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Westergaard (Harold M.)


Harold Westergaard was a Danish structural engineer who pioneered many structural and geotechnical concepts used today in concrete flooring.

Technical Information

In Technical Report 34 he provides assistance in the calculation of:
  • Ground supported slab behaviour under loading.
  • Modulus of subgrade reaction.
  • Radius of relative stiffness in a ground supported slab.

In his design concept, Westergaard assumes a concrete slab acts as a homogenous, isotropic, elastic solid in equilibrium with the reactional forces from the subgrade (that are proportional to the deflections of the slab).

Westergaard also introduced the concept of the ‘Modulus of Subgrade Reaction’, k, an important value to know when calculating the deflection in soil due to loading on the surface.

Westergaard also introduced the concept of the radius of relative stiffness, l, for ground supported slabs, which is determined in equation 20 (Chapter 7.5 TR34). This displays the distribution of elastic bending moments for internal loads (both singular and combined).

  • Some of his publications include:
  • Moments and stresses in slabs (1921)
  • Stress in concrete pavements computed by theoretical analysis (1926)
  • Computation of stresses in concrete roads (1926)
  • Computation of stresses in bridge slabs due to wheel loads (1930) Bearing pressures and cracks (1939)

Related Definitions


  1. The Concrete Society: Technical Report 34; 5.6, 7.5.

  2. Karl-Eugen Kurrer, The History of the Theory of Structures: From Arch Analysis to Computational Mechanics, 2008. 


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