Saturday, 26 July 2014

BIM - Lessons Learned

Having just submitted BIM models for a large and complex healthcare project in London, it is time to consider lessons learned as there have been many. In a time of transition to BIM Level 2, at present we are not going to do things perfectly as the industry is finding it's way to a new way of doing business with new technologies and standards. What I have learned is that certain aspects of BIM are more important than others and it is really important that everyone knows how important they are as BIM is collaborative.

1. Shared Coordinates

If your linked models don't sit on top of each other accurately, you have a big problem and it is time to stop and sort this out. Each model should have a common survey point and base point. The Information Manager or Project Lead should ensure this is in place. The best way to standardize this is issue a master survey 2D CAD drawing which uses the correct coordinate system i.e. Ordnance Survey UK coordinates using True North. Each organisation can then acquire the coordinates from this linked drawing. The recommended base and survey points should be indicated on the drawing. If the survey is in BIM format, the coordinates can be acquired from the linked survey model.

2. Model File Naming

If you are working to BS1192:2007, then use it explicitly, no deviations.

  • Agreed a Project Code from the start of the project. This is not an organisational project number. The Employer or Client should be asked to contribute this code or agree to a code proposed by the Information Manager.
  • The Information Manager should agree a list of Originator codes or acronyms that are consistent.
  • The zones or assets should be agreed with the Employer or Client. A zone or asset can be a building or part of a building that undertakes a particular function for the Employer. The models will be broken up by this zone or asset, so consider it carefully.
  • Levels or Locations should be agreed from the start. Often 01, 02, etc is used for upper floors. 00 is used for ground floor and B1, B2 used for basements.
  • The type is from a predefined list in BS1192:2007 and extended in PAS1192-2. M3 is used for 3D BIM Models.
  • Classification is optional. Uniclass 2 is the recommended classification. Beware, Uniclass 2 is still not complete, so avoid this for now.
  • Number is used when all the previous field values don't ensure the file name is unique. This is a 4 character number e.g. 0001, 00002, etc.

Eample: PRJX-ACM-P1-ZZ-M3-A-0001

Suitability and Revision can be optionally appended to the model file name, but I would recommend not doing this. Many online document management systems rely on the file name being constant for revision control. If the file name is changing with each revision or status change, this will not work. I would recommend placing the Status and Revision codes in the splash sheet.

3. Keynotes

Although NBS have released NBS Create, there is still some creases to be ironed out. Create is a very good product but some fundamental functionality needs to be in place to make it the new standard for specifications. In the meantime, Keynotes are brilliant. If Revit is using UK based settings, out of the box, Revit comes with the CAWS (Common Arrangement of Worksections) keynotes. US will be based on the Omniclass system. There are possibly some offices out there adding these references to objects but I think this maybe few. The difficultly is that there are many specification clauses for each object so there isn't a one-one relationship between clause and BIM object. A better alternative is T-Sheets. T-Sheets stands for Technical Sheets and is a loose system made popular by Schumann Smith which are now part of AECOM. T-Sheets are an index of building elements that are cross referenced with the specification and drawings. For example PAR-01 is a plasterboard, metal stud partition which provides 30 minutes fire rating and a few other performance criteria. PAR-001 can be associated with K10 for Partitions and M20 for the skim finish. The PAR-01 code can now be added to the drawings. The wonderful part about this system is that with little information, both the specification writer and BIM modeler can progress immediately. The T-Sheet system allows designers to think in terms of performance of assembled objects. If a 1 hour rated partition is required or one that provides specific acoustic performance, PAR-02 can be added. Once the specification writer and designer understand the parameters for that element, everyone can get on with their work.
Keynotes can be written for any system you wish to use and are relatively simple to create.

