STM Resources: What are B- and D-Regions?

Post date: Feb 21, 2014 6:4:22 AM

B- (Beam or Bernoulli) Regions or D- (Disturbed or Discontinuity) Regions. B-Regions are parts of a structure in which Bernoulli's hypothesis of straight-line strain profiles applies. D-Regions, on the other hand, are parts of a structure with a complex variation in strain. D-Regions include portions near abrupt changes in geometry (geometrical discontinuities) or concentrated forces (statical discontinuities). Based on St. Venant's principle, the extent of a D-Region spans about one section depth of the region on either side of the discontinuity.

In the figures for buildings and bridges, the unshaded area with a notation B indicates B-Region, and the shaded area with a notation D is used to indicate D-Region. The notations h₁, h₂, h₃, ... are used to denote the depth of structural members. The notations b₁ and b₂ denote the flange width of structural members.

The examples of B and D Regions in a Building.

The examples of B and D Regions in a Bridge.

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