Flexural Behaviour of Locally Milled Steel Reinforced Concrete Beams with Tension Lap-Splices in Normal, Medium and High Strength Concrete

Abstract

This study investigated the flexural behaviour of reinforced concrete beams reinforced with locally milled medium- to high-yield steel bars containing tension lap splices. The work examined the effects of lap length, concrete grade and bar diameter on tensile and flexural performance under four-point loading. Beam specimens were produced using concrete grades C25, C30 and C35 and reinforced with 12, 16 and 20 mm bars. Lap lengths of 10d, 15d and 20d were evaluated, together with control beams containing continuous reinforcement. The results showed that lap length was the main parameter governing splice performance. Beams with 10d lap splices exhibited marked reductions in strength and developed wider, more localised cracks, indicating premature bond failure. Increasing the splice length to 15d and 20d improved crack distribution, load-carrying capacity and ductility, although full theoretical strength was not always achieved. Higher concrete grades improved cracking resistance and enhanced bond behaviour, particularly when combined with adequate splice length. Larger bar diameters delayed crack initiation in some cases but reduced bond efficiency at ultimate load because of less favourable stress transfer conditions. Overall, the findings indicate that the flexural response of lap-spliced beams depends on the combined effects of splice length, concrete strength and reinforcement diameter.