WG1 – Performance indicators

Life-cycle analyses methods are used for the assessment of new and existing bridges, as well as for the evaluation of maintenance strategies. Management systems, capturing different degradation processes, are very often used in relation to such life-cycle analyses methods. Such systems, developed for a structural condition assessment, are usually based on deterministic performance prediction models which describe the future condition by a functional correlation between structural condition attributes, such as the structural age, and the mechanical, chemical and thermal loading processes.

The practical implementation of such models requires detailed information about its variables, but due to the non-consideration of uncertainties in input variables (scattering values), it does not allow any statement about the quality of the prediction. However, probabilistic performance prediction models, which can be considered as a relevant goal, presume the incorporation of uncertainties in the descriptive variables by probability distribution functions and support conclusions about the quality of the performance prediction.

Deterioration could lead to a decrease of performance to such an extent that a structure could not be able to satisfy the basic serviceability and safety requirements before the design life has expired. In order to prevent the premature failure of a construction, structural codes provide several practical principles and application rules such as the use of protective systems for material exposed in aggressive environment, the construction detailing aimed at avoiding the initiation of degradation, the maintenance actions to be regularly performed, etc.

Each construction, during its life cycle, will face with deterioration depending on several factors such as the environmental condition, the natural aging, the quality of the material, the execution of works and the planned maintenance. Therefore, several design procedures based on the prediction of the deterioration that will likely act on the structure will be developed in the framework of the international research. In addition, performance indicators for the present and future structural conditions on deterministic and probabilistic level will be defined and determined.

It is known that management systems are supported in QC plans which in turn are supported by performance indicators. Therefore, it is extremely important to analyse such indicators in terms of used assessment frameworks (e.g. what kind of equipment and software is being used), and in terms of the quantification procedure itself. In this particular work package, the objectives will be the definition of:

Technical indicators: the goal in the first step is to explore those performance indicators of bridge structures, in the course of international research cooperation, which capture the mechanical and technical properties and its degradation behaviour. These properties are already partly covered by norm specifications but not their complex time variable performance. Moreover, environmental condition, natural aging, and the quality of the material regarding to determined indicators will be investigated and evaluated in their meaningfulness. These considerations, however, also include service life design methods, aimed at estimating the period of time during which a structure or any component is able to achieve the performance requirements defined at the design stage with an adequate degree of reliability. On the basis of the quality of input information (mainly concerning with the available degradation models), as sketched in the above description, it is possible to distinguish among deterministic methods, usually based on building science principles, expert judgment and past experience, which provide a simple estimation of the service life, and probabilistic methods;

Sustainable indicators: in addition to technical performance indicators, which characterize the ultimate capacity as well as serviceability conditions, sustainability indicators, environmental based, will be also formulated. These variables characterize the environmental impact of a structure in the course of its total life cycle, expressed in terms of total energy consumption, carbon footprint (CO2 emission), balance of raw materials, etc. These indicators can be separated into direct and indirect indicators, where the former are related to the construction/maintenance itself and the latter are caused e.g. as a consequence of limited functionality;

Other indicators: other sustainable indicators, economic and social based, may be used to evaluate a bridge performance. These indicators capture, based on the technical performance of a structure, additional aspects that may influence the decision process and typically represent the discounted (accumulated) direct or indirect costs associated with construction and maintenance. Summed up over the full life-time, they represent part of or the full life-cycle costs. They can, in the context of multi-objective optimization, be understood as a weighting scheme to arrive to a single objective function that is to be minimized.

The milestone for this task is the publication of a report on these performance indicators until the end of year 1. Such report will address a general description of these indicators, how they are assessed (e.g. visual inspection, non-destructive tests and monitoring systems), with what frequency, what values are generally obtained and, finally, some general recommendations. This outcome will be one of the main inputs of WG5, being also used by WG3. The main achievements will be published in refereed scientific journal papers and in international conferences. A summary of obtained results will be also available at both website and web 2.0 (e.g. facebook). A joint workshop on this field will be organized at the end of this task.

