Chapter: Civil : Highway Planning and Alignment : Design Of Flexible And Rigid Pavements
Equivalent single wheel load
Equivalent single wheel load
To carry maximum load with in the specified limit
and to carry greater load, dual wheel, or dual tandem assembly is often used.
Equivalent single wheel load (ESWL) is the single wheel load having the same
contact pressure, which produces same value of maximum stress, deflection,
tensile stress or contact pressure at the desired depth. The procedure of
finding the ESWL for equal stress criteria is provided below. This is a
semi-rational method, known as Boyd and Foster method, based on the following
assumptions:
equalancy concept is based on equal stress; contact area is
circular; influence angle is 45o; and
soil
medium is elastic, homogeneous, and isotropic half space. The ESWL is given by:
where P is the wheel load, S is the center to center distance
between the two wheels, d is the clear distance between two wheels, and z is
the desired depth.
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