3D BIM Model of Military Barracks

Benchmarq was recently commissioned to develop a 3D BIM model of this long abandoned military barracks in the South of England, closed after the Cold War in 1995 and derelict ever since.

Working closely with our survey partners, we took 140 GB of point cloud data and imagery gathered on-site to use as the basis for constructing the model.

The first task was to carefully evaluate and process the complete data for the structure, making use of powerful filtering software, then to structure it into more manageable chunks to help with the process of feature extraction and 3D tracing of the slabs, walls, columns, stairwells and openings that make up this 60 year old structure.

In total, the structure measured 11m in width x 150m in overall length, arranged in a dog-leg plan configuration, with 7-9 storeys including 2 basement levels supporting the main structure on some 50 columns. Construction is reinforced concrete throughout.

The Challenge

  • Floor slab levels – after discussion with the Client, the significant deviations in slab levels were managed by spot level labelling where they were outside of tolerance.
  • Determination of key building axis angle – establishing the original design and construction intent from the mass of point cloud data so that a usable model could be delivered to the Client.
  • Large number of ‘parallel’ walls. See ‘Solutions’ below.
  • Partitioning of point cloud data into manageable chunks to make the 3D BIM modelling task easier; also to provide the client with a more manageable series of reference point clouds for their own validation and checking purposes.

The Solution

When bringing an existing real-world building or structure into the digital environment, no software solution is perfect. In general, the BIM modelling tools are designed for use as design origination tools rather than tools ideally suited to modelling the as-built condition. Typically this means that walls are never straight, parallel or plumb, slabs are never level, perfect or near perfect right angles are rarely encountered.

Inevitably that means that the modelling process is a matter of creating elements which are a ‘best-fit’ to the data captured on site.

However, here at Benchmarq we maintain an ongoing programme of development of in-house tools for BIM modelling, not only for our own benefit but also in the interests of delivering a much more usable 3D model to the Client.

For example, in a structure such as this one, if walls which are not perfectly parallel to one another are modelled with absolute accuracy the resulting element will not report its location to adjacent elements. In simple terms, it means that distances between adjacent walls are not  automatically annotated/dimensioned, meaning that the 3D model is rather less usable to the Client than it should be.

If the Client is planning to use the model as the basis for further design development, this can create a significant productivity issue.

Our solution has been to develop a series of in-house routines which consider how ‘out-of-parallel’ walls actually are and, within tightly controlled (mm) tolerances, generate a model where the walls are parallel and therefore can be automatically annotated with the distance to adjacent walls.

The images below illustrate the point:

In this case, the grey wall is slightly out-of-parallel with the highlighted blue wall. The distance between them is therefore not automatically reported.

In this second example, our ‘orthoganalisation’ routine has created a (blue) wall element which is exactly parallel to the adjacent (grey) wall element, thus ensuring that auto-annotation of the distance between them is possible.

The tolerances required to enable this function are small – millimetres – well within the construction tolerances of the structure itself and of the laser scan survey used to capture it.

However, the result enables us to provide the Client with a much more usable BIM model than might otherwise be the case.

On a structure containing hundreds of cells, this improvement provides a considerable advantage

Project Deliverables

A 3D BIM Revit model file was produced for the Client, to be used as the basis for the refurbishment of the structure and the re-purposing to a high specification residential apartment development.

This particular development is part of a larger, long term regeneration plan for the area going back many years with the first phases completed in time for the 2012 Olympics. A mixed use project, the scheme has also required the construction of complex flood defences and new facilities for both business and leisure in order to support new housing.

The construction of the building itself will provide technical challenges for its conversion to apartment units, notably the extensive diamond cutting of openings to create the required access.

The project will also include the addition of external balconies and extensions to former equipment rooms to create penthouse apartments, adding attraction to prospective tenants.

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