The compressive behavior of advanced double hull structure—A review of current research at David Taylor

It has long been recognized that the compressive behavior of primary ship structural components plays a vital role in the design of surface ship hulls. This is equally as true for the new advanced double hull concept as it is for the more conventional surface ship configurations. What is different, however, is the nature of the structural mechanics phenomena which must be addressed due to the double hull's more radical departure from conventional design and construction practices. With increasing interest and attention being shown in this new concept, the David Taylor Model Basin has over the past few years initiated a number of research efforts which have and are continuing to address various aspects of the behavior of double hulls and their components to primary compressive loadings. These studies have as their ultimate goal the development of practical, user oriented design methods for double hull structure and as such currently focus on more approximate, rather than mathematically rigorous, approaches to the various structural phenomena being considered. This paper is in essence a progress report on a selected number of these efforts and describes the results achieved to date as well as the ongoing efforts and those planned for the future. This report focuses primarily on three recent studies: (1) a preliminary look at the relative significance of local versus general instability failure of double hull structure; (2) small scale experimental analysis of double hull sections using rigid vinyl modelling; and (3) the application of beam-on-elastic-foundation analysis methods for high aspect stiffened plates as it relates to double hull structure. In addition to these major topics, the report also includes a brief discussion of other ongoing and planned efforts relevant to the advanced double hull.     

Transport decision-makers speak: the Seaport Development in the European Communities Research Project†—Part II

This paper, in two parts, reports on the Seaport Development in the European Communities Research Project wherein forty interviews with decision-makers were held in European seaports, and another forty were held with shipowning organizations. This part of the paper reports on analysis of the open-ended tape-recorded responses of the interviewees to six separate sets of propositions they were shown. The first major conclusion is that decision-makers in the ports and shipping industries have a great deal to offer in helping to shape future EC policies about seaports. The second is that these decision-makers on the whole agree with students of the subject, but outside the industries, that a step-by-step approach is possible towards a Common Seaports Policy. Indeed, without prompting, some respondents even confirmed a previously published suggestion for the first stage of this process—the necessity for an agreed standard basis for ports' accounts. It is believed that a small secretariat within the Brussels Commission could weld representatives of the industries into a working group which could make real progress by consulting their colleagues through interviews similar to those successfully conducted for this project.     

Short sea shipping: a Canadian perspective

Short sea shipping has begun to receive attention from governments worldwide, as they seek to reduce traffic congestion and greenhouse gases. Despite a long coastline and its interest in international maritime affairs, the Canadian government had, until 2003, placed greater emphasis on resolving the issues of other transport modes. In July 2003, Canada and the United States signed a Memorandum of Cooperation on Sharing Short Sea Shipping Information and Experience. Subsequently, the federal government embarked on an assessment of short sea shipping through a series of workshops. This paper explores the key issues with respect to further development of short sea shipping from a Canadian perspective. It examines the critical limitations and impediments to further growth of short sea services in Canada and trans-border trade with the USA, and identifies a number of questions Canadian policymakers need to answer.     

Development and Evaluation of a High Voltage Supply Unit for Electrorheological Fluid Dampers

Controllable dampers using electrorheological (ER) fluids have attracted considerable interest in recent years. They are proposed for use in semi-active suspensions for ground vehicles. The main advantages of ER fluid dampers are their fast response, ease of control, simple construction and low power requirements. This paper describes the development and testing of a high-voltage supply unit for modulating the damping force of an ER fluid damper. Experimental results on the vibration isolation characteristics of an ER fluid damper with different control strategies, obtained using a quarter-car model test rig, are also presented.     

Application of Sensitivity Methods to Analysis and Synthesis of Vehicle Dynamic Systems

The development and application of sensitivity methods for determining the effects of parameter changes on the response of vehicle dynamic systems is presented. The procedures shown can be used to enhance the analysis and synthesis processes of virtually any road or rail vehicle system regardless of its complexity. The parametric sensitivity of vehicle models in time domain, steady state models and vehicle models in frequency domain can be investigated using different types of sensitivity functions, both dimensional and dimensionless including first order standard, percentage, logarithmic, second order standard, and logarithmic and percentage sensitivity measures. These sensitivity functions and measures are determined as functions of partial derivatives of system variables taken with respect to system parameters. In the case of sensitivity functions in the frequency domain the variable values are computed as either the magnitude or phase angle of a complex element of the transfer function matrix. The methods presented enable to determine the influence of all system primary (constant) and secondary (non-constant) parameters on system primary and secondary variables. The primary variables are state variables or elements of the transfer function matrix and the secondary variables may be any functions of primary variables and system parameters. Typical secondary system parameters which can be examined include initial conditions, time variant coefficients, natural frequencies, loads, and typical secondary variables are forces, weight transfers, stability factors and energy components. The analysis of sensitivity results obtained for three vehicle handling models in both linear and nonlinear regimes of vehicle performance and utilizing various types of sensitivity functions is also presented.