Cost analysis has always had a huge impact in the construction industry. It is one of the most important factors for owners, designers and contractors in critical decision-making. Traditional methods are very laborious and susceptible to human error, and involve volumetric calculations for complex geometry and manual data input. The process of cost estimation is tightly tied to quantities take-off. A well-prepared take-off can make cost estimation less labor-intensive, faster and less prone to omissions due to human errors. Therefore, using 2D documentation is inefficient in contrast with advanced tools in 3D CAD environment. However, in the early stages of design, a BIM model is a prototype with many uncertain parameters and lacks many details. Reinforcement steel is one of these missing details, which makes it very difficult to get reliable steel quantities, while it is a very important factor in terms of cost. The purpose of this study is to develop a method that aims to improve the accuracy of cost estimation for reinforced concrete elements in early stages of design using BIM technology. This research consists of the following two stages:  The first stage is feeding the database. It starts with getting the required reinforcement from structural design reports, then generating reinforcement in BIM models. Afterwards, load parameters are implemented and filled for reinforced concrete elements, and lastly, information (dimensions, reinforcement, loads, etc.) is collected and exported to database.  The second stage is calling from the database; no structural design reports required in this stage. Firstly, loads and dimensions of reinforced concrete elements in a BIM model are gathered, and then an iterative search for elements with similar loads and dimensions is carried out through the database. Reinforcement generation based on previous experiences stored in database is the next step. Finally, quantity take-off for reinforcement steel is extracted from the BIM model and information is collected and sent to update the database again. This method was tested on real-life projects designed by “Bollinger und Grohmann” and results were compared to conventional methods. Moreover, the product of this research can also be used to generate reinforcement in advanced stages of design.     «

Cost analysis has always had a huge impact in the construction industry. It is one of the most important factors for owners, designers and contractors in critical decision-making. Traditional methods are very laborious and susceptible to human error, and involve volumetric calculations for complex geometry and manual data input. The process of cost estimation is tightly tied to quantities take-off. A well-prepared take-off can make cost estimation less labor-intensive, faster and less prone to o...     »