J.A. Fraguela

Floating boom performance under waves and currents.

Floating booms constitute a fundamental tool for the protection of marine and coastal ecosystems against accidental oil spills. Their containment performances in exposed areas are often impaired by the action of waves, currents and winds in a manner which is dependent on the booms response as a floating body, and which is not fully understood at present. In this work the relationship between the design parameters of a floating boom section and its efficiency against the mode of failure by drainage under a variety of wave and current combinations is investigated by means of physical modelling. Seven boom models with different geometries and buoyancy-weight ratios are tested with an experimental setup that allows them to have and rotate freely. The model displacements under waves (both regular and irregular) and currents, as well as those of the free surface adjacent to the model, are measured with a Computer Vision system developed ad hoc. Two efficiency parameters are defined-the significant and minimum effective boom drafts-and applied to the results of an experimental campaign involving 315 laboratory tests. Thus, the manner in which the design parameters influence the booms efficiency under different wave and current conditions is established.

Influence of the towline material: Steel or high-modulus polyethylene on towing gear design and tug deck fittings

The traction force or bollard pull and specific function of a tugboat determine the size of its towing gear and deck fittings. These dimensions must enable the tug to carry out a manoeuvre safely. This article considers proposals made in the implementing regulations for calculating the length and diameter of the towline. It analyses the possibility of using high-modulus polyethylene fibre and the way it would affect the design of the towing gear and deck fittings, including the fairleads and bits. It would be useful if regulations provided further guidance on towline length for port tugs. The final part of this study analyses the solutions informed by a sample of 51 port tugs, the majority of which are escort tugs.

Complexity and Project Management: A General Overview

As projects have become more and more complex, there has been an increasing concern about the concept of project complexity. An understanding of project complexity and how it might be managed is of significant importance for project managers because of the differences associated with decision-making and goal attainment that are related to complexity. Complexity influences project planning and control; it can hinder the clear identification of goals and objectives, it can affect the selection of an appropriate project organization form, or it can even affect project outcomes. Identifying the different concepts associated to project complexity, its main factors and characteristics, the different types of project complexity, and the main project complexity models, can be of great support in assisting the global project management community. In this paper, we give a general overview of how complexity has been investigated by the project management community and propose several ideas to address this topic in the future.