The mechanism of the lateral reaction of piles in an elastic-plastic medium is examined. Plane strain is first assumed. The analytical solution for a circular section in an elastic medium is given. The influence of pile section (square pile), disturbance of a soil ring around the pile, plastic yield of soil in undrained behaviour (Tresca's criterion) are studied by means of the finite element method. All these factors affect strains and stresses only in the vicinity of the pile. Graphs are given making it possible to calculate the corresponding corrective terms to be applied to the analytical solution. In a second step, which defines the value of the outside radius of this two-dimensional model, the simplified three-dimensional problem of a horizontally-loaded vertical axis in a semi-infinite elastic solid is studied using Mindlin's solution for a point force. The influence of the relative soil-pile rigidity, head loading and fixing conditions, which have an effect especially on distant fields, are taken into account and quantified by simple rules for determining this outside radius. Finally, a specific numerical application of the results is made and the solution is very satisfactory compared with experimental measurements. On étudie le mécanisme de réaction latérale des pieux en milieu élasto-plastique. On suppose tout d'abord que la déformation est plane. La solution analytique pour une section circulaire dans un milieu élastique est donnée. Les influences de la forme de la section du pieu (pieu carré), du remaniement d'un anneau de sol autour du pieu, de la plastification du sol en comportement non drainé (critère de Tresca) sont étudiées à l'aide de la méthode des éléments finis. Tous ces facteurs ne jouent sur le champ des déformations et des contraintes que dans le voisinage du pieu. Des abaques sont donnés, permettant de calculer les termes correctifs correspondants, à appliquer à la solution analytique. Dans un deuxième temps, pour préciser la valeur à prendre en compte du rayon extérieur de ce modèle bidimensionnel, on étudie le problème tridimensionnel simplifié d'un axe vertical chargé horizontalement dans un massif élastique semi-infini, en sommant la solution de Mindlin pour une force ponctuelle. Les influences de la rigidité relative sol-pieu, des conditions de chargement et d'encastrement en tête, qui affectent surtout les champs au loin, sont ainsi prises en compte et quantifiées par des règles simples de détermination de ce rayon extérieur. Enfin une application numérique concrète des résultats est faite et la solution est très satisfaisante, comparée aux mesures expérimentales.
Objective: Outcomes and treatment costs for coronary artery disease involving the left anterior descending coronary artery (LAD) are influenced by the type of treatment, which can be either isolated minimally invasive revascularization of the LAD using the internal thoracic artery (ITA) (MIDCAB) or percutaneous coronary intervention (PCI) on the LAD. This retrospective study sought to evaluate long-term survival, freedom from re-intervention and cost analysis after MIDCAB compared to PCI on the LAD. Methods: Between 2006 and 2012, from a total of 561 patients, 106 consecutive patients with LAD stenosis underwent a MIDCAB procedure whereas 100 patients underwent elective PCI. Urgent and emergent cases were excluded from the present study (n = 355). Detailed analysis of the outcome data was performed for both groups. A Kaplan–Meier survival estimation with up to 10-year follow-up was applied for both groups for survival analysis and freedom from re-intervention. Results: There were no statistically significant differences in terms of clinically relevant baseline characteristics. The outcome in the MIDCAB group was superior regarding long-term overall survival, accounting for 100% versus 92.8% at 1 year, 98.5% versus 82.1% at 6 years and 79.6% versus 61.5% at 10 years (Log Rank (Mantel-Cox) p = 0.011) and freedom from re-intervention at 10 years (97.2% vs. 86.7%, Log Rank (Mantel-Cox) p = 0.001). Intensive care unit (ICU) stay (p = 0.020) and total hospital stay (p<0.001) were significantly longer in the MIDCAB group, which was also associated with higher in-hospital costs (10,879 € vs. 4009 €, p<0.001). Conclusions: Whereas patients undergoing MIDCAB remained longer on ICU and in hospital, causing higher costs, this procedure was associated with a significantly lower incidence of repeat revascularization and significantly lower mortality compared to PCI on the LAD.
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