effective section modulus for angles

[JokaSteel]

Does anybody known how to calculate the effective section modulus for angles. The design is by Eurocode and for a 3"x3"x5/15" angle, SAP2000 give me Weff,y=0.707 in^4 and Wy=1.746in^4. Also the effective area is igual the section area. I would expect such sections with the same modulus.
Anybody could help me appointing what is wrong.
Thanks,
JokaSteel.

 

[homostructural]

Is your cross-section class 3 or 4? According to EN 1993-1 the effective section modulus is needed for the calcs of class 3 & 4 cross sections or else the plastic or elastic section modulus is used. You might find an answer here!

 

[johnbridge231]

If the cross section is class 4, then the effective area depends on the examined load condition according to Eurocode.
According to the most general case, the effective cross sectional area is estimated for pure axial load, then for pure bending moment about one principal axis and finally for pure bending moment about the other axis.
Then, interaction formalae apply for estimating the capacity of the 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

 

[emilywalters]

I have a similar problem - I need the effective section modulus and effective area of a class 4 circular hollow section. johnbridge231 - how exactly do you go about estimating the effective cross sectional area for pure axial load (or pure bending?)

 

[johnbridge231]

For the case of pure compression, you will only need to reduce the thickness of the chs section.
With regard to pure bending, things get complicated, since you shoule only the whole section part under tension and only the effective part under compression. All these differ from code to code. For instance, Eurocode 3, Part 1-3 provides the basic principles for such calculations.

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