I agree with Connectegr..., you need much more info. on the member forces, moments, stresses, section properties, etc. before your question can really be discussed in a meaningful way. 2" web and 2.5" flg. plates make for a fairly husky column section, but it is quite likely that it doesn’t have to have CJP welding. Preheat, interpass temps. and post heating might more likely be issues. And, on columns made up of plates this thick, many times you want to mill or saw cut the ends for good bearing on the base plates. It seems that if these types of structural design details and problems are within the scope of your work you had better know a great deal more about this subject matter than your O.P. suggests. You really need some text books on subjects like Strength of Materials and Structural Design in Steel, and welding ref. books to study on your own. These kinds of questions can’t be fully addressed, long distance, on a forum.