Återbruk av limträbalkar : En analys av förbandszoner och hållfasthetsreduktion vid demontering - sex dimensioneringsfall

Sammanfattning

Purpose: The purpose of this degree project was to investigate the reuse potential of glulam beams with a particular focus on damages in connection zones, strength downgrading, and possibilities for disassembly. The study aimed to evaluate the structural performance of reused beams and identify key factors that affect their safe reimplementation in new constructions. Method: The methods used included a literature review, visual documentation of reused glulam beams, hand calculations according to Eurocode 5, and comparative analysis of six reuse cases (A–F). Calculations considered bending, shear, and deflection in both ultimate limit state (ULS) and serviceability limit state (SLS). Results: The results show that the reuse of glulam beams is feasible, but serviceability requirements often become the governing factor due to increased deflections. Strength downgrading to GL24c was applied when documentation of material quality was missing, which significantly influenced performance outcomes. The analysis demonstrated varying load-bearing capacity and deflection behavior across the six cases. Conclusions: This project concludes that reused glulam beams can be safely reimplemented if careful documentation, conservative strength classification, and appropriate design checks are performed. Serviceability criteria are critical in most reuse cases, and detailed inspections of end zones and connections are necessary. Furthermore, strategies for design for disassembly can enhance future reuse potential. Case A – Original beam (GL30c, 6,0 m span): 100% capacity, ULS and SLS satisfied. Case B – -10% height reduction: ULS satisfied, SLS satisfied. Case C – Cut ends (5,4 m span): ULS satisfied, SLS satisfied. Case D – Downgraded to GL24c: ULS satisfied, SLS satisfied. Case E – -5% height reduction: ULS satisfied, SLS satisfied. Case F – -20 % height reduction: ULS satisfied, SLS not satisfied (deflection exceeded).