Seismosoft | Earthquake Engineering Solutions

Dear Sir,
Thanks a lot for your reply with the example. I want to make sure that I understand the procedure correctly.
1. When the column base is fixed like the first story column of my steel frames, I am calculating the chord rotation following the procedure you mentioned.

displacement at top of column - displacement at bottom of column)divided by(column height)

2. For the 2nd story column, I have to adjust due to the rotation of the column end. So I am calculating the chord rotation as follows:
Chord rotation at bottom of column = (displacement at top of column - displacement at bottom of column)divided by(column height)+ nodal rotation at column bottom obtained from seismostruct analysis.

3. For beam I am assuming the nodal rotation at beam ends are giving me the approximate chord rotation.

I will be really grateful to you if you kindly give me your feedback regarding this.
Again thanks for your assistance.

Regards
Amy

You will also have to be careful about signs conventions amy.

Let's start with the definition of chord rotation at a member end as the "angle between the normal to the cross section at that end and the chord connecting the two member ends".

Keep this definition in mind and observe that a positive relative displacement between the top and bottom ends would produce a clockwise chord rotation. A counter-clockwise top end rotation would increase the chord rotation.

This is just a single example and I am by no means an expert in this issue. So I recommend two things:

1. Do a bit of research on calculating chord rotations in the literature. I believe you will find some valuable guidance there.

2. Draw your own sketches (my example is my interpretation using the definition I give and a simple sketch) to convince yourself that you are calculating the chord rotations correctly.

I hope this helps a bit to get you moving in the right direction.

Best of luck amy.