Investigating the Effect of Construction Joints on the Shear Capacity of Reinforced Concrete Walls in High-Rise Buildings

Reinforced concrete walls in high-rise buildings serve as primary lateral load resisting elements, and the shear capacity across horizontal construction joints is a critical parameter governing overall wall performance under wind and seismic loading. Despite the ubiquity of construction joints in cast-in-place reinforced concrete walls, their effect on shear capacity is frequently neglected in design practice in Nigeria. This study investigates the shear capacity of reinforced concrete wall panels with horizontal construction joints of varying surface preparation quality and reinforcement crossing details, using experimental and analytical approaches relevant to high-rise construction in Port Harcourt and Lagos in the South South and South West geopolitical zones. Fourteen wall specimen pairs were constructed with construction joints prepared by wire brushing, sandblasting, and roughened surface treatments, and with vertical crossing reinforcement ratios of 0.25, 0.5, and 0.75 percent. Specimens were tested under diagonal compression and direct shear loading protocols. Shear stress at peak load, pre-peak stiffness, post-peak ductility, and failure mode were recorded. Results indicate that sandblasted joints with 0.5 percent crossing reinforcement achieved 87 percent of the equivalent monolithic wall shear capacity, while wire-brushed joints with the same reinforcement reached only 71 percent. Roughened surface treatment produced results intermediate between the two mechanical preparation methods. Failure in all jointed specimens was governed by shear-friction along the joint plane rather than diagonal tension in the panel body. An empirically modified shear-friction model is proposed that provides improved capacity predictions compared to ACI 318 for joint conditions representative of Nigerian construction practice. Keywords: construction joints, shear capacity, reinforced concrete walls, shear-friction, high-rise buildings.