## defining moment rotation relation for members

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UMUT AKIN
Posts: 18
Joined: Tue Oct 19, 2010 4:19 am
Location: Middle East Tech. University

### defining moment rotation relation for members

Hello,

Is there anyway to define the moment-rotation relationship for beams and columns. I tried placing 2D rotational springs at the connection points of beams and columns with the joint and assigning the hysteretic material but the damage coefficients complicates the definition and the result is not satisfactory.

Is there any other way to define the moment rotation relationship of a spring ?

felipe_cordero
Posts: 18
Joined: Wed Jun 02, 2010 2:05 pm

### Re: defining moment rotation relation for members

Hello,

Defining the moment-rotation relationship for beams and columns is possible. Look at this:

http://opensees.berkeley.edu/wiki/index ... Aggregator

UMUT AKIN
Posts: 18
Joined: Tue Oct 19, 2010 4:19 am
Location: Middle East Tech. University

### Re: defining moment rotation relation for members

thank you felipe. i will go through it.

UMUT AKIN
Posts: 18
Joined: Tue Oct 19, 2010 4:19 am
Location: Middle East Tech. University

### Re: defining moment rotation relation for members

I studied the manual and want to ask a question, the relation to be defined in section is Moment-Curvature, not Moment-Rotation, isn't it? (I am trying to add Mz relation to my section)

vesna
Posts: 3033
Joined: Tue May 23, 2006 11:23 am
Location: UC Berkeley

### Re: defining moment rotation relation for members

You can define your spring using either moment-rotation of moment-curvature relationship:

If you want to use moment-curvature relationship here is a simple example:

set Mp 103.0474
set EI 71963.55; #sectionsl stiffness
set b 0.01
set matTag 1
set secTag 1
set eleTag 1
uniaxialMaterial Steel02 \$matTag \$Mp \$EI \$b 20 0.925 0.15
section Aggregator \$secTag \$matTag Mz;
element zeroLengthSection \$eleTag \$nodeR \$nodeC \$secTag

If you want to use moment-rotation here is a simple example:

set phi_y 0.01; # rotation at yielding
set Mp_phi_y [expr Mp/phi_y]
uniaxialMaterial Steel02 \$matTag \$Mp \$Mp_phi_y \$b 20 0.925 0.15
element zeroLength \$eleTag \$nodeR \$nodeC -mat \$matTag -dir 6

Make sure to constrain \$nodeR and \$nodeC usein equalDOF command:
equalDOF \$rNodeTag \$cNodeTag 1 2

UMUT AKIN
Posts: 18
Joined: Tue Oct 19, 2010 4:19 am
Location: Middle East Tech. University

### Re: defining moment rotation relation for members

thank you for the reply and the examples Vesna.

I want to define using Hysteretic material, to be able to control the total rotation mechanism of the beams and columns.
I assign the predefined Hysteretic material to hinge sections of Beamwithhinges element. Does this change the situation since if I define moment-rotation (moment-curvature*hinge length) the results semms to be out of order.

vesna
Posts: 3033
Joined: Tue May 23, 2006 11:23 am
Location: UC Berkeley

### Re: defining moment rotation relation for members

When defining a section you need to define your material to represent moment-curvature relationship. If you are using zeroLenght element to define rotational spring, then you can define your material to represent moment-rotation relationship.

UMUT AKIN
Posts: 18
Joined: Tue Oct 19, 2010 4:19 am
Location: Middle East Tech. University

### Re: defining moment rotation relation for members

I understand. Thank you very much for your help and also for the fast reply.

Best regards...