Quantifying Redundancy and Robustness of Structures

Abstract

The paper presents the different definitions proposed for structural robustness and redundancy, as well as the different measures to quantify them, according to the proposed definition. From this review, it is emphasized that almost all proposed definitions are related to sudden damages (impacts, explosions, ...) and unforeseen events. For this reason, in the present paper a new approach to robustness is defined in terms of the ability of the structure to respond to continuous deteriorating processess as corrosion. The paper also shows how most of the proposed measures of robustness are relative, in the sense that they may help identify which structure is more or less robust than another. However, a target or threshold value that defines the border between what is robust or not, normally does not exist. Finally, an example of application of the new proposed measure of robustness to an existing reinforced concrete bridge, in advanced state of deterioration due to corrosion attack, is presented.

Admissible geometrical domains and graphic statics to evaluate constitutive elements of structural robustness

“…The bridge is used as a footbridge but has also been designed to carry busses and trams. It is a hybrid typology between an arch bridge and a bow-string bridge, with a clear span of 130 m and a total length of approximately 145 m. The bridge is composed of a ~20 m wide steel deck, UB610 × 305 × 179 steel hangers, and two ~1.4 m-diameter and 55 mm thick tubular steel arches supported by embedded connections to concrete foundation blocks which section varies from 1.77 × 1.95 to 1.77 × 2.20 m 2 .…”

A geometrical approach to evaluating constitutive elements of structural robustness

“…A series of methods are proposed in literature to characterise robustness [1,3]. Four major approaches can be identified: risk-based, probabilistic, deterministic and energetic approaches.…”

“…It consists of integrating the space below the curve that characterises the stain-stress relation of the structure up to the collapse point. The energetic approach considered here is slightly different and is adapted from the deterministic approach of Starossek and Haberland [7,1]…”

“…Most methods proposed today for assessing the robustness of structures are based on probabilistic approaches [1]. Of the few that have adopted a deterministic formulation, all provide a type of survey that is based on an in-depth analysis of the structure once it has been designed, according to specific scenarios.…”

On the robustness to corrosion in the life cycle assessment of an existing reinforced concrete bridge

“…Robustness is qualitatively defined in several codes, including the Eurocodes. However, no code presents methodologies to quantify the robustness of a particular structure, and significant discussion exists on the advantages and disadvantages of different methodologies proposed in the literature (Cavaco et al, 2013a).…”