Sunday, August 28, 2016

ARABIC DOORS

This is a post that's been sitting around waiting to happen for 18 months now.  I just can't find the time to devote to this blog that I would like to, even though it consumes most of my weekends.  The folder is called "arabic doors" and dates back to January 2015, but the topic is rather broader than that.  Actually there is a post from that date and this is basically a carry-over: material that I wasn't able to include in that post.

Bridging the Gulf

Around that time I did a lot of family development work for a project that is now on site, one that attempts to conjure up the atmosphere of an "old quarter" in one of the Gulf towns.  Arabic doors are a well-known motif from that style of architecture: richly carved planks of hardwood nailed to cross-pieces to form two narrow leaves, opening inwards.



These doors typically lead into long narrow rooms, roofed over with palm trunks beams.  The walls are lined with a rhythm of niches and shuttered windows.  You can get an idea of the construction techniques from the images below, which I took about 10 years ago in an abandoned settlement in the north of the country.  If you look carefully you can see the remnants of round pegs sticking out of the walls that would have carried oil lamps.  You can also see cement plaster, smeared over the original material, with its tendency to peel off in sheets (new wine in old bottles?)



Gypsum and lime would have been the traditional binders of course and there is a strong tradition of decorative plaster work.  You can see it in the reconstructed fort below, rather too precisely geometric I think, a common temptation in renovation work.



There is of course a strand weaving through the architecture that originates in a much more delicate and temporary style of building.  People lived in tents, some permanently, others seasonally.  These are portable dwellings of course, that can be rolled up and packed onto your beasts of burden.




But there are other ways of building lightweight structures that encourage air movement, ways that are better adapted to a dense urban setting.  This is the Areesh or Barasti style of work based on palm fronds and reeds, ranging from matting to open mesh walls.



It can be used for small houses, or shopkeeper's kiosks in the bazaar, and it can also be adapted as a style for interior decoration, lining the niched walls that we saw earlier with a softer and more intimate kind of finishing layer. 



There are other well-known typical elements: the wind towers, wooden gargoyles, perforated screens and so on.  But the challenge for the modern architect, (and for the would-be BIM modeller) is how to capture the charming informality and irregularities of a traditional vernacular style like this one.



That was the topic for one of my presentations at RTC Washington, and you can take a look at that on my Docs.com site if you wish.  I have taken the position that this blog is for roughing out ideas and recording my working processes, whereas the more polished end products can be collected together on Docs.com.  Also, the blog is targeted more at BIM addicts and Revit fanatics, whereas Docs.com can be a bit more amenable to the general reader who really has no interest in picking up "tips and tricks" (how I hate that expression with its implications of shallowness and deception)

Highly Irregular (Powerpoint)

Going Organic with Revit (Handout)

So here are one or two images from Revit to justify this being a blog post.  The first is a lozenge that fits within a door panel.  It's a nested component so X and Y are going to be linked to parameters in the door family.  The extrusion sketch comprises four lines with ends locked to reference planes.  I'm assuming you all know how to "tab-lock" a line end to the intersection of two reference planes (separately locking to the two planes really, but the aim is to have the line end track the intersection as this moves in response to user input.



Returning to the challenge that I glossed over earlier, in practice this decorative element would be slightly irregular and probably embellished with a decorative flourish or two.  But in BIM we have to consider Mr LOD.  What does he have to say about the appropriate level of complexity for this situation?  In this case I was interested in capturing the idea of a particular style of door as simply and economically as possible.  There is going to be a typical detail of that door type to guide the tradesman responsible for making it in the workshop.  And there will be a whole process of shop drawings and approval of samples or mock-ups. 



The main model ("the BIM" as some would have it) is there to help us to coordinate our work.  We want to see how all the elements fit together and interact.  Do we have the proportions right?  Are there any technical issues?  So we want to recognise the 8 different styles of door that have been chosen for the project, but we don't want to be distracted by too much detail.  And we definitely don't want the MEP consultant's CPU to explode just because we decided to show the door carvings in exquisite detail, and she is obliged to load our model in the background in order to place her ducts.  Perhaps we will have been considerate enough to place all the doors on a separate workset, but then she might want to see the door swings in plan when placing her electric sockets and light switches.  So we should definitely consult Mr LOD at regular intervals and take strategic decisions about levels of complexity.



Irregularity is harder to convey.  It's fairly easy to skew walls by two or three degrees in plan for example, but virtually impossible to model the subtle curves and undulations that you would expect to see in the plaster work of an old building.  I have never tackled this on a real project, but in studies I have shown that you can fake it to some extent by skewing the reveals of doors and windows, which is where the irregularities show up most obviously when you stand in an old room.



It's all a question of "trompe l'oeil": fool the eye.  Our brains leap to conclusions.  They have to in order to interpret the complexity of life in real time.  So quite simple cues can get the message across, and most of the time that is enough.  We have a team of people who are sharing ideas, working together to develop a design proposal for a building.  We are all making hundreds of small decisions each day, and from time to time rather large and important strategic moves.  The idea of BIM is to provide a single, live context where we can see the consequences of all those choices evolving over time.  We want to make informed decisions in a rich context.



Our brains need enough information to assess and review.  Sensory overload is not going to help.  Look at a typical infographics dashboard.  See how simplified and abstract they have become.  Perhaps we need to set aside our obsession with reproducing "reality" and think in terms of diagrams that support decision making.



Section views are diagrams.  They help us to decide how a building will be assembled, as a sequence of trade operations.  For this project I developed a series of detail items that could be embedded in recess families that are used either stand-alone or above doors and windows.



The thick walls are created using cavity construction and the outer leaf steps back wherever a recess is needed.  That's how it works in real life, but in Revit a recess is simply a void, cutting into the outer leaf.  Sometimes it will emulate "wrapping" for the plaster layer, in plan views, but in section it will just cut away, leaving blockwork apparently exposed.  My detail items show up in section views to represent the recessed blockwork, plaster and a smal lintel above to make the transition.  None of this material will calculate and schedule of course.




This approach is fine for square headed recesses, but less so for an arched niche.  The detail item knows nothing about the sections that cut through the family so it can't adjust itself to their position.  Probably you have set it to show a section through the dead centre of the opening.  Unfortunately that will not always be where you section lies, and the result is a bit of wall poking out below the lintel.  You can solve this by doing the detailing manually for each and every view, but that kind of defeats the idea of BIM, and falls down completely when someone else decides to adjust the section position at the last minute without realising that those details are now out of whack.




Many of the wooden shopfronts on this project have external folding shutters.  This was an interesting challenge.  I didn't try to make the angle variable, but I did need a family that would adapt to different sizes.  This involved hosting a nested component on reference lines and locking the ends to reference planes.  Looking back at this now, I'm rather astounded that it all worked, but it did. Once again it provided enough contextual information for us to visualise what was going on and anticipate various kinds of problems on site.  And in the end we had a set of drawings that could be used to tender the project.



Finally here are some images of archways.  There were lots of different styles based on nested "corbels" that could be swapped out.  Once you have this set up, it's easy to add in another style of decorative corbel, and you can use the same corbels in families with different jamb details.  These arches were a very effective way of introducing "organic variety".  You can have three in a row of the same design, then turn the corner and find on that is slightly different.  You can have some buildings that are relatively plain and others that are more ornate. 



Irregularity, vernacular, challenges for BIM tools, Mr LOD, random thoughts, all for now.

1 comment:

  1. Very fascinating topics in this blog
    I'm trying to find how to make the door more to clarify its details, is there more details of the steps?

    ReplyDelete

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