Shear reinforcement for pushover analysis in SAP2000 / ETABS

[paladin]

Dear members of Civilea,
I need help.
I have problem with shear reinforcement for pushover analysis using SAP2000 / ETABS
How to add "shear reinforcement" in section designer of beam & column ?
How to accomodate / consider "shear reinforcement" of beams & columns for pushover analysis ?
Thanks
Paladin

[iceman84]

As far as I know you can't add shear reinforcement for pushover analysis in either of the two software. But you can check the shear force for each step and compare it with the capable shear force.

[paladin]

Dear iceman84
I still do not know, why some engineers still "assign" shear pushover hinge to both ends & mid of beam & column with fact we can not add shear reinforcement in beam & column ?
Can you guide me how "check the shear force for each step and compare it with the capable shear force" ?
Thanks for your time & your answer.
Regards
Paladin

[mig21]

hi

"How to accomodate / consider "shear reinforcement" of beams & columns for pushover analysis ?"

define a new hinge property controlled by shear and assign them to frame members just like you do for bending hinges ,,, thats the way to consider shear.

regards

[iceman84]

The capable shear force (you can take into account the stirrups or you can refer only to the concrete shear capacity) is computed using the code formula for shear. The software will give you the shear force at each step of the loading at a certain node. So you can compare the two values. If the shear force from the analysis is larger, you know you have a shear failure of that element.

[paladin]

Dear iceman84 & mig21,
[ Topic 1]
For example, in the last step of pushover, appear red hinge ( indicate failure ) in beam.
The questions :
1) How I know this failure is flexure failure or shear failure ?
---
If the failure is shear failure :
2a) Does etabs already connect with etabs concrete design so that etabs already consider the shear capacity of concrete with shear reinforcement based on shear demand of element ( beam in this case ) ?
---
2b) Or etabs only "read" this beam as "pure concrete" ( concrete without shear reinforcement, because we can not add shear reinforcement ), then still need check separately as you told to me ( check shear capacity of concrete manually or use etabs conc. design & compare with shear force at a step of pushover ) ?
---
[ Topic 2]
I need suggestion based on your experience, do I need locate the "shear" pushover-hinge at both ends plus at mid span of beam/column OR only at both ends of beam/colum ?
---
Thanks for your time & your answers
Regards
Paladin

[iceman84]

If you have moment hinge it is a moment failure. If you have shear hinge it is shear failure.
I think the beam is considered as "pure concrete", if you have a moment hinge. Anyway, what I mentioned above is the manner in which I checked the shear. Other solutions are also possible.
I believe you need to locate shear hinges at both ends for beams and probably at mid span and both ends for columns.

[Sumatra]

Hi Paladin,

Herein my contribution to overcome your problem.

1) How I know this failure is flexure failure or shear failure ?

>>as far as i knew, there is no auto feature to detect flexural-shear failure in sap2000 or etabs, hence you need to find out manually from the numerical output.

If the failure is shear failure :
2a) Does etabs already connect with etabs concrete design so that etabs already consider the shear capacity of concrete with shear reinforcement based on shear demand of element ( beam in this case ) ?
2b) Or etabs only "read" this beam as "pure concrete" ( concrete without shear reinforcement, because we can not add shear reinforcement ), then still need check separately as you told to me ( check shear capacity of concrete manually or use etabs conc. design & compare with shear force at a step of pushover ) ?

>>sap2000 or etabs has no auto flexural-shear hinge. you need to specify flexural-shear hinge manually. it is meant if you run nonlinear static analysis based on auto hinge from concrete design, the program gives you M2, M3, PMM hinges result only. see SapRefer.pdf file in your etabs or sap2000 folder for further.

I need suggestion based on your experience, do I need locate the "shear" pushover-hinge at both ends plus at mid span of beam/column OR only at both ends of beam/colum ?

>> for this question, I agree with the last sentence of ICEMAN84.

>> Hope it helps.
>> adekajeng

[paladin]

Dear iceman84 & adekajeng
Both of you agree : "need to locate shear hinges at both ends for beams and probably at mid span and both ends for columns"
Locate shear hinge at mid of column I think to accomodate possibility of buckling in column, plz give me correction if I'm wrong.
Why we do not need to locate shear hinge in mid of beam ? Plz give me reasons.
Thanks for your time & your help
I really appreciate your effort to help me.
Regards
Paladin

[iceman84]

My reason for this is the following: the beam has gravity loads, which means that the bending moment diagram can't have single curvature bending moment, so the shear force can't be large in the middle of the beam where the stirrups are placed at smaller distance. But, for the columns a single curvature bending moment diagram (without change of sign of bending moment) is possible, so the shear force can be large in the middle of the column, where the stirrups are not placed at the same distance as in the plastic hinge region.