Using the Frame Analysis Spreadsheets

Following some recent questions in the comments, here are some answers:

How can nodal moments be created?

The current versions only allow for forces to be applied to beams, but any point load or moment applied at the start or end of a beam will in effect be applied at the node, so set “Position” to zero for any beam starting at the node, or to the beam length for a beam ending at the node.  In Frame 4 (the 2D version) all moments are applied about the Z axis.  In 3DFrame moments are applied about the global axis specified in “Direction XYZ” (Column C).

How can hinge or spherical joints, or bushing joints be created?

Both Frame4 and 3DFrame allow either end of a beam to be given a rotational spring stiffness.  If the stiffness is set to a very low value the beam ends will in effect be free to rotate.  In Frame4 rotations are about the Z axis.  In 3DFrame the rotations are relative to the beam principal axes, which are described here:  3D Frames, axes and stiffness matrices.

3DFrame also allows beams ends to be allocated a translational spring release along any of the three principal axes.

The example frame in each of the download files illustrates the use of the beam end springs.

How can multiple point restraints be applied?

Nodes can in effect be restrained to move together by connecting with very stiff members, with any required end hinge conditions, to provide the required restraint.

 

Advertisements
This entry was posted in Excel, Finite Element Analysis, Frame Analysis, Newton, VBA and tagged , , , , . Bookmark the permalink.

2 Responses to Using the Frame Analysis Spreadsheets

  1. metrox says:

    Hello,
    Can you please explain how point load should be defined? It is point related or beam related?
    In input section Position for point loads?
    Lets say I have simple truss and I wan’t to define point loads on it’s top chord nodes. What I need to put? In your example with truss there are 0 and 10.

    Like

    • dougaj4 says:

      Hi metrox.
      Point loads are applied to beams, but if they are applied exactly at the start or end of a beam it has exactly the same effect as applying directly to a node.
      So if you want to apply to a node the easiest thing to do is to select a beam that starts at that node and apply with position = 0. If the node only has beams connected at end 2 then select one of those beams and apply the load at position = beam length.

      Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s