For the system in Problem P5.15, assume that two 180-lb workers are going to be standing on the system to repair a bridge, one on each platform. The following design requirement must be met: The stretch of each cable must be less than 0.01 in. at the worst-case loading condition for each cable. Determine the minimum diameter required for each cable.

Problem P5.15

A two-tier system to repair bridge infrastructures is supported by two steel cables for each platform (Figure P5.15). All the support cables have a diameter of 0.50 in. Assume the applied loads are at the midpoint of each platform. Determine how much each cable stretches at points A–D.

Figure P5.15

140 in. 90 in. 250 lb 185 in. A 190 in. 400 lb D