12-22-2010, 06:53 AM
@ concreteok,
First of all, we shall not mix braced/unbraced & sway/no sway frames.
May people considers column as braced if framing beam exists and unbraced if framing beam does not exists in particular direction. But this is very approximate assumption and most of codes do not use this terms(i.e. braced/unbraced).
Most codes uses sway/no sway terms for consideration of effective length factors (slenderness). There are also some approximate formulas to estimate moments due to slenderness.
Regarding your question on limit on max. effective length factor for unbraced (may be sway) columns. Code has limit upto infinity. But you can not go upto that, because it will result in very large cross section of member with very high amount of reinforcement. Thus, member size and reinforcement will indirectly control max. effective length factor.
First of all, we shall not mix braced/unbraced & sway/no sway frames.
May people considers column as braced if framing beam exists and unbraced if framing beam does not exists in particular direction. But this is very approximate assumption and most of codes do not use this terms(i.e. braced/unbraced).
Most codes uses sway/no sway terms for consideration of effective length factors (slenderness). There are also some approximate formulas to estimate moments due to slenderness.
Regarding your question on limit on max. effective length factor for unbraced (may be sway) columns. Code has limit upto infinity. But you can not go upto that, because it will result in very large cross section of member with very high amount of reinforcement. Thus, member size and reinforcement will indirectly control max. effective length factor.