UNCERTAINTY ANALYSIS OF STRENGTH AND DUCTILITY OF CONFINED REINFORCED-CONCRETE MEMBERS

The strength and ductility of reinforced concrete beam and column cros s-sections with varying geometries and levels of confinement are inves tigated. Material properties are modelled as random variables and thei r effect on section behaviour is assessed through fibre modelling and the Response Surface Methodology. The section ductility is in many cas es found to be mainly dependent on the ultimate concrete strain. The u ncertainty involved in the estimation of the latter using various mode ls for confined concrete is examined with the aid of existing experime ntal data. Other failure criteria such as first hoop fracture and buck ling of the longitudinal bars are also considered. Monte Carlo simulat ions show that a significant amount of variability exists in both the strength and ductility of confined concrete sections due to variations in material properties. In the case of ductility, this variability is greatly enhanced if model uncertainty is taken into account, especial ly for high axial loads. Furthermore, simple expressions are derived f or the estimation of the strength parameters for any cross-section sub ject to varying material properties. Finally, the confined concrete mo del and curvature ductility provisions of Eurocode 8 are evaluated. (C ) 1998 Elsevier Science Ltd. All rights reserved.