Realization probabilities of estimated costs of main construction items in domestic and international construction projects with Monte Carlo simulation

The construction industry contains a lot of risks due to its complex structure. These risks are often ignored or not adequately addressed by construction managers. Possible risks may cause deviations in quality, time or cost targets specific to the project. Especially if the cost estimates are not realized correctly, the Project managers can get into a very difficult situation. Therefore, risks should always be well analyzed. In this study, it is aimed to determine how much the main cost items of domestic and international construction deviate from the estimated cost with the help of Monte Carlo Simulation. The probability of realization of cost estimations is simulated separately in the triangular distribution, uniform distribution and PERT distribution. The minimum and maximum deviation values of the main construction cost items were taken as the averages of the results of the survey made to the member companies of the Turkish Contractors Association. As a result of this study, it is aimed to compare the probabilities of realization of costs in domestic and foreign construction projects and to compare three different probability distributions in the simulation. Some of the findings are that the minimum and maximum deviation of the earthworks cost item in domestic construction projects is higher than the other items, and that the tax and insurance cost item in foreign construction projects is less likely to be realized in the projected cost. Due to the low standard deviation of the PERT distribution, which is one of the statistical probability distributions in the simulation, and the high standard deviation of the uniform distribution, the optimum value is accumulated in the PERT distribution, while the values closer to the minimum and maximum points are seen in the uniform distribution. As a result of the study, it has been understood that the probability of cost calculations in construction projects is very important and the choice of probability distribution to be used in the simulation will directly affect the result.