[Bldg-sim] Modelling simplification for structural concrete columns

Jeff Haberl jhaberl at tamu.edu
Wed Mar 13 20:27:14 PDT 2013


FYI.

ASHRAE RP1468, just finished, which provides BIM-to-thermal modeling examples, contains example modeling DOE2 input files and BIM files for concrete thermal bridging, and  other examples like curved windows, etc.

The final report can be I obtained from Mike Vaughn at ASHRAE.

Jeff

Jeff S. Haberl, Ph.D., P.E., FASHRAE, FIBPSA
Department of Architecture
Texas A&M University
College Station, Texas 77845-3581
Office: 979-845-6507, Lab: 979-845-6065
Fax: 970-862-2457, jhaberl at tamu.edu<mailto:jhaberl at tamu.edu>, www.esl.tamu.edu<http://www.esl.tamu.edu>

On Mar 12, 2013, at 10:36 PM, "Patrick Bivona" <patrick.bivona at gmail.com<mailto:patrick.bivona at gmail.com>> wrote:

Hi everyone,

I'm wondering how best to simplify a model when considering structural concrete columns.
My modelling is in the context of the LEED whole building energy modelling. So I'm concerned with accuracy as much as acceptability by the LEED reviewers. I've read the ASHRAE 90.1 user's manual but didn't find a satisfactory answer.

Here's an example:

        ----
wall   |    | wall
-------|    |------
       |    |
        ----
   concrete column

I can see 3 options for simplifying, each with its own issues:

1. Make the external surface of the column at the same level of the surrounding walls and model the column surface as having its true thickness . The issue is that it alters the area of the space inside and doesn't account for the shading effect of the column.

2. Follow the internal boundary of the column, which introduces 3 surfaces. Not sure what construction thickness to assign to these surfaces. This preserves the internal space area but alters the shading effect of the column.

3. Follow the external boundary of the column. This also introduces 3 surfaces. Not sure what construction thickness to assign to these surfaces either. It preserves the shading effect of the column but alters the area of the internal space.

I'm leaning towards option 1. What do you think? Are they other better options I overlooked?

Of course, things get a bit more complicated when the walls either side are not aligned or in the same plan...

Thanks!
Patrick

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