Explanation Given: Number of single axle traffic at 8 , 000 lb each are 1300 . Number of single axle traffic at 40 , 000 lb each are 20 . Number of tandem axle traffic at 15 , 000 lb each are 900 Number of tandem axle traffic at 40 , 000 lb each are 200 . The reliability of the pavement is 70 % . The overall standard deviation is 0.5 . The value of Δ PSI is 2.0 The value of TSI is 2.5 The drainage coefficient is 1 The load transfer coefficient is 3.0 . The modulus of subgrade reaction is 300 lb / in 3 . The design life is 20 year . The modulus of elasticity is 4 million lb / in 2 . The thickness of slab is 8.5 inches . Formula Used: Write the expression for the total axle load factor. W n = A F n × Number of axles …… (I) Here, W n is the total axle load factor, A F n is the axle load factor for a particular load. Write the expression for the total equivalent load factor. T L EL = W 22.5 S + W 25 T + W 39 T + W 48 Triple …… (II) Here, T L EL is total equivalent load factor. Write the expression for the 18-kip equivalent single axle load. W 18 = T L EL × D L × 365 …… (III) Here, W 18 is the 18-kip equivalent single axle load and D L is the design life. Write the expression for the 18-kip equivalent single axle load. log 10 W 18 = [ Z R S 0 + 7.35 [ log 10 ( D+1 ) ] − 0.06 + log 10 [ Δ PSI / 3 ] 1 + [ 1.624 × 10 7 ( D + 1 ) 8.46 ] + ( 4.22 − 0.32 TSI ) log 10 ( S c ′ C d [ D 0.75 − 1.132 ] 215.62 J { D 0.75 − [ 18.42 ( E c k ) 0.25 ] } ) ] …… (IV) Here, Z R is the reliability of the standard normal distribution, S 0 is the overall standard deviation, Δ PSI is the loss in serviceability from the time the pavement is new until it reaches its TSI, TSI is the terminal serviceability index, C d is the drainage coefficient, J is load transfer coefficient, E c is the modulus of elasticity, k is the modulus of subgrade reaction , S c ′ is the modulus of rupture and W 18 is the 18 -kips equivalent axle load. Calculation: Refer Table 4.6 “Axle load equivalency factors for Rigid pavement, Single Axles. And TSI = 2.5 ” of the book “Principles of Highway Engineering and traffic, 6 th Edition. The axle load equivalency factor corresponding to pavement slab thickness 8 inch and axle load 8 kips is 0.033 The axle load equivalency factor corresponding to pavement slab thickness 9 inch and axle load 8 kips is 0.032 Calculate the axle load equivalency factor corresponding to pavement slab thickness 8.5 inch and axle load 8 kips using interpolation. x = 0.033 − [ ( 8.5 − 8 ) ( 0.033 − 0.032 ) 9 − 8 ] = 0.033 − ( 5 × 10 − 4 ) = 0.0325 Substitute 0.0325 for AF 8 S and 1300 for number of axles in equation (I). W 8 S = 1300 × 0.0325 = 42.25 The axle load equivalency factor corresponding to pavement slab thickness 8 inch and axle load 40 kips is 25.7 The axle load equivalency factor corresponding to pavement slab thickness 9 inch and axle load 40 kips is 26.3 Calculate the axle load equivalency factor corresponding to pavement slab thickness 8.5 inch and axle load 8 kips using interpolation. x = 25.7 − [ ( 8.5 − 8 ) ( 25.7 − 26.3 ) 9 − 8 ] = 25.7 − ( − 0.3 ) = 26 Substitute 26 for AF 8 S and 20 for number of axles in equation (I). W 40 S = 20 × 26 = 520 Refer Table 4.7 “Axle load equivalency factors for Rigid pavement, Tandem Axles. And TSI = 2.5 ” of the book “Principles of Highway Engineering and traffic, 6 th Edition. The axle load equivalency factor corresponding to pavement slab thickness 8 inch and axle load 14 kips is 0.049 The axle load equivalency factor corresponding to pavement slab thickness 8 inch and axle load 16 kips is 0.084 The axle load equivalency factor corresponding to pavement slab thickness 8 inch and axle load 15 kips is Axle load Factor = 0

The modulus of rupture of the rigid pavement.

PRINCIPLES OF HIGHWAY ENGINEERING+TRAFF

7th Edition

ISBN: 9781119688372

Author: Mannering

Publisher: WILEY

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