SSC JE Civil Engineering 29-Oct-2020 Shift 1 Paper

The Indian Code IS 800 has adopted multiple column curves, which are based on Perry-Robertson approach. Theses curves are called buckling curve and these are classified into four categories (namely curve $\mathit{a},\mathit{b},\mathit{c},\mathit{d}$ ) based on $\frac{{\mathit{f}}_{\mathit{c}\mathit{d}}}{{\mathit{f}}_{\mathit{y}}}$ and $\mathrm{\lambda }$, where
${\mathrm{f}}_{\mathrm{cd}}$ is the design compressive strength
${\mathrm{f}}_{\mathrm{y}}$ is the yield strength
$\mathrm{\lambda }$ is the non-dimensional slenderness ratio, which is given as
$\mathrm{\lambda }=\sqrt{\frac{{\mathrm{f}}_{\mathit{y}}}{{\mathrm{f}}_{\mathit{c}\mathit{r}}}}$
${\mathrm{f}}_{\mathit{c}\mathit{r}}$ is the Euler's Buckling stress
These buckling curves are shown below: It is clear from the above figure that for a given value of non-dimensional slenderness ratio, $\mathrm{\lambda }$ , the buckling curve ‘a’ has maximum value of $\frac{{\mathrm{f}}_{\mathrm{cd}}}{{\mathrm{f}}_{\mathrm{y}}}$ ratio and hence, has maximum axial compressive stress by keeping constant ${\mathrm{f}}_{\mathrm{y}}$ and $\mathrm{\lambda }$ constant and buckling curve ‘d’ has minimum axial compressive stress.