Optimum Working Time

by Marvin Gates, (F.ASCE), Pres.; Construction Estimating, Inc., West Hartford, Conn.; Lect., Worcester Polytechnic Inst., Worcester, Mass.,
Amerigo Scarpa, (F.ASCE), Pres.; Gates-Scarpa and Assocs., Inc., West Hartford, Conn.; Lect., Hartford State Technical Coll., Hartford, Conn.,

Serial Information: Transportation Engineering Journal of ASCE, 1977, Vol. 103, Issue 6, Pg. 773-781

Document Type: Journal Paper


The familiar problem relating to the tradeoff between direct and indirect cost relative to project duration is solved in closed form. Elementary cost minimizing methods give simple algebraic expressions that optimize constraints. The following rule evolves: The optimum working time for a particular operation is when the total cost for variable overheads (time dependent) equals the total cost to mobilize and demobilize all of the crews. This least-cost solution is not altered by working overtime as a means of reducing equipment requirements. The theoretical solution is illustrated with a solved problem employing the derived formulas as well as by iteration for comparison and sensitivity. The solution to the problem of optimum working time also gives the solution to the problem of the optimum number of crews that should be employed.

Subject Headings: Construction costs | Closed form solutions | Optimization models | Time dependence | Equipment and machinery | Comparative studies

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