very basic euler end conditions

huangyhg

very basic: euler end conditions?
let me first say i'm by no means an engineer, however i am involved to a degree in the design process, and in the end everything is stamped by one of our pe's anyway. now my question:
in looking at the euler formula for determing critical loads in columns, i see that there are several end conditions given, each with different k factors. can someone please give a 'real world' example of such end conditions? i've seen various terms for each, it seems like these are the most common:
pinned (a.k.a hinged), free, guided, fixed (a.k.a clamped)
typically i/we design simple structures to support equipment, piping, etc... very often square tube is used for the columns welded directly to the frame on top and with bearing plates at the floor which are either lagged into the concrete directly or grouted & lagged into the concrete.
to me this would seem like a "fixed" ends situation, but not being familiar with the terminology i want to be sure. some of the conditions such as "guided" and "free" i can't imagine an application.
thank you.
if your column is relatively weak and the fixing at the base strong, and it is also the case with the foundation, a fixed based is acceptable. where not, usually the assumption of pinned end is accepted, because this way the   
if you are interested there is an inexpensive book that covers all the bases in weldments, especially machine design, legs, columns, etc.
the book is:
design of weldments by omer blodgett
james f. lincoln arc welding foundation
the cost is about $15.00 and worth every penny of it.
it can be ordered from the foundation.
it's a pretty difficult concept to explain briefly.  you probably have access to a steel manual (aisc asd or lrfd).  try checking out the commentary for the "frames and other structures" for some insight into the effective k factor.
all of the end conditions are "idealized".  for your case, you might be able to assume a fixed-fixed condition, but then you must design these connections for those "fixed" reactions.  it also depends on whether there is x-bracing or some other condition to prevent sidesway at failure.  from a euler pt of view, a column can be a horizontal   
thank you for the quick responses.
given the example beow, this is my understanding of the issue:
lets say i have a simple structure sitting on a concrete pad. all the steel is 4x1/4 square tube. on top the columns are welded to the steel deck. down on the ground the each columns is welded to an 1/2x8 square bearing plate that is lagged into the concrete sufficiently.
i would think the following:
my columns are obviously not pinned, nor do they seem to be 'free' or 'guided'. i would say the bottom of each column is fixed - i'm unclear as to whether or not the top end of the column would be fixed also (in this case i would think so).
i do have a question or two regarding bracing and how it affects the above. i would think that bracing each column at the midpoint would in effect let each column act like 2 shorter columns. is that fair to say?
a good knee brace should suffice, but what about simply running a horizontal   
rowe, i wasn't thinking of a horizontal column, this makes more sense with what ishvaaag said.
earlier today i was looking at the same link you posted, in my case though it doesn't really help. i do have my aisc books, both asd & lrfd. i'll take a look at the section you mention.
the pe we use is only contracted when we need him, so i don't have access to his knowledge at all times. our need is to decrease the lead time it takes to get work from engineering to the shop, time spent re-designing things that would have fallen over is the reason i'm trying to do some "pre-engineering".
thanks.
jacobd,
your end restraint is typical of everyday problem in engineering.  it is never quite black or white but comes in a shade of grey.
i would assess your restraint as "fixed".
a fixed restraint can offer reactions in 3 translational directions (x, y & z) and 3 rotational directions (rotating about x, y & z).
a pinned end = hinges end can offer the 3 translational reactions but none of the rotational restraints.
a guided end is somewhere in between of the above two.  the guided direction can expand freely and has no translational reaction but transversely it is clamped (or not allowed to bend) and therefore able to transmit bending moment or offer rotational restraint in that direction.
it is a fundamental assumption that with a fixed end the structural member must always remain perpendicular to the support (assuming the member originally fixed at right angle to support) no matter how much you bend it, even to the destruction of the member.  so to ensure a fully fixed condition, you need to ensure the support cannot fail before the   
from your description, i imagine your structure is similar to a table top with 4 legs.  if your welded connection to the "table top" is sufficient in strength and detail to transfer moment (see framing details in the aisc manual) and the connection to the floor is also sufficient for moment, then you can assume a "fixed-fixed" condition. however, without x-bracing, you must use the stability equations regarding "sidesway permitted".
rowe
i admit that making a belt is admitted by many as bracing. relative bracing would be a more proper way of defining it. that these elements are effective in adding stability we may find in lots of wooden chair designs. but you are adding more rigidity to the system than bracing itself.
however, a more traditional understanding of bracing uses to ensure a complete path of the stabilizing forces to firm ground. that transverse members to beams are understood to provide bracing to the same is more based in that the transverse   
any member in compression is subject to euler buckling, local buckling (thin flanges, etc.) and lateral torsional buckling.  other members that frame into the column may (or may not) affect any or all of the buckling modes, depending on the connections and how the connecting members are themselves braced.
as i stated before beam/column behavior is such a very broad subject.  the answer to one question always seems lead to another question.
with regard to the "belt" point made above, it was my intent to show that lateral bracing of a   
..."the belt, if sufficiently connected to the leg, would indeed cause the leg to act like 2 shorter columns - but, that does not mean that the whole structure is necessarily more stable."...
thats basically what i was getting at several posts back.
i've got a better picture now of the column conditions (i think!). i've been looking at the euler as well as j.b. johnson formula - and you're right more questions keep bubbling up.
can i ask just one more, then i'll try to leave you guys alone... the euler formula refers to the "proportional limit" of the material beyond which buckling is inelastic. for practical purposes can the proportional limit be considered the same as the yield strength? the only way to know the true proportional limit would be through testing would it not?
thanks to all who have posted, it really does help.