Analyse expérimentale et modélisation du comportement de structures précontraintes

This work aims to study the mechanical behavior of partially prestressed structures and to evaluate the influence of the post-tensioning system: bonded tendons, individual unbonded greased and sheathed strands. Under the scope of the safety and durability of nuclear containments, specific attention is devoted to the concrete cracking behavior and to the role of the mechanical tendons-structure bond. The proposed approach is divided into three successive parts. It starts with an experimental study of damage mechanisms at the structural level (4-point bending tests on prestressed concrete beams) and at the local scale (cracking, delayed strains of concrete, reinforcement-concrete bond, tendons-structure bond with pull-out tests and tension tests on reinforced concrete ties). The used instrumentation (DIC, optical fibers) allows for the robustness of the approach. Numerical models are then developed, based on the previous characterized mechanisms. A particular interest is focused on the meso-modeling of the reinforcement-concrete interface and on the macro-modeling of the tendons-injected grout bond. The use of the developed models, considering in parallel the influence of the evolutive delayed strains of concrete, provides a predictive analysis of the mechanical behavior of the studied prestressed structures. A final application to a part of a nuclear containment offers an accurate prediction of the influence of the post-tensioning system on the cracking behavior of the structure.Ces travaux ont pour but d'étudier le comportement mécanique de structures précontraintes et d'évaluer l'influence de la technologie de précontrainte utilisée : précontrainte par torons adhérents, précontrainte par torons non-adhérents TGG. Le champ d'application final porte sur l'analyse de la sûreté et de la durabilité des enceintes de confinement de centrales nucléaires. L'attention est alors portée principalement sur le comportement à la fissuration du béton et au rôle de la liaison mécanique torons de précontrainte-structure.La démarche proposée se décompose en trois étapes successives. Elle débute par la caractérisation expérimentale des mécanismes de dégradation à l'échelle de la structure (essais de flexion 4 points sur poutres précontraintes) et à l'échelle locale du matériau (fissuration, déformations différées du béton, liaisons armatures passives-béton et torons-structure par des essais d'arrachement et de traction sur tirants). Une instrumentation multiple (CIN, fibres optiques) favorise la robustesse de la démarche. Des modèles numériques sont ensuite développés pour décrire les mécanismes caractérisés expérimentalement. Un intérêt particulier est porté à la modélisation mésoscopique de l'interface armatures-béton et macroscopique de l'interface torons-coulis d'injection. L'utilisation des différents modèles, couplée à la prise en compte de l'évolution temporelle des déformations différées du béton, favorise une analyse prédictive du comportement des structures étudiées.L'application à une tranche d'enceinte de confinement permet de prédire l'influence de la technologie de précontrainte utilisée sur le comportement à la fissuration de la structure

Readmission following both cardiac and non-cardiac acute dyspnoea is associated with a striking risk of death

Readmission and mortality are the most common and often combined endpoints in acute heart failure (AHF) trials, but an association between these two outcomes is poorly investigated. The aim of this study was to determine whether unplanned readmission is associated with a greater subsequent risk of death in patients with acute dyspnoea due to cardiac and non-cardiac causes.; Derivation cohort (1371 patients from the LEDA study) and validation cohort (1986 patients from the BASEL V study) included acute dyspnoea patients admitted to the emergency department. Cox regression analysis was used to determine the association of 6 month readmission and the risk of 1 year all-cause mortality in AHF and non-AHF patients and those readmitted due to cardiovascular and non-cardiovascular causes. In the derivation cohort, 666 (49%) of patients were readmitted at 6 months and 282 (21%) died within 1 year. Six month readmission was associated with an increased 1 year mortality risk in both the derivation cohort [adjusted hazard ratio (aHR) 3.0 (95% confidence interval, CI 2.2-4.0), P < 0.001] and the validation cohort (aHR 1.8, 95% CI 1.4-2.2, P < 0.001). The significant association was similarly observed in AHF (aHR 3.2, 95% CI 2.1-4.9, P < 0.001) and other causes of acute dyspnoea (aHR 2.9, 95% CI 1.9-4.5, P < 0.001), and it did not depend on the aetiology [aHR 2.2, 95% CI 1.6-3.1 for cardiovascular readmissions; aHR 4.1, 95% CI 2.9-5.7 for non-cardiovascular readmissions (P < 0.001 for both)] or timing of readmission. CONCLUSION​S: Our study demonstrated a long-lasting detrimental association between readmission and death in AHF and non-AHF patients with acute dyspnoea. These patients should be considered 'vulnerable patients' that require personalized follow-up for an extended period

