고체역학 (Gere) — Axially Loaded Members: Problem 2.4-12

2.4-12 The fixed-end bar $ABCD$ consists of three prismatic segments, as shown in the figure. The end segments have a cross-sectional area $A_1 = 840\text{ mm}^2$ and length $L_1 = 200\text{ mm}$. The middle segment has a cross-sectional area $A_2 = 1260\text{ mm}^2$ and length $L_2 = 250\text{ mm}$. Loads $P_B$ and $P_C$ are equal to $25.5\text{ kN}$ and $17.0\text{ kN}$, respectively. (a) Determine the reactions $R_A$ and $R_D$ at the fixed supports. (b) Determine the compressive axial force $F_{BC}$ in the middle segment of the bar.