Abstract
A model for the strength analysis of high-strength concrete (HSC) columns subjected to eccentric loading is proposed. The model is based on a stability analysis of pin-ended columns using the theoretical sinusoidal equation for the deflected shape of the column. The reduction in column stiffness as the axial load increases, representing the basic characteristic of the inelastic response of columns, is considered subject to equilibrium conditions, compatibility requirements, and constitutive relationships for the concrete and reinforcement. The tension-stiffening effect was taken into consideration. The column integrity is limited by either the material or the instability mode of failure. The method was applied to a wide range of experimental data and was compared with the Egyptian, European, and American building codes of practice. The ultimate strength predicted by the proposed model showed excellent agreement with the test results and was in good agreement with the codes of practice. The mean predicted-to-experimental ultimate load ratio was 0·94, with a coefficient of variation of 10·8%.
Highlights
The use of high-strength concrete (HSC) in reinforced concrete columns reduces the column proportions, heightening the adverse effects of the slenderness and potential instability on the column capacity
The mean value of the ultimate load ratio was 1·11 with a coefficient of variation (CoV) of 11·4% for the ECP-203 predictions compared with 0·89 and 18·8% for the ACI 318 results
The proposed model for the strength analysis of eccentrically loaded pin-ended braced HSC columns assumes that column deflection is dependent on the initial eccentricity, the level of applied load and a buckling load based on variable column stiffness
Summary
The use of high-strength concrete (HSC) in reinforced concrete columns reduces the column proportions, heightening the adverse effects of the slenderness and potential instability on the column capacity. Based on extensive investigation of the response of HSC columns, Légeron and Paultre (2003) developed a stress–strain model for confined HSC that considers the effects of concrete strength and transverse and longitudinal reinforcement parameters on the significance of confinement. ACI 318 (ACI, 2014) employs a moment magnifier factor, δ, to account for second-order effects assuming implicitly a halfwave sinusoidal shape for the deflection curve of the column Both EC2 and ACI 318 specify empirical equations for determination of the EI value, allowing for the effects of cracking, creep, and non-linearity of the stress–strain relationship of the concrete. The buckling load was assumed to be subject to the tangent flexural rigidity of the effective section at the column mid-height It is formulated by dividing the critical section into steel and concrete layers through its depth. Perfect bond between the reinforcing bars and concrete was assumed
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