Reliability-based calibration of fatigue design guidelines for ship structures

A simple reliability-based framework is applied to calibrate a new set of fatigue design guidelines. This new guideline considers two different approaches for the assessment of both loads, stresses and local stress raising effects, and partial safety factors must be given for any combination of these approaches. For the calibration, the lognormal reliability format is adopted because the hereby-derived partial safety factors can be combined arbitrarily. This means that with a few basic partial safety factors, the combination of partial safety factors to be applied together with any combination of calculation approaches can be determined easily. In the present paper both the adopted reliability format, the applied modeling of uncertainties and the selected target safety index are explained. Based on this, a new guideline is calibrated and the derived partial safety factors are presented. Finally, the new guideline is applied through a numerical example in order to show the applicability of the calibrated partial safety factors, and satisfactory results are found.     

Multi-objective optimization of oil tanker design

Parametric optimization was applied to a double-hull AFRAMAX tanker design in order to reduce oil-outflow probability and increase cargo carrying capacity, and the results are presented here. A multi-criteria optimization procedure was set up in modeFrontier ^® using the cargo volume, the mean oil-outflow parameter and the steel weight of the cargo block as the objective functions. Calculations are based on a parametric geometric model of the ship created in NAPA ^®, and on a structural model created in POSEIDON ^®. Integration of the above software packages leads to an automated optimization procedure that provides improved feedback to the designer regarding the trade-off between the various design parameters and optimization criteria involved. The results obtained suggest notable improvements in transport capacity and oil-outflow performance for known, well-established yard designs. The presented work derives from a joint industrial project between Germanischer Lloyd (GL) and the Ship Design Laboratory of the National Technical University of Athens (NTUA-SDL), which continues the work done and coordinated by NTUA-SDL within the SAFEDOR project on the same subject.     

Accessibility, entropy and the distribution and assignment of traffic revisited

An optimizing model which minimizes average generalised trip cost subject to constraints on the entropy was given in a previous paper. In this note the model is placed in a planning context.     

Real Time Detection and Classification of Arrow Markings in Urban Streets

For highly automated driving in urban regions it is essential to know the precise position of the car. Furthermore it is important to understand the surrounding context in complex situations, e.g. multilane crossings and turn lanes. To understand those situations there is not only the task to detect the lane border, but to detect the painted information inside the lane. The paper is facing and evaluating two methods to classify this additional lane information. Therefore the images from five cameras mounted around the car are used. Four of them with fisheye lenses. The methods have in common, that the input images are transformed into a bird view projection. First introduced method is to extract contours from the transformed images and collect geometrical features and Fourier coefficients. The second introduced way, is to calculate histograms of oriented gradients and use it as input for the classification step. Both classification approaches are implemented and evaluated as multiclass and single class detectors for each arrow type. Furthermore, the classification results from a support vector machine and random forest were faced for this classification problem. The results from the multiclass detectors are evaluated and presented in form of confusion matrices. With the introduced approaches a high detection confidence could be achieved, proofed with validation datasets and in practical use.     

The Influence of In-Plane Tyre Dynamics on ABS Braking of a Quarter Vehicle Model

For efficient analysis it is important to choose the proper model that fits the problem that needs to be solved. This paper discusses three pragmatic simulation models for longitudinal behaviour of a passenger car tyre (Steady State, Transient and Rigid Ring) that may be used in e.g. an ABS simulation. The characteristics of the simulation models are evaluated using some simple simulations. Simulations with a quarter vehicle model that includes load transfer effects are carried out to determine the deviation in results between the mentioned tyre models for an ABS application. The results show that the Steady State model may only be used below 10 Hz and that the Transient model is valid up to about 30 Hz. The results from the ABS simulation with the Rigid Ring model are most reliable and are clearly different from the Steady State and Transient model, which indicates that ABS simulations should be carried out with the Rigid Ring model. Additionally it is demonstrated that for tyre behaviour on uneven roads the influence of the tyre belt cannot be neglected.     

On the estimation of trip matrices in the case of missing and uncertain data

The problem of missing data in the base (calibration) year is of major importance when applying the gravity model in transportation planning, because base year data are used for calibration of the model. In this article, this problem is tackled by solving an optimization problem for the prediction year for values of the entropy level and the proportions of trips in a given stratification of the cells of the trip matrix estimated in the base year. The problem of uncertain data in the prediction year is handled by replacing equality constraints for the marginal totals in the prediction year by interval constraints. Computational results are given for trip data from the Linköping area.