Behavior of Eccentrically Loaded Slender High-Strength Concrete Columns.(Dept.C)

Abstract

The buckling behavior of slender High-Strength Concrete (HSC) columns under axial load with different end eccentricities has been studied experimentally. The results of these tests have been used to examine the applicability of the design requirements of Normal Strength Concrete (NSC) columns of the Eurocode 2 (EC-2), the Egyptian code (ECC-9S) and ACI 318-99 building code, when applied to slender HSC columns with a characteristic compressive strength of 85 MPa. The program included tests of22 columns with slenderness ratios λ1 ranged between 17.3 and 69.3. The main parameters examined in this study were the values of end eccentricity of the applied axial load (e/t=O.3, 0045 and 0.90), the transverse reinforcement ratio (p v) and the longitudinal reinforcement ratio (Pt ). The results of this experimental work showed that, slender columns constructed with HSC increased the ultimate load of the tested columns in comparison with the same columns constructed with NSC. The Model Column method. used by EC·2 and also the Moment Magnifier method used by ACl 318-99 building code for the design of HSC slender columns showed to be conservative for r design of HSC slender columns. The slenderness ratio limit between short and long columns required by the ECC-95 need to be modified when applied for HSC columns. Based on the results or these tests. the second order effect should be taken into account for HSC columns when λ1> 40 (λb> 12 ).