CENTER FOR INTEGRATED FACILITY ENGINEERING
Formalizing Construction Sequencing Constraints for Rapid Generation of Schedule Alternatives
By
Bonsang Koo and Martin Fischer
CIFE Working Paper #75 January 2003
STANFORD UNIVERSITY
Copyright 2003 by
Center for Integrated Facility Engineering
If you would like to contact the authors, please write to:
c/o CIFE, Civil and Environmental Engineering Dept., Stanford University Terman Engineering Center Mail Code: 4020 Stanford, CA 94305-4020
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Formalizing Construction Sequencing Constraints for Rapid Generation of Schedule Alternatives Bonsang Koo, Martin Fischer Abstract
Construction planners today use CPM-based schedules to represent the planned logical sequence of activities to perform a project. A construction schedule typically represents the sequence of multiple trades that perform individual work while sharing common workspaces or resources. The logic or "rationale" behind activity sequences of these schedules can include physical relationships between components (e.g., supported by), trade interactions (e.g., workspace competition) or safety and code regulations (e.g., testing). Due to changing project demands, planners frequently need to modify activity sequences during the course of a project. More than one alternative can exist, and hence planners need to develop and evaluate alternative sequences correctly and rapidly to make well-informed decisions. When developing sequencing alternatives, planners need to understand the physical or technical "role" an activity plays on following activities. They also need to distinguish between activities that may or may not be delayed. Planners infer the role and "status" (i.e., whether an activity may be delayed) of activities based on the initial rationale and flexibility of the constraints between activities. However, the current CPM framework only distinguishes the temporal aspects of constraints (e.g., FS precedence relationship) and only distinguishes the time-criticality of activities. Consequently, determining the role and status of activities can only be performed in the planner's minds. Hence, identifying and developing sequencing alternatives using CPM-based schedules is today an error-prone and time-consuming process. In this paper, we introduce research to determine how sequencing constraints can be represented to enable planners to describe rationale accurately. We also introduce an activity classification mechanism that can be used by a computer system to automatically determine the role and status of activities. We describe a formalized process that utilizes the representation and classification mechanism to assist planners in developing sequencing alternatives correctly and accurately. Finally, we discuss the necessary research to validate the generality and power of the proposed approach more fully.

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