Why Structural Engineers Focus On Delivering LOD The Right Way


Technology application in construction, although at a nascent stage when compared to mature markets in the western world, is impacting the industry handsomely in the form of cost-effectiveness, on-time project delivery, lesser request for information (RFIs) i.e., lesser delays and more importantly, improved precision and reliability. And ‘Precision’ in Building Information Modelling (BIM) is nothing but LOD i.e. Level of Development. LOD was first published by the American Institute of Architects (AIA) in 2009 and was further developed by the American General Contractors (AGC), which has since been steadily expanding the definition. In a nutshell, the term “Level of Development” refers to the reliability and detailing of a virtual model. As a basic premise, the LOD specifications acknowledge the different phases of BIM lifecycle, and help specify the needs at every stage of the lifecycle. It tries to specify the requirements for geometric content and model data for each discipline and each “level”, thereby helping the information to be organized and easy to work on. Based on the degree of accuracy and steadfastness, structural engineers have the option to deliver between 6 levels of LODs available.

Higher The Level, Higher The Precision

While LOD 100 refers to conceptual and overall building massing, indicative of the area, height, volume, location, and orientation, we will find generic placeholders in LOD 200 along with approximate quantities, size, shape, location, and orientation of the modelled elements. These approximate quantities turn accurate at LOD 300 along with specific assemblies for all model elements. At LOD 350, model elements are graphically represented within the model with all the details necessary for cross-trade coordination and construction layout, which is where we can term a model as being constructible.

The next two levels are even more accurate and detailed. At LOD 400, model elements are not only modelled as specific assemblies with accurate quantities in terms of size, shape, location, quantity, and orientation; they also feature complete information for fabrication, assembly and detailing. Finally, at LOD 500 the model elements are field-verified representations in terms of size, shape, location, quantity, and orientation.

Higher levels of LOD lead to more confidence in prefabrication stages, as clients can track the completion of milestones with the scope of work. More importantly, it is possible to identify and document changes according to the scope.


Delivering LOD The Right Way

It is imperative for the structural engineers to deliver LOD appropriately as it directly impacts the success to both contractor and the client. The significantly reduced number of RFIs, design conflicts, timely project delivery, profitability, etc. are the major reasons why delivering LOD the right way is critical.

Profitability: In BIM, LOD up to 300 level produces just a conceptual model, while it is only after 400 level that the constructible model is generated, which is ready for workshop planning, fabrication, and assembly, thus amplifying the effectiveness of the project. Further, LOD 500 models are analogous to the reality, which is designed in an extremely precise manner and then verified on the site of construction. By applying the suitable LOD, the accuracy achieved in terms of quantity, size, shape, location, and orientation boosts the prospect of profitability for the client and contractor. Further, the non-geometric information may also be attached to the model elements.

On-Time Delivery: With increasing detailing, disagreement between different stakeholders and increasing numbers of RFIs, often delays the project beyond the expected timeline. But by opting the right level of LOD, structural engineers have significantly reduced the project delivery time. This is a consistent outcome not only in India, but across the globe. For example, LOD 350 allowed the construction of 10 Hudson Yards in New York, a state-of-the-art building project, to shave off six months from the original schedule. Realizing the expensiveness of real estate in New York, completing a project six months early corresponds to real and significant dollar gains.

Further, RFIs often lead to change in orders and requests for rework, which effects project timelines and leads to unavoidable delays. As an engineering professional remarked, “it is faster for me to model part of the project to LOD 350 or 400 than to come back to the project two months later and answer another RFI.” It implies that delivering LOD the right way significantly reduces the numbers of RFI. The structural engineering team received just 10 RFIs on account of using LOD 350 for the Port Canaveral Welcome Centre project in Florida. Similarly, for the Quantico Hangar project at Quantico Marine Corps Base, only one RFI was received.

Cost Effectiveness: This is another significant consideration in any project because it maximizes profitability. Deciding the appropriate LOD throughout the lifecycle of a scheme is central in using BIM efficiently and successfully. Structural engineers, by choosing the optimum LOD, facilitate the project planner to budget and plan the material and manual cost appropriately, and the information provided by BIM further gives the pricing an edge.

Design Conflict Resolution: A higher LOD facilitates the architects and structural engineers to defend their design with greater confidence in case of any disagreement. MEP designs are known to often clash with structural engineering designs and many times in such case the structural engineers must rework their design to resolve the issue. But in BIM with LOD 350 and above, the information provided is so comprehensive that the compulsion to resolve the clash can no longer be attributed just to the structural engineers.

The Future Of Construction Industry Belongs To Choosing LOD The Right Way

Globally, clients and contractors both insist on reliable building information models as well as drawing documentation. For structural engineering consultants, delivering higher LOD in their design model helps reduce miscommunication and RFIs, and creates greater value for their clients. Clients can be more satisfied that they are getting full value from models produced by their design team, while the accuracy of deliverables boosts contractor’s confidence. The software companies in the field of construction are assisting the structural engineers with their latest software and expert teams in delivering the LOD right way. At Trimble, our professional services team understands it is increasingly difficult to keep up with changing technology, evolving industry standards, and rigorous project requirements, therefore it offers the most advanced and inclusive BIM software for the construction industry.

From India’s outlook, estimates suggest that India’s construction market will be the third largest in the world, with a size of $1 trillion by 2025 and the importance of using technologies like LOD cannot be more emphasized.  The construction industry has been using hardware tools that enable designers to preview and analyse images and ideas, thus allowing them to employ the best action-to-physical assembly of a model for some time now. New technologies allow to project these ideas in a three-dimensional space, and these advances are profoundly revolutionizing the construction sector. The next ideal step is to move on to LOD and India is truly ready for it.

Although India seems ready for this digital transformation but there’s still some hesitation amongst certain companies, especially small-mid-sized firms, which is hampering adoption of tech across the construction ecosystem. Though some of the more progressive construction firms have adopted technology in their construction processes with full gusto, a significant number of small to mid-sized firms are yet to adopt it in full earnest, which means that technology adoption still has some way to go before it starts to make a meaningful impact across the wider construction ecosystem.


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