Structural BIM

[edit] Structural BIM

Structural Building Information Modelling represents the digital creation and management of the load bearing components of a facility. A structural model accurately maps the physical characteristics of materials to reflect existing conditions or proposed designs.

Commonly modelled structural systems include:

• Reinforced concrete frames and floor slabs.
• Structural steel frameworks and bracing.
• Space frames and complex trusses.
• Hybrid structures combining steel and concrete.
• Timber construction and wooden framing.

By creating a parametric database of the structural frame, a Structural engineer can extract precise material quantities, generate two dimensional fabrication drawings, and document existing conditions for future renovations and asset management.

[edit] Structural BIM versus Structural Analysis Models

It is important to distinguish a structural building information model from a structural analysis model. While both are essential to the engineering design phase, they serve fundamentally different technical purposes.

Key characteristics of a structural building information model:

• Acts as a high fidelity physical representation of the built asset.
• Details the exact geometric dimensions, spatial locations, and physical properties of elements.
• Focuses primarily on spatial coordination, constructability, and physical clash prevention.

Key characteristics of a structural analysis model:

• Functions as a mathematical abstraction for testing structural integrity.
• Reduces physical beams and columns to simplified wireframe lines and structural nodes.
• Calculates load paths, shear forces, and bending moments across the structural grid.

The engineer remains responsible for load analysis and safety design decisions, using the geometric data extracted from the physical building information model to construct their analytical calculations.

[edit] Coordination and Clash Avoidance

The structural frame forms the rigid geometric baseline for the entire construction project. Once the structural components are authored, the files are typically exported into open formats such as Industry Foundation Classes. These files are then combined with architectural and mechanical models to create a comprehensive Federated model.

Bringing all distinct engineering disciplines into a single digital environment is critical for Clash avoidance. Coordination software can automatically detect physical interferences before construction begins. Typical spatial conflicts resolved during this phase include:

• Large mechanical ventilation ducts intersecting primary steel beams.
• Plumbing drainage pipes clashing with reinforced concrete slabs.
• Electrical cable trays obstructing access to critical structural connections.

Resolving these spatial conflicts digitally in the pre construction phase prevents costly onsite delays. Furthermore, it ensures that the structural integrity of the building is not compromised by unplanned penetrations requested by mechanical contractors on the site.

[edit] Capturing Existing Structures and Concealed Elements

Creating a structural model for an existing building often begins with a Structural survey using three dimensional laser scanning technology. This reality capture method generates a dense Point cloud, providing a millimetre accurate reference for modelling the as built frame.

However, this process presents significant technical challenges when dealing with concealed structures. Laser scanners rely on direct line of sight and cannot penetrate solid surfaces. Consequently, several elements often remain hidden from the survey data:

• Structural members concealed behind architectural finishes or suspended ceilings.
• Steel columns completely encased in thick fireproofing layers.
• Foundation details and structural footings buried below ground level.

To accurately model these obscured elements, engineering professionals must cross reference the survey data with legacy construction drawings. In cases where the exact internal composition cannot be verified, the model must be carefully annotated to inform future stakeholders that certain geometric assumptions were made regarding the hidden structural supports.

[edit] The Standardised Modelling Process

The creation of a highly accurate structural model follows a rigorous industry methodology. This structured process ensures that every load bearing element aligns accurately with the reference documentation or physical site conditions.

1. Scope analysis involves reviewing the raw laser scan files alongside any available legacy drawings and site photographs to determine the required level of detail and project limits.
2. Project setup establishes the shared coordinate system and prepares the digital workspace to ensure absolute alignment with architectural and mechanical disciplines.
3. Primary modelling focuses on placing the core load bearing elements, including structural columns, primary beams, and load bearing walls.
4. Secondary modelling introduces finer details such as floor slabs, bracing, trusses, and specific mechanical penetrations requested by the wider design team.
5. Structural continuity checking ensures that all modelled elements connect logically, verifying that beams correctly intersect columns without unexplained floating geometry or disconnected nodes.
6. Internal quality control requires dedicated specialists to review the model using sectional cuts and deviation analysis to confirm all elements sit within the specified tolerance thresholds.
7. Model optimisation reduces overall file sizes by purging unused parametric families and ensuring the data structure remains highly responsive for downstream users.
8. Cross disciplinary review allows the wider project team to inspect the structural model, run preliminary clash detection, and request any necessary adjustments for spatial coordination.
9. Project closing finalises the native software files and exports the required deliverables for archiving, fabrication, and long term facility management.

[edit] Industry Standards and Quality Control

Maintaining geometric reliability requires strict adherence to international information management frameworks, such as ISO 19650. The geometric detail and non graphical data requirements are governed by specific standards like the Level of detail for BIM.

Different project stages dictate varying levels of modelling detail:

• Conceptual frames might be modelled at a lower level to show only the overall volume and orientation of primary structural members.
• Fabrication ready models require the highly precise placement of stiffeners, haunches, base plates, nuts, and bolts.

Furthermore, strict dimensional tolerances are enforced during the quality control phase. The spatial position of each modelled beam and column is verified against the raw point cloud to ensure deviations remain within acceptable limits. Quality control specialists check the detail of the element separately from its spatial accuracy, ensuring that a highly detailed structural connection is immediately rejected if it sits in the wrong position relative to the physical survey data.

Reference: 3D BIM Explained: Definition, Benefits and Workflow for Construction - Published by ViBIM