Using the data given in Table 14.1, determine the total overhaul cost if the free haul is 700 ft and the overhaul cost is $10 per cubic yard station. Stations of the free haul lines are 1 + 80 and 8 + 80 and 10 + 20 and 17 + 20.

Question

What will be an ideal response?

Answer 1

The first step is to construct the mass diagram shown in Figure 14.17 from the

data in Table 14.1. The data required to solve this problem using the method of

moments are shown below. Note that the ordinate is zero at station 9+60, and

other ordinates as given in Table 14.1 are shown.



First, find the moments and overhaul distances about stations 1 + 80 and 8 + 80.

About sta. 1 + 80: [(100/2 + 80)/100](130) + [(80/2)/100](374 – 130) =

266.6 yd3-sta

Overhaul distance: (266.6 yd3-sta) / 374 yd3 = 0.713 sta

About sta. 8 + 80: [(60/2 + 20)/100](299) + [(20/2)/100](374 – 299) =

157.0 yd3-sta

Overhaul distance: (157.0 yd3-sta) / 374 yd3 = 0.420 sta

The overhaul cost for the first section (between sta. 0 + 00 and sta. 9 + 60) can be

calculated as:

Overhaul cost = (0.713 sta + 0.420 sta)(374 yd3)($10.0/yd3-sta) = $4237

Then, find the moments and overhaul distances about stations 10+20 and 17+20.

About sta. 10 + 20: [(40/2 + 20)/100](201) + [(20/2)/100](255 – 201) =

85.8 yd3-sta

Overhaul distance: (85.8 yd3-sta) / 255 yd3 = 0.336 sta

About sta. 17 + 20: [(43/2)/100](255) = 54.8 yd3-sta

Overhaul distance: (54.8 yd3-sta) / 255 yd3 = 0.215 sta

The overhaul cost for the second section (between sta. 10 + 20 and sta. 17 + 20)

can be calculated as:

Overhaul cost = (0.336 sta + 0.215 sta)(255 yd3)($10.0/yd3-sta) = $1405

Total overhaul cost = $4237 + $1405 = $5642.