고체역학 (Beer) — Pure Bending: Problem 4.195

4.195 A thick-walled pipe of the cross section shown is made of a steel that is assumed to be elastoplastic with a yield strength \(\sigma_Y\). Derive an expression for the plastic moment \(M_p\) of the pipe in terms of \(c_1\), \(c_2\), and \(\sigma_Y\).