When using BIM models to calculate engineering quantities, several important points should be considered:
1. Measurement Units for Engineering Quantities
The units used in construction quotas may differ from those in budget quotas for certain items. Therefore, when compiling statistics, it is essential to ensure that the measurement units for the project match those used in the construction quota. This alignment allows for direct application of the construction quota when calculating labor and material needs, avoiding unnecessary unit conversions.
2. Construction Methods
The calculated engineering quantities should correspond with the chosen construction methods to accurately reflect the actual construction conditions. For example, factors such as earthwork excavation techniques, whether to slope the excavated soil, the size of the working face, and the slope angle can significantly impact the quantity calculations.
3. Compliance with Construction Organization Requirements
During project planning, construction should be divided into layers and sections, with quantities listed for each. If the quantities across floors and sections show little variation, it may be sufficient to calculate the quantity for one floor and one section, then multiply by the total number of floors and sections to estimate the overall quantity.
4. Using BIM Software (e.g., Revit) for Quantity Calculation
While BIM software like Revit can calculate geometric quantities, practical application remains challenging and requires highly accurate models. The process involves complex computations including deductions and classifications. For instance:
• The area of a beam alone holds limited practical value. Its significance increases only when physical properties—such as formwork, plastering, or painting—are assigned. These require proper classification.
• Deduction issues must also be addressed. For example, when painting beams on three sides, decisions about including or excluding certain sections depend on the actual context, including deductions for intersections with columns, beams, slabs, and walls.
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