Microstran V8

[civeng80]

Im currently learning how to use microstran V8 software. Im plotting a fairly simple hexagon structure for analysis but get the error message "error, angle between AC and AB is too small". I read the manual but for the life of me cannot work out where the C is and hence which angle they are refering to. Anyone else come across this and what is the solution?

 

[apsix]

If your are a licensed user you should be able to get help from the Microstran website. I do for my analysis package, even sending the model file across sometimes.

 

[engsys]

The error message means that it is impossible for Microstran to orient the section axes because you have specified an illegal/impossible reference node or axis. Microstran uses a third node (C) to orient the section axes. With the A and B nodes for the member, C forms a plane in which the member local y axis is located - this is what's normally the section YY axis. By default, Microstran assigns a reference axis to each member - columns usually use -X (global) and other members -Y or -Z, whichever is up. With a reference axis, the C node is effectively at an infinite distance along the axis. Your error would occur if you specified a column with the up axis being the reference axis. The error message means that A, B, and C do not form a plane, but rather, they are collinear.

 

[civeng80]

But I'm analysing just a plane 2 d frame !

 

[engsys]

Select all members, click Properties on the pop-up menu, then enter D (for default) for the reference node/axis. You should not get the reported error message if you do this.

 

[civeng80]

Thanks engsys !

Im just playing around with a complex frame which I remember back in my University days (not an actual job!), which turns out to be a critical form structure (i.e. a mechanism for small displacements), so should have no solution ! (a simple hexagon pinned at the external nodes and diagonal internal bracing to all external nodes). Turns out that way after doing what you suggested.

Pardon my ignorance

But shouldn't the reference node/axis be in the default mode already ? and what was the specified node/axis before I made it the default axis anyway ?

Thanks !!

 

[engsys]

When you input a member Microstran will allocate a reference node/axis depending on several factors but it would never allocate a value that gave rise to the error above. This error would usually be caused by rotating the structure after it was initially input.

 

[civeng80]

I may have used virtual reality and rotated the image, so you think this may have caused the node/axis to change then ?

 

[engsys]

No, the VR view can't affect the structure. Why don't you send the job to support - maybe they can tell you what caused the problem.

 

[civeng80]

OK thanks engsys your comments were very helpful. All the best !