Do “Second-Order Analysis+Design” include “Beam Buckling Analysis” as well?
“Second-Order Analysis + Design” will check section classification, beam buckling and so on. “Second-Order Analysis + Beam Buckling” and “Second-Order Analysis only” will not do section check such as use of elastic modulus for semi-compact sections but sometimes we need to do this for research studies on buckling of a structure unaffected by other factors.
For Plastic Advanced Analysis, there are two options, one is plastic hinge and one is plastic elements. I assumed it is refer as “plastic hinge model” and “plastic zone model” respectively in structural use of steel 2005. The manual has clear definition on it but the applicability, advantages or disadvantages has not been touch on. Can you give us some advice on these two methods?
Both “Plastic hinge” and “Plastic element” are based on the plastic hinge approach. However, “Plastic element” is more conservative than “Plastic hinge”. The former keeps the resistance of the force and moment of the failed member constant when the section capacity factor is greater than 1.0 while the latter will keep the moment resistance of the failed member constant when the section capacity factor is greater than 1.
What is the difference between PEP element and Curved Stability Function? The default value for the program is PEP element, under what circumstance shall we pick Curved Stability Function?
Both PEP element and Curved Stability Function are suitable for practical second-order analysis. However, they are two different approaches. In general, PEP is faster convergent and Curved Stability Function can be used for very large axial force case which is really too important for practical design.
Under what circumstance shall we pick variable load increment for post-buckling analysis?
For most cases, the "Constant Load Increment" (i.e. Newton-Raphson) method can give a quick good solution. If you want to trace the "Post-Buckling behavior", you can try "Variable Load Increment" method, i.e. "Arc-length + Minimum Residual Displacement". You can adjust the iterative and incremental parameters to control the load increment.
Default Delta x L/1000 as indicated in the following picture? What value shall we input? I originally believed it is for imperfection. Thank you very much!
It should be pointed out that the initial imperfections are so important for second-order analysis that we cannot ignore them. To avoid the user’s improper input, the minimum member imperfection defined by "delta x L/1000" will be automatically assigned to members when performing second-order analysis. This parameter is to ensure the structure as "imperfect".
