## Displacement Response

**Moderators:** silvia, selimgunay, Moderators

### Displacement Response

Dear Dr. Silvia

I'm still working on why my fiber model Lateral Displacements under earthquake excitation are so small. I was wondering if you could tell me why even your example ( I mean Ex2c.Canti2D.InelasticFiberSection.EQ.tcl) has small lateral displacement too.

http://opensees.berkeley.edu/OpenSees/m ... nual/HTML/

It is around 0.001 in. I have increased the PGA in above-mentioned example but model was failed.

I would appropriate it if you could explain more about this small displacement.

I'm still working on why my fiber model Lateral Displacements under earthquake excitation are so small. I was wondering if you could tell me why even your example ( I mean Ex2c.Canti2D.InelasticFiberSection.EQ.tcl) has small lateral displacement too.

http://opensees.berkeley.edu/OpenSees/m ... nual/HTML/

It is around 0.001 in. I have increased the PGA in above-mentioned example but model was failed.

I would appropriate it if you could explain more about this small displacement.

Mostafa Tazarv

Dear Dr. Silvia

I have asked about your example "Ex2c.Canti2D.InelasticFiberSection.EQ.tcl", not my fiber model.

Generally, for a column with 60"*60" dimension and 10.97m height, 0.001 inch under "BM68elc.acc" is too small. I have increased GMfatt up to 1000 in Ex2c, as you know well it is an imaginary Ground motion (PGA increased to 50g), but maximum Lateral Displacement was 6inch.

I was wondering if could give even an additional reference to study more if you were busy to a answer more comprehensive.

I have asked about your example "Ex2c.Canti2D.InelasticFiberSection.EQ.tcl", not my fiber model.

Generally, for a column with 60"*60" dimension and 10.97m height, 0.001 inch under "BM68elc.acc" is too small. I have increased GMfatt up to 1000 in Ex2c, as you know well it is an imaginary Ground motion (PGA increased to 50g), but maximum Lateral Displacement was 6inch.

I was wondering if could give even an additional reference to study more if you were busy to a answer more comprehensive.

Mostafa Tazarv

my example was not very realistic in dimensions, it was just for demonstration.

if you are really interested in this specific case, you should plot the response spectrum for this ground motion, and plot where the example structure is -- even just elastically.

if you are really interested in this specific case, you should plot the response spectrum for this ground motion, and plot where the example structure is -- even just elastically.

Silvia Mazzoni, PhD

Structural Consultant

Degenkolb Engineers

235 Montgomery Street, Suite 500

San Francisco, CA. 94104

Structural Consultant

Degenkolb Engineers

235 Montgomery Street, Suite 500

San Francisco, CA. 94104

first of all, I don't like to pick an example and conclude that OpenSees isn't good. I am just finding out why my model, my friend's models and also your models have small lateral displacements under severe ground motion in spite of accurate period . I just want to solve it with your advice and go ahead.

anyway, I have done whatever you told me. I plotted displacement sectrum for "BM68elc.acc" with three damping ratio (0, 2 & 5%).

By opensees calculation, the period of "Ex2c.Canti2D.InelasticFiberSection.EQ.tcl" was 1.17 Sec. The minimum displacement in this period (with these three damping ratio) was 3 Cm that are considerably more than its nonlinear lateral displacements( 0.001 inch).

I would appretiate it if you could put a script of SDOF here which its nonlinear lateral displacement under an earthquake was greataer that 15Cm.

anyway, I have done whatever you told me. I plotted displacement sectrum for "BM68elc.acc" with three damping ratio (0, 2 & 5%).

By opensees calculation, the period of "Ex2c.Canti2D.InelasticFiberSection.EQ.tcl" was 1.17 Sec. The minimum displacement in this period (with these three damping ratio) was 3 Cm that are considerably more than its nonlinear lateral displacements( 0.001 inch).

I would appretiate it if you could put a script of SDOF here which its nonlinear lateral displacement under an earthquake was greataer that 15Cm.

Mostafa Tazarv

please do give me such a SDOF structure and the corresponding ground motion.

you know, if you run the entire ground motion, rather than the 10 seconds in the example, you do get 0.003 inches.

if you look at the acceleration file, the peak acceleration is 0.06 inch/sec^2, that's like 0.00016g.

please do scale the ground motion up to maybe 0.5g, so a factor of 3000 and you do get something like 25 inches, that's like 62 centimeters....

Please do check you response-spectrum analysis.

you know, if you run the entire ground motion, rather than the 10 seconds in the example, you do get 0.003 inches.

if you look at the acceleration file, the peak acceleration is 0.06 inch/sec^2, that's like 0.00016g.

please do scale the ground motion up to maybe 0.5g, so a factor of 3000 and you do get something like 25 inches, that's like 62 centimeters....

Please do check you response-spectrum analysis.

Silvia Mazzoni, PhD

Structural Consultant

Degenkolb Engineers

235 Montgomery Street, Suite 500

San Francisco, CA. 94104

Structural Consultant

Degenkolb Engineers

235 Montgomery Street, Suite 500

San Francisco, CA. 94104

Dear Dr. Silvia

I really appreciate your time.

I had done this example with GMfatt=1000 around 35 Sec before start bothering you. But there is something in script in GMfatt line ( Ex2c.Canti2D.InelasticFiberSection.EQ.tcl) that shows Input ground motion is in g unit not in in/sec^2 as below:

"set GMfatt 1.0; # data in input file is in g Units -- ACCELERATION TH"

Therefore, the peak acceleration is 0.06g and also by scale factor 3000 as you mentioned the PGA will increase around 180g.

again I appreciate your time and I will send you another model.

I really appreciate your time.

I had done this example with GMfatt=1000 around 35 Sec before start bothering you. But there is something in script in GMfatt line ( Ex2c.Canti2D.InelasticFiberSection.EQ.tcl) that shows Input ground motion is in g unit not in in/sec^2 as below:

"set GMfatt 1.0; # data in input file is in g Units -- ACCELERATION TH"

Therefore, the peak acceleration is 0.06g and also by scale factor 3000 as you mentioned the PGA will increase around 180g.

again I appreciate your time and I will send you another model.

Mostafa Tazarv

### Re: Displacement Response

Does it still work? I must try this to see how could it be