Problem $3$: $(15$ Points$)$

$($a$)$ Why is Euler critical load always greater than practical buckling load in a column in a real structure? $(3$ Points$)$

$($b$)$ In the column load tables the following ${}_c{P}_n$ values can be found:

HE $500A$:$KL=11\mathrm{.}0m,{}_c{P}_n=1333\mathrm{.}0kN$ for $F_y=355$MPa

HE $500A$:$KL=11\mathrm{.}0m,{}_c{P}_n=1333\mathrm{.}0kN$ for $F_y=275$MPa

However, for $KL=5\mathrm{.}0m$ :

HE $500A$:$KL=5\mathrm{.}0m,{}_c{P}_n=4243\mathrm{.}5kN$ for $F_y=355$MPa

HE $500A$:$KL=5\mathrm{.}0m,{}_c{P}_n=3502\mathrm{.}3kN$ for $F_y=275$MPa

Why are the capacitics of the columns are the same for $KL=11\mathrm{.}0m,$ but different for $KL=5\mathrm{.}0m?(3$ Points$)$

$($c$)$ Why is$,K,$ effective length factor, always less than one in braced frames? $(3$ Points$)$

$($d$)$ What does $G=0$ define in the alignment charts? $(3$ Points$)$

$($c$)$ What does $G=$ infinity detine in the aligenment chart? $(3$ Points$)$

Haberler