On alternative mixed integer programming formulations and LP-based heuristics for lot-sizing with setup times

We address the multi-item, capacitated lot-sizing problem (CLSP) encountered in environments where demand is dynamic and to be met on time. Items compete for a limited capacity resource, which requires a setup for each lot of items to be produced causing unproductive time but no direct costs. The problem belongs to a class of problems that are difcult to solve. Even the feasibility problem becomes combinatorial when setup times are considered. This difculty in reaching optimality and the practical relevance of CLSP make it important to design and analyse heuristics to nd good solutions that can be implemented in practice. We consider certain mixed integer programming formulations of the problem and develop heuristics including a curtailed branch and bound, for rounding the setup variables in the LP solution of the tighter formulations. We report our computational results for a class of instances taken from literature

A Performance Measurement Framework and Solution Approach for the Integrated Facility Layout Problem With Uncertain Demand

The integrated facility layout problem (IFLP) focuses on the simultaneous determination of the relative locations of multiple copies of capacitated equip- ment or machinery in a facility, as well as the material ow between these units. In this paper, we consider the IFLP in the existence of uncertain demand for the products of the facility. Motivated by the framework for next generation facility layouts by Benjaafar et al. (2002), we extend the approaches in the lit- erature for distributed facility layouts to the case of dynamic demand and the possibility of relayouts, and propose a heuristic solution approach to minimize the expected total material handling cost over the planning horizon. We also analyze the performance of the resulting solutions in terms of empty travel of the material handling equipment and waiting time. Our computational results reveal that when demand is dynamic and stochastic, the relationship between the level of uncertainty and relayout cost plays an important role in determin- ing layout performance, and therefore a priori assumption of using a certain layout type may lead to detrimental results

The Storage Replenishment Problem in Rectangular Warehouses

In warehouses, storage replenishment operations involve the transportation of items to capacitated item slots in forward storage area from reserve storage. These items are later picked from these slots as their demand arises. While order picking constitutes the majority of warehouse operating costs, replenishment operations might be as costly in warehouses where pick lists generally consist of only a few lines (e.g., order fulfillment warehouses). In this study, we consider the storage replenishment problem in a parallel-aisle warehouse, where replenishment and order picking operations are carried out in successive waves with time limits. The aim is to determine the item slots that will be replenished and the route of the replenishment worker in each replenishment wave, so as to minimize the total labor and travel costs, and ensure the availability of items at the start of the wave they will be picked. The problem is analogous to the inventory routing problem due to the inherent trade-o between labor and travel costs. We present complexity results on different variants of the problem and show that the problem is NP-hard in general. Consequently, we use a heuristic approach inspired by those from the inventory routing literature. We use randomly generated warehouse instances to analyze the elect of different storage policies (random and turnover-based) and demand patterns (highly skewed or uniform) on replenishment performance, and to compare the proposed replenishment approach to those in practice

Order picking in parallel-aisle warehouses with multiple blocks::complexity and a graph theory-based heuristic

In this paper, we consider the order picking problem (OPP), which constitutes one of the special cases of the Steiner travelling salesperson problem and addresses the costliest operation in a warehouse. Given a list of items to be picked and their locations in the warehouse layout, the OPP aims to find the shortest route that starts from a depot point, picks all the items in the list, and returns to the depot. This paper fills two important gaps regarding the OPP. First, to the best of our knowledge, we present the first complexity results on the problem. Second, we propose a heuristic approach that makes use of its graph-theoretic properties. Computational experiments on randomly generated instances show that the heuristic not only outperforms its state-of-the-art counterparts in the literature, but it is also robust in terms of changing problem parameters

Potential effects of logistics clusters: The case of Turkish Freight Villages

Freight Villages (FV) are logistics clusters in which all activities related with freight transportation are realized. Various operators conduct business under one roof in FVs. Coordination and collaboration are the essential part for creating harmony to achieve sustainability. The establishment of such facilities in Turkey has been realized in late 2000s. In this paper, the aim is to provide a broad overview of the FVs in Turkey and shed light into their potential for the future. To do so site visits to all existing operational public FVs and a private FV have been made, where interviews with the management units have been conducted and comparisons to global counterparts have been made. As a result of these, it has been observed that currently, FVs in Turkey are overwhelmed due to lack of coordination and collaboration. However, also light has been shed into possible alternative working principles for Turkish FVs, and it has been showed that if coordination and collaboration could be realized, significant positive effects can be achieved in terms of different aspects regarding sustainability and social equity

Freight villages: A literature review from the sustainability and societal equity perspective

The purpose of this study is to present a state-of-the-art literature review on Freight Villages from the sustainability and equity perspective, and discuss their impacts and place in the supply chain and logistics networks while focusing on the core concepts of freight transportation. With an understanding of the structure of freight villages, it is clear that they have potential for a number of merits with the increase in freight transportation activities. However, our review shows that current literature does not present satisfying evidence that these villages fulfill their purpose in terms of sustainability and social equity

The Order Picking Problem in Fishbone Aisle Warehouses

A recent trend in the layout design of unit load warehouses is the application of layouts without conventional parallel pick aisles and straight middle aisles. Two examples for such designs are flying- V and fish bone designs for single and dual command operations. In this study, we consider the same layout types under the case of multiple-item pick lists and show that, for both layout types, the routing problem can be solved in polynomial time. We also propose simple heuristics for this problem inspired by those put forward for parallel-aisle warehouses. Our computational results reveal that under certain cases, fish bone design can perform as high as 30% worse than an equivalent parallel-aisle layout, and a modification of the aisle-by-aisle heuristic produces good results compared to other heuristics

Dataset for "Inventory Routing in a Warehouse: The Storage Replenishment Routing Problem"

This dataset relates to testing of a heuristic approach using operational research techniques for a specific routing problem in a warehouse, defined as the Storage Replenishment Routing Problem. There are a total of 620 instances, stored as .dat or .txt files, classified into two groups depending on the sizes of the instances. The 300 smaller instances consist of different settings ranging from 25 to 150 pick items and from 3 to 15 replenishment periods. Each setting consists of 10 instances randomly generated by changing the items to be picked in the warehouse, their locations in the warehouse, initial inventory levels, and maximum storage capacities in the forward storage area. The 320 larger instances involve 450 pick items and 15 replenishment periods, with each setting including 10 random instances generated by changing the items to be picked in the warehouse, their locations in the warehouse, initial inventory levels, maximum storage capacities in the forward storage area, and the skewness of the demand (ranging from uniform to 20-80 skewness). To use any of the instances, the user needs to read the data given in the corresponding text file into the optimisation software or the platform where their heuristic is coded in. The target audience for this dataset is operational researchers working on developing heuristic approaches for similar routing problems in warehouses.The data has been generated using warehouse parameters from "Roodbergen, K.J. and de Koster, R.B.M. (2001). Routing methods for warehouses with multiple cross aisles. International Journal of Production Research, 39(9): 1865-1883." and using the inventory routing parameters from "Solyali, O. and Sural, H. (2011). A Branch-and-Cut Algorithm Using a Strong Formulation and an A Priori Tour-Based Heuristic for an Inventory-Routing Problem. Transportation Science, 45(3): 335-345." Each instance setting consists of 10 instances, randomly generating the picking demand, maximum inventory levels and initial inventories.No third-party datasets were directly used, but the methodology used in two different papers were replicated. Please see Data Collection Method for sources.The data has been generated using a random instance generator coded in C++ using Microsoft Visual Studio 2019