Plastic Section Modulus
Zp is the Plastic Section Modulus
Resisting moment Mp = fy x Zp
The plastic section modulus assumes the entire section yields.
If the failure is considered till the plastic zone
(breaking point) then we consider plastic modulus
The plastic modulus is after yielding.
Zp is used to determine the maximum bending moment at the point where all fibers have yielded elastically and the entire section is behaving plastically. This is the point when the so-called plastic hinge has developed.
Elastic Section Modulus
Ze is the Elastic Section Modulus
Resisting moment My = fy x Zy
The elastic section modulus assumes the section remains elastic.
If the failure is considered till the elastic
zone then we consider elastic modulus.
Elastic modulus is the steel modulus based on the stress strain curve before yielding.
Ze is used to determine the maximum bending moment up to the point where the extreme fiber has yielded elastically. All other fibers will be below their elastic yield stress.
