After writing last night’s post about a problem with the shift key, I started wondering why I was using the shift key in the first place. Whilst the shift key is the default key to use in AutoCAD, the last place I worked on contract, they had reconfigured the keyboard and I had to get use to using the ctrl key instead. Since I got used to using the Ctrl key instead, I modified my Autocad/LT menu to be compatible with either shift key or the ctrl key, and I used the ctrl key as a matter of habit. But now using ProgeCAD I am back to using the shift key. So why?

Just checked [22:07] ProgeCAD documentation, seems it doesn’t support button menus, and therefore I cannot, define the function of the mouse button and control key combinations. So I’m using the shift key because I wasn’t able to change or add extra definitions. Though ProgeCAD does allow me to define keyboard shortcuts: though that doesn’t seem  convenient. I suppose I could go back to using the Autosketch approach: selecting object snaps from a toolbar.

On the other hand after doing Friday admin, I spent most of the day working in ProgeCAD and seemed to have less hassle than previous attempts.

Perpendicular seems to be more of a hassle than in AutoCAD, and point filters don’t seem as convenient. but besides some irritation with the operation of object snaps, and a lack of proper screen refresh after commands to identify command as actually completed: the main problem I have is unexpected termination of a command which at present I am attributing to a keyboard response problem.

Speedwise probably not an issue except for myself, as I cannot draw up multiple design options as quickly as I would like. However from prior work on contract, I typically draw faster than most: even with the headache of the employers CAD system being heavily customised and few if any AutoCAD commands operating has they should. So speed is my issue: I want to throw drawings together and I am not as able to do so, as I once was able to. Still I’ve been able to draw up three different structural framing arrangements, and draw up some structural timber details.

After drawing up my timber details, the floor, I mentioned raising yesterday, I raised further again. I was hoping to set a grid of cross beams flush, but at the moment cannot dream up a suitable connection at the supporting posts. I could displace the posts, but then would require heavier beams. Alternatively I could use more posts, in which case I could get rid of the grid.

Which raises an issue: Is it possible to optimise a grid structure? I have a space with an object in the way, I could possible rest on the object, but it would be preferable to span over the object. I initially looked at some span tables I discovered I had. From the span tables it seemed that keeping clear of the object using timber wasn’t possible. Then it became apparent that I could tweak the tables: taking into consideration that the tables are for internal structural members equally spaced apart, and for such situation load width of the structural member equals the spacing of the members. Whilst my situation was for external or edge members, for which the load width is half the spacing of the members.

So I had a spacing of 5000 mm or greater and the tables only went up to 4800 mm. But my structural members are edge beams and therefore have a load width of 2500 mm, the tables I have go down to spacing of 2400 mm, with next increment of 3600 mm: so could interpolate between the two for 2500 mm. Whilst this resolved the issue of bearers, it didn’t help completely as joists cannot span the 5m between the bearers. Hence I created a grid, to reduce the spans for the joists. The problem with this approach is that it has rotated the span of the flooring 90 degrees. Since the flooring comprises of individual boards with necessary gaps between there is a potential problem if the structure needs to provide access for wheels: wheel chairs, bicycles, prams, toolboxes and other work trolleys. Though checking out photos around the internet the other night it seems that, may be, not really a problem.

As indicated above the depth of the members is a problem in terms of getting height clearance above obstacles on site, the required span is also actually greater than 5m, if I have to keep clear of the obstacle: which would be preferable. And from the spans tables 5m seems to be the limit achievable with timber for the required loads. Ignoring loads and my general assumption is that the limit for timber is 6m: that is cannot get a stick longer than 6m: well not unless use manufactured timbers like glulams and LVL’s. So this puts me into using steel for the primary structure to get the required spans and minimise the floor height: though higher floor does have a benefit in this situation.

Anyhow have a few options which hopefully I can get to discuss and select a set of conditions to continue more detailed design. May do some quick steel calc’s to get an idea of steel member sizes, ready for next week. Plus draw up some more details to connect steel and timber.

… draw, assess … draw, assess … repeat until find suitable solution. Solution? Something suitable.

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