Uncertainties in resistance models for sound and corrosion-damaged RC structures according to EN 1992-1-1

Abstract

Resistance of civil engineering structures is primarily dependent on material properties, geometry and uncertainties related to an applied model. While materials and geometry can be relatively well described, the resistance model uncertainty is not yet well understood. The present paper improves the general concept for the model uncertainty from the Probabilistic model code of the Joint Committee on Structural Safety. Influences affecting results obtained by tests and models and effects of actual structural conditions are overviewed. Statistical characteristics of the uncertainties in resistance of reinforced concrete members are then provided considering simple engineering formulas based on EN 1992-1-1 models and effects of deterioration. To facilitate practical applications the partial factors for the model uncertainties are derived using a semi-probabilistic approach. It appears that the model uncertainties are substantial for shear resistances while they are less significant for the well-established models used for bending resistance and axial compression without buckling. Uncertainty in test procedures seems to be less important in common cases. The effect of the resistance uncertainties on structural reliability seems to be more significant for corrosion-damaged structures than for sound structures. Consequently the quantification of the model uncertainties is a key issue when assessing corrosion-damaged reinforced concrete structures. Further research should be focused on model uncertainties related to the models for shear and corrosion-damaged structures considering the fib Model Code 2010.

Uncertainty in Crack width Estimates According to Fib Model Code 2010

“…The recent study [6] shows that crack widths can by well predicted by FEM. However, uncertainty in maximum crack width estimates seems to be in all cases much larger than that related to the models for Ultimate Limit State verifications [7].…”

Uncertainty in resistance models for historic cast-iron columns

“…The concept of the model uncertainty proposed in [5][6][7] is adopted here. The uncertainties in resistance models are obtained from comparisons of physical tests and model results; real structure-specific conditions need then to be taken into account when they significantly deviate from test conditions.…”

“…Treatment of the test uncertainty was proposed in [6]. It was shown that unbiased test results with coefficient of variation around 0.05 can be assumed for tests of common reinforced concrete members.…”

Requisitos de seguridad estructural basados en los riesgos para las personas

“…También se debe tener en cuenta la influencia de las condiciones de contorno del ensayo. De esta manera, la ratio establecido según la ecuación (6.60) se puede considerar como siendo de carácter intrínseco al modelo, aplicado a la probeta i. Eso a pesar de que en realidad existen incertidumbres adicionales, relacionadas con la determinación tanto de las variables básicas como del valor r e,i [Sykora 2014]. …”

“…Por ejemplo, el código modelo probabilista contiene modelos para estos coeficientes, asociados con los principales mecanismos de resistencia y materiales constitutivos de los elementos estructurales [JCSS 2001]. La reciente publicación [Sykora 2014], por otro lado, contiene información detallada sobre las incertidumbres asociadas con los modelos de resistencia para las estructuras de hormigón armado según el Eurocódigo [EN 1992[EN -1-1 2004. Este tipo de información, disponible en la literatura, se utiliza como base para la identificación de los modelos probabilistas para las variables de los modelos que intervienen en las funciones de estado límite establecidas en el Apartado 5.4.…”