strain regions are areas within a concrete member where plane sections do
not remain plane after the member is deformed. Disturbed strain regions
occur in portions of all reinforced concrete members. Typically, the
disturbed regions are at the boundary regions, concentrated loading
points, geometric discontinuities, and in members with relatively small
span-to-depth ratios such as deep beams. Recently, more rational
procedures have been developed for design of the disturbed regions of
reinforced concrete, including strut-tie and compressive field procedures.
Such design procedures combined with recent test results have indicated
that the traditional design rules and guidelines are frequently
unnecessarily conservative. This is particularly so where efficient
reinforcing details are adopted such as the headed reinforcement discussed
in this article.