Beers $4\mathrm{.}22($Circular Shape steel strip$)$

A $900-mm$ strip of steel is bent into a full circle

by two couples applied as shown. Determine $($a$)$

the maximum thickness $t$ of the strip if the

allowable stress of the steel is $420$MPa,$(b)$ the

corresponding moment $M$ of the couples. Use

$E=200$GPa.