Fatigue life prediction of welded ship details

Ship structures are submitted to variable cyclic loading during navigation. The cyclic motion of waves induces variable and complex loadings in the structure, which could generate fatigue damage. Moreover, most of these metallic structures are welded assemblies. This technique generates local stress concentrations at the weld toe, which becomes a critical area regarding fatigue. In previous works, a methodology to predict fatigue life was developed and tested on butt-welded and cruciform joints. The present work focuses on other welded assemblies in order to extend fatigue crack initiation life evaluation to a wider range of ship details. The strategy could be split into two steps. First, a finite element calculation is performed under constant or variable amplitude loadings, in order to analyze the elastic shakedown of the structure. To characterize the material heterogeneity of the welded joint, experimental tests together with micro-hardness measurements, are performed on a simulated heat-affected zone. If there is a shakedown in the structure, a post-treatment is applied to predict the fatigue crack initiation. It is based on a two-scale damage model, initially developed by Lemaitre et al. and again includes the heterogeneity of fatigue properties. To validate this methodology, some experimental tests have been performed on welded assemblies which are typical of shipbuilding applications, using a fatigue machine. These comparisons between experimental and numerical fatigue lives are encouraging.     

Port Specialization and Efficiency—The Case of Ghana

The US Shipping Act of 1984 permits ocean liner vessel operators and shippers to make use of service contracts to further their mutual interests. However, starting from the very day this novel provision was incorporated into the Act, it has remained as a bone of contention between shippers and carriers serving US trade routes. This article highlights the major issues that have sprouted subsequent to the introduction of service contracts in ocean liner shipping. The author concludes with some logical suggestions to fine-tune the Act, without interfering with its legislative framework.     

Ramp metering and freeway bottleneck capacity

This study aims to determine whether ramp meters increase the capacity of active freeway bottlenecks. The traffic flow characteristics at 27 active bottlenecks in the Twin Cities have been studied for seven weeks without ramp metering and seven weeks with ramp metering. A methodology for systematically identifying active freeway bottlenecks in a metropolitan area is proposed, which relies on two occupancy threshold values and is compared to an established diagnostic method – transformed cumulative count curves. A series of hypotheses regarding the relationships between ramp metering and the capacity of active bottlenecks are developed and tested against empirical traffic data. It is found that meters increase the bottleneck capacity by postponing and sometimes eliminating bottleneck activations, accommodating higher flows during the pre-queue transition period, and increasing queue discharge flow rates after breakdown. Results also suggest that flow drops after breakdown and the percentage flow drops at various bottlenecks follow a normal distribution. The implications of these findings on the design of efficient ramp control strategies, as well as future research directions, are discussed.     

Delivering trusting partnerships for route bus services: A Melbourne case study

The Thredbo Conference series has developed the idea of negotiated performance-based contracts as effective public transport service delivery mechanisms, with trusting partnerships between authority and operators providing an environment likely to maximise the performance of this delivery mode. However, there is a distinct lack of relevant case study material on trusting partnerships in public transport to affirm this proposition. This paper seeks to redress the balance. It outlines the system development directions that are being implemented for bus services in Melbourne, Australia, and the way that a broad-based constituency has been built to support those directions. It then illustrates the extension of the tactical trusting partnership approach between purchaser and provider to the level of the individual operator contract, showing how this should create a flexible yet disciplined environment to manage and cope with change and growth. The broad nature of the new contracts is summarised and, building on the findings from Thredbo 9, processes that are being implemented to manage the on-going relationship between purchaser and providers are outlined. Finally, the paper argues for extending KPIs beyond the operator to encompass the authority/regulator and the partnership of authority/operator, to extend performance pressures beyond the operator and recognise the interdependence of partners in a true partnership.     

Obituary - Professor Michael E. Beesley,CBE

Abstract

The French motorway network is now more than 6 000 km long, whereas it was virtually nonexistent in 1960. This paper aims at identifying and analysing the key factors, and their interplay, in the process of conception, decision and realization which led to such a transformation. We first deal with the network as a whole.

Next, we concentrate on one among the relevant factors: cost‐benefit analysis. More precisely we examine the part it has played as a means of communication and negotiation between the involved public bodies, as well as a device to enhance an image of rationality attached to the decisions made. Finally we consider a specific link, that between Orleans and Clermont‐Ferrand.     

Information Management in Beach Planning

Abstract

This article concerns optimizing the use of environmental information for creative planning. It arose from a detailed study of the status and management of the coastal dunes of New South Wales, Australia, and discusses the way in which ideas for optimizing the management process were developed, and applied to three beach environments on the coast of New South Wales, Australia.

The problem of coastal beach/dune management may be thought of as being similar to a production function in which the inputs are the land resource, the skills and knowledge of managers, finance, and materiel. The outcomes are in the form of experiences, or opportunities for experiences, either passive or active, either consumption values or option values, desired by the coastal user population (which includes the resource managers themselves). The resource manager's task is to manipulate the “production function”; in order that the outputs will best mesh with the expectations of the user population and with the capability of the land resource to deliver on a sustained basis. An aim of the project was to develop a method for the specification of different possible outputs from the production function, in different beach/dune environments, and that could be used to assist in the preparation of advice on appropriate recreational development, allowing decisions to be based on both environmental data and information on the expectations, activities, and amenity preferences of beach users.     

CO2 emissions: Are land-use changes enough for California to reduce VMT? Specification of a two-part model with instrumental variables

With vehicle miles of travel increasing at a faster pace than population, one strategy being actively pursued by both state and local governments is compact development. California recently passed legislation that aggressively promotes sustainability by endorsing and rewarding compact development. Likewise, the California Air Resources Board has set a statewide reduction target of 5MMT of greenhouse gas reductions from land use, based largely on achieving compact development patterns. In this paper, we use a multivariate two-part model with instrumental variables, which corrects for residential location self-selection bias. We use a much larger and more geographically representative travel survey on household travel patterns and socio-economic characteristics than represented in previous California studies; this allows us to robustly consider other influences on travel. Our results indicate that, all else equal, a 10% in residential density would reduce VMT by 1.9%. This elasticity is larger than the reported in previous econometric studies for the US, and specifically for California. However, as we show, the magnitude of this impact is still low considering reasonable ranges for policies aimed to increase residential density.     

Competition and ownership in land passenger transport: The 7th International Conference

This is the fourth time that Transport Reviews has published a summary of the workshop sessions from the Thredbo Conference. The intention is to disseminate more widely the main findings and conclusions from these sessions at this important international conference. Interested readers are also encouraged to view the full papers presented at the Institute of Transport Studies, University of Sydney website.