Masonry Lintel Bearing Length (TMS 402)
What masonry-lintel-loading stops short of: the load reaches a support, and the support needs length. Effective span = clear span + depth capped at the support centers (2.3.3.4.1), reaction from the UDL, required bearing = reaction / (allowable stress x width), governed by the 4-in code minimum (2.3.3.4.3). For an ordinary 6-ft lintel the stress check wants 0.44 in and the code minimum governs at 4 - which is exactly why a stress calculation alone misleads. The allowable stress is YOUR input: published sources disagree on the coefficient, so no number is shipped.
Formula and source
Effective span = min(clear span + depth, distance between support centers); reaction = udl x eff span / 2; required bearing length = reaction / (allowable bearing stress x bearing width); governing = max(required, 4 in).
TMS 402 (MSJC) lintel provisions by section number: 2.3.3.4.1 effective span (clear span plus depth, not more than the distance between support centers) and 2.3.3.4.3 end bearing not less than 4 in.
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