Evaluation of Column Slenderness and Buckling Risk in High-Rise Buildings Under Construction in Lagos Island

The proliferation of high-rise construction on Lagos Island in the South West geopolitical zone has intensified scrutiny of column design practices, particularly regarding slenderness ratios and the risk of buckling failure during both the construction and service phases. This study evaluates column slenderness and buckling risk in ten multi-storey buildings under construction on Lagos Island, assessing compliance with Eurocode 2 slenderness limits and identifying conditions under which instability may develop before structural completion. Column dimensions, unsupported heights, and reinforcement details were obtained from construction drawings and field measurements at each site. Slenderness ratios were calculated for all column locations in each building, and effective length factors were assigned based on the restraint conditions provided by beams and slabs at each floor level. Buckling load estimates were derived using the Euler critical load formula and compared against applied construction loads at the time of assessment. Findings indicate that twenty-two percent of all assessed columns exceeded the limiting slenderness ratio of 140 specified in Eurocode 2 for braced frames, with the exceedances concentrated in open-plan podium levels where column spacing is large. In three buildings, construction loads applied through temporary works were found to approach fifty percent of the theoretical buckling load under temporary out-of-plumb conditions. The study recommends stricter enforcement of temporary propping requirements during slab curing, mandatory construction stage structural checks, and enhanced Lagos State Building Control Agency oversight at critical construction milestones. Keywords: column slenderness, buckling, high-rise construction, Lagos Island, Eurocode 2.