Monday, November 22, 2010

Revit User Group, Leeds.

I have been speaking to Chris Senior author of Revit Elemental about the possibility of setting up a Revit User Group in the Leeds area. I think the opportunity to share knowledge, make business contacts, and make new friends is something worth setting up.

If this would interest anyone in the Leeds area, comment on this post, leave me your email address (I will not publish the comments, so don't worry your email addresses are safe!) these will be collected and used for the basis of a mailing list.

If enough interest can be generated, something will hopefully take shape early in the new year!

Friday, November 12, 2010

Concrete Volume Scheduling - Cautions

Recently I was asked to schedule the concrete volumes for a building that had been modelled in one of our other offices.

The task was fairly straight forward, schedule every concrete element in the building to obtain an approx concrete volume for pricing. In todays competetive market it is essential to be as accurate as possible with your estimates.

I decided to start with the columns, and almost straight away noticed a problem with the volumes that were scheduled. The volume in the schedule was almost half the actual volume of the column. So, I decided to investigate the cause, and soon found the problem.

We had a wall with a column that was placed at the end of the wall (as shown in the image below)

The wall and column schedules shown below are the initial numbers the schedule produced.

I soon realised what the problem was, the wall was intersecting the column, and it was the wall that Revit assumed would be the prime element, so by default it was cutting the column.

The solution was to move the wall back to but up against the face of the column.

The column and wall schedules are now correct.

I decided to do some further testing, does this also happen with beams?

The simple answer is yes.

If a wall is joined to a beam in the 'wrong' way, then the schedules produced will be incorrect.

The wall should stop at the underside of the beam over.

Is this a problem with the software we use? Maybe. Is this a problem with modelling techniques, possibly.

Either way, this could cause problems on large scale projects that require accurate volume estimates. That said, a disclaimer and the word 'estimate' should cover you to some degree.

I guess we all have to pay that extra bit of attention to how we construct our models if we know we will be using the information rich BIM to schedule quantities and produce estimates.

Monday, November 8, 2010

Linked Models

For me, linking Revit models has it's advantages, but certain steps need to be taken to ensure projects run smoothly.

I always suggest a Revit team meeting, (similar to an initial design team meeting but for the Revit team only), this is to put in place the 'guidelines' for the Revit team.

Key points to discuss.
  • Nomination of a Revit manager for large projects - responsible for setting up a new central file each week, or each fortnight, and re-linking other disciplines models.

  • How often models will be exchanged - weekly in the early stages of the design, fortnightly in later stages.

  • Set timescales and discuss what each member of the team expects at what stage. For me, I expect the Architectural grids, levels, and building footprint to be locked before starting the structural model. (I find too many changes early on just eat away at the project fee)

  • The most important point is to discuss who models what. It is important that each discipline only models what belongs to them.

Point 4 is the most critical for making the most of linked models, at construction stage architects shouldn't model columns and framing, if a concrete wall has a plaster or brick faced finish, the architects shouldn't model the concrete wall, only the finishes. The Structure should be shown through the linked file, and view templates used to control the visibility. This will make sure each disciplines documentation is fully coordinated as the model is constructed.

This will open up the lines of communication between disciplines, if a concrete wall needs to be moved, or needs it's profile to be changed, conversation will have to take place and that concrete wall will have to be changed within the structural model. Rather than what I have seen happen many times, the architect changing the wall profile within his / her model, and this not be picked up in the structural model. (Although if you are using copy / monitor, this should be picked up) I prefer not to use copy monitor for anything other than column positions, floor outlines, grid lines and levels. Especially NOT walls. You will see why below.

If you follow point 4, this means you only do things once, and everyone owns and only models what belongs to them. This means the model will be coordinated as it is constructed, as opposed to coordination reviews taking place at set stages during the design and documentation stages. This can only result in increased productivity, and improved documentation.

While this method will mean a certain degree of manual coordination needs to take place, I feel the model will be constructed much more thoroughly because every team member will be forced to consider the other disciplines elements within the building.

This is one step towards a full BIM model, constructing a model that will be a true representation of what will be built on site.

I must apologise that this post has a slight biased towards Revit Structure users and perhaps a little negativity towards some Revit Architecture practices, this is a Revit Structure blog, and I can only comment on past experiences ;-)

Copy / Monitor Cautions
When users copy/monitors walls, a couple of things need to be taken into consideration.

You can't use a different wall type during the copy/monitor process because the feature only uses Wall Centreline for the alignment of the copied wall. If the wall thickness is going to change, it is best done after the copy/monitor process.

Openings in copy/monitored walls are not reliable. The opening size is equal to the overall geometry of the family doing the cutting, not just the cut opening in the wall.