Revit Structures 2014 - issue with analytical model

[sibannister]

Hi,

I'm working on a project on which I've been having issues with the analytical model. This is the first full BIM project that I've worked on and it's a client requirement that the modelling software (Revit) and the structural analysis software use the same model by the use of bi-directional linking of files between the 2. I'm having a couple of issues with the positions of the analytical elements in relation to their 3D model counterparts.

Firstly, for example, if I place a structural column centred on a gridline intersection, its analytical model will be somewhere off centre in plan. If I use the 'analytical adjust' tool and move the analytical column to its correct position, it will snap back to its original wrong position if I edit or add anything else in the area, or edit or move the column itself.

Secondly, and again for example, when editing analytical floor edge/node positions, sometimes when trying to drag certain node points, they consistently snap to some random point at a distance away from where I've just dragged them to, even when it seems like you've got it right when the mouse pointer's over the right point and it's all highlighted correctly. The same can also happen when trying to use 'align' as well.

An example of both issues is shown in the 2 attached .JPGs, showing a column and slab edge in the correct positions in the structural model in one, and the same column and slab's analytical equivalent positions (after attempting to edit) in the other.

Has anyone come across either of these things before? It's really preventing us from going any further with our project, and we'd rather not have to go down the route of separate parallel structural and analytical models, not only because it's against our BEP but also to ensure changes to one model are reflected immediately in the other.

A third issue that I've just remembered is that where we have slab steps, when viewed in 3D it seems that the analytical model just shows the slabs at the same plane/level and overlaps them in the region of the step. Is this right? Or am I missing something as it seems wrong...

Any help anyone can give would be most gratefully received. Thanks in advance,

[okapawal]

In case of Analytical Model adjustment you can use element or edge projection to selected gridline if possible.  It is more stable than manual adjust.

Concerning overlapping analytical floor it all depends how the structural analysis software will treat it.  Sometimes it is not allowed.  I would recommend adjusting the edges of these two floors to a single common line.

[sibannister]

Hi okapawal, thanks for your answer.

Unfortunately, I have comparatively few elements that are actually on grid in this project so that would only help for a small portion of the problems. I was looking to see if anyone knew ofr a reason as to why the default positions of the analytical columns isn't on the centreline of the structural model.

Also - for the bit about slabs, maybe I wasn't clear enough. I wanted to know why the z-position of an analytical slabs doesn't match the z-position of the structural model when it is set down from its reference level, i.e. at a slab step. The analytical slab remains at the reference level.

[okapawal]

I think all the behavior is caused by auto-detect functionality in Revit Analytical Model.

This Automatic element adjustment tries to build coherent and connected Analytical Model.

You may see some examples in Revit help http://help.autodesk.com/view/RVT/2014/ENU/?url=http://help.autodesk.com/cloudhelp/2014/ENU/Revit/fi...

In your cases auto-detect adjustment  could:

-        Change analytical column position and stick it to a wall,

-        Change analytical floor boundary to align with columns

-        Align analytical slabs to one level

Pay attention that the analytical Adjustment Methods instance properties is set to Auto-Detect for an element and its individual ends. This is the default justification method for all analytical elements.

Depending on your needs, you may change these parameters to some other projection values.

Remember that Automatic adjustment is performed, as long as the Analytical Model of the adjacent element is within tolerance. You may change the tolerance In the Structural Settings dialog on Analytical Model Settings tab.  This is a global value for the whole model.

Hope it helps a little.