Hinges Location in Pushover Analysis

[venkateshyadav]

Hi,
How to know the hinges location in Opensees while performing Pushover Analysis step by step?
In SAP2000, we get to know by color, since visualization is not possible in Opensees, is there any command for it to know the location point?

[EricsonEncinaZ]

It depends on the element you are using. If you are using lumped plasticity then read the "rotational" pring you defined, if you are using distributed plasticity then read the integration points of the elements to check where is the plastic hinge forming.

[venkateshyadav]

Hi EricsonEncinaZ,
Thanks for your reply.
I didn't get what you mean by read the integration points? Can you please explain a little bit further. Am new to opensees
Thanks in advance

[EricsonEncinaZ]

For elements with distributed plasticity, i.e. either force-based (http://opensees.berkeley.edu/wiki/index ... mn_Element) or displacement-based (http://opensees.berkeley.edu/wiki/index ... mn_Element) elements, you have to define the number of integration points (sections) as part of the definition of the element. This integrations point will be the sample point where the element will sample the demands to workout the element output (according to what I understand) . So if you want to see if a section is developing plastic strains then you have to record the response of that section, as in the example shown at the bottom here http://opensees.berkeley.edu/wiki/index ... t_Recorder.

[venkateshyadav]

EricsonEncinaZ wrote:
> For elements with distributed plasticity, i.e. either force-based
> (http://opensees.berkeley.edu/wiki/index ... mn_Element)
> or displacement-based
> (http://opensees.berkeley.edu/wiki/index ... mn_Element)
> elements, you have to define the number of integration points (sections) as
> part of the definition of the element. This integrations point will be the
> sample point where the element will sample the demands to workout the
> element output (according to what I understand) . So if you want to see if
> a section is developing plastic strains then you have to record the
> response of that section, as in the example shown at the bottom here
> http://opensees.berkeley.edu/wiki/index ... t_Recorder.

Hi EricsonEncinaZ, Thanks for your reply. Am working on RC frame.
How many BC elements to be used for forceBC element and dispBC element? I had seen somenone writing 1 forceBC element is enough, where 4 to 5 dispBC elements are required to analyse a structure. But is that 1 forceBC element same of both beam and column elements? or is it different?
I had read that the file in Opensees wiki FBE VS DBE. From that I had got the information.
Can you please explain these lines which is given in that file:
"The force-based approach relies on the availability of an exact
equilibrium solution within the basic system of a beam-column
element. Equilibrium between element and section forces is exact,
which holds in the range of constitutive nonlinearity.
• Section forces are determined from the basic forces by interpolation
within the basic system.
- Interpolation comes from static equilibrium and provides constant
axial force and linear distribution of bending moment in the
absence of distributed element loads."

Thanks in advance

[EricsonEncinaZ]

There is no magic recipe to determine the amount of elements you need, you have to select the amount of elements depending on each element's capabilities and your specific problem. In the FBE vs DBE presentation the slides 6 and 10 provides a really good explanation of what each element does, and also slides 18 and 25 provide quite useful summaries. Have a look to the figures that slides 6 and 10 have at the bottom.