Decision Support System for Risk Assessment in Construction Projects AHP-Simulation Based Technique

ABSTRACT Unpredicted risk factors may occur through project execution, which lead to increase in the overall budget and duration. These risk factors may be due to site conditions, resources, project parties…etc. Some researchers developed their researches concerning the time contingency or cost contingency or both of them. This paper presents a model for assessing cost and time contingencies. The model presented here depends on Analytical Hierarchy Process (AHP). In the new formulation both cost and schedule overruns, and risk response will be taken into consideration simultaneously to decrease cost and time contingency. Results showed that cost and schedule overruns can be defined as normal probability distribution with a mean value of 34.5% and 37.9%, respectively. On the other hand, if risk response taken into consideration these values are reduced to 15.4% and 9.1%, respectively.A Sensitivity analysis was carried out to investigate the impact of changing input: attributes and sub-criterions on the model output values (% change in schedule and cost overruns).The main contributions were: the two attributes, management strategy and unexpected surface conditions have 16.51%, and 13.83% impact on cost overrun and schedule overrun for best case scenario when risk response considered. On the other hand, for sub-criterions: owner, and site location these values are 9.86% and -9.47% on cost overrun for best case scenario and on schedule overrun for worst case scenario when risk response considered.Validation of the developed model using three case study projects revealed that the model assess cost and schedule overruns with an accuracy of 91%. This value demonstrates that the obtained results are fairly good and acceptable.