Reliability-based approach to the robustness of corroded reinforced concrete structures

Currently, decisions on the maintenance and repair of infrastructural assets, structures in particular, are mostly based on the results of inspections and the resulting condition index, neglecting system robustness and therefore not making optimal use of the limited funds available. This paper presents a definition and a measure of structural robustness in the context of deteriorating structures which are compatible with asset management systems for optimal maintenance and repair planning. The proposed index is used to define the robustness of existing reinforced concrete (RC) structures to rebar corrosion. Structural performance and the corresponding reliability index are assessed using combined advanced reliability and structural analysis techniques. Structural analysis explicitly includes deterioration mechanisms resulting from corrosion, such as reinforcement area reduction, concrete cracking, and bond deterioration. The first-order reliability method, combined with a response surface algorithm, is used to compute the reliability index for a wide range of different corrosion levels, resulting in a fragility curve. Finally, structural robustness is computed and discussed based on the results obtained. A robustness comparison of different structures can then be used to determine structural types more tolerant to corrosion and these results used for planning maintenance and repairs

Comportamiento mecánico y corrosión marina de diversas aleaciones férricas utilizadas en buques y en sus componentes

Programa Oficial de Doutoramento en Enxeñaría Marítima. 550V01[Resumo] A corrosión é un problema que afecta diferentes partes do barco, tanto as expostas aos elementos como o interior do buque. Un factor importante no cumprimento de prazos é motor, pero tamén que a súa fabricación garanta a fiabilidade. Para determinar a adecuación do material do motor, as distintas partes son examinadas por medio dun análise químico, e unha análise de espectografía e unha proba de tracción. Os procesos que causan corrosión foron estudados no Cuarto capítulo como estudio previo aos seguintes capítulos. Revisáronse os posibles elementos implicados na súa aparición e a nomenclatura diferente dependendo da mesma, e os seus efectos. Posteriormente a corrosión interna tras tanques dun buque é estudada por ultrasóns examinando materiais tanques de auga e tanques de lastre, examinando as diferenzas en canto ao fin ao que está dedicado cada tanque. Finalmente, estúdianse dous casos de corrosión, un en cuberta e outro no casco do buque. Realízase un estudo dos resultados tras a medición de ultrasóns do grosor da folla e reflicte na súa función da localización dos efectos de fallo. A inspección realizouse tanto na obra morta do buque como na obra viva.[Resumen] La corrosión es un problema que afecta a diferentes partes del buque, tanto para las expuestas a la intemperie como las interiores del buque. Un factor importante a la hora de cumplir plazos establecidos es el motor, pero también su fabricación que asegura la fiabilidad del mismo. Para determinar la idoneidad del material del motor, las diferentes piezas se han examinado a través de un análisis químico, espectográfico y de un ensayo de tracción. Los procesos que provocan la corrosión han sido estudiados en el capítulo Cuarto como estudio previo a los siguientes capítulos. Se han revisado los posibles elementos implicados en su comienzo y la diferente nomenclatura dependiendo de los mismos, así como, sus efectos. Posteriormente se estudia la corrosión interna de los tanques de un buque, examinando por medio de ultrasonidos los materiales de los tanques de agua y los tanques de lastre, examinando las diferencias según el fin al que está dedicado cada tanque. Finalmente se estudian dos casos de corrosión en cubierta y en el casco del buque. Se realiza un estudio de los resultados obtenidos tras la medición del espesor mediante ultrasonidos de la chapa y se reflexiona sobre sus efectos dependiendo de la localización del fallo. La inspección se realiza tanto la obra muerta del buque como en la obra viva.[Abstract] The corrosion is a problem that it affects to different parts of the ship, so much for exhibited outdoors like the interiors of the ship. An important factor at the time of fulfilling established period is the engine, but also its manufacture that assures the reliability of the same one. To determine the suitability of the material of the engine, the different pieces have been examined across a chemical analysis, spectrographic test and of a tensile test. The processes, that cause the corrosion, have been studied in the chapter Fourth as previous study of the following chapters. There have been checked the possible elements involved in its beginning and the different nomenclature depending on the same ones, as well as, its effects. Later, it is studied the internal corrosion of the tanks of a ship, examining by means of ultrasounds the materials of the water tanks and the ballast tanks, examining the differences as the end to which every tank is dedicated. Finally, two cases of corrosion are studied in the deck and in the hull of the ship. A study of the results obtained after the measurements of the thickness was realized by means of ultrasounds of the sheet and one reflects on its effects depending on the location of the mistake. The inspection was realized in the parts which was or not submerged

Parameterized Seismic Reliability Assessment and Life-Cycle Analysis of Aging Highway Bridges

The highway bridge infrastructure system within the United States is rapidly deteriorating and a significant percentage of these bridges are approaching the end of their useful service life. Deterioration mechanisms affect the load resisting capacity of critical structural components and render aging highway bridges more vulnerable to earthquakes compared to pristine structures. While past literature has traditionally neglected the simultaneous consideration of seismic and aging threats to highway bridges, a joint fragility assessment framework is needed to evaluate the impact of deterioration mechanisms on bridge vulnerability during earthquakes. This research aims to offer an efficient methodology for accurate estimation of the seismic fragility of aging highway bridges. In addition to aging, which is a predominant threat that affects lifetime seismic reliability, other stressors such as repeated seismic events or simultaneous presence of truck traffic are also incorporated in the seismic fragility analysis. The impact of deterioration mechanisms on bridge component responses are assessed for a range of exposure conditions following the nonlinear dynamic analysis of three-dimensional high-fidelity finite element aging bridge models. Subsequently, time-dependent fragility curves are developed at the bridge component and system level to assess the probability of structural damage given the earthquake intensity. In addition to highlighting the importance of accounting for deterioration mechanisms, these time-evolving fragility curves are used within an improved seismic loss estimation methodology to aid in efficient channeling of monetary resources for structural retrofit or seismic upgrade. Further, statistical learning methods are employed to derive flexible parameterized fragility models conditioned on earthquake hazard intensity, bridge design parameters, and deterioration affected structural parameters to provide significant improvements over traditional fragility models and aid in efficient estimation of aging bridge vulnerabilities. In order to facilitate bridge management decision making, a methodology is presented to demonstrate the applicability of the proposed multi-dimensional fragility models to estimate the in-situ aging bridge reliabilities with field-measurement data across a transportation network. Finally, this research proposes frameworks to offer guidance to risk analysts regarding the importance of accounting for supplementary threats stemming from multiple seismic shocks along the service life of the bridge structures and the presence of truck traffic atop the bridge deck during earthquake events

Probabilistic modelling of structural degradation (editorial)

This special issue was initiated by the Editor, Carlos Guedes Soares in response to the growing awareness that the deterioration and corrosion of materials used in ageing physical infrastructure is matter of increasing concern to assets owners and managers both in private enterprise and in the public domain. Safety to users and to the public, disruption of service and overall economic costs are among the main reasons for concern. Sensible management able to meet both regulatory requirements and economic imperatives increasingly requires application of rational economic evaluations, including risk assessments. A key issue is the expected degradation of an infrastructure system both in the short and the long-term future. In a manner analogous to the discount rate for economic assessment, the rate of degradation can markedly influence economic assessments. It also has important implications for the setting of rational assets management policies, strategies and practices