INTRODUCTION
In the last decades, international shipping trade has experienced a considerable growth and ports have been extended to satisfy the increasing demand. Many operations are performed simultaneously in port areas, and they are subjected to a set of random agents, such as maritime climate, sequence of ship arrivals and other factors related to port services and exploitation criteria. Due to this, port management has become a difficult task that cannot be dealt with using traditional tools. In this context, harbours need an aid decision making tool that is capable not only to reproduce maritime operations through simulations but also to assess the uncertainty in the performance of a given harbour management strategy and to compare the effectiveness of different alternatives.
In this work, a port operations simulation software, based on the methodologies proposed in [1], [2], and [3], is presented. For a given port management strategy, the software uses simulation techniques to obtain realizations of the time series that characterize climate and use and exploitation variables. With these variables it reproduces port operations and obtains a series of indicators that measure the performance of the alternative in regard to operationality, waiting times, occupancy and use of harbour services. The performance of the alternatives is characterized from a statistical point of view. The tool also implements the Stochastic Multicriteria Decision Method SMAA-2 [4] that allows to compare different strategies and to rank them according to their performance taking into account multiple criteria.
THE SOFTWARE
The software comprises several modules to (1) define the case study, (2) simulate port operations, (3) analyse the results and (4) compare different scenarios.
- The case study is defined by the (i) harbour configuration, namely, the elements used by ships, such as entrance, channels, docks, anchorages, etc.; (ii) the information to simulate the climate conditions that affect ship operations (sea level, waves, wind, currents and visibility); (iii) ship traffic characterized in terms of ship arrivals, climate thresholds to operate, dimensions or port services demand (pilot, tug, mooring), navigation, time at docks, etc.; (iv) harbour services offered by the port, namely, pilots and tugs assistance and mooring and (v) management and operational criteria, such as priorities for a certain kind of ships or safety procedures related to dangerous goods ships or climatic conditions (visibility, wind intensity, wave severity).
- Once the case study is defined, the software reproduces during a certain time interval (one year) the time series that define the climate and exploitation variables (ship arrivals, dimensions, demanded services, etc.). With that information, the software reproduces ship movements at the harbour and checks the viability of the movement considering operational criteria (climate thresholds, priorities) and availability of resources (harbour services, berths). As a result, the movement will be done or the ship will have to wait. All this information is registered accordingly. The previous step is reproduced a large number of times so that a representative sample of the harbour performance indicators is obtained. This sample is then used to infer the distribution functions that characterize in probabilistic terms the behaviour of the case.
- The results module shows the variables and functions that characterise the port performance.
- The software can be applied to different alternatives of a given case and used to select the best alternative. The methodology takes into account multiple criteria, the uncertainty of the preferences of the decision-makers and the stochastic nature of the variables that define the criteria.
VALIDATION CASE
The software has been validated with a real case study of the Port of Algeciras. The Port of Algeciras is located at the south of Spain, in the strait of Gibraltar. Because of the strategic location, the Port of Algeciras is the busiest Spanish port and the fifth port in Europe.
The port performance has been measured through a set of parameters, such as berth or harbour services occupancy rates. These real values were calculated using information related to the use of berths, docks and harbour services, registered and provided by the Port Authority.
Then, a real case study based on the Port of Algeciras has been simulated with the software. The port was modelled within the software using information provided by the Port Authority, such as docks and berths configuration, ships arrivals and their characteristics, port services, etc.
The simulated values obtained from the simulations were compared to the real calculated values. It was observed that the software provides similar values to the real ones, for berth and harbour services occupancy rates, as well as for use of harbour services. Variables like the percentage of time in which N tugs are working simultaneously have been reproduced accurately.
CONCLUSIONS
The presented software has proven to be a useful decision support tool for port management and planning, which reproduces the port performance precisely. Thus, the software is able to help port managers to detect bottlenecks at ports where traffic is high and randomness plays an important role, to optimize infrastructure management criterions and as a decision support tool for berths and anchorages planning, among many other applications.
AKNOWLEDGEMENTS
The software has been developed by Proes Consultores and FCC Industrial, and the Port of Algeciras as pilot-port. The project was co-funded by the European Regional Development Funds.
REFERENCES
[1] Benedicto, I., A. Baquerizo, F. Santos, I. Sanchidrián and M. A. Losada (2013). Software de optimización de la operatividad portuaria mediante técnicas de simulación. XII Jornadas Españolas de Ingeniería de Costas y Puertos.
[2] Optimizing harbor operations through simulations techniques, 2009-2012. CIT-460000-2009-021. Final Project Report.
[3] García Morales, R., A. Baquerizo and M.A. Losada (2015). Port management and multiple-criteria decision making under uncertainty. Ocean Engineering, Vol. 104,31-39 doi: 10.1016/j.oceaneng.2015.05.007
[4] Lahdelma, R. and P. Salminen (2001). SMAA-2 : Stochastic multicriteria acceptability analysis for group decision making. Operations Research, 49 , 444-454.