ASSESSING ALTERNATIVE PREFABRICATION METHODS:. LOGISTICAL INFLUENCES

Robert Seaker1 and Sang-Hoon Lee2

1Department of Information and Logistics Tech., University of Houston, TX 77204, USA
2Department of Engineering Technology, University of Houston, TX 77204, USA
E-mail: RFSeaker@central. uh. edu, sleel5@uh. edu

Abstract

Any construction project that is completed on-time at the lowest total cost requires the consideration of logistics processes and economics. This study investigates the cost implications of moving and transforming materials in various materials network configurations associated with popular prefabrication construction methods. Efforts focus on the trade-offs that exist among contract-to-completion times, transportation costs, and assembly costs for the alternative construction methods. The findings suggest that the competitive advantage of prefabrication methods can be enhanced through an optimal combination of reduced construction times as well as the number, distance, and configurations of materials and sub-assembly shipments.

Introduction

The expression “time is money” appropriately applies to commercial initiatives, particularly construction projects. The duration of a construction project – from the time the contract is initiated to when the structure is completed – has a direct impact on the cost of the job. Bids from competing contractors, costs of construction loans, and earnings streams of business enterprises dependent on the finished structures are all affected by the time necessary to construct a building.

Prefabrication is a construction alternative that is primarily chosen because of its ability to reduce the total time for completing a project. Prefabricated construction refers to the utilization of sub­assembled structural components generally manufactured off-site (CII, 2002). From fully – manufactured buildings to those assembled from modularized, panelized, or even pre-cut components, the incremental degrees to which prefabrication can be employed is limitless. The reduction in construction times that these approaches provide can be mainly attributed to the degree of independence between site preparation and sub-assembly, more dependable job scheduling, and greater production efficiencies at the prefabrication sites as well as at the construction site (CII, 2002; Haas and Fagerlund, 2002; Kupitz and Goodjohn, 1991; Tatum et al., 1987).

While the reduction in construction time is perhaps the most visible and important benefit of prefabrication techniques, the costs associated with off-site activities pertaining to the movement of materials can impact the extent to which a particular level of prefabrication is economically feasible. The number, distance, and configurations of supply and sub-assembly shipments can add tens of thousands of dollars to projects of even a modest size. To gain further clarity regarding this issue, the effects of logistical activities associated with common prefabrication processes were investigated. The time and cost relationships that exist among these variables were identified, modeled, and analyzed. Efforts focused on the trade-offs that exist among contract-to-completion times, transportation costs, and assembly costs for alternative construction methods across multiple applications. Recommendations for strategies and configurations for improved economics are then offered.

607

M. Pandey et al. (eds), Advances in Engineering Structures, Mechanics & Construction, 607-614. © 2006 Springer. Printed in the Netherlands.