No abstract

The Paper presents the results of a systematic parametric investigation of the static and dynamic response of single free-head piles embedded in a soil stratum, the modulus of which increases linearly with depth. The study is conducted by means of a dynamic finite-element formulation which accounts for the three-dimensionality of soil deformation while properly reproducing the radiation damping characteristics of the system. The soil is modelled as a linear hysteretic continuum and the excitation consists of a sinusoidally time-varying horizontal force or moment, applied at the pile head. Comprehensive plots of the results are presented in non-dimensional form, for a wide range of the most significant dimension-less groups of problem parameters. For the response of flexible piles, in particular, simple algebraic expressions are developed in terms of the ratio Ep/Es, of the pile and soil moduli. These expressions, being valid for several values of Poisson's ratios of the soil, compare favourably with results from previous studies and are expected to be useful in practical design calculations. Cet article donne les résultats de recherches paramétriques systématiques sur la réponse statique et dynamique des pieux libres en tête encastrés dans une couche de sol dont le module s'accroît linéairement avec la profondeur. L'étude est basée sur une formulation d'éléments finis dynamiques qui tient compte de la nature tridimensionelle de la déformation du sol, en même temps qu'elle reproduit de façon correcte les caractéristiques d'amortissement du systéme. Le sol est modehsé comme un continuum avec hystérśsise linéaire et l'excitation consiste en une force horizontale qui varie de façon sinusoidale dans le temps appliquée en tête du pieu. Les résultats sont tracés de maniére compréhensive sous une forme non-dimensionnelle pour une grande variété des groupes les plus importants des paramétres sans dimensions caractérisant le probléme. Plus particuliérement pour la réponse des pieux flexibles des expressions simples algébriques sont présentées en fonction du rapport Ep/Es des modules du pieu et du sol. Ces expressions, qui sont valables pour plusieurs valeurs du coefficient de Poisson pour le sol sont supérieures à celles fournies par les etudes précédentes, et on s'attend à ce qu'elles soient utiles pour els calculs pratiques des projects de fondations.

The increasingly mechanical requirements of offshore structures have established the relevance of fracture mechanics-based quality control in welded joints. For this purpose, crack tip opening displacement (CTOD) at a given distance from the crack tip has been considered one of the most suited parameters for modeling and control of crack growth, and it is broadly used at the industrial level. We have modeled, through multivariate analysis techniques, the relationships among CTOD values and other material properties (such as hardness, chemical composition, toughness, and microstructural morphology) in high-thickness offshore steel welded joints. In order to create this model, hundreds of tests were done on 72 real samples, which were welded with a wide range of real industrial parameters. The obtained results were processed and evaluated with different multivariate techniques, and we established the significance of all the chosen explanatory variables and the good predictive capability of the CTOD tests within the limits of the experimental variation. By establishing the use of this model, significant savings can be achieved in the manufacturing of wind generators, as CTOD tests are more expensive and complex than the proposed alternatives. Additionally, this model allows for some technical conclusions.

The aim of the present work is to verify the microstructural behavior of a B 521 tantalum alloy UNS Grade R05200 after welding, in relation to the welding thermal cycle. The joint design was a 1.5 mm thickness circumferential butt welding, on a 32 mm outside diameter pipe, welded in 1 G position (horizontal, flat, and rotating). The chosen welding process was gas tungsten arc welding (GTAW). The microstructural analysis showed the presence of coarse, dendritic-columnar structures, as well as a hexagonal cell, with no cracks noted. Hardness tests showed an increase in hardness, from 120 HV to 425 HV, in the heat-affected zone. Through finite element methods, the behavior of the temperature field was estimated and compared.

This work presented salient features of the steel behavior of seven metallic bridges close to, or over, 100 years old, among the Spanish conventional rail network as well as the results of a fatigue life expectancy study. A preliminary study of the properties of the constituent materials obtained from the bridges samples was carried out followed by dynamic fatigue tests under service representative loads. Due to the steelmaking techniques in the late 19th and early 20th centuries, disperse fatigue behavior results were obtained. However, the wide safety margins with which these bridges were designed, as well as the mechanical properties of the steel (relatively good mechanical resistance but with low ductility), seem to guarantee a long fatigue life. This estimate decreases sharply with increasing loads.