A reliable technique for estimating construction projects total durations in order to reduce crashing risks and avoid slow progress

Abstract EN

One of the major measures of success of construction projects is the validity of finishing such projects within the anticipated total duration.

However, a 1992 worldwide survey reported that the majority of construction projects fail to achieve the objectives of the schedule due to unforeseen events that even experienced construction managers couldn’t anticipate [8].

On many of these projects a schedule overrun did not seem probable at the beginning of the projects.

Moreover, a survey by Laufer and Stukhart (1992) [10] of 40 U.S.

construction managers and owners indicated that for scope and design objectives, only 35 % of projects, with average cost of $5,000,000, had low uncertainty and the remaining 65 % had medium to very high uncertainty at the beginning of construction.

Another report by Laufer and Howell (1993) [9] went even further by indicating that 80% of projects at the beginning of construction possessed a high level of uncertainty.

Accordingly, the amount of uncertainty in the internal and external environments of a project is an important factor in determining whether there will be a schedule overrun or not.

This paper introduces a method that adopts reliability principles in the evaluation of the total duration of construction projects.

The method is tested through simulation.

The case study here is a construction project involving ten major activities, with uncertain durations, planned in the form of four paths till the end of construction.

The constructed building is assumed composed of a ground floor for parking and four floors for commercial centers.

The analysis assumes that the activities durations are independent random variables.

In addition, the distributions of the different activities are assumed normal distributions.

A Monte Carlo simulation is applied on the studied project chart to obtain the project critical path in a probabilistic sense.

The risk associated with different total project durations is evaluated.

Finally, based on a separate criterion to assume a suitable amount of risk in the solved problem, an estimate of what can be defined as reliable contract total project duration is obtained.