Glossary

TERMDESCRIPTIONSOURCE
Acoustic emission non-destructive passive method of monitoring which makes use of the elastic energy released when a material undergoes a change at the atomic scale, such as plastic deformation or cracking. Piezoelectric sensors attached to the surface of the structure detect the surface waves caused by these events and produce a voltage output. Signals which reach any sensor with amplitude greater than a user defined threshold are recorded and subsequently stored on an AE acquisition system.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
AcceptanceAgreement of the stakeholders (i .e. owners, users, contractors, society) to take over the structure or a part of it as its own property.Definitions Model Code 2010
Adverse stateState in which a performance criterion is not met.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Asset management broadly defined, refers to any system that monitors and maintains things of value to an entity or group. It may apply to both tangible assets such as buildings and to intangible concepts such as intellectual property and goodwill. Asset management is a systematic process of operating, maintaining, upgrading, and disposing of assets cost-effectively. Alternative views of asset management in the engineering environment are: The practice of managing assets to achieve the greatest return (particularly useful for productive assets such as plant and equipment), and the process of monitoring and maintaining facilities systems, with the objective of providing the best possible service to users (appropriate for public infrastructure assets).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
AvailabilityThe probability that a component or system is functioning at a time t.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Bayesian decision theoryis based upon Utility theory and is formulated in reference. It represents a probabilistic framework to quantify the utility and decision attributes (such as costs, benefits, consequences for human safety). It is differentiated between a prior, posterior, pre-posterior and a Value of information analysis.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Bayesian updatingtakes basis in the Bayes theorem.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
BenefitA benefit constitutes a decision attribute associated with a gain.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Capacityability of a member or a component, or a cross-section of a structure to action without mechanical failure e.g. bending resistance, buckling resistance, available ductility.. (IRIS-CEN modified).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Condition assessmentthe process of reviewing information gathered about the current condition of structure or its components, its service environment and general circumstances, allowing a prognosis to be made of current and future performance, taking account of active deterioration processes and actual damage and, if appropriate, predictions of potential future deterioration processes and future damage.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Condition monitoringdamage identification in rotating and reciprocating machinery.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Control measurementMeasurement to monitor selected physical quantities (e.g. geometrical characteristics or structural deformations)Definitions Model Code 2010
Damagephysical disruption or changes to the material and/or geometric properties of these a systems, including changes to the boundary conditions and system connectivity, which adversely affect the system’s performance.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Damage assessmentProcess of ascertaining the severity of the damage to a structure.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Damage detectionProcess of ascertaining whether the damage to structure exists or not.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Damage featurequantifiable property or pattern sensitive to damage. It can be either directly monitored (e.g., strain) or extracted from monitoring data (e.g., modal characteristics from accelerometer measurements).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Damage feature extractionExtracting a quantifiable property or pattern sensitive to damage from monitoring data (e.g., modal characteristics from accelerometer measurements) (based on definition of damage feature in).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Damage identification In addition to damage detection, localization and assessment, damage identification includes ascertaining the cause of the damage and its consequences.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Damage localizationProcess of ascertaining where the damage to structure is located.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Damage prognosisprediction of remaining useful life of a damaged system.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Data cleansingThe process of identifying and correcting corrupted or erroneous measurements from a data set. Typical examples of refers to identifying incomplete records (missing data), incorrect values (outliers), or inaccurate values due to temporary malfunctioning of the monitoring system or its components (sensors, communication lines, etc.). The corrupted data is mostly removed, and sometime modified or replaced using some pre-defined algorithms. (IRIS)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Data-driven approachdata interpretation approach performed utilizing computer algorithms to calculate or recognize damage features from measurement datasets. They do not need building a physical model of the structure.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Decision analysis and theorySee Bayesian decision analysis.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Decision options/alternativesDecision options or alternatives represent decision scenarios for which the utility and/or decision attributes are quantified. In the context of the quantifying the value of Structural Health Monitoring (SHM) decision alternatives may constitute different SHM strategies encompassing e.g. technology, locations and algorithms.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Decision treeA decision support tool that uses a tree-like graph or model of decisions and their possible consequences, including probabilities and costs or utilities. COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
DefectA specific deficiency or inadequacy in the structure or its components which affects their ability to perform according to their intended function at the required level , either now or at some future timeDefinitions Model Code 2010
DeficiencyImperfection , possibly arising as a result of an error in design or construction, which affects the ability of the structure to perform according to its intended function, either
now or in the future
Definitions Model Code 2010
