Steel Angle Plastic Section Modulus
Steel Angle Plastic Section Modulus
(OP)
I am working on making a generalised spreadsheet for steel angles that can handle user input data. The sections to be evaluated will generally come from one steel which are the most commonly available hot-rolled products in Australia.
Link to one steel’s product guide: http://www.onesteel.com/images/db_images/productsp...
Angles are on pages 21-26.
(Note that in Australia “S” denotes Plastic Section Modulus whilst “Z” denotes Elastic Section Modulus).
Enlarged key diagram: http://i.imgur.com/Atev7w4.png
I am after trying to find the plastic section modulus about both local axes (x & y) after having calculated them for the global axes (n & p). Is there a way I can transform global to local using Morh’s circle to evaluate plastic section properties?
Any advice would be greatly appreciated.
Link to one steel’s product guide: http://www.onesteel.com/images/db_images/productsp...
Angles are on pages 21-26.
(Note that in Australia “S” denotes Plastic Section Modulus whilst “Z” denotes Elastic Section Modulus).
Enlarged key diagram: http://i.imgur.com/Atev7w4.png
I am after trying to find the plastic section modulus about both local axes (x & y) after having calculated them for the global axes (n & p). Is there a way I can transform global to local using Morh’s circle to evaluate plastic section properties?
Any advice would be greatly appreciated.






RE: Steel Angle Plastic Section Modulus
Try the links below, on the link ending with pdf scroll down till you find clause 9.10., the links will explain how to use the Mohr circle to get to the principle axis of the angle.
http://books.google.co.uk/books?id=hGtgVkHmoz4C&am...'s+circle+second+moment+of+area&source=bl&ots=puRdoJqttR&sig=FVJOgaVcoLib8LUuah7Xb2BUpbo&hl=en&sa=X&ei=qSc1Uqf_A4XPhAe944CIBQ&ved=0CC0Q6AEwAA#v=onepage&q=mohr's%20circle%20second%20moment%20of%20area&f=false
http://ocw.nthu.edu.tw/ocw/upload/43/763/static_ch...
http://www.roymech.co.uk/Useful_Tables/Sections/U_...
RE: Steel Angle Plastic Section Modulus
I have been using morh's circle to rotate the second moments of area from global to local (this is a piece of cake). Doing so requires you to find the product of inertia (denoted Ixy when dealing with the second moment of area). In my case, I don't know how to evaluate the plastic section modulus term that would replace the product of inertia. In other words, having already calculated Sn and Sp, how do I calculate Snp - which would be the product of plastic section modulii (does this even exist/mean anything mathematically?)?
RE: Steel Angle Plastic Section Modulus
On the other hand, such transformations are not valid for section moduli. So you will have to recalculate the plastic modulus with respect to the axes x and y. This is time demanding but inevitable if you are doing that by hand..
Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis
http://www.engissol.com/cross-section-analysis-des...
RE: Steel Angle Plastic Section Modulus
Sorry I thought you just needed to transform it, its quite complicated and all I could find was this:-
http://en.wikipedia.org/wiki/Section_modulus
scroll down till you see plastic section modulus
RE: Steel Angle Plastic Section Modulus
Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis
http://www.engissol.com/cross-section-analysis-des...
RE: Steel Angle Plastic Section Modulus
BA
RE: Steel Angle Plastic Section Modulus
You've all confirmed what I thought may be the case - I'll be simplifying the geometry down to a set of rectangles and go from there.
BAretired, why can't an angle go fully plastic? Is it because the case where the unrestrained ends of the legs in compression are likely to buckle before ever going plastic? The Australian steel code (AS4100) will allow you to design an angle based on its slenderness - the first check of which is the "compact section modulus" (I think this is the british equivalent of class 1) which is defined as the minimum of: 1.5 x Elastic Section Modulus and the Plastic Section Modulus.
RE: Steel Angle Plastic Section Modulus
RE: Steel Angle Plastic Section Modulus
The term "plastic section modulus" is not defined for the global axes (n & p) so it is not clear to me what you calculated. Where would the neutral axis be located?
It may be feasible to calculate the plastic section modulus for the principal (you called them local) axes, particularly for an equal leg angle because the section has one way symmetry about the x axis and a form of symmetry about the y axis.
BA