$13\mathrm{.}1$ Derive expressions for the maximum uniform load

that can be carried in the isotropically reinforced slabs

shown in Fig. P$13\mathrm{.}1.$

$($a$)$

$($b$)$

$($c$)$

All positive moments $m_u^{+}$; all negative moments $m_u^{-}$

FIGURE P$13\mathrm{.}1$