B-region and D-region

Definition of B- and D-Region

1. B-Region
B-Region means “Bernoulli region” or “Beam region“.
The strains in concrete structures follow a linear distribution.
The design of B-Region is bending behavior can be predicted by simple calculation.

2. D-Region
D-Region means “Discontinued region” or “Disturbed region“(such as deep beams or corbels).
D-Region could not be designed or analyzed by simple calculations. So, engineer requires ability to predict capacity of member.
The capacity of member is very complicated computations such as finite element analysis.

Below pictures are B- and D-region of the structural member.
Defining the Boundaries of D-region

A discontinuity in the stress distribution occurs at a change in the geometry of a structural element or at a concentrated load or reaction. St. Venant’s principle indicates that the stresses due to axial force and bending approach a linear distribution at a distance approximately equal to the overall depth of the member, h, away from the discontinuity. For this reason, discontinuity regions are assumed to extend a distance h from the section where the load or change in geometry occurs.

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Reference

1. American Concrete Institute (2014) Building Code Requirements for Structural Concrete (ACI 318M-14) and Commentary(ACI 318RM-14), Farmington Hills, Michigan, USA.
2. Korean Concrete Institute (2012) Design Specifications for Structural Concretes, Kimoondang, Seoul, South Korea (in Korean).
3. Korean Concrete Institute (2013) Examples of Strut-Tie Model Design of Structural Concretes, 2nd Edition, Kimoondang, Seoul, South Korea (in Korean).

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