Modelling the boundaries of project fast-tracking

Abstract

Fast-tracking a project involves carrying out sequential activities in parallel, partially overriding their original order of precedence, to reduce the overall project duration. The current predominant mathematical models of fast-tracking are based on the concepts of activity sensitivity, evolution, dependency and, sometimes, information exchange uncertainty, and aim to determine optimum activity overlaps. However, these models require some subjective inputs from the scheduler and most of them neglect the merge event bias.In this paper, a stochastic model for schedule fast-tracking is proposed. Relevant findings highlight the existence of a pseudo-physical barrier that suggests that the possibility of shortening a schedule by more than a quarter of its original duration is highly unlikely. The explicit non-linear relationship between cost and overlap has also been quantified for the first time. Finally, manual calculations using the new model are compared with results from a Genetic Algorithm through a case study.

Non-linear time-cost trade-off models of activity crashing: Application to construction scheduling and project compression with fast-tracking

“…One of the more advanced models on project fast-tracking was proposed by Ballesteros-Pérez in 2017 [63]. Ballesteros-Pérez's model allows fully stochastic analysis of activity overlaps which is an important feature allowing for a fair comparison to be made with the model(s) proposed here.…”

“…Impact Risk (19) where Δci ≤ ci and 0 ≤ oi ≤ MIN (ds i , dp i + li). For more details on the justification and development of this expression, including the multi-predecessor case, please refer to [63].…”

“…Therefore, a general conclusion is that, for lower levels of compression, fast-tracking will be a less expensive and thus a better option for most projects. However, with fasttracking, compression is very limited (indeed it is mathematically impossible for a project to be fast-tracked beyond 25%, and generally not beyond 10 to 20%, of its original duration [63]) . This means that, for significant levels of compression, activity crashing alone or in combination with fast-tracking will provide better (cheaper) configurations.…”

Do Projects really end late? On the shortcomings of the classical scheduling techniques

“…Going back to the causes of project delays, many factors have been identified: poor planning and controlling practices (Assaf & Al-Hejji, 2006;Assaf, Al-Khalil & Al-Hazmi, 1995), poor site management (Abdul-Rahman, Berawi, Berawi, Mohamed, Othman & Yahya, 2006;Alaghbari et al, 2007), labor shortage and lower productivity (Odeh & Battaineh, 2001;Sweis, Sweis, Abu Hammad & Shboul, 2008), problems with materials supply chain and procurement (Lo, Fung & Tung, 2006;Ballesteros-Pérez, del Campo-Hitschfeld, Mora-Melià & Domínguez-Santos, 2015), reworks of defective units or units with insufficient quality (Ballesteros-Pérez, 2017a;Forcada, Rusiñol, Macarulla & Love, 2014), contractor's and/or client's financial difficulties (Mansfield, Ugwu & Doran, 1994;Ogunlana et al, 1996), design changes (Arditi, Akan & Gurdamar, 2006;Mezher & Tawil, 1998), poor communication and co-ordination (Fimpong & Oluwoye, 2003), unexpected field interferences (Alarcón, Diethelm, Rojo & Calderon, 2005), adverse weather (Ballesteros-Pérez, del Campo-Hitschfeld, González-Naranjo & González-Cruz, 2015;Ballesteros-Pérez et al, 2017), legal disputes (Yogeswaran, Kumaraswamy & Miller, 1998), to cite just a few. It may not be a surprise then that delays in the final completion of projects are acknowledged in many sectors as one of the most common, costly, complex, and risky problems a project manager can face (Fawzy & El-adaway, 2012).…”

Obras rápidas de varejo: caracterização e proposta de diretrizes e produtos para planejamento e controle de tempos.

“…A demanda constante por redução no prazo vem estimulando cada vez mais, em diferentes países, estudos e pesquisas sobre o tema, em que apresentam essa nova abordagem como uma boa alternativa em busca da competitividade no setor. A sua definição consiste na abordagem de processo em que as fases de projeto e as fases da construção são sobrepostas, em que a obra se inicia antes da finalização total da fase de projetos (FAZIO, 1988;DESHPANDE, 2009;CHO, 2010;BALLESTEROS-PÉREZ, 2017).…”