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Vural Aksakalli – One of the best experts on this subject based on the ideXlab platform.

  • A stochastic approximation approach to spatio-temporal Anchorage planning with multiple objectives
    Expert Systems with Applications, 2020
    Co-Authors: B. Madadi, Vural Aksakalli

    Abstract:

    Abstract Globalization and subsequent increase in seaborne trade have necessitated efficient planning and management of world’s Anchorage areas. These areas serve as a temporary stay area for commercial vessels for various reasons such as waiting for passage or port, fuel services, and bad weather conditions. The research question we consider in this study is how to place these vessels inside a polygon-shaped Anchorage area in a dynamic fashion as they arrive and depart, which seems to be the first of its kind in the literature. We specifically take into account the objectives of (1) Anchorage area utilization, (2) risk of vessel collisions, and (3) fuel consumption performance. These three objectives define our objective function in a weighted sum scheme. We present a spatio-temporal methodology for this multi-objective Anchorage planning problem where we use Monte Carlo simulations to measure the effect of any particular combination of planning metrics (measured in real time for an incoming vessel) on the objective function (measured in steady state). We resort to the Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm for identifying the linear combination of the planning metrics that optimizes the objective function. We present computational experiments on a major Istanbul Straight Anchorage, which is one of the busiest in the world, as well as synthetic Anchorages. Our results indicate that our methodology significantly outperforms comparable algorithms in the literature for daily Anchorage planning. For the Istanbul Straight Anchorage, for instance, reduction in risk was 42% whereas reduction in fuel costs was 45% when compared the best of the current state-of-the-art methods. Our methodology can be utilized within a planning expert system that intelligently places incoming vessels inside the Anchorage so as to optimize multiple strategic goals. Given the flexibility of our approach in terms of the planning objectives, it can easily be adapted to more general variants of multi-objective spatio-temporal planning problems where certain objects need to be dynamically placed inside two or even-three dimensional spaces in an intelligent manner.

  • Capacity Planning in Non-uniform Depth Anchorages
    Intelligent Decision Technologies, 2015
    Co-Authors: Milad Malekipirbazari, Vural Aksakalli, Ali Fuat Alkaya, Volkan Aydogdu

    Abstract:

    Commercial vessels utilize Anchorages on a regular basis for various reasons such as waiting for loading/unloading, supply, and bad weather conditions. Recent increase in demand for Anchorage areas has mandated a review of current Anchorage planning strategies. In particular, current state-of-the-art Anchorage planning algorithms assume that the Anchorage areas are of uniform depth, which is quite unrealistic in general. In this study, we introduce an algorithmic modification to current Anchorage planning methods that takes into account non-uniformity of Anchorages. By exploiting the depth non-uniformity, our algorithm significantly improves the number of vessels that can be accommodated in an Anchorage and it can easily be incorporated into existing Anchorage capacity planning decision support systems.

  • An Anchorage planning strategy with safety and utilization considerations
    Computers & Operations Research, 2015
    Co-Authors: Vural Aksakalli, Ali Fuat Alkaya, Volkan Aydogdu

    Abstract:

    Heavy maritime traffic and the subsequent increase in vessel density in Anchorages have recently become a focal issue in maritime traffic safety. In this study, we consider the problem of determining the optimal berth locations of incoming vessels in an Anchorage area with the goals of maximizing utilization and minimizing the risk of accidents. We introduce novel performance metrics aimed at measuring achievement of these two goals. In this context, we propose a multi-objective optimization strategy and benchmark it against current state-of-the-art Anchorage planning algorithms using real-world data as well as Monte Carlo simulations. Our results indicate that the proposed strategy yields much safer berth locations while maintaining similar utilization levels. HighlightsWe study the problem of determining optimal Anchorage positions of incoming vessels.We consider the goals of maximizing utilization and minimizing risk of accidents.We introduce performance metrics aimed at measuring achievement of these goals.We propose a multi-objective Anchorage planning strategy.We benchmark it against current state-of-the-art Anchorage planning algorithms.

B. Madadi – One of the best experts on this subject based on the ideXlab platform.

  • A stochastic approximation approach to spatio-temporal Anchorage planning with multiple objectives
    Expert Systems with Applications, 2020
    Co-Authors: B. Madadi, Vural Aksakalli

    Abstract:

