Helpful Information - Znet Calculation

[Ganesh Persaud]

A lot of persons don’t know the math formula to calculate Znet, the net plactic section modulus. AISC design manual table 15-3, the znet values are given there based on the bolt size, plate thickness. Etc, see code for more info.

Let’s say for example, we have a shear plate, and we want to calculate the znet manually.

First calculate Zx, plastic section modulus,
Zx = (length of plate^2 * thickness)/4
Znet = Zx - (Plate thickness * dia of bolt hole * gage * no of bolt^2)/4

That’s it, hopefully it helps in the future.

 

[IRstuff]

If you think this is really helpful, you could create an FAQ in this forum

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[BAretired]

I think it is more helpful to describe the process rather than a formula. Unless I'm mistaken, the plastic modulus can be calculated by finding the area of the section, 'A' then determining the line where half the section is above and half below. Then Z = A*d/2 (edited) where d is the distance between centroids of the upper and lower portion. I'm not sure whether it agrees with your formula or not.

BA

 

[r13]

In addition to BA's line of thinking, the plastic section modulus is the sectional property of any shape that is stressed to fully yield condition - half of the cross section area is yielded in tension, and another half is yielded in compression. The areas are on each side of the geometry neutral axis, that is A_T=A_C.