고체역학 (Gere) — Stresses in Beams (Basic Topics): Problem 5.5-17

5.5-17 A simple beam $AB$ of a span length $L = 7 \text{ m}$ is subjected to two wheel loads acting at a distance $d = 1.5 \text{ m}$ apart (see figure). Each wheel transmits a load $P = 14 \text{ kN}$, and the carriage may occupy any position on the beam. (a) Determine the maximum bending stress $\sigma_{\text{max}}$ due to the wheel loads if the beam is an I-beam having section modulus $S = 265 \text{ cm}^3$. (b) If $d = 1.5 \text{ m}$, find the required span length $L$ to reduce the maximum stress in part (a) to $124 \text{ MPa}$. (c) If $L = 7 \text{ m}$, find the required wheel spacing $d$ (labeled $s$ in the text) to reduce the maximum stress in part (a) to $124 \text{ MPa}$.