고체역학 (Beer) — Pure Bending: Problem 4.76

4.75 and 4.76 A beam of the cross section shown is made of a steel that is assumed to be elastoplastic with \(E = 29 \times 10^6\) psi and \(\sigma_Y = 42\) ksi. For bending about the \(z\) axis, determine the bending moment at which (a) yield first occurs, (b) the plastic zones at the top and bottom of the bar are 1 in. thick. [Fig. P4.76 shows an I-shaped cross section with the following dimensions: flange width = 3 in. (1 in. + 1 in. + 1 in.), flange thickness = 1 in., web width = 1 in., web height = 2 in. Total height of the section = 4 in.]