Strukturna optimizacija broda za prijevoz ukapljenog prirodnog plina

Cilj rada je prikazati glavne rezultate strukturne optimizacije broda za prijevoz ukapljenog plina koja je provedena u okviru EU FP6 istraživačkog projekta IMPROVE. Izgrađen je grubi model konačnih elemenata koji obuhvaća tri teretna prostora korištenjem programskog paketa MAESTRO. Proračun čvrstoće proveden je prema Pravilima Bureau Veritas (BV). Cilj cjelokupnog optimizacijskog postupka bio je optimalna redistribucija materijala s ciljem smanjenja težine/cijene i poboljšanja sigurnosti. Provedena je studija senzitivnosti s ciljem istraživanja utjecaja razmaka okvirnih rebara, razmaka uzdužnjaka i tipa materijala na definirane projektne ciljeve. Strukturna optimizacija, na razini jednog skladišta, rezultirala je u smanjenju mase oko 424 t (10.8%), cijena je smanjenja za oko 5%, sigurnost je povećana, dok je VCG je blago smanjen za oko 20cm, u usporedbi s prototipnom konstrukcijom

Analysis of Underwater Repair Technology on the Jack-Up Platform Spud Can

Underwater welding has been used widely in construction and maintenance of off-shore facilities. With state-of-the-art equipment and fi ller materials it is possible to achieve high quality of welded joints, particularly if underwater dry welding is applied. On the other hand, wet underwater welding has several advantages from the aspects of fl exibility and cost effi ciency, but some serious problems could emerge due to weld quality and safety of divers. In this paper analysis of applicable technologies of underwater repair of a jack-up platform spud can is made, including description of possible problems that may occur. Also, a comment on specifi c details of proposed techniques has been given and a comparative analysis of considered techniques focused on the economic and technological aspects of repair has been made

A Thorough Analysis of the Engineering Solutions Deployed to Stop the Oil Spill Following the Deepwater Horizon Disaster

International audienceThe Deepwater Horizon drilling accident that occurred on 20 April 2010 was a two-fold catastrophe. The initial total loss of the drilling rig was followed by one of the worst environmental disasters in recent history. The four million barrels of oil that were released into the Gulf of Mexico continue to impact human activities in the area. The Macondo well incident (Mississippi Canyon 252-1, leased by BP as the primary operator) was the first deep subsea blowout in the history of the oil and gas industry, and both the United States’ government and the private sector were unprepared to deal with it. All of the safety system’s lines of defense failed and the response required multiple courses of actions to be taken to address an unprecedented situation. It was imperative to deliver the best engineering solutions under intense and ongoing pressure in a very harsh and highly stressful operational environment. In this paper we review the engineering solutions considered by the response teams. The first part of the paper gives a brief presentation of our approach to the case study. The second reviews post-blowout events, the initial organizational response and the discovery of leaks. The final part presents how the statement of the problem was developed by the organization and how the response was structured. We then analyse the engineering solutions and finally, show how the organization implemented these solutions to control the source of the spill, recover the effluent and seal the well. In conclusion, we provide an overview of the engineering work that was carried out and preview our forthcoming work. We assume that the response to the Deepwater Horizon oil spill was efficient from an operational point of view. Therefore, our findings will be used to develop a new approach to the analysis of major accidents and ultimately shape the design of a new set of disaster management guidelines

Advanced SBAS-DInSAR technique for controlling large civil infrastructures: an application to the Genzano di Lucania dam

Monitoring surface deformation on dams is commonly carried out by in situ geodetic surveying, which is time consuming and characterized by some limitations in space coverage and frequency. More recently microwave satellite-based technologies, such as advanced-DInSAR (Differential Synthetic Aperture Radar Interferometry), have allowed the integration and improvement of the observation capabilities of ground-based methods thanks to their effectiveness in collecting displacement measurements on many non-destructive control points, corresponding to radar reflecting targets. The availability of such a large number of points of measurement, which are distributed along the whole structure and are characterized by millimetric accuracy on displacement rates, can be profitably adopted for the calibration of numerical models. These models are implemented to simulate the structural behaviour of a dam under conditions of stress thus improving the ability to maintain safety standards. In this work, after having analysed how advanced DInSAR can effectively enhance the results from traditional monitoring systems that provide comparable accuracy measurements on a limited number of points, an FEM model of the Genzano di Lucania earth dam is developed and calibrated. This work is concentrated on the advanced DInSAR technique referred to as Small BAseline Subset (SBAS) approach, benefiting from its capability to generate deformation time series at full spatial resolution and from multi-sensor SAR data, to measure the vertical consolidation displacement of the Genzano di Lucania earth dam

The effect of increasing the thickness of the ship’s structural members on the Generalised Life Cycle Maintenance Cost (GLCMC)

