PRESCRIPTIVE SPECIFICATION DESIGN: THE IMPACT ON COST AND CONSTRUCTABILITY – CASE HISTORY

摘要

This paper outlines how specification driven design has made Toronto Area transit infrastructure projectsrnmore expensive than similar private projects, and provides a case study of the results of an excavation atrnLaunch Shaft 1 (LS1) for the Eglinton Crosstown Light Rail Transit project in Toronto, Ontario. Thernpaper will describe the impact specification driven design parameters can have on design economy,rnconstructability, and schedule and will suggest an alternative approach utilizing the ObservationalrnMethod. As a result of the initial specification based design, Isherwood was retained by both the GeneralrnContractor and the Specialty Excavation Shoring Contractor to provide value engineering leveraging thernObservational Method to improve constructability and construction schedule. By using well known,rnaccepted design methods coupled with local experience in lieu of the specified design pressures andrnparameters, the redesigned bracing scheme reduced construction cost and schedule. This excavation casernhistory can be a lesson learned for future transit projects.