Question

The following data pertains to the number of commercial vehicles per day for the design of a flexible pavement for a national highway as per IRC : 37 - 1984.

Type of commercial vehicle	Number of vehicle per day considering the number of lanes	Vehicle damage factor
Two-axle trucks	2000	5
Tandem-axle trucks	200	6

Assuming a traffic growth factor of 7.5% per annum for both the types of vehicles, the cumulative number of standard axle load repetitions (in million) for a design life of 10 yrs is

• A. 78
• B. 44.6
• C. 62.4
• D. 57.8

Answer 1

The correct option is D 57.8

Traffic growth factor,
r = 7.5% per annum

Design life, n = 10 yrs
For two axle trucks
Number of vehicles per day (A) = 2000

Vehicle damage factor (F) = 5
Cumulative number of standard axle load repetitions

$N_{s_1}=\frac{365A[{(1+r)}^n-1]}{r}\times F$

$=\frac{365\times 2000\left({\left(1+0.075\right)}^{10}-1\right]}{0.075}\times 5$

$=51.63\times {10}^6=51.63msa$

For tandem axle trucks
Number of vehicle per day
A = 200
F = 6

$N_{S_2}=\frac{365A\left[\right(1+r{)}^n-1]\times F}{r}$

$=\frac{365\times 200\left[\right(1.075{)}^{10}-1]\times 6}{0.075}$

= 6.19 msa

Total number of standard axle load repetitions,
$N_s=N_{s_1}+N_{s_2}$
= 57.8 msa