(1) Complex structures are seldom represented accurately. When using computational software to estimate quantities for certain construction projects, creating 3D models is necessary. During the modeling process, complex structural components with unique shapes—such as specially designed column heads—often appear. Inexperienced new employees tend to avoid software modeling and instead rely on manual calculations, which can lead to significant errors. Additionally, manually extracting quantities later becomes difficult. The complex column example is shown in Figure 1.
Figure 1: Detailed drawing of the roof column head in a high-rise residential building
(2) Inaccurate recognition during drawing-based modeling.
When modeling, cost estimators often use the drawing recognition feature in modeling software to save time and increase efficiency. However, this method requires the design drawings from the design institute to be precise enough. Unfortunately, drawings rarely achieve the accuracy needed for software to automatically identify all components correctly. Many beams, slabs, and columns are only partially recognized, resulting in numerous unidentified or incorrectly identified elements, as shown in Figures 2 and 3. Without strong graphic recognition skills, modelers risk producing overdrawn or inaccurate models.
Figure 2: Numerous beams remain unrecognized by the modeling software
Figure 3: Unrecognized column samples in the software modeling group
(3) Neglecting special component tie bars.
New employees often overlook the treatment of tie bars and reinforcement bars in certain components. These elements are typically included in the overall design specifications within the construction drawings but can be easily missed by inexperienced staff. Figure 4 illustrates the schematic of tie bars. In large-scale projects, neglecting these details can lead to significant underestimation and inaccuracies.
(a) Drill holes in the board to reinforce ribs
(b) Reinforcement at wall tops and beam bottoms
Figure 4: Schematic diagram of reinforcing bars and tie bars from the design description
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