Eect of learning on line-of-balance scheduling David Arditi *, Onur Behzat Tokdemir, Kangsuk Suh Department of Civil and Architectural Engineering, Construction Engineering and Management Program, Illinois Institute of Technology, 3201 South Dearborn Street, Chicago IL 60616, USA Received 8 October 1998; accepted 18 November 1998 Abstract An approach to formulate learning rates and include them in line-of-balance (LOB) calculations is proposed in this paper. Learning rates are generated by modifying historical learning rates of typical construction activities and by incorporating the impact of relevant factors such as, number of operations in one unit, activity complexity, and job and management conditions. Fuzzy set theory is used to develop production rules to treat both factual and uncertain information. An S-type membership function is used to interpret the fuzzy data and produce adjustment factors that are in turn used to modify consecutive learning rates, until an adjusted learning rate is obtained. The adjusted learning rate is then used to calculate expected worker-hours and activity durations at each unit of production (e.g., a ¯oor in a high-rise building, a mile of pavement work, etc.). A ®nal LOB diagram is generated using this information. Dierent pairs of curves represent the start and the ®nish times of each activity in sets of units that make use of dierent numbers of crews. Learning reduces project duration and resource requirements. The proposed approach demonstrates the potential for formalizing the inclusion of learning eects into the LOB scheduling of repetitive-unit construction. # 2001 Elsevier Science Ltd and IPMA. All rights reserved. Keywords: Line-of-balance scheduling; Repetitive construction; Learning model 1. Introduction Linear scheduling methods are planning and scheduling techniques,mostlyusedinindustrieswhereoperationsare of repetitive nature. The line-of-balance (LOB) technique is a linear scheduling method that allows the balancing of the operations such that each activity is continuously and eciently performed in each consecutive unit. Some construction projects that involve sets of tasks orga- nized in repeating sequences are similar to continuous manufacturing processes in their structure. Examples of such projects include pavement construction, multi- housing projects, and high-rise building construction. One of the important issues in repetitive operations is the eect of learning. It is obvious that a repetitive operation oers better opportunities to achieve higher productivity. It is indeed widely recognized that labor productivity improves when repetition is involved in an operation. However, only few attempts have been made to incorporate the eects of learning into linear sche- duling techniques [1]. The objective of this paper is to present a philosophical justi®cation for the development of a learning model to be used in association with linear scheduling methods. An attempt to develop a quantitative model to capture and simulate learning eects is presented. A simple approach that can be used to determine the impact of contextual factors on learning is introduced. A con- ceptual model for incorporating learning data into the LOB method is presented. The methodology used to formulate a learning model is discussed after a review of the related literature. The impact of learning eect on LOB is demonstrated by means of an example. The concluding section summarizes the results of the study and proposes areas of further research and develop- ment. 2. Line-of-balance scheduling The LOB technique was originated by the Goodyear Company in the early 1940s and was developed by the 0263-7863/01/$20.00 # 2001 Elsevier Science Ltd and IPMA. All rights reserved. PII: S0263-7863(99)00079-4 International Journal of Project Management 19 (2001) 265±277 www.elsevier.com/locate/ijproman * Corresponding author. Tel.: +1-312-567-5751; fax: +1-312-567- 3540. E-mail address: arditi@iit.edu (D. Arditi).