Experimental and numerical analysis of partially prestressed concrete structures

Ces travaux ont pour but d'étudier le comportement mécanique de structures précontraintes et d'évaluer l'influence de la technologie de précontrainte utilisée : précontrainte par torons adhérents, précontrainte par torons non-adhérents TGG. Le champ d'application final porte sur l'analyse de la sûreté et de la durabilité des enceintes de confinement de centrales nucléaires. L'attention est alors portée principalement sur le comportement à la fissuration du béton et au rôle de la liaison mécanique torons de précontrainte-structure.La démarche proposée se décompose en trois étapes successives. Elle débute par la caractérisation expérimentale des mécanismes de dégradation à l'échelle de la structure (essais de flexion 4 points sur poutres précontraintes) et à l'échelle locale du matériau (fissuration, déformations différées du béton, liaisons armatures passives-béton et torons-structure par des essais d'arrachement et de traction sur tirants). Une instrumentation multiple (CIN, fibres optiques) favorise la robustesse de la démarche. Des modèles numériques sont ensuite développés pour décrire les mécanismes caractérisés expérimentalement. Un intérêt particulier est porté à la modélisation mésoscopique de l'interface armatures-béton et macroscopique de l'interface torons-coulis d'injection. L'utilisation des différents modèles, couplée à la prise en compte de l'évolution temporelle des déformations différées du béton, favorise une analyse prédictive du comportement des structures étudiées.L'application à une tranche d'enceinte de confinement permet de prédire l'influence de la technologie de précontrainte utilisée sur le comportement à la fissuration de la structure.This work aims to study the mechanical behavior of partially prestressed structures and to evaluate the influence of the post-tensioning system: bonded tendons, individual unbonded greased and sheathed strands. Under the scope of the safety and durability of nuclear containments, specific attention is devoted to the concrete cracking behavior and to the role of the mechanical tendons-structure bond. The proposed approach is divided into three successive parts. It starts with an experimental study of damage mechanisms at the structural level (4-point bending tests on prestressed concrete beams) and at the local scale (cracking, delayed strains of concrete, reinforcement-concrete bond, tendons-structure bond with pull-out tests and tension tests on reinforced concrete ties). The used instrumentation (DIC, optical fibers) allows for the robustness of the approach. Numerical models are then developed, based on the previous characterized mechanisms. A particular interest is focused on the meso-modeling of the reinforcement-concrete interface and on the macro-modeling of the tendons-injected grout bond. The use of the developed models, considering in parallel the influence of the evolutive delayed strains of concrete, provides a predictive analysis of the mechanical behavior of the studied prestressed structures. A final application to a part of a nuclear containment offers an accurate prediction of the influence of the post-tensioning system on the cracking behavior of the structure

Analyse du comportement de poutres en béton précontraint: Instrumentation des torons de précontrainte par fibres optiques

Une analyse expérimentale et numérique de poutres en béton précontraint est proposée dans cette communication. Une instrumentation des torons de précontrainte par fibres optiques est validée et utilisée afin d’évaluer la contribution des câbles au cours d’un chargement mécanique de la structure. Les résultats expérimentaux obtenus sont comparés à des simulations numériques éléments finis, à des échelles locales et globales

Molecular test of Paget's disease of bone in families not linked to SQSTM1 gene mutations

Purpose: Paget's disease of bone (PDB) is a focal metabolic bone disorder characterized by an increased bone remodeling. Fifteen to 40 % of PDB patients have a familial form with an autosomal dominant inheritance. Disease-causing mutations of the SQSTM1 gene have been linked to PDB in about 40 % of families whereas genes linked to the remaining families are unknown. Several single nucleotide polymorphisms (SNPs) have been associated with PDB in unrelated patient non-carriers of a SQSTM1 mutation. The current clinical practice guidelines still recommend the measure of serum total alkaline phosphatase (sALP) for PDB screening. In unrelated individual non-carriers of SQSTM1 mutations, we previously developed a genetic test combining male sex with five genetic markers (rs499345, rs5742915, rs2458413, rs3018362, rs2234968), giving rise to an area under the curve (AUC) for PDB phenotype of 0.73 (0.69; 0.77). A combination of male sex with total calcium corrected for albumin and Procollagen type I N-terminal propeptide (P1NP), had an AUC of 0.82 (0.73; 0.92). Combining both genetic and biochemical tests increased the AUC to 0.89 (0.83; 0.95). Objective: This study aimed at estimating the performance of our previous test of PDB, in families not linked to SQSTM1 mutations with disease-causing genes yet unknown, and at developing a new algorithm if the performance is not satisfactory. Methods: We genotyped the five SNPs cited above, and measured calcium corrected for albumin and P1NP in 181 relatives, with PDB or not, from 19 PDB families not linked to SQSTM1 mutations. Bivariate and multivariate logistic regression models including male sex were fitted to search for a molecular test that could best detect PDB in these families. A receiving operating characteristics analysis was done to establish a cut-off point for continuous variables. Results: Logistic regression estimates of our previous molecular test gave rise to a high sensitivity of 78 %, 97 % and 88 % for the genetic, biochemical, and combined test but the specificity was very low, 35 %, 11 % and 21 %, respectively. This poor specificity persisted even when the cut-off point was changed. We then generated in these families, new logistic regression estimates but on the same parameters as mentioned above, giving rise to an AUC of 0.65 (0.55; 0.75) for the genetic test, of 0.84 (0.74; 0.94) for the biochemical test, and 0.89 (0.82; 0.96) for the combination test, the latter having a sensitivity of 96 % and specificity of 57 %. By comparison serum P1NP alone gave rise to an AUC of 0.84 (0.73; 0.94), with a sensitivity of 71 % and a specificity of 79 %. Conclusion: In PDB families not linked to SQSTM1 mutations, the estimates of our previous molecular test gave rise to a poor specificity. Using new estimates, the biochemical and combined tests have similar predictive abilities than our former test. Serum P1NP is a bone marker of interest for the screening for PDB in families not linked to SQSTM1 mutations

