What is Westergaards theory?
Westergaard’s Theory Assumptions: Elastic medium of semi-infinite extent but containing numerous, closely spaced horizontal sheets of a negligible thickness of an infinite rigid material which permits only downward deformation as a whole without allowing it to undergo any lateral strain.
What are the critical stresses in rigid pavements as per Westergaard’s analysis?
Design of rigid pavements is based on Westergaard’s analysis, where modulus of subgrade reaction, radius of relative stiffness, radius of wheel load distribution are used. For critical design, a combination of load stress, frictional stress and warping stress is considered.
What are the factors influencing stresses on rigid pavement?
Stresses in rigid pavements result from a variety of causes, including wheel ioads, cyclic changes in temperature (warping and shrinkage or expansion), changes in moisture, and volumetric changes in the subgrade or base course.
What are the types of stresses in rigid pavements?
Summary
- Curvature and Stresses Caused by Bending.
- Relative Stiffness of Slabs.
- Modulus of Subgrade Reaction.
- Stresses due to Warping.
- Stresses due to Friction.
- Effects of Warping, Contraction, and Expansion.
- Plain versus Reinforced Pavements.
- Definition of Joint Types.
What are the assumptions involved in Boussinesq’s and Westergaard’s theory?
The Boussinesq theory assumes that the soil mass is isotropic. Actual sedimentary soils are generally anisotropic. Thin layers of sand are usually embedded in a homogeneous clay deposit. Westergaard’s theory assumes that thin sheets of rigid material are sandwiched in a homogeneous soil mass.
What are differences between boussinesq’s and Westergaard’s theories?
Boussinesq’s theory considers that the medium of soil is isotropic while Westergaard’s theory considers that the medium of soil is anisotropic.
What are frictional and temperature stresses?
The frictional resistance depends on the self weight of the slab and coefficient of friction at the interface. Due to friction resistance at the interface, compressive stress is induced at the bottom of the slab. Similarly, during winter as the mean temperature of the slab decreases, the concrete pavement contracts.
How many critical stress locations are there in a rigid pavement?
three critical positions
Explanation: When the rigid pavement is subjected to wheel loads and temperature changes, it experiences the stresses in different positions. There are three critical positions namely, interior, corner and edge.
What are the limitations of rigid pavement?
~ High initial cost required for construction. ~ Maintenance is difficult than flexible pavement. ~ Requires at least 28 days of curing before high traffic movement because concrete gains its 99% efficiency/strength in 28 days.
What are the functional requirements of rigid pavement?
Rigid pavements support loads through rigidity and high modulus of elasticity of concrete slab. The loads will distribute to natural soil layer through different layers of rigid pavement. The compostion and structure of rigid pavement tells us about the function of each layer of rigid pavement as explained below.
What is the minimum factor of safety for rigid pavement?
1.1
The minimum factor of safety is 1.1 and if it doesn’t satisfy then the pavement thickness is revised.
What is ESWL in pavement?
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.
What is Westergaard method of rigid pavement design?
The design of rigid pavements by the Westergaard method is still commonly used today for rigid pavements loaded by non-highway vehicles. The Westergaard method for rigid pavement design involves a calculation of the stresses acting in the pavement under the wheel load.
What is the Westergaard’s analysis used for?
Arora (2003) has reported that the Westergaard’s analysis is used for design of rigid pavements. The stresses in the concrete slab are determined using Westergaard’s theory. Westergaard considered the rigid pavement as a thin elastic plate resting on soil subgrade.
What is the edge loading condition in a Westergaard analysis?
When using the edge loading condition in a Westergaard analysis of rigid pavements it should be noted that the design assumptions are quite conservative. It assumes the wheel load is applied to the very edge of the slab and that no load transfer between adjacent slabs is present.
What is the critical condition in rigid pavements?
The edge loading condition in the design of rigid pavements by the Westergaard method is more frequently used as the critical condition. This condition assumes a loaded patch on the edge of the slab which would represent a wheel load crossing the edge of the slab where no load is transferred into any adjacent slabs.