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  • Culver Epps

BIM, Archicad and slabs...the saga continued...

As I mentioned in my previous post a big stumbling block for us back when we first started using Archicad in 2014 was the fact that slabs in food environments are inherently complex due to the drainage strategy required.


How can we model this?


Out of the box Archicad can model a slab very nicely as long as its as flat as a pancake (never built like that by the way). We thought about this issue long and hard, as I previously mentioned, on how we would over come this until I had a 'eureka' moment (a bit of an extravagant term but at the time it made me happy at least followed by a few pints of Harvest Pale to celebrate). We didn't want to use a tool such as 'morphs' which are objects that are completely adjustable in a 3D environment as they would end up being overly complex and unmanageable.


The single object we wanted to design needed to do have these satisfy these parameters as a minimum;


1. Ability to set the general fall of the floor.

2. Be fully parametric and adjustable in all directions.

3. Be able to show a gully or a channel drain.

4. Show the falls (calculated by the model) in 2D including the levels.


Not much of an ask eh?


Most of our floor designs can be sub-divided into triangles as they all fall toward a central gulley or drain. I realised that if we modelled the floor in two separate layers, one being the slab that is 'flat' and the other as a set of triangles which we would then removed from the original slab leaving a slab with falls. Confused yet?


Imagine a layer of plasticine (a) which is the thickness you require (and flat) and create a model of what you need to cut out of it (b). Now you tell the model to show you a-b=c (slab that is left). You do this for all 4 areas of slab you want (the triangles) and the slot for the gulley or channel and you are left with a single object which shows you the slab to fall.


Brain hurts...so here are some pictures...



Image shows how the systems work in 2D. Once a fall is set the model code calculates the fall in the other direction. This is automatically adjusted if the object is manipulated (as below). This happens in real time and no need for the user to calculate the adjusted fall. The position of the channel/gulley can also be adjusted to be asymmetrically located within the slab in both the x and y axis.

Image showing and alternative layout with a gulley pot instead of a channel with adjusted falls and level of gulley pot


Image showing the floor slab in 3D. Image also shows the oversight concrete which is included to allow install of kerbs to the main level of the floor slab (these can be turned on/off individually)

Slab with wall/kerb elements showing how they integrate

The code in 3D was remarkably straightforward once the principal was established, 2D was another matter altogether and when I look at it now it confuses the hell out of me but I put that down to it being inefficient and my ageing brain. I will revisit...one day.



List of parameters to allow the slab to be fully adjustable

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