DegradationWorsening of condition with time (see also Deterioration).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Demandrequest (resistance, ductility,…) coming from all the actions applied to the structure. COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
DeteriorationProcess that adversely affects the structural performance, including the reliability over time. Deterioration of structural performance can be caused by various reasons, such as: naturally occurring chemical, physical and biological actions; repeated actions such as those causing fatigue; normal or severe environmental influences; wear due to use; improper operation and maintenance of the structure.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Direct risk The risk associated with consequences directly related to the structure, engineering system or its immediate users, such as physical damages in a structure, or injuries and fatalities caused by structural failures).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
DismantlementDemolition of a structure with separation of the structural members and structural materials, fulfilling disposal requirements .Definitions Model Code 2010
DurabilityThe capability of structures, products or materials to fulfil the requirements defined, determined after a specified period of time and usageDefinitions Model Code 2010
EconomyModerate use of financial means and natural resources in relation to the whole period of design, execution and serviceDefinitions Model Code 2010
Failurestate in which the performance requirements are not satisfied. NOTE: (1) Failure is associated with the specific performance goal and the associated performance requirements (2) Failure is not synonymous with collapse.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Failure modeFailure modes are quasi-permanent or transient situations that violate code specifications or owner’s/ operator’s provisions. This includes but is not limited to overall bridge collapse. Some of these situations, e.g. Ultimate Limit State and Serviceability Limit State, are specified in bridge design. Due to slow (deterioration) and sudden (e.g. natural hazard) processes, damages may occur that result in additional failure modes. Finally, owners/operators may define situations (e.g. spalling, corrosion traces, etc.) that are regarded as failure modes since they might comprise public perception of safety.Definitions COST Action TU 1406 WG 3 Report
Fault detectionFault detection, isolation, and recovery (FDIR) is a subfield of control engineering which concerns itself with monitoring a system, identifying when a fault has occurred, and pinpointing the type of fault and its location. Two approaches can be distinguished: A direct pattern recognition of sensor readings that indicate a fault and an analysis of the discrepancy between the sensor readings and expected values, derived from some model. In the latter case, it is typical that a fault is said to be detected if the discrepancy or residual goes above a certain threshold. It is then the task of fault isolation to categorize the type of fault and its location in the machinery. Fault detection and isolation (FDI) techniques can be broadly classified into two categories. These include Model-based FDI and Signal processing based FDI (Wikipedia).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Indirect riskThe risk associated with consequences that follow from a failure event, but are not direct consequences. These are consequences associated with loss of system functionalities. (JCSS 2008). These include business interruptions due to failures in transportation or energy networks.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Information In the context of a Value of Information analysis, information represent any model parameter gained by means of an experiment but also by analytical, numerical or empirical methods related to the decision scenarios. Information (Sample): Knowledge that describes a realization of the value or state of a random property. Information (Perfect): Knowledge that describes the true value/state of a deterministic property.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
InspectionOn-site, non-destructive examination to establish the present conditions of the structure. A visible inspection performed on regular base is called the routine inspection and a more detailed inspection usually performed as a follow-up to a routine inspection to identify any deficiencies discovered is called the in-depth inspection. COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Key performance indicators (KPIs)Generally, there is no clear distinction between PIs and KPIs. In this project, the KPIs relate to a whole bridge and are as follows: • Reliability is the probability that a bridge will be fit for purpose during its service life. It is the complement to the probability of structural failure (safety), operational failure (serviceability) or any other failure mode. • Availability is the proportion of time a bridge is open for service. It does not include failure-related service outages but the ones due to planned maintenance interventions. Alternatively, the Availability can be measured as additional travel time due to an imposed traffic regime on bridge. • Safety is the situation of life and limb being protected from harm during the service life of a bridge. Loss of life and limb due to structural failure is not included by this definition (since it would overlap with the Reliability). • Economy is related to minimizing the long-term cost of maintenance activities over the service life of a bridge. Herein the user costs incurred due to detours and delays are not included. • Environment is related to minimizing the harm to environment during the service life of a bridge.Definitions COST Action TU 1406 WG 3 Report
Lifecycle cost (LCC) Cost of an asset or its parts throughout its lifecycle, while fulfilling its performance requirements.Definitions COST Action TU 1406 WG 1 Report
Life-cycle (action)Long-term action that extends over entire lifespan of the structure, from the construction until the decommissioning or dismantling. (IRIS modified)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
LikelihoodA general concept that expresses qualitatively (e.g. high, medium, and low) or quantitatively (e.g. frequency or probability) the chance that an event may occur in a specific time period (IRIS).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Limit stateState beyond which the structure no longer satisfies the relevant performance criteriaDefinitions Model Code 2010
MaintainabilityThe ability of a structure to meet service objectives with a minimum expenditure of maintenance effort under service conditions in which maintenance and repair are performed.Definitions Model Code 2010
