STRUCTURAL INTEGRITY ASSESSMENT OF A DISTRESSED BUILDING IN UNWANA USING NON DESTRUCTIVE TESTING

Abstract The study investigated the structural integrity of a distressed building located at Unwana Afikpo,, Ebonyi State, Nigeria. Visual inspection was conducted and visible cracks were identified on walls and columns of the distressed building. Geotechnical investigations such as Dynamic Cone Penetration Test (DCPT) and laboratory tests were conducted on the disturbed soil samples at 0.37m and 0.90m depth to evaluate the soil properties. Also, Non Destructive Test (NDT) technique using Schmidt hammer apparatus was used to test the grade of the hardened concrete of the distressed building. The results obtained from the laboratory tests conducted for the soil samples revealed that at 0.37m depth, the plastic Limit (PL), Liquid Limit (LL) and Plasticity Index (PI) of the disturbed sample collected were 6.2%, 16.1%, 9.9% respectively and based on USCS and AASHTO soil classification, the soil was GC (clayey gravel) and A-2-4 (silty or clayey gravel) as PI > 7 and LL < 40. The result of PL, LL and PI at 0.9m depth for the disturbed soil sample was found as 34.2%, 52.2%, and 18% respectively and based on USCS and AASHTO soil classification, the soil was MH (inorganic silt) and A-7-5 (clayey soil) as PI < 30 and LL >50. DCP test result revealed that the soil was clayey soil with low bearing capacity of 53KN/m2. The soil characteristics indicated that the soil will be problematic for construction due to clayey contents and has tendency to undergo volume changes with moisture fluctuations. The NDT result gave an average compressive strength of 20N/mm2 indicating that the grade of concrete was fair for the distressed building. The Investigations showed that the strip foundation and column base at 0.37m and 0.9m depth respectively were not adequate to withstand the design loads of the building due to the clayey nature of the soil. It was recommended that the soil should be treated and foundation repairs provided to improve the life span of the building and prevent possible collapse that may lead to loss of lives and properties.