In the context of the EU funded IMPROVE project, the research work of a Generalised Life Cycle Maintenance Cost (GLCMC) was initiated in order to investigate the influence of a weight oriented ship structural design on its production and operational characteristics. Following this, an increase in the structural scantlings of the ship was examined following the IACS Common Structural Rules (CSR) for double hull oil tankers. A case study for a Chemical tanker is shown considering an addition in its bottom plate thickness and three different cases of mean annual corrosion rates applied. A comparison regarding the “Gross gains”, “Gross expenses” and “Net gains” for this ship is also presented. Moreover, an evaluation of the extra cost for the additional steel weight used is shown together with the outcome on the repair-free operation of the ship for different additional plate thickness. Finally, a sensitivity analysis is carried out for the most likely case (“Case 2”) and the variation of different amount of days spent in the ship repair yard

PNEUMATIC HYDROPOWER SYSTEMS

The following thesis investigates the performance and economics of a Pneumatic Water Engine capable of extracting energy from differential heads of water in the two to three metre range. Initial concepts are discussed and a system configuration is physically modelled at a laboratory scale. Outline designs using a variety of materials are developed and these provide a basis for the estimation of a probable capital cost using standard Civil Engineering methods. The proposed system is mathematically modelled using a lumped mass approach to the complex hydrodynamics. The resultant differential equations are solved by means of a variable Runge Kutta numerical analysis. The model includes the thermodynamic aspects of the system's compressible airflow. A computer program has been developed from the mathematical model and Is utilized in a series of parametric studies. An economic assessment based upon both the average power output achieved during the parametric studies and the probable capital cost of the system is presented, together with an estimate of the cost per kilowatt-hour of the electricity produced. This assessment takes into account maintenance costs, expected value of the energy produced and the possible effects of both Water Abstraction Charges and Local Authority Rating. In addition to the parametric studies a final, more rigorous optimization of the system involving a number of the many interacting variables has been undertaken. This optimization is achieved via Cumulative Evolutionary Design techniques involving the use of Genetic Algorithms. An optimal design of the chamber shape is achieved in the same manner.Energy Technology Support Unit (ETSU), Harwel

Application of CE-QUAL-W2: Wachusett Reservoir Contaminant Spill Modeling

This research was done to investigate the fate and transport of a simulated contaminant spill into Wachusett Reservoir using the CE-QUAL-W2 model. The reservoir is located in central Massachusetts (north east of Worcester) and was first filled in 1908. The Massachusetts Water Resource Authority (MWRA) uses the reservoir as a primary source of drinking water for the metropolitan Boston area. The 65-billion-gallon reservoir is replenished by 9 tributaries and also supplemented by the transfer of water from Quabbin Reservoir (412 billion-gallon capacity) through the Quabbin Aqueduct. This transfer is used to meet system water demands, manage the water surface elevation at the Wachusett Reservoir and improve Wachusett water quality. The MWRA withdraws reservoir water at the Cosgrove Intake (CIT) where it flows by gravity to the John J. Carroll Water Treatment Plant at Walnut Hill in Marlborough

Effects of sediment flushing operations versus natural floods on Chinook salmon survival

Flushing is a common measure to manage and reduce the amount of sediment stored in reservoirs. However, the sudden release of large volumes of sediment abruptly increases the suspended solids concentration and alters the riverbed composition. Similar effects can be produced also by natural flood events. Do flushing operations have more detrimental impacts than natural floods? To answer this question, we investigated the impact of flushing on the survival of the Chinook salmon ($\textit{Oncorhynchus tshawytscha}$) in the Sandy River (OR, USA), assuming that sediment is flushed from hypothetical bottom gates of the, now decommissioned, Marmot Dam. The effects of several flushing scenarios are analyzed with a 2D morphodynamic model, together with habitat suitability curves and stress indicators. The results show that attention has to be paid to duration: the shorter the flushing operation, the lesser the stresses on fish survival and spawning habitats. Flushing causes high stress to salmon eggs and larvae, due to unbearable levels of suspended sediment concentrations. It also decreases the areas usable for spawning due to fine-sediment deposition, with up to 95% loss at peak flow. Without the dam, the corresponding natural flood event would produce similar effects, with up to 93% loss. The study shows that well-planned flushing operations could mimic a natural impact, but only partly. In the long-term, larger losses of spawning grounds can be expected, since the removal of fine sediment with the release of clear water from the reservoir is a lengthy process that may be undesirable due to water storage reduction

Global design of hydraulic structures optimised with physically based flow solvers on multiblock structured grids

peer reviewedThis paper presents the numerical studies lead by the Laboratory of Applied Hydrodynamics and Hydraulic Constructions of the University of Liège (HACH) for the rehabilitation of the 21-meter high Nisramont dam in Belgium. After determination of the up-to-date 1000-year return flood using the hydrological runoff model WOLFHYDRO on the global 74,000 ha watershed real topography coupled with statistical analyzes, and after validation on the existing situation and for extreme observed events, the 2D finite volume multiblock flow solver WOLF2D has been applied to the design of the new stilling basin and to the bottom outlet rehabilitation impact study. The multiblock solver possibilities allow mesh refinement close to interesting areas, such as dam spillway and stilling pool, without leading to prohibitive CPU times, while suitable shallow water equations formulation allows the computation of the flows on the strongly vertically curved bottom of the spillway. In the described simulation, 270,000 structured finite volumes, from .25 to 1 meters long, are used to simulate as a whole the flows in the upstream reservoir, dam, spillway, stilling basin and downstream river, this on a real topography