SRi h
3 1 Pi 3 h 2
Eh3 4v 1 v 1.18 1 2 a 1.84 ln 4 3 2 l 100ka for i 1, 2 Sf
(2.53)
Where and E denote Poisson‟s ratio and modulus of elasticity of cement concrete respectively. l , a, h and S f denote radius of relative stiffness, radius of load contact areas thickness of the slab and flexural strength of concrete respectively. The relation between
Ni and SRi
for single axle load i 1 and tandem axle i 2 is expressed as per IRC
58- 2002 below-
Ni if SRi h 0.45 4.2577 Ni SRi h 0.4325 0.9718 SRi h 0.0828
Ni 10
(2.54)
3.268
if 0.45 SRi h 0.55
if SRi h 0.55
(2.55)
(2.56)
Therefore three cases will come up for consideration to demonstrate the stress ratio in terms of fatigue life and axel load. Case I : When Eq.(2.54) is influenced over the Eq.(2.52), the DR remain unchanged as Eq.(2.54) as the relation is trivially true Case II: When Eq.(2.55) is influenced over the Eq.(2.52) the DR is transforms into
3.268 n 2 6.536 2 F1 l , h, k , A1 , A2 365 1 r 1 SR1 h 0.4325 SR2 h 0.4325 A1 A2 0.5 4.2577 r 2
(2.57) Case 3: When Eq.(2.56) is influenced over the equation Eq.(2.52), the DR is expressed as
365 1 r 2 1 0.25 SR1 h SR2 h 23.47 Log A A F2 l , h, k , A1 , A2 2 Log 1 2 r 0.25 0.0828
(2.58) In the above expression A is initial number of axle per day in year which is not greater than the sum of initial number of axle per day due to single axle A1 and initial number of axle per day due to tandem axle A2 . Deflection Analysis for Subgrade
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