To convert a member in the structure into an arc

§    Select the member or members to be changed

§    Choose Convert Member to Arc  from the Geometry menu

A dialog box will appear with a field for the number of members you wish to subdivide the member into and settings for the shape of the arc.

§    Enter the number of arc segments to be created

§    Choose the size of the arc using one of the three methods

§    Choose the direction of the arc relative to the member using the radio buttons on the right

§    Click the OK button

Normally, you will want the new members to connect with any existing members in the structure.  If you do not want this to happen, uncheck the check box at the bottom of the dialog.

It is a good idea for you to test the accuracy of this approximation to a curve, by generating arcs with different numbers of members and examining the effect this has on the results of analysis.