This is a web site with structural design spreadsheets I've created with CalcPad:
Spreadsheets are located in the 'Library' section. Most are free to use. Some require registration that unlocks 10 days free trial access to the whole library.
The main advantage of CalcPad is that calculation formulas are automatically displayed in the output and values are substituted. It is easy to check and follow the results.
You only have to fill the input boxes and click 'Calculate'. Then you can print the results from the browser.
It is also very easy to program with CalcPad. Source codes are simple math formulas, mixed with text/html comments in 'quotes'.
Here is one free online design spreadsheet for column design to Eurocode
I am only not quite sure about the method for second order effects. I think it is the nominal stiffness method.
From EN 1994-1-1
126.96.36.199(4) If the plastic resistance moment exceeds 2,5 times the plastic resistance moment of the steel member alone, additional checks on the adequacy of the shear connection should be made at intermediate points approximately mid-way between adjacent critical cross-sections.
What additional checks mentioned in this article?
First of all those kinds of connections are considered to be shear only connections (if their bolts are not preloaded), thus once should not use these for cantilever applications, by which I mean not cantilevering the long beam in the direction perpendicular to the fin plates which make up the connection but rather parallel to them (in the direction of uniformly distributed loads). Besides of that the two plates should not exhibit a lot of torsion from the long beam cantilevering out perpendicular to the plates, because of their low stiffness in torsion - they will make up a moment by two opposite reactions to fix the long cantilever beam. To get the exact value of torsional moment in every plate you should do FEA.