ITS Berkeley

Shipment Composition Enhancement at a Consolidation Center

Daganzo, Carlos F.
1988

When items of different shapes, sizes and weights are transported, some item combinations make most effective use of a vehicle's capacity. A consolidation center, receiving shipments of various items from different origins, can act as a point where those combinations can be formed. While sending shipments through the center invariably increases the total item-miles traveled, judicious shipping can reduce the vehicle-miles traveled. This paper examines ways in which loads should be made up to achieve as large a reduction in vehicle-miles as possible. The paper first considers a building...

A Comparison of In-Vehicle and Out-of- Vehicle Freight Consolidation Strategies

Daganzo, Carlos F.
1988

This paper addresses physical distribution problems, in which items have to be distributed from an origin to many destinations, and it examines ways to reduce inventories. Under certain conditions, a peddling strategy with no transshipments is shown to be superior to any strategy with transshipments. Although the conditions leading to this result are not always met, the results suggest that transshipments are undersirable for freight distribution, unless of course they serve a purpose unrelated to inventory. This is contrast with many-to-many shipping operations which, under the same...

Crane Productivity and Ship Delay in Ports

Daganzo, Carlos F.
1989

This paper studies the effect of crane operations on ship service at port terminals. It first proposes a simple, approximate approach to calculate the maximum berth throughput during periods of congestion. The key assumption is that the workload distribution (over time) for the ships at berth is the same as the workload distribution for the ship population as a whole. The validity of this assumption is tested with simple, exact models for a variety of scenarios involving different kinds of ships and crane operating strategies. The paper then examines the effect that two extreme crane...

Impact of Parallel Processing on Job Sequences in Flexible Assembly Systems

Udomkesmalee, Narumol
Daganzo, Carlos F.
2025

Parallel processing offers several advantages. However, when processing times are allowed to vary, it can result in unpredictable job sequences. This issue must be addressed in assembly systems where it is necessary to match specific jobs with specific materials downstream. This research analyses job sequences after parallel processing and provides strategies for dealing with jobs getting out of sequence. One strategy involves re-sequencing materials using material buffers and another involves re-sequencing jobs using job buffers. A simple analysis determines the size of material buffers....

The Crane Scheduling Problem

Daganzo, Carlos F.
1989

This paper examines crane scheduling for ports. It starts with a simple static case and uses it as a building block to develop a better understanding of the dynamic problem with berth length limitations. The paper assumes that ships are divided into holds and that (usually) only one crane can work on a hold at a time. Cranes can be moved freely from hold to hold, and ships cannot depart until all their holds have been handled. In the most general case, ships arrive at different times and must queue for berthing space if the berths are full. The objective is to turn around (serve) all the...

Approximate Expressions for Queueing Systems with Scheduled Arrivals and Established Service Order

Sabria, Federico
Daganzo, Carlos F.
1989

This paper studies single server queueing systems where customers arrive according to a schedule, but not punctually, and where service might be provided in the scheduled order; thus, customers may leave the system in a sequence different to that of their arrivals. The situation arises in connection with maritime container terminals. The steady state solution to the problem follows an integral equation that may be solved numerically. When congestion is light (as is usual in well managed ports) approximate analytic solutions to the integral equation can be found. As an illustration,...

Storage Space Versus Handling Work in Container Terminals

Taleb Ibrahimi, Mounira
Daganzo, Carlos F.
1990

This paper describes handling and storage strategies for export containers at marine terminals and quantifies their performance according to the amount of space and number of handling moves they require. Identifying a “best” strategy is complicated because the optimization problem is combinatorial in nature—strategies are characterized, among other things, by the order in which future ship arrivals claim preferential space in the storage area. Given a certain traffic, the paper first examines the minimal storage space needed to implement the recommended strategies. This analysis may...