CHARACTERIZATION AND IMPACT RESISTANCE OF SOLID AND GLULAM EKKI TIMBER FOR USE AS RAILWAY SLEEPERS
Keywords:
Ekki timber; Lophira alata; glued laminated timber; railway sleepers; impact resistance; EN 338; EN 408; drop-weight test; structural reliability; Nigeria; West AfricaAbstract
This study presents a comprehensive characterization and impact resistance evaluation of Nigerian-grown Ekki (Lophira alata) timber in both solid and glue-laminated (glulam) forms for application as railway sleepers. Mechanical property testing was conducted in accordance with EN 408:2012 to determine density, compressive strength (parallel and perpendicular to grain), tensile strength (parallel and perpendicular to grain), bending strength (modulus of rupture, MOR), modulus of elasticity (MOE), and shear strength. Characteristic values were derived in accordance with EN 384:2016 and compared against EN 338:2016 strength class thresholds. Two glulam configurations were fabricated using a structural epoxy adhesive compliant with EN 301:2017 (Type I) and ASTM D2559-12a, and evaluated: GLT-1 (five 15 mm laminations) and GLT-2 (two 37.5 mm laminations), both producing a 75 × 75 mm cross-section. Static performance was assessed through rail seat and central bending tests, while impact resistance was determined using the ACI 544-based drop-weight impact test. Based on the tested samples (n = 10 per property), Nigerian-grown Ekki indicates potential classification within the EN 338 D70 strength class—the highest hardwood classification—with a characteristic density of 1,138 kg/m³, characteristic bending strength of 94.32 MPa, and mean MOE of 20 GPa. Glulam sleepers demonstrated superior load-carrying capacity under rail seat loading, with GLT-2 achieving 163.4 kN versus 129.6 kN for solid Ekki. Under drop-weight impact, GLT-2 absorbed approximately 82% more energy than solid Ekki, attributed to crack-arrest mechanisms at laminate interfaces. The findings indicate that Ekki timber in solid and glulam forms is a structurally promising, high-performance material for railway sleeper applications in tropical regions; the results are preliminary and limited by sample size, and confirmation through expanded multi-source sampling is recommended.References
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