A quadratic complementarity problem related to the optimal design of a pipeline freely resting on a rough sea bottom

A submarine pipeline resting on a rigid, frictionless seabed assumes an equilibrium configuration which can be determined by solving a unilateral contact problem, i.e. a quadratic program or a variational inequality.When the sea bed is irregular, its profile along the sealine can be modified, in present offshore technology, by means of costly trench excavations or artificial supports, in order to avoid excessive bending moments in the pipe. Thus, the problem arises of determining the minimum cost of the profile changes provided that a specified curvature is nowhere exceeded.This optimal design problem is solved by assuming a quadratic cost function and reducing it to a sequence of convex quadratic programming problems leading to the optimal design situation. Upper and lower bounds on the absolute minimum cost and optimality conditions are established. A suitable algorithm for solving the problem in a finite number of steps is developed. Its generalization to allow for ‘fixed charges’ due to the equipment mobilization cost is presented. Two numerical examples illustrate the optimum (minimum cost) proposed design method.     

The Italian national survey of indoor radon exposure

An investigation is being developed by the Camitato Nazionale per la Ricerca e per lo Sviluppo dell'Energia Nucleare e delle Energie Alternative, ENEA, to assess the indoor exposure of the Italian population. The programme, which started in 1982, includes regional and local surveys in all the administrative districts and intensive investigations of factors which influence indoor radon levels. The survey is organized by statistical areas of sampling to obtain representative samples of houses. The definition of the areas takes into account basic parameters e.g. geolithological environments, radon soil gas from underlying soils and rocks, specific activities of local building materials, climatic and seasonal variations, building technology, types of houses and town planning. The collected data may also be used for the compilation of radon risk maps to plan special monitoring and remedial actions if needed. Preliminary results concerning the above items are discussed.     

Buckling of tube-stiffened prolate domes under external water pressure

The paper describes experimental tests carried out on three tube-stiffened prolate hemi-ellipsoidal domes under external water pressure.The tubes were stuck to the internal surfaces of these three domes, in their flanks, and the experimental tests showed that the tubes increased the buckling pressures of these domes, especially in one case, when the tube was subjected to an initial internal pressure.All three domes failed by lobar buckling, in their flanks, and showed buckling resistances much larger than similar unstiffened domes.     

Prediction of the effectiveness of rolling dynamic compaction using artificial neural networks and cone penetration test data

Rolling Dynamic Compaction(RDC),which is a ground improvement technique involving non-circular modules drawn behind a tractor,has provided the construction industry with an improved ground compaction capability,especially with respect to a greater influence depth and a higher speed of compaction,resulting in increased productivity. However,to date,there is no reliable method to predict the effectiveness of RDC in a range of ground conditions. This paper presents a new and unique predictive tool developed by means of artificial neural networks(ANNs) that permits a priori prediction of density improvement resulting from a range of ground improvement projects that employed 4-sided RDC modules;commercially known as"impact rollers". The strong coefficient of correlation(i.e. R0.86) and the parametric behavior achieved in this study indicate that the model is successful in providing reliable predictions of the effectiveness of RDC in various ground conditions.     

Arsenic-sulfides confound anion exchange resin speciation of aqueous arsenic

A field-portable anion exchange resin method (often cited as the Ficklin method (1983)) has been extensively used to distinguish between dissolved arsenite (As(III)) and arsenate (As(V)) species in natural waters. As(III) occurs largely as As(OH)(3), which is uncharged at ca. pH 7, while As(V) is negatively charged and will sorb to the resin. However, we show that negatively charged As(III)-sulfide (thioarsenite) species, important at sulfide concentrations >10 microM, also bind to the anion exchange resins, and therefore might be interpreted incorrectly as As(V). Furthermore, we show that nitrogen-purging, which results in a conversion of As(III)-sulfides to arsenite, can be used to obtain accurate arsenic speciation when resins are used on sulfidic water samples.     

A contribution to the study of some greek marbles

The use of marble in Architecture began on the 7th century B.C. and continued to be used without stop untill today. Greece and especially the East Macedonia region is an extremely privileged area on marble deposits both in quantities and qualities and colours. In the present work the main physical and engineering properties of some varieties of greek marbles are given and a comparison with the international standards is made. The experimental material (marbles) was from East Macedonia, Argolida-Arcadia and Magnessia, three of the biggest marble deposit areas in Greece. From the results obtained, it is concluded that the marbles examined satisfy all the international standard codes and thus they can be used as building stones and decoration materials.     

Reliability of corrosion-damaged steel structures using interval probability theory

Engineering decisions concerning the performance of existing structures must be made in the presence of uncertainties. The remaining capacity of corroded steel structures provides a good example of different aspects of uncertainty. These include: an unknown or partially known extent of damage; a variability in loading and an uncertain reserve of structural capacity depending on the mode of failure. The theory of structural reliability has been developed to provide a method of analysis for structural safety. In this paper, methods are proposed to compute the component reliability of corrosion-damaged steel members. The application of a recently developed theory called interval probability theory for system reliability is illustrated using the data obtained from actual samples of corroded beams.     

A study of the effect of stiffness distribution on nonlinear seismic response of multi-degree-of-freedom structures

The ductility requirement of elastoplastic multi-d.o.f. shear structures is studied by analysing the response obtained through step-by-step integration of the equations of motion for some recorded accelerograms. In view of the high dependence of the structural strength reserve beyond the elastic range on the distribution of plastic deformations in the structure, this paper aims to establish the influence of the stiffness distribution and of the earthquake features on the local ductility demand. Attention is also paid to the analysis of the influence of variation in excitation intensity and duration on the seismic behaviour of the structural models considered. Numerical results show that overall structural ductility alone is not sufficiently representative to evaluate the ultimate state of multi-d.o.f. structures. Local ductility must also be specified in order to create a reliable aseismic design. In this context, the important role played by the distribution of stiffness over the structure is emphasized.     

Method of Determining Strength and Deformation Characteristics of Soils from Results of Deep Impression of Rod Plates

The possibility of determining strength and deformation characteristics of soils under field conditions using rod plates is discussed. The mutual relationship between these characteristics is established from results of deep impression of these rods.