고체역학 (Gere) — Axially Loaded Members: Problem 2.3-2

2.3-2 A long, rectangular copper bar under a tensile load P hangs from a pin that is supported by two steel posts (see figure). The copper bar has a length of 2.0 m, a cross-sectional area of 4800 mm\(^2\), and a modulus of elasticity \(E_c = 120\) GPa. Each steel post has a height of 0.5 m, a cross-sectional area of 4500 mm\(^2\), and a modulus of elasticity \(E_s = 200\) GPa. (a) Determine the downward displacement \(\delta\) of the lower end of the copper bar due to a load \(P = 180\) kN. (b) What is the maximum permissible load \(P_{\text{max}}\) if the displacement \(\delta\) is limited to 1.0 mm?