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BIM steel modeling, large span structures

Gabriele Lantini
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Revit, Workflow

A major problem related to Revit Structure in the last years is the BIM steel modeling of structural elements to a level of development "LOD 400" (BIM Forum - LOD).

The work was related to the management of the BIM steel modeling for the structures for a new high-speed train station, based on structural drawings already designed and verified by the structural engineering company. One of the main objectives of the modeling was to be able to make every single element computable within the Revit platform. The model has been created to LOD 400 to recognize all the "clash detection" that could have arisen between the structural model and the architectural and plant engineering models.

Revit is not designed to automatically create a BIM steeel modeling for structural design, so the roads to be taken where 3:

  1. Find an optimal workflow within Revit using the tools currently available within the software;
  2. Use the "plugins" offered by various companies in order to implement the model and pass it from one LOD 300 to LOD 400;
  3. Create the structural model within another structural BIM software (such as Tekla) and import items through the IFC interoperability format.

The need to efficiently manage the quantity takeoff of each structural element (from a single deck up to the bolt) inside Revit, the choice has been the No. 1 solution.

Impalcato in acciaio - Vista assonometrica

Building description:

The decks have the function of connecting the commercial area placed at a higher level than the rail level and rest on brackets projecting from the side concrete cores adjacent through support devices, constituted by elastomeric seismic isolators. They are also connected through bracings floor, provided for the upper compressed current stability.

Particolare trave in acciaio

Workflow for BIM stell modeling:

We created a workflow that involves "nesting" of families in other families: this allowed, once established the category, to count every single element. The modeling of the decks, given the considerable structural complexity and the continuous geometric diversity, was created in part by parametric objects and partly through the classic three-dimensional modeling commands. For the steel plates we created custom parametric families because the lateral continuity of the solution decks foresaw a different modeling of the lateral cover strips, of the top and bottom flange of each beam type.

Piastra in acciaio

For horizontal bracings, we created families of parametric beams due to the fact that the distance of them could change at the ends and in the areas where shafts were provided.

Controventi orizzontali - Vista assonometrica

Once set the structural material of each type of steel with the respective specific weights through the Revit schedules, it was possible to extrapolate the weight of each structural element and the number of bolts and nuts inside the model, according to each area and project level depending on the WBS established by the client.

Abaco delle travi strutturali Abaco delle connessioni strutturali

Advantages:

  • Model created in a single BIM sofware which also contains other displipline (architectural and plant) ensuring transparency and interoperability of models
  • Modeling coincident with the structural design required by the structural engineering firm
  • Bill of quantities synchronized with the structural model

Disadvantages:

  • Complex workflow and modeling, possible only with the help of structural engineering experts and Revit modeling professionals
  • Excessive time for model creation due to the difficulty to automate detail element creation for the steel structure
  • very heavy files with navigational and query model difficulties

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Gabriele Lantini
is Structural BIM Lead at BIMon, focused on structural components and management of complex projects for engineering major companies.