MaintenanceTechnical intervention during the service life of a structure aimed to preserve its required performance. (IRIS modified)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Model-driven approachdata interpretation approach performed comparing the responses of a structure with those of a predicted model (analytical model or finite element model) based on physical and mechanical characteristics of a structure.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Monitoring systemThe set of all the means destined to carry out measurements or observations and to register them is called a monitoring system. Monitoring system has two subsystems: measurement and observation subsystem and data management subsystem. The measurement and observation subsystem consists of sensors, observation tools, and the data acquisition system – data acquisition hardware (including reading units, accessories, and channel switch) and data acquisition software. The data management subsystem consists of data management hardware and data management software. Various monitoring systems can be used for structural health monitoring, operational monitoring, and security monitoring, but they all have, in general, the above mentioned subsystems. Nowadays, there is a large number of monitoring systems, based on different functioning principles, and which system will be used in a specific application depends on specifications of the monitoring system such as resolution, measurement error, maximal measurement rate, data management software, etc.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Non-destructive testingoff-line local method after damage detection.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
ObservationIt is a datum (i.e. piece of information) from a primary source, which may be acquired by human senses or by measuring/recording of some properties via adequate instruments. Observations can be qualitative i.e. only the absence or presence of a property is noted, or quantitative if a numerical value is coupled to the observed phenomenon by counting or measuring. The observation is a perception of human senses or data measured by instrument that is regarded as relevant within the context of the inquiryDefinitions COST Action TU 1406 WG 3 Report
OntologyA set of concepts and categories in a subject area or domain that shows their properties and the relations between them. In this report, the Entity Relationship Diagram is used to describe the ontology of the Quality control framework.Definitions COST Action TU 1406 WG 3 Report
Performancebehaviour a structure must exhibit under various acting forces, to achieve human safety, construction functions, and user comfort.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Performance assessmentA set of activities performed to verify the reliability of an existing structure for future use.Definitions COST Action TU 1406 WG 1 Report
Performance criteria Quantitative limits, defining the border between desired and adverse behaviour (i.e. failurecriteria). NOTE: In context of Limit State Approach, performance criteria are the threshold values that describe for each limit state the conditions to be fulfilled.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Performance evaluationProcess of determining measurable results.Definitions COST Action TU 1406 WG 1 Report
Performance goalType of structure property (behaviour) that is required based on assessment of different performance indicators.Definitions COST Action TU 1406 WG 1 Report
Performance indexAn assessed parameter of the bridge, dimensionless number or letter on a scale that evaluates the parameter involved on an X to XN scale, X being a very good condition and XN a very poor one.Definitions COST Action TU 1406 WG 1 Report
Performance indicator a metric measured or computed to provide evidence of a system's performance.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Performance levelQualification of a structure or a structural element, which is established by verifying its behaviour against the performance requirements. A satisfactory performance level is reached when a structure or a structural element has demonstrated a sufficient behaviour to meet the performance requirements. In the opposite case, the performance level of a structure or a structural element is considered to be unsatisfactory.Definitions Model Code 2010
Performance levelQualification of a structure or a structural element, which is established by verifying its behaviour against the performance requirements. A satisfactory performance level is reached when a structure or a structural element has demonstrated a sufficient behaviour to meet the performance requirements. In the opposite case, the performance level of a structure or a structural element is considered to be unsatisfactory.Definitions COST Action TU 1406 WG 1 Report
Performance modellingProcess of simulating various system loads against varying system configurations by using a mathematical model.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Performance requirement A condition used to describe a required service quality with regard to specific performance goal, established by means of performance indicator(s) and associated performance criteria with constrains, related to service life and reliability.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Performance thresholdA value that constitutes a boundary for purposes such as: a) monitoring (e.g. an effect is observed or not), b) assessing (e.g. an effect is low or high), and c) decision-making (e.g. an effect is critical or not).Definitions COST Action TU 1406 WG 1 Report
Posterior decision analysisA decision analysis with additional information. COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Pre-posterior decision analysisA decision analysis with unknown information.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Prior decision analysisA decision analysis with known information.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Probabilistic deterioration model A predictive model of deterioration, which considers prediction uncertainty by modelling parameters and/or deterioration states as random variables or random processes.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Probabilistic risk analysisA formal approach to computing the risk of a system, based on probability theory.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Probabilistic risk assessmentA probabilistic risk analysis followed by an appraisal of the risk.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Quality control planThe quality control plan specifies all activities and tools, needed to ensure quality requirements related to bridge performance aspects (e.g. safety, serviceability, etc.). It defines the extent and the interval of inspections or investigations and data necessary to estimate key performance indicators and forecast their future development. Quality control plan also includes decision model that suggest maintenance action based on the forecast of key performance indicators. In this sense the quality control plan overlaps with the Strategic Asset Management Plan (SAMP) as defined in ISO 55000.Definitions COST Action TU 1406 WG 3 Report