    Abstract Globalization and subsequent increase in seaborne trade have necessitated efficient planning and management of world’s Anchorage areas. These areas serve as a temporary stay area for commercial vessels for various reasons such as waiting for passage or port, fuel services, and bad weather conditions. The research question we consider in this study is how to place these vessels inside a polygon-shaped Anchorage area in a dynamic fashion as they arrive and depart, which seems to be the first of its kind in the literature. We specifically take into account the objectives of (1) Anchorage area utilization, (2) risk of vessel collisions, and (3) fuel consumption performance. These three objectives define our objective function in a weighted sum scheme. We present a spatio-temporal methodology for this multi-objective Anchorage planning problem where we use Monte Carlo simulations to measure the effect of any particular combination of planning metrics (measured in real time for an incoming vessel) on the objective function (measured in steady state). We resort to the Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm for identifying the linear combination of the planning metrics that optimizes the objective function. We present computational experiments on a major Istanbul Straight Anchorage, which is one of the busiest in the world, as well as synthetic Anchorages. Our results indicate that our methodology significantly outperforms comparable algorithms in the literature for daily Anchorage planning. For the Istanbul Straight Anchorage, for instance, reduction in risk was 42% whereas reduction in fuel costs was 45% when compared the best of the current state-of-the-art methods. Our methodology can be utilized within a planning expert system that intelligently places incoming vessels inside the Anchorage so as to optimize multiple strategic goals. Given the flexibility of our approach in terms of the planning objectives, it can easily be adapted to more general variants of multi-objective spatio-temporal planning problems where certain objects need to be dynamically placed inside two or even-three dimensional spaces in an intelligent manner.

Özgür Anil – One of the best experts on this subject based on the ideXlab platform.

  • Experimental study on the stress distribution at the interface between CFRP and three different types of masonry units
    Composites Part B-engineering, 2016
    Co-Authors: Özgür Anil, Cengizhan Durucan, Serdar Wali Din

    Abstract:

    Abstract In this study, stress distributions between externally bonded CFRP strips and three types of masonry surfaces were experimentally investigated. Furthermore, ultimate load and slip displacement behavior between the same surfaces were examined. The main variables considered in the experimental study were CFRP strip width (50 mm and 100 mm), bond length (200 mm and 280 mm), masonry unit type and presence of Anchorages. CFRP strips were externally bonded to aerated concrete, hollow and clay brick masonry units. Total twenty-four tests were conducted while half of them were tested without any Anchorages and other half of them were tested with the presence of fan type CFRP Anchorage. From the test results, the ultimate load and slip displacement behaviors, stress distributions on CFRP strips and ultimate load values were obtained and compared with the results obtained using analytical models. From the comparison of analytical and experimental results it was observed that the results obtained from analytical models and experimental study were not in good agreement for many cases. Furthermore, simple analytical models, based on the conducted experiments, were proposed to estimate the load–slip displacement behavior of CFRP strip and masonry unit interface.

  • Retrofitting of shear damaged RC beams using diagonal CFRP strips
    Journal of Reinforced Plastics and Composites, 2011
    Co-Authors: Sinan Altin, Özgür Anil, R Özgür Ocakli, Yağmur Kopraman

    Abstract:

    The results of an experimental investigation for the retrofitting of shear-damaged RC beams using diagonal CFRP strips are presented in this article. The experimental study consisted of seven shear-deficient, T-cross-sectioned, ½-scale, simply supported beam specimens. One beam is used as the reference specimen. The remaining six specimens are tested in two stages. At the first stage, specimens are shear damaged severely and the shear-damaged RC beams are retrofitted using diagonal CFRP strips by wrapping them around the beam in the shape of a ‘U’. Then, retrofitted beams are tested to failure. In this study, 50 mm wide CFRP strips are used with three different spacings such as sf = 125, 150, and 200 mm. One of the two specimens with the same spacing is tested with Anchorages at the ends of the CFRP strips. Although the strips without Anchorages improved the shear strength of the shear-damaged beam, they could not prevent the shear failure. Shear-damaged specimens that are retrofitted with Anchoraged CFRP…

  • Retrofitting of shear damaged RC beams using CFRP strips
    Steel and Composite Structures, 2011
    Co-Authors: Sinan Altin, Özgür Anil, Tolga Toptas, M. Emin Kara

    Abstract:

    The results of an experimental investigation are presented in this paper for retrofitting of shear damaged reinforced concrete beams by using U shaped CFRP strips. The experimental program is consisted of seven shear deficient T cross sectioned 1/2 scale simply supported beam specimens. One beam was used as reference specimen, and the remaining six specimens were tested in two stages. At the first stage, specimens were shear damaged severely, and then were retrofitted by using CFRP strips with or without fan type Anchorages. Finally, retrofitted beams were tested up to failure. Three different CFRP strip spacing were used such as 125 mm, 150 mm, and 200 mm. The effect of Anchorages on shear strength and behavior of the retrofitted specimens is investigated. CFRP strips without Anchorages improved the shear strength, but no flexural failure mode was observed. Specimens showed brittle shear failure due to peeling of CFRP strip from RC beam surface. Shear damaged specimens retrofitted with Anchoraged CFRP strips showed improved shear strength and ductile flexural failure. Maximum strains at Anchoraged strips were approximately 68% larger than that of strips without Anchorages.