Plastic hinging

[DDRJ]

Hi guys!

As I google the definition of plastic hinging one of the answer states that, "a condition where a member can bend further but there will be no increase in resisting moment".

I would like to ask what contributes to this mechaninsm (strain hardening maybe).
I have used ACI chapter 21 requirements for design of special moment resisting frame and i know it considers the action of plastic hinging but to grasp a better concept of design I would like to know more about plastic hinging and its effect on the structure.

Thank!

 

[hokie66]

No, it is not strain hardening. A plastic hinge is yielding. Just look at a stress-strain curve of structural steel, and you should then understand. When there is enough strain, then strain hardening occurs, but that is beyond the range of a plastic hinge.

I have little insight into plastic hinging in concrete structures, but it would involve yielding of the reinforcement.

 

[DDRJ]

Thanks hokie66!

I see. Thanks for clarifying that plastic hinging is not a result of strain hardening because such hardening occurs beyond ultimate strength of the material far beyond its yield point, Im a correct?

I beleive plastic hinging is really dependent on yeilding of reinforcement. hokie66, your little insight wil be a great help to me.

If you could post any material for further reading it will be much appreciated.

 

[DDRJ]

Attached link stisfies my question beyond expectation.

Great forum!!!

 

[desertfox]

I found this relating to plastic hinges in beams

http://uacg.bg/filebank/att_1392.pdf

 

[shin25]

I agree with hokie66. Since under a design earthquake, a plastic hinge could undergo enough straining to get into the range of strain hardening, it is very important to also consider possibility of strain hardening that could deliver additional member capacity during capacity protection design of the members that away from the plastic hinges of the seismic force resisting system.

 

[johnbridge231]

This mechanism is based on the non-linear bahaviour of the strcutral elements of a cross section (concrete and steel). Their stress-strain diagrams are not linear, thus a non-linear moment vs. curbature relationship appears at the scope of the whole cross section.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis

http://www.engissol.com/cross-section-analysis-design.html