Blueprint: Sacrificial Crack-and-Strain Witness Strip — Build Specification

Build specification for a passive sacrificial crack-and-strain witness strip for small bridges and culverts: a glass-epoxy strip with a 100 mm free gauge carrying eight graded sacrificial ligaments that break in fixed order and uncover high-contrast stripes, plus an identical reference strip for temperature comparison. DESIGN BLUEPRINT - SIMULATED, NOT MEASURED - NOT BUILT, NOT LOAD-TESTED. All performance numbers are from the source paper: trigger thresholds 0.20 to 1.25 mm in steps of 0.15 mm (2,000 to 12,500 microstrain), reading uncertainty plus/minus 0.075 mm, probability of a correct level 0.987 or better at a band centre, worst-case temperature-driven apparent opening 0.0235 mm against a first threshold of 0.20 mm (margin factor 8.51, residual 0.00705 mm with the reference strip), governing computed service life 8.63 years with replacement capped at 5.0 years, parts cost USD 9.45 per crossing point.