Schematic cost estimating model for super tall buildings using a high-rise premium ratio

Abstract

Super tall building construction involves considerable financial uncertainty due to its potentially low returns despite high investments. To reduce this financial risk, it is crucial to accurately estimate the schematic construction cost of such projects. However, traditional cost estimating practices (TCEP) are not effective at predicting the cost of schematic design phase design alternatives that involve the change in the number of building stories. To address these issues, this research proposes a schematic cost estimating model (SCEM). The SCEM estimates the schematic construction cost of super tall building alternatives using a simulation mechanism that considers variation in the number of building stories (i.e., +/- 5, +/- 10, +/- 15, +/- 20 stories). First, the limitations of the traditional practices are identified. Then, three pilot alternatives (i.e., one schematic design and two design alternatives) are designed and estimated in detail. Next, cost simulation mechanism is constructed based on the relationships between design scale, material quantity, unit cost rate, and construction cost. In addition, after determining which dominant factors affect construction cost when the number of building stories changes, the high-rise premium ratio and its theoretical framework are introduced. This ratio is used to identify the productivity ratios of super tall buildings and to simulate construction cost as the building design changes. Finally, the SCEM is validated through a case study of an actual super tall building. It is found that schematic construction cost increases as the unit cost rate rises due to a low productivity ratio in the case of a higher number of building stories. Conversely, this cost decreases as the unit cost rate goes down due to a high productivity ratio in the case of a lower number of building stories. Ultimately, the SCEM is developed to support effective decision-making during the schematic design phase.