Reliability The probability that a component or system has not failed (until time t).COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
RepairTechnical intervention on a damaged or degraded structure aimed to restore its required performance. (IRIS modified)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Resilienceis the ability of a structure to resist, absorb, accommodate to and recover from the effects of a hazard in a timely and efficient manner, including through the preservation and restoration of its essential basic structures and functions. (UNISDR modified)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
RiskThe possibility of a loss. In a probabilistic setting, it is defined as the expected value of adverse consequences. In its simplest form, this reduces to the probability of a failure event multiplied with the consequence of the failure event. COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Risk analysis A formal approach to computing the risk of a system.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Risk-based inspectionsA systematic approach to plan and perform inspections, in which inspections are prioritized according to their effect on the system risk. The RBI approach aims at optimizing the sum of cost (of inspection and maintenance) and risk (due to non-treated damages). COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Robustnessratio between the direct risks and the total risks, (total risks is equal to the sum of direct and indirect risks), for a specified time frame and considering all relevant exposure events and all relevant damage states for the constituents of the system.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
SafetyThe condition of a structure being protected against failure, damage, design errors, accidents, or harms, in both causing and exposure.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Service lifeThe period for which the required performance of a structure or structural element is achieved, when it is used for its intended purpose and under the expected conditions of use.Definitions Model Code 2010
ServiceabilityAbility of a structure or structural element to perform adequately for normal use under all (combinations of) actions expected during the service life.Definitions Model Code 2010
Serviceability limit stateCondition in which a structure or component becomes unfit for service and is judged to be no longer useful for its intended function under normal usage.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Standardizationprocess of implementing and developing technical standards (Wikipedia)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Strain gaugesdevice used to measure strains. Jargon synonym for “electrical resistance strain gauge”. (IRIS modified)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
StrengtheningTechnical intervention on a structure aimed to improve its performance. (IRIS modified)COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Structural Health Monitoring(SHM) the process of identifying the presence and quantifying the extent of damage in a system based on information extracted from the measured system response.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Structural integrityThe ability of structural components to act together as a competent single entity.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
SustainabilityAbility of a structure or structural element to contribute positively to the fulfilment of the present needs of humankind with respect to nature, society, economy and wellbeing, without compromising the ability of future generations to meet their needs in a similar manner.Definitions Model Code 2010
System identificationprocess of building mathematical models of dynamic systems and of estimating physical parameters from observed data.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
TaxonomyA classification – in this case different bridge types and main girder cross-sections are classified according to construction material, static system and geometryDefinitions COST Action TU 1406 WG 3 Report
Thresholdboundary defined to compare different statesCOST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Ultimate limit stateCondition in which a structure or component becomes unfit for service and is judged to have reached its ultimate capacity.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Ultrasonic technology non-destructive inspection method based on the Lamb waves, ultrasonic elastic waves that propagate along the surface of plates and can be generated and acquired using piezoelectric transducers. The ultrasonic interact with obstacles/flaws/borders in the structure and reflect back to the transducer. The comparison between the initial and reflected signal gives information about the obstacles/flaws/borders COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
UncertaintyAn uncertainty constitutes any imprecision of a model parameter. Uncertainties can be classified by their origin in the following types, namely (1) model uncertainty, (2) statistical uncertainty, (3) measurement uncertainty or error, (4) human and organization error. Uncertainties can be categorized in epistemic uncertainties due to a lack of knowledge and in aleatoric uncertainties due to randomness. Epistemic uncertainties maybe reduced by means of knowledge gain. Aleatory uncertainties constitute the inherent randomness of e.g. a process which cannot by be reduced.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Usage monitoringthe process of acquiring operational loading data from a structure or system, which preferably includes a measure of environmental conditions (e.g. temperature and moisture) and operational variables.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
UtilityA numerical (most often monetary) measure that corresponds with a certain procedure/decision that has been followed.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Value of InformationA pre-posterior decision analysis quantifying a utility or decision attribute increase as the difference between a prior or posterior decision analysis and a pre-posterior analysis.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Vulnerabilityratio between the risks due to direct consequences and the total value of the considered asset or portfolio of assets considering all relevant exposures and a specified time frame.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary
Vulnerable zonesThese are the segments and or elements of a bridge structure in which damages have the largest impact on safety and serviceability. One vulnerable zone may be related to several failure modes.Definitions COST Action TU 1406 WG 3 Report
X-ray technology non-destructive inspection method based on the use of X-rays to detect variations of density in the material which is a function of the amount of radiation that passes through.COST Action TU 1402 https://www.cost-tu1402.eu/resources-downloads/glossary