Model for construction project delay occurrence (PDO)

Extensive research work was conducted in relation with evaluating and ranking delay causes in construction projects, but limited research was performed to discuss the delay issue in theory. This paper discusses the theoretical basis for how delay occurs and propagates during project construction. A set of suggested assumptions were proposed to build a theoretical model for delay occurrence. These assumptions were driven from the analysis of construction project environment, and the concept of project implementation. The construction delay occurrence (PDO) model assumes that some of the root delay causes can convert by themselves and/or other triggers toward direct delay causes. Contractor management deficiency, project contract and procurement strategy, and contractor financial problems are examples of the root delay causes, which have significant influence on project delay and resource availability. The model assumes that construction resources unavailability is the underpinning driver for project delay. Graphical presentation of the PDO model is used to illustrate how delay is generated, propagated during the project life, and converted to be a real and physical delay. Interview questionnaires were used to verify the model bases. This is followed by statistical analysis to ascertain the model assumptions and Delphi technique to confirm questionnaire results. The correlation factors for the two rounds of questionnaires showed that there is a great enhancement for respondents' answers regarding the effect of resource shortage on root delay causes. The study shows that the proposed set of root delay causes and their effect on project delay and their influence on resource availability were statistically accepted. The study results can be used as a basis for assessing root delay causes and predicting the prone of a project to delay before it starts.