4. Family Naming - BS8541-1

BIM Level 2 requires families to be named according to BS8541-1. Do this from the start. If you are a designer creating generic objects, family names will be in the format Source_Type_Subtype. Use Organisation Acronyms for the source. Types should be IFC names and be consistent i.e. Use Door and not doors. The IFC names are included in BS8541-1. Subtypes are flexible but should be structured to ensure there is a consistent system for naming. I use the T-Sheet code and an optional description e.g. ME_Door_IDR-Dbl-Eq for an internal equal size leaf double door created by me. Obviously replace the Source acronym for your company acronym.

5. Copy / Monitor tool

The copy/ monitor tool should be used for Grids and Levels. It is normal practice for the Architect to setup the grids and levels and other consultants to copy/ monitor these. The copy/ monitor tool can also be used for coordination with other consultants where there are overlaps in design. For example, doors are often placed in RC walls. If the wall is in the structural engineers model, how can the architects door be placed in the wall as it cannot be done in a linked model. The copy/ monitor tool can be used to create a copy of the structural wall in the architects model. The door can be placed in the copy. When the architects model is sent to the engineer and he or she links the model, they will get a warning that there is a new opening in their wall. This is a process that needs careful refinement.

6. Clash Detection

Start the process early. The first time it is done it takes some time to setup. Allow 2-3 days. Objects must be grouped into sets and clash tests setup to specifically target certain clash tests e.g. structural slab versus facade. Don't run a clash detection on everything i.e. structural model versus architectural model, the number of clashes will be overwhelming and difficult to manage. Organize objects into sets. Sets can also include subsets e.g. Structure can contain floors, roofs, columns, etc. This will allow a test to be carried out against the entire structure or a subset. Use the group tool to group clashes for selected objects. This will make the process of creating sets very quick. Once this is done properly at the beginning, clash reports will run smoothly and quickly afterwards. Number and name the clash reports e.g. PRJX-ABC-P1-ZZ-CR-A-012_Structural Walls, Columns, Beams and Floors vs Architectural Finishes. Everyone will then know what you are referring to on the phone or at a workshop when you mention Clash Report 12. If you are using navisworks, use NWC files. Set up a 3D view in Revit specifically for exporting for clash detection. Download an install the NWC export utility for Revit. Use NWF (Links to NWC files are live) files for clash detection. Use NWD (links are embedded) files when issuing to third parties.

Summarize findings when issuing the clash detection reports. This helps the person who has to deal with the clashes focus on the critical items.

7. BIM programme

Create a BIM programme. Start at a deadline and work backwards. BIM Workshops should occur every two weeks and should either overlap with the Design Team meeting and even better still be part of the Design Team meeting. Model transfers should happen every week. Shared Models should be issued before the workshop and Work In Progress models in the interim. Again, allow time for generating the clash detection reports.

8. Unique Object IDs

If you are using clash detection tools such as Navisworks, Solebri or Tekla, these applications rely on unique IDs for each object to allow them to track objects. For clash detection it is important to understand if a clash is new, old (active) or resolved. This is the foundation of the process of resolving or progressively tracking clashes. Therefore it is important that once the Clash Detection process is started that the model is not trashed for a newer file or objects are copy pasted into another file as all these IDs are lost and all the clash detection knowledge is lost with them.

9. Splash Sheets and BIM Coordination Documents

Use splash sheets and ensure there are setup as the starting view. The Revision Code and Status Code should be clearly indicated and should follow BS1192:2007. A Revision schedule can be included in a splash sheet just like a standard sheet. I use BIM Cordination Documents which are basically issue sheets for models to help track the status of consultants models. These should be standardized from the beginning.

10. BIM is collaborative

BIM won't work without collaboration. BIM exists because of technology and a desire to improve the construction process. It isn't easy as there is a tendency in the business to carry on as usual. There is a growing unease that long term targets cannot be met through business as usual and that process that have developed over the past 40 years are not fit for purpose. Providing an adequate and cost effective supply of places for people to live and work sustainability in the near future is very challenging. Individually we can go fast but collectively we can go far.

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