Prediction of Cost Overrun Risk in Construction Projects

The paper proposes a cost overrun risks prediction model, the structure of which is based on the fuzzy inference model of Mamdani. The model consists of numerous inputs and one output (MISO, multi-input-single-output), based on processes running consecutively in three blocks (the fuzzy block, the interference block, and the block of sharpening the representative output value). The input variables of the model include the share of element costs in the building costs (SE), predicted changes in the number of works (WC), and expected changes in the unit price (PC). The developed rule base makes it possible to determine the risk of cost overruns in the following categories: very low, quite low, average, quite high, and very high. Twenty-seven rules were assumed in the interference block. The operation of the model was illustrated by the example of selected elements of a road object and was validated by checking the correctness of the assumptions made at the design stage of the inference block rule base. It has been proven that with the increase of the share of element costs in the building costs (SE), predicted changes in the number of works (WC), and expected changes in the unit price (PC), the value of the risk exceeding the costs of a given element of the construction project (R) increases naturally and smoothly. It was emphasized in the conclusions that the cost overrun risks prediction model is intended for general contractors who subcontract many stages of works to their subcontractors in accordance with the agreed division into work elements.