Forums >> Revit Structure >> Technical Support >> Column, Gider & joists workflow

ddbapiplus

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Joined: Thu, Apr 2, 2009
10 Posts

Is there a structural engineer that can explain the workflow for a simple roof structural system. I'm thinking of a typical 100 foot wide x 100 foot deep commerical shell that has a flat roof 1/4"/12" slope to the rear.

Given I've setup my grid lines, placed my wide flange columns on my grid lines, giders and K series roof truses on the gridlines set their reference to the roof level and aligned the roof truss beam system to the roof slope and the girders, how are the girders then locked to the top of the columns so that when I change the roof level height and or the roof slope it all flexes?

 It seems to me that a column should control an attached girder position (workpoint), the girder should control the joist bearing (workpoint) and the roof should be attached to the top of joists(beam system). Is this not possible in Revit Architecture?

Thanks,

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pdoug

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Joined: Mon, Mar 24, 2008
87 Posts

Some things that have worked best for me when working with sloped steel roof framing in my models...

Assuming your levels and grids are in place...I first place columns by grid - then beams (with the 3d snap turned on) and make sure I am placing the end of each beam(girder) on the center of the column (if you tab to toggle thru the snaps you'll see you can snap right to the center of the column) - then I place either a joists by way of the beam system tool or individually by again (making sure the 3d snap is on) and again by making sure it's the beam I am snapping each end of the joist to.

 This has always worked - now when a column height changes the girders move with the column. and same for the joists.

RST 2011

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ddbapiplus

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Joined: Thu, Apr 2, 2009
10 Posts

pdoug,

 Thanks for you advice. I was able to get the 3d snapping to work when adding my girder. I have to add my girders with the sloped reference plane set active (named Roof slope) for the girder to align with the roof slope.  Unfortunately, I can't lock the angle of the reference plane to the metal decking.

I can flext the gridlines and roof height without getting warnings. (This is without the joist beam system placed yet) 

But I noticed that each girder has a different offset from the reference level. Should I be able to select all the girders and adjust their offset to accomodate the roof joist seat height? Do you create a level target for the joist girder and if you do, should I set that height to the lowest bottom cord of girder?

 I wish that sloped levels references were possilbe. Then the could dimension lock could be used.

Thanks,

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pdoug

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Joined: Mon, Mar 24, 2008
87 Posts

There are a couple different ways you can set the beams to account for the joist seat.

(1) you can select your beam and go into the the properties and adjust the level offsets both start and end for the depth of the joist.  using:

=(current elevation number -/+ joist seat depth)

(2) would be to change the z-Direction Justification to other and then set the z-Direction Offset Value the amount needed for the seat depth

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ddbapiplus

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Joined: Thu, Apr 2, 2009
10 Posts

pdoug,

My roof trusses flex with the roof slope and my columns are attached to the roof and flex, but I can't get the girder joists to flex with the tops of the columns. How do I constrain the girders to the columns so if I change the roof slope or the roof height so it all flexes?

thanks

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