.02-56.76], P =.005). Peak transvalvular pressure gradient (PG) was lower in the Successful BPD group (14[12-22] mm Hg) than in the Failed BPD group (18[16-23] mm Hg, P =.029), and did not rise in either group during follow-up (median [IQR], 364[161-739] days). Conclusion: BPD was performed in 39% of patients who received a SE-THV, and was successful in the majority of attempts. BPD failure was more likely in patients with a small postdilatation balloon-to-annulus diameter ratio. Effective BPD improved THV hemodynamic performance, and this was maintained in the intermediate-term post-TAVI.

Background: Balloon post-dilatation (BPD) is often needed for optimizing transcatheter heart valve (THV) implantation, since paravalvular leak (PVL) after transcatheter aortic valve implantation is associated with poor outcome and mortality. Quantitative assessment of PVL severity before and after BPD is mandatory to properly assess PVL, thus improving implantation results and outcomes. Objective: To investigate a quantitative angiographic assessment of aortic regurgitation (AR) by videodensitometry before and after BPD. Methods: Videodensitometric-AR assessments (VD-AR) before and after BPD were analysed in 61 cases. Results: VD-AR decreased significantly from 24.0[18.0-30.5]% to 12.0[5.5-19.0]% (p < 0.001, a two-tailed p < 0.05 defined the statistical significance). The relative delta of VD-AR after BPD ranged from -100% (improvement) to +40% (deterioration) and its median value was -46.2%. The frequency of improvement, no change, and deterioration were 70% (n = 43), 25% (n = 15) and 5% (n = 3), respectively. Significant AR (VD-AR > 17%) was observed in 47 patients (77%) before and in 19 patients (31%) after BPD. Conclusions: VD-AR after THV implantation provides a quantitative assessment of post-TAVI regurgitation and can help in the decision-making process on performing BPD and in determining its efficacy. Resumo Fundamento: A pós-dilatação com balão (PDB) é normalmente necessária para otimização do implante da válvula cardíaca transcateter (THV), uma vez que o “escape” ou leak paravalvar (PVL) após implante de valva aórtica transcateter está associada com desfecho ruim e mortalidade. A avaliação quantitativa da gravidade do PVL antes e após a PDB é mandatória para se avaliar adequadamente o PVL e, assim, melhorar os resultados e os desfechos do implante. Objetivo: Investigar uma avalição angiográfica quantitativa da regurgitação aórtica (RA) por videodensitometria (VD-RA) antes e após a PDB. Métodos: Resultados da VD-RA antes e após a PDB foram analisados em 61 casos. Resultados Houve diminuição significativa da VD-RA de 24,0(18,0-30,5)% para 12,0(5,5-19,0)% (p < 0,001; p < 0,05 bilateral foi definido como significância estatística). O delta relativo de VD-RA após a PDB variou de -100% (melhora) a +40% (piora) e o valor mediano foi -46,2%. As frequências de melhora, ausência de mudança, e piora foram 70% (n = 43), 25% (n = 15) e 5% (n = 3), respectivamente. Observou-se RA significativo (VD-RA > 17%) em 47 pacientes (77%) antes e em 19 pacientes (31%) após a PDB. Conclusões: A VD-RA após o implante de THV possibilita a avaliação quantitativa da regurgitação pós-TAVI, e pode auxiliar na tomada de decisão quanto à realização ou não da PDB, bem como na avaliação de sua eficácia.

The beneficial effect provided by external Fiber-Reinforced Polymers (FRP) confinement on the compressive behaviour of masonry columns has been widely demonstrated by experimental results. Conversely to FRP-confined concrete, for which some reliable stress–strain theoretical models have been developed, in case of confined masonry any unified model has been yet provided. In this paper, after the elaboration of a database containing experimental results on FRP-wrapped masonry columns tested under axial loads, new design-oriented stress–strain constitutive relationships for FRP-confined masonry are proposed. These laws—which have general validity for whatever confined masonry—were derived from the existing Lam and Teng’s model originally developed for FRP-confined concrete, and here adapted to confined tuff masonry. Two functions rule the shape of theoretical stress–strain curve: a second order parabola defines the elastic behaviour, while a straight-line describes the post-elastic behaviour. The entire axial stress–strain response is completely defined by unconfined masonry mechanical properties, composite material characteristics and by a single unknown parameter. This latter takes into account of the dispersion of experimental data and has been evaluated by means of the regression analyses procedure based on the least-squares optimization criteria. The outputs of the proposed constitutive laws were compared with the experimental results currently available in literature. A good matching is observed between the experimental results and the theoretical predictions in terms of axial stress–strain curves.

The femoral venous approach for percutaneous edge-to-edge repair of the mitral valve with the MitraClip system (Abbott Vascular, Santa Clara, California) may not be possible in patients with occlusion or congenital anomalies of the inferior vena cava (IVC) or limited by the presence of an IVC filter

Transcatheter aortic valve implantation (TAVI) is undeniably invading the “surgical” space and expanding its indication. Over the last five years, there has been a real revolution in TAVI technology with the introduction of newer devices that aimed to simplify the procedure1. These swift advances have transformed the landscape in structural heart disease and culminated in a broader use of TAVI in clinical practice2,3. The procedure is not only spreading worldwide but is also becoming less aggressive for the patient with the so-called “minimalist approach”.

