University of California Transportation Center

Loading ships as they are unloaded (double-cycling) can improve the efficiency of a quay crane and container port. This dissertation describes the double-cycling problem, and presents solution algorithms and simple formulae to estimate benefits. In Chapter 2 we focus on reducing the number of operations necessary to turn around a ship. First an intuitive lower bound is developed. We then present a greedy algorithm that was developed based on the physical properties of the problem and yields a tight upper bound. The formula for an upper bound on the greedy algorithm's performance can be used to accurately predict crane performance. The problem is also formulated as a scheduling problem, which can be solved optimally using Johnson's rule. The problem is extended to include an analysis of double-cycling when ships have deck hatches.

In Chapter 3 we consider at the longer term impact of double cycling on port operations including crane, vessel, and berth productivity. We use another double cycling sequence that is operationally convenient, easy to model, and nearly optimum. We compare the performance of this sequence to those determined by a greedy algorithm and Johnson's rule. A framework is developed for analysis, and a simple formula is developed to predict the longer term impact on turn around time. The formula is an accurate predictor of performance. We then show that double cycling can reduce the requirements for landside vehicles and rivers. We also comment on strategies for altering port operations to support double cycling such as segmenting vessel storage, and streamlining traffic flows. We show that double cycling can reduce the amount of time required to complete vessel loading and unloading operations by 10%, improving vessel, crane, and berth productivity. It can reduce by about 20% the requirement for landside vehicles and drivers. Further, for wheeled operations, we suggest a method to reduce the requirement for chassis by about 25%. In Chapter 4 we consider somewhat broader issues, including the interaction of double cycling and security regulations, as well as ship design and routing. We estimate the financial impact of these benefits, which total approximately $70.00 per container moved, and address obstacles to implementation.

The research demonstrates that double cycling can create significant efficiency gains in vessel, crane, and berth productivity while simplifying some aspects of port operations. We also offer an explanation as to why a method that offers such significant benefits at low cost has not been rapidly adopted. We demonstrate that complementary analytical methods can be used to gain broad insight, and that simple, general models, are often of more value than more complex, detailed models.

In Chapter 3 we consider at the longer term impact of double cycling on port operations including crane, vessel, and berth productivity. We use another double cycling sequence that is operationally convenient, easy to model, and nearly optimum. We compare the performance of this sequence to those determined by a greedy algorithm and Johnson's rule. A framework is developed for analysis, and a simple formula is developed to predict the longer term impact on turn around time. The formula is an accurate predictor of performance. We then show that double cycling can reduce the requirements for landside vehicles and rivers. We also comment on strategies for alteringn port operations to support double cycling such as segmenting vessel storage, and streamlining traffic flows. We show that double cycling can reduce the amount of time required to complete vassel loading and unloading operations by 10%, improving vessel, crane, and berth productivity. It can reduce by about 20% the requirement for landside vehicles and drivers. Further, for wheeled operations, we suggest a method to reduce the requirement for chassis by about 25%. In Chapter 4 we consider somewhat broader issues, including the interaction of double cycling and security regulations, as well as ship design and routing. We estimate the financial impact of these benefits, which total approximately $70.00 per container moved, and address obstacles to implementation.

The research demonstrates that double cycling can create significant efficiency gains in vessel, crane, and berth productivity while simplifying some aspects of port operations. We also offer an explanation as to why a method that offers such significant benefits at low cost has not been rapidly adopted. We demonstrate that complementary analytical methods can be used to gain broad insight, and that simple, general models, are often of more value than more complex, detailed models.