American Society of Civil Engineers

Estimating Precipitation Impacts for Scheduling

by Gary R. Smith, M.ASCE, (Asst. Prof., Dept. of Civ. Engrg., Penn. State Univ., University Park, PA 16802) and Donn E. Hancher, F.ASCE, (Prof., Dept. of Civ. Engrg., Texas A&M Univ., College Station, TX 77843-3136)

Journal of Construction Engineering and Management, Vol. 115, No. 4, December 1989, pp. 552-566, (doi:

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Document type: Journal Paper
Abstract: Contract managers are expected to evaluate requests for contract extensions due to abnormal weather. However, they may not have a definition of normal weather impact for comparison. The implicit assumption in a contractor’s time-extension request is that normal weather disruptions are included in the original schedule. While subjective estimates can be prepared for weather impact, analytical approaches have been limited. The development of an analytical technique for evaluating impact will provide a basis for comparing planned and actual weather impact. A conceptual model for evaluating precipitation impact is presented. The method utilizes a Markov process for prediction of rainfall events, combined with an impact evaluation utilizing basic fuzzy-set operations. The treatment of information for the impact analysis stresses the individual treatment of activities. An example of a calculation is provided to demonstrate the technique. The proposed method provides an opportunity to evaluate normal weather impact to schedules, for planning purposes. If the normal weather impact can be defined, the difficulties of evaluating time-extension requests can be reduced.

ASCE Subject Headings:
Construction management
Markov process
Rainfall frequency
Weather conditions