Strength enhancement of laminated veneer lumber (LVL) beams using steel bars

: This paper presents a novel method for reinforcing laminated veneer lumber (LVL) beams with steel bars, featuring a systematic comparison of four distinct reinforcing configurations. Experimental tests were conducted on full-scale beams with nominal dimensions of 45×160×3300 mm. The reinforcement consisted of 12 mm diameter B500SP steel bars bonded into pre-drilled grooves within the tension and compression zones. Four different reinforcement placement configurations were investigated. An epoxy-based adhesive was utilized for bonding. In accordance with European standards, four-point bending tests were performed on a total of 20 reinforced and 10 unreinforced beams. The reinforced beams achieved significant improvements in mechanical properties relative to the reference elements. For a cross-sectional reinforcement ratio of 4.71%, the maximum mean increases in load-bearing capacity and stiffness were 93% and 94%, respectively. Conversely, the minimum increases for these parameters were 45% and 34% at a reinforcement of 1.57%. The reinforced beams exhibited enhanced ductile behaviour resulting from the plasticisation of the compression zone. However, in many cases, ultimate failure was governed by the fracturing of the LVL in the tension zone. Consequently, the variation in ductility gain between the series was substantial, ranging from a minimum of 8% to a maximum of 37%. In summary, utilizing conventional, widely available, and relatively inexpensive steel reinforcement – as an alternative to composite bars – can significantly enhance the structural characteristics of veneer-based beams.