Originally Posted by TANSL
I corrected my previous post because the allusion to pillars in tanks was not correct. The hollow pillars are strictly prohibited inside the tanks.
I did not look in Lloyd's rules but frankly, I do not know how you can get a full penetration into a tubular pillar. How to access the inner face to clean the root cord and weld ?. Should you place a backing plate and weld with inert gas? It seems very complicated.
Originally Posted by TANSL
In my previous post I talked about the welding with backing plate to achieve a full penetration but with the condition of welding with inert gas to avoid having to clean the root.
Thank you for trying to clarify this matter, but I insist on clarifying that I have never spoken of welding between pipes.
In the first post that I have quoted above you asked a very specific question "I do not know how to get full penetration on a tubular pillar"
I responded by giving you a link but should have referenced Figure 3.9, lower right hand quadrant.
You will see a straight bevel as well as a radius that goes to the root, This enables better filler and vertical member mixing when welding. It also shows a root spacing to ensure that the entire vertical member and the flat plate gets penetrated. It is not complicated.
Yes, in your second quote above, I referenced one side welded, not backed, pipeway butt connections only because there are millions of them made without backing and have stood the test of time but more importantly have stood non-destructive x-ray inspection as to the quality of the weld. They are not complicated
The OP asked a straight forward question as to what he believes to be an excessive requirement for a full penetrating weld on a column that is subject, at least in his understanding of the loading, to ONLY COMPRESSIVE FORCES that might be able to be covered by a fillet weld.
I am guessing here of course but I suspect then the OP thinks that by stabilizing the column from moving laterally, you should not need an FP weld
Ad hoc replied that an FP weld will probably guarantee that the weld will be strong enough to carry any load that may exist or could exist that the column could be placed under.
This is obviously correct. (Adhoc, I did not quote you precisely but this is what I took you to mean)
Without seeing the actual designed pillar and loadings, I have to guess at a few things but because there is a pillar whose primary function is to resist a compression load, this might not be the only load that the column might be subjected to.
Long slender columns can bend/buckle even at pure axial loaded conditions and produce bending stresses in the column.
Euler derived an equation to determine a critical load based on the area moment of inertia, length and material type.
You can google Critical Loads in Columns, or Buckling Considerations in Columns, for the theory behind this
In columns that are not long and slender but where the loads are non concentric, this loading will induce tension bending stresses in the column
In situations where ONLY axial loading is not guaranteed, such as a where the structure is flexing causing loading not to be concentric, such as a ship, the critical load will be much lower than a pure axial, concentric load. In the event of a failure, maybe brought on by a grounding, you might want the column to provide more load carrying capability than pure compression.
The full penetration weld would be one way to ensure that any tension stresses caused by bending/deflection would be able to be carried by the welding and an FP is the easiest way to accomplish this.