Synthetic-Fiber Strip Reinforcement of Glulam Beams: Bond, Recovery, and Flexural Response

This study reanalyzes an archived experimental program on textured polyethylene terephthalate (PET) and polyester-fiber strips used as internal tensile reinforcement in glued-laminated timber (glulam) beams. The pull-out stage comprised one specimen (n = 1) per reinforcement-morphology/anchorage condition, while the beam stage comprised two specimens (n = 2) per configuration. For adhesively bonded pull-out specimens, maximum loads of 1.957, 2.762, and 1.213 kN were recorded for PET, non-laminated polyester fibers, and laminated polyester, respectively; the additionally stapled specimen reached a lower maximum load in each individual pair. PET- and non-laminated polyester-fiber-reinforced beams were subjected to loading–unloading cycles at approximately 10 and 20 mm mid-span displacement before final loading to failure. Secant stiffness, Secant Stiffness Ratio, Recovery Ratio, and Anchorage Performance Ratio were used as author-defined descriptive indicators. Recovery and secant response did not show a consistent specimen-level correspondence, and PET reinforcement did not produce a consistent peak-load increase relative to the reference beams. The first non-laminated polyester-fiber-reinforced beam (R-FIBP-1) reached the highest individual peak load (76.2 kN), corresponding to a 24.8% difference relative to the mean of the two reference beams, whereas the second specimen of the same configuration (R-FIBP-2) did not reproduce this response. The results are therefore interpreted as exploratory, hypothesis-generating observations rather than statistically representative strengthening effects. The reanalysis suggests that reinforcement/interface characteristics may contribute to reinforcement mobilization and warrants replicated testing with complete material and interface characterization.