LOD 350- when you can’t see the join

The Invisible Puzzle: Unlocking LOD 350 Detail in Heritage BIM Models

Imagine trying to assemble a jigsaw puzzle where half the pieces are missing, and the picture on the box is long gone. That's the challenge facing BIM professionals when tasked with creating LOD 350 models of heritage structures. While the grandeur of the facade and the sweep of the staircase might be readily captured, the devil, as they say, is in the detail – and often, that detail is frustratingly hidden.

LOD 350 demands accurate representation of not just the individual elements, but also the intricate connections between them. How do the beams join? What type of mortar holds the stones together? How are the ornate cornices anchored to the walls? These are crucial questions for a comprehensive BIM model, yet in heritage buildings, the answers often lie concealed beneath layers of history.

The Challenge of the Unseen

Unlike modern construction with its standardised components and accessible documentation, heritage buildings present unique obstacles:

• Hidden Connections: Years of alterations, plasterwork, and decorative finishes obscure the underlying structural connections.
• Deterioration and Decay: Time takes its toll, and crucial details may be damaged, decayed, or simply missing.
• Limited Access: Fragile structures or sensitive historical contexts may restrict invasive investigations.
• Lack of Original Documentation: Blueprints or construction records might be incomplete, inaccurate, or non-existent.

Strategies for Unlocking the Invisible

Despite these challenges, achieving LOD 350 in heritage BIM is possible with a combination of ingenuity, technology, and expert collaboration:

1. Historical Detective Work:

• Archival Research: Scour historical documents, photographs, and even paintings for clues about construction methods and materials common to the building's era and style.
• Expert Consultation: Engage historians, conservation architects, and structural engineers with expertise in the specific type of heritage structure to gain insights into likely connection methods.

1. Technological Prowess:

• Advanced Scanning Techniques: Utilise high-resolution laser scanning, photogrammetry, and even ground-penetrating radar to capture comprehensive data, including hidden features and subsurface details.
• Point Cloud Analysis: Employ sophisticated software to process point cloud data, filter noise, and extract features that may indicate connections or structural elements.
• Multi-Sensor Integration: Combine data from multiple sources, such as laser scans, photogrammetry, and thermal imaging, to create a more complete picture of the building's structure.

1. Intelligent Modelling and Inference:

• Deductive Reasoning: Based on the visible structure, material properties, and historical context, make educated deductions about the likely types of connections and their locations.
• Parametric Modelling: Use parametric modelling tools to create flexible and intelligent connections that adapt to the unique geometry of the heritage building.
• Hypothetical Modelling: When definitive information is lacking, create hypothetical models of connections based on best practices and expert knowledge, clearly documenting assumptions made.

1. Iterative Refinement and Validation:

• Collaboration and Review: Continuously engage with heritage experts and structural engineers throughout the modelling process to validate assumptions and ensure accuracy.
• On-site Verification: Conduct careful on-site inspections to compare the model with the actual structure, identifying any discrepancies or areas requiring further investigation.
• Model Updates: Regularly update the model based on new information and feedback, ensuring the LOD 350 model accurately reflects the connections and structural details of the heritage building.

The Importance of Transparency

It's crucial to acknowledge that achieving LOD 350 in heritage BIM often involves a degree of interpretation and inference. Transparency is key. Clearly document any assumptions made, data sources used, and the level of confidence associated with the modelled connections.

By embracing these strategies, BIM professionals can unlock the invisible puzzle of heritage structures, creating comprehensive LOD 350 models that serve as valuable tools for preservation, restoration, and future management of these irreplaceable cultural assets.