Shear Performance of Timber-Steel Hybrid Beams: Experimental Investigation

The building sector accounts for approximately 40 % of global CO₂ emissions, setting the demand for efficient and resource-efficient structural systems. Timber structures offer significant sustainability advantages but exhibit mechanical limitations, particularly regarding shear strength and stiffness. Steel-based strengthening therefore represents a promising strategy to improve the structural performance of timber elements while maintaining a high percentage of the renewable material timber.
This study investigates a strengthening approach for timber beams using slender steel profiles that are adhesively bonded into the timber cross-section. Three-point bending tests with a span of 0.74 m were conducted to generate shear-dominated loading conditions. Strengthened beams were compared with timber reference beams of identical geometry using two material combinations: GL 24h with S355 and LVL 48p with S420. The strengthening significantly improves structural performance. The load-carrying capacity increases by 99 % for GL 24h and 77 % for LVL, while the shear stiffness increases by factors of 5.7 and 4.0, respectively. Whereas the timber reference beams fail in a brittle shear mode, the strengthened beams exhibit a more ductile response due to plastic deformation of the steel profiles combined with timber failure. ... mehrThe results demonstrate the high potential of steel-based strengthening for shear-critical timber members.