Activity of the adrenomedullin system to personalise post-discharge diuretic treatment in acute heart failure

Quantifying the activity of the adrenomedullin system might help to monitor and guide treatment in acute heart failure (AHF) patients. The aims were to (1) identify AHF patients with marked benefit or harm from specific treatments at hospital discharge and (2) predict mortality by quantifying the adrenomedullin system activity.; This was a prospective multicentre study. AHF diagnosis and phenotype were centrally adjudicated by two independent cardiologists among patients presenting to the emergency department with acute dyspnoea. Adrenomedullin system activity was quantified using the biologically active component, bioactive adrenomedullin (bio-ADM), and a prohormone fragment, midregional proadrenomedullin (MR-proADM). Bio-ADM and MR-proADM concentrations were measured in a blinded fashion at presentation and at discharge. Interaction with specific treatments at discharge and the utility of these biomarkers on predicting outcomes during 365-day follow-up were assessed.; Among 1886 patients with adjudicated AHF, 514 patients (27.3%) died during 365-day follow-up. After adjusting for age, creatinine, and treatment at discharge, patients with bio-ADM plasma concentrations above the median (> 44.6 pg/mL) derived disproportional benefit if treated with diuretics (interaction p values < 0.001). These findings were confirmed when quantifying adrenomedullin system activity using MR-proADM (n = 764) (interaction p values < 0.001). Patients with bio-ADM plasma concentrations above the median were at increased risk of death (hazard ratio 1.87, 95% CI 1.57-2.24; p < 0.001). For predicting 365-day all-cause mortality, both biomarkers performed well, with MR-proADM presenting an even higher predictive accuracy compared to bio-ADM (p < 0.001).; Quantifying the adrenomedullin's system activity may help to personalise post-discharge diuretic treatment and enable accurate risk-prediction in AHF

Effect of a Strategy of Comprehensive Vasodilation vs Usual Care on Mortality and Heart Failure Rehospitalization Among Patients With Acute Heart Failure: The GALACTIC Randomized Clinical Trial

Short-term infusions of single vasodilators, usually given in a fixed dose, have not improved outcomes in patients with acute heart failure (AHF).; To evaluate the effect of a strategy that emphasized early intensive and sustained vasodilation using individualized up-titrated doses of established vasodilators in patients with AHF.; Randomized, open-label blinded-end-point trial enrolling 788 patients hospitalized for AHF with dyspnea, increased plasma concentrations of natriuretic peptides, systolic blood pressure of at least 100 mm Hg, and plan for treatment in a general ward in 10 tertiary and secondary hospitals in Switzerland, Bulgaria, Germany, Brazil, and Spain. Enrollment began in December 2007 and follow-up was completed in February 2019.; Patients were randomized 1:1 to a strategy of early intensive and sustained vasodilation throughout the hospitalization (n = 386) or usual care (n = 402). Early intensive and sustained vasodilation was a comprehensive pragmatic approach of maximal and sustained vasodilation combining individualized doses of sublingual and transdermal nitrates, low-dose oral hydralazine for 48 hours, and rapid up-titration of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or sacubitril-valsartan.; The primary end point was a composite of all-cause mortality or rehospitalization for AHF at 180 days.; Among 788 patients randomized, 781 (99.1%; median age, 78 years; 36.9% women) completed the trial and were eligible for primary end point analysis. Follow-up at 180 days was completed for 779 patients (99.7%). The primary end point, a composite of all-cause mortality or rehospitalization for AHF at 180 days, occurred in 117 patients (30.6%) in the intervention group (including 55 deaths [14.4%]) and in 111 patients (27.8%) in the usual care group (including 61 deaths [15.3%]) (absolute difference for the primary end point, 2.8% [95% CI, -3.7% to 9.3%]; adjusted hazard ratio, 1.07 [95% CI, 0.83-1.39]; P = .59). The most common clinically significant adverse events with early intensive and sustained vasodilation vs usual care were hypokalemia (23% vs 25%), worsening renal function (21% vs 20%), headache (26% vs 10%), dizziness (15% vs 10%), and hypotension (8% vs 2%).; Among patients with AHF, a strategy of early intensive and sustained vasodilation, compared with usual care, did not significantly improve a composite outcome of all-cause mortality and AHF rehospitalization at 180 days.; ClinicalTrials.gov Identifier: NCT00512759