In principle, the accuracy of BIM models should align with traditional design standards, which progressively evolve through the stages of scheme design, preliminary design, detailed design, and construction drawing design. To address varying model requirements at different design depths, the concept of Levels of Detail (LOD) is introduced. By assigning rendering resources based on the LOD, the complexity and quantity of non-critical structures can be reduced, thereby improving design efficiency.
Bridge design typically begins with road planning to establish the span layout. Once the bridge location is confirmed, the site environment and structural form are analyzed to develop the bridge scheme design. This process is followed by preliminary design, then further detailed design, ultimately culminating in construction drawings. The model requirements for each stage are outlined as follows:
1. Scheme Design Phase (LOD100): At this initial stage, the model captures the bridge’s structural form, span arrangement, and connections to approach bridges. Detailed design is not yet required; instead, the focus is on clearly conveying the general layout and appearance to support scheme selection.
2. Preliminary Design Stage (LOD200): The model advances to include material specifications, dimensions, and cross-sectional details for each bridge component. It also addresses the design of the superstructure, substructure, and foundation. Connections between approach bridges or ramps and the main bridge are refined, alongside the construction plan.
3. Detailed Design Phase (LOD300): At this level, the model closely represents the actual bridge entity, incorporating local details and improvements at key structural nodes. Components such as stiffening beams, main cables, and suspension rods are defined. The model reflects the overall framework of a self-anchored suspension bridge, supporting BIM applications for full lifecycle management. This approach balances structural accuracy with model lightweighting.
4. Construction Drawing Design Stage (LOD400): The model matches the real-world scale and includes detailed structures like stiffening beam welds, main cable anchorage zones, and cable saddle clamps. This level provides the necessary detail to guide construction activities such as manufacturing, processing, installation, and assembly. Additional ancillary facilities can also be incorporated. Models at this stage facilitate inspection and management of detailed components like cable saddles, clamps, and supports.
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