Tuesday, October 26, 2010

The 'I' in BIM - Reinforcement Estimates

This post is the first of many, where I will explore the 'information' in the BIM model.

This is a topic I was due to present at
Autodesk University 2010, due to unforeseen circumstances I am unable to attend. As a result I will share the information here in the form of regular posts titled The 'I' in BIM with a sub-heading.

I was recently asked about Revit and it's ability to provide reinforcement estimates, without spending too many man hours on the task. The problem for many consultants in today's market is trying to be competitive. If your estimate is too high, the contractor will not be happy, if your estimate is too low and as a result you have to increase the weight of reinforcement later in the design stage, the contractor will be even more unhappy!

In the current economic climate, it is critical to try and provide estimates that are as accurate as possible.

Revit can schedule reinforcement estimates, but this requires each element to have its reinforcement fully modelled. I know what you are thinking, time consuming and costly!

Thanks to the Reinforcement Extensions, I have a quick solution.

Using concrete columns as an example, generally most columns within the structure that are the same size and height will have the same reinforcement content. (with a few exceptions of course)

When I schedule concrete columns I break each column down by size, and give each column a Type Mark, C1, C2, C3, etc... If there is a need to break each column down one more level, i.e. the type of concrete used (C35 concrete, C40 concrete, etc..) I will suffix the Type Mark with a letter. C1a, c1b, etc.

Once the columns are modelled, and you have added any descriptive information you require in your schedule to the columns type properties, it is time to add some reinforcement to obtain an estimate.

Whilst I DO NOT like using the Reinforcement Extensions to detail reinforced concrete, they do come in use for this task.

Set up a 3D view with all concrete columns visible. The Reinforcement Extensions will only allow you to reinforce multiple columns as long as they are the same size and height.

Use the 3D view to isolate sets of identical columns, and begin to reinforce these columns (in sets) using the Reinforcement Extensions.

Repeat that step for the rest of the columns in the view.

Now to set up a schedule, I generally add Type Mark, Type, Description (if I want to add the concrete type for example, I add this to the description parameter), Volume (to schedule concrete volumes) and Estimated Reinforcement Volume.

Under the formatting tab, make sure you tick the box to calculate the totals for both Volume, and Estimated Reinforcement Volume. Also make sure you itemise every instance, otherwise the Volume parameters will be left blank in the schedule.

Once you hit OK, the information is added to the schedule and is ready to be sent out to assist the QS, and help the contractor.

The estimate produced will save the engineer time, and will be much more accurate than the engineers estimate!

This really is a quick and easy process, the larger the project the machine would have to be 64-bit with 8GB minimum of RAM.

Although I managed to schedule a Reinforcement Estimate for every column in the building below using an old machine with only 2GB of RAM....!!

2 comments:

  1. Hi Glenn, thanks for the tip. Have you had a chance to try and estimate reinforcement of slabs and beams?

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  2. Hi,

    I have used similar principles as described above for estimating beam reinforcement and foundation reinforcement.

    As for slabs, if the slab is flat, it is fairly quick to manually model some bars, placing the bar in section and setting the centres. From there you can get a good RC estimate for a slab.

    Cheers

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