Background: No data exist about the characteristics of infective endocarditis (IE) post-transcatheter aortic valve replacement (TAVR) according to transcatheter valve type. We aimed to determine the incidence, clinical characteristics, and outcomes of patients with IE post-TAVR treated with balloon-expandable valve (BEV) versus self-expanding valve (SEV) systems. Methods: Data from the multicenter Infectious Endocarditis After TAVR International Registry was used to compare IE patients with BEV versus SEV. Results: A total of 245 patients with IE post-TAVR were included (SEV, 47%; BEV, 53%). The timing between TAVR and IE was similar between groups (SEV, 5.5 [1.2–15] months versus BEV, 5.3 [1.7–11.4] months; P =0.89). Enterococcal IE was more frequent in the SEV group (36.5% versus 15.4%; P P =0.01; valve leaflet, SEV, 23.9%; BEV, 38.5%; P =0.01). BEV recipients had a higher rate of stroke/systemic embolism (20.0% versus 8.7%, adjusted OR: 2.46, 95% CI: 1.04–5.82, P =0.04). Surgical explant of the transcatheter valve (SEV, 8.7%; BEV, 13.8%; P =0.21), and in-hospital death at the time of IE episode (SEV, 35.6%; BEV, 37.7%; P =0.74) were similar between groups. After a mean follow-up of 13±12 months, 59.1% and 54.6% of the SEV and BEV recipients, respectively, had died ( P =0.66). Conclusions: The characteristics of IE post-TAVR, including microorganism type, vegetation location, and embolic complications but not early or late mortality, differed according to valve type. These results may help to guide the diagnosis and management of IE and inform future research studies in the field.

Objectives To report clinical, angiographic characteristics, outcomes, and predictors of unsuccessful procedures in patients who underwent chronic total occlusion (CTO) percutaneous coronary interventions (PCI) in Latin America. Background CTO PCI has been increasingly performed worldwide, but there is a lack of information in this region. Methods An international multicenter registry was developed to collect data on CTO PCI performed in centers in Latin America. Patient, angiographic, procedural and outcome data were evaluated. Predictors of unsuccessful procedures were assessed by multivariable analysis. Results We have included data related to 1,040 CTO PCIs performed in seven countries in Latin America (Argentina, Brazil, Chile, Colombia, Ecuador, Mexico, and Puerto Rico). The mean age was 64 ± 10 years, and CTO PCI was performed mainly for angina control (81%) or treatment of a large ischemic area (30%). Overall technical success rate was 82.5%, and it was achieved with antegrade wire escalation in 81%, antegrade dissection/re-entry in 8% and with retrograde techniques in 11% of the successful procedures. Multivariable analysis identified moderate/severe calcification, a blunt proximal cap and a previous attempt as independent predictors of unsuccessful procedures. In-hospital major adverse cardiovascular events (MACE) occurred in 3.1% of the cases, death in 1% and cardiac tamponade in 0.9% CONCLUSIONS: CTO PCI in Latin America has been performed mainly for ischemia relief. Procedures were associated with a success rate above 80% and low incidence of MACE. Predictors of unsuccessful procedures were similar to those previously reported in the literature.

Aims We sought to evaluate the outcomes of transcatheter mitral valve replacement (TMVR) for patients with degenerated bioprostheses [valve-in-valve (ViV)], failed annuloplasty rings [valve-in-ring (ViR)], and severe mitral annular calcification [valve-in-mitral annular calcification (ViMAC)]. Methods and results From the TMVR multicentre registry, procedural and clinical outcomes of ViV, ViR, and ViMAC were compared according to Mitral Valve Academic Research Consortium (MVARC) criteria. A total of 521 patients with mean Society of Thoracic Surgeons score of 9.0 ± 7.0% underwent TMVR (322 patients with ViV, 141 with ViR, and 58 with ViMAC). Trans-septal access and the Sapien valves were used in 39.5% and 90.0%, respectively. Overall technical success was excellent at 87.1%. However, left ventricular outflow tract obstruction occurred more frequently after ViMAC compared with ViR and ViV (39.7% vs. 5.0% vs. 2.2%; P

Nel 2007 veniva pubblicato, sotto l’egida del Consiglio Nazionale delle Ricerche, il documento DT 206/2007 avente ad oggetto le “Istruzioni per la Progettazione, l’Esecuzione ed il Controllo delle Strutture di Legno”. Con tale documento il CNR, tramite la propria Commissione di studio per la predisposizione e l'analisi di norme tecniche relative alle costruzioni, intendeva fornire un contributo tecnico di supporto agli operatori impegnati nelle varie fasi della costruzione di strutture di legno, in linea con le conoscenze più avanzate del settore. Da allora, il mondo dell’ingegneria delle strutture di legno si è largamente avvalso del suddetto documento, divenuto via via lo strumento indispensabile e più diffuso per l’impiego strutturale del legno, aprendo i mercati e favorendo la competizione e le nuove applicazioni. In questi anni nuovi studi, ricerche e proposte innovative hanno accompagnato l’attività di produttori, costruttori e progettisti, promuovendone l’evoluzione e la (talvolta disordinata) crescita. Il quadro dei riferimenti normativi e di prodotto, europei ed italiani, si è anch’esso evoluto. E’ per queste ragioni che, dopo un decennio dalla pubblicazione del DT 206/2007, una sua nuova aggiornata ed ampliata versione si è resa più che opportuna e viene qui presentata alla comunità scientifico tecnica nazionale con l’acronimo DT 206-R1, in un testo che cerca, ancora una volta, di cogliere al meglio l’esperienza maturata a livello internazionale nello specifico ambito normativo, senza perdere di vista le singolari caratteristiche della realtà italiana. Il documento è frutto della spontanea collaborazione di un gruppo aperto di specialisti e di operatori del settore basata, com’è tradizione nel nostro paese, sull’ampia discussione del comune patrimonio di conoscenze e di esperienze scientifiche e tecniche. Si richiama esplicitamente all’attenzione del lettore la circostanza che le Istruzioni, per loro genesi e natura, non sono norme cogenti, ma rappresentano soltanto un ausilio offerto ai tecnici impegnati nella progettazione delle strutture di legno.