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(Structural) performance indicator (PIs)A measurable and/or testable parameter (i.e. characteristic of materials and structures) that quantitatively describes property of the structure and/or of the aspect of its performance and are used to qualify fitness of the structure for its purpose during service life.
Actiona) set of forces (loads) applied to the structure (direct action);

b) set of imposed deformations or accelerations caused, for example, by temperature changes, moisture variation, uneven settlement or earthquake (indirect action);

c) climatic loads (wind, snow, temperature) and other (physical and chemical) environmental exposures (CO2, chlorides, sulphates etc.) (environmental actions).
ComponentIndividually identifiable part of an object consisting of one or more elements, designed to provide a specific function for the object e.g. deck, installations, foundations.
ConditionLimitations, deficiencies or inadequacies (or lack thereof) which can be identified by means of condition survey and are related to ability a structure to meet specified performance requirements.
Condition assessmentA process of reviewing information gathered about the current condition of a structure, its components and/or elements, its service environment and general circumstances, allowing a prognosis to be made of future condition, taking account of active deterioration mechanisms and, if appropriate, predictions of potential future damage.
Condition controlThe overall process for safeguarding the condition of a structure during its lifetime, involving condition survey, structural performance assessment and evaluation, decision-making for life-cycle management activities and interventions, performed as a part of the through-life management
Condition SurveyThe process of acquiring information related to the current condition of a structure, conducted with the aim of recognizing important limitations, defects and deterioration relevant for the ability of a structure to meet specified performance requirements (e.g. appearance, functionality and structural performance requirements1
1 Condition survey would also seek to gain an understanding of the (previous) circumstances which have led to the development of that state, together with the associated mechanisms causing damage or deterioration
Condition thresholdA boundary defined to compare different measurable characteristic of a structural components and/or structural members, which is a measure of the probability that the component and/or structural members will not meet specific performance requirements within a specific period of time.
Condition-based maintenance (CBM)Preventive maintenance which includes a combination of condition monitoring and/or inspection and/or testing, analysis and the ensuing maintenance actions, and entails prescribed criteria related to one (or more) condition thresholds to enable decisions about interventions based on physical evidence that exceedance of the condition threshold(s) is occurring or is about to occur.
ConformityFulfilment of specified requirement
Corrective maintenanceMaintenance carried out after fault recognition and intended to put an item into a state in which it can perform a required function at a required performance level.
DamageChange in the condition of a structure, structural components or structural members that can unfavourably affect its current of future structural performance.
Damage assessmentProcess of ascertaining the severity of the damage to a structure
Damage characterizationProcess of determining the time of occurrence, the physical location, the size and other features of the damage.
Damage detectionProcess of ascertaining whether the damage to structure exists or not
Damage featureQuantifiable property or pattern, sensitive to damage. It can be either directly monitored or extracted from inspection, monitoring or testing data.
Damage indicatorA measurable and/or testable parameter that serves for quantitative or qualitative damage detection, damage localisation and/or damage characterisation.
Damage localizationProcess of ascertaining where the damage to structure is located
DataDiscrete and objective observations, facts and/or records of events with a potential to be transformation into applicable information
Data acquisitionGathering data from all of the data sources that were identified as relevant for the acquisition objectives.
Data aggregationIntegrating multiple data sets together to arrive at a unified view, reconciling differences in e.g. data structure or semantics.
Data analysisTransformation of data into applicable information, which typically involves one or more types of analytics.
Data cleansingEstablishing validation rules, identifying, removing and/or correcting and any invalid (e.g. corrupted or erroneous measurements) from a data set
Data extractionRemoving disparate data and transforming it into a format that the underlying solution can use for the purpose of the data analysis
Data filteringFiltering for the removal of corrupt data or data that has been deemed to have no value to the data analysis objectives.
Data formatPredetermined arrangement of data on a data medium
Data setNamed collection of data quantifying something that can or could be observed in reality.
Data storageUse of recording media to retain data sets.1
1 The most prevalent forms of data storage are file storage, block storage, and object storage, with each being ideal for different purposes.
DemolitionThe process of dismantling and removal of existing structures.
DependabilityAbility to perform as and when required.1,2
1 Dependability includes availability, safety, security, durability, economics and their influencing factors (reliability, maintainability, maintenance support performance, conditions of use and operators influence).
2 Dependability is used as a collective term for the time-related quality characteristics of an item.
ElementPhysically distinguishable part of an component of an object e.g. beam, slab, foundation pile1
1 Elements which are parts of structural components are referred to as structural members.
EventOccurrence or change of a particular set of circumstances.1,2
1 An event can be one or more occurrences, and can have several causes.
2 An event can be a risk source.
FunctionAn intended task of a system that is being performed.
Functional requirementPrimary requirement set for the function.
HazardPotential source of undesirable consequences.1
1 Actions on structures are source of potential harm and present hazards to structures.
InformationData collated (i.e. collected and combined) to derive meaningful conclusions according to its contextual requirements.1,2
1 Information is structured, processed and presented with assigned meaning that improves the reliability of the data acquired.
2 Knowledge is gained from contextual information, experiences, and insights that establish a framework for evaluation
Information modelDescription of the organization of information giving structure and meaning (‘semantics’) to an information set.
Information setNamed collection of information describing or specifying something can or could be pointed at in reality.
Information storageUse of recording media to retain information sets.
Infrastructure assetAny infrastructure (networks, objects and/or components thereof) with potential or actual value that is owned, operated or controlled by an organization or an economic entity.
InspectionOn-site examination within the scope of quality control and damage and/or condition assessment, aiming to assess the present condition of a structure.
InterventionA general term relating to an action or series of activities taken to preserve or modify the performance and future serviceability of a structure, its components and/or elements.1
1 Intervention options include: structural interventions such as maintenance, rehabilitation (incl. interventions for repair and interventions for upgrading), and demolition, and operational interventions such as inspection, maintenance, monitoring and change of use.
Investigation (or Survey)Procedure related to a collecting quantitative information about network, object, component or element, performed in order to determine or identify change of its status of the items in population.1,2
1 Surveying activities may involve document search, inspection, testing and/or monitoring.
2 Alternatively, investigation may be referred to as survey
Key (structural) performance indicators (kPIs)Sub-set of performance indicators that carry most significant of information about present performance of a structure and are used to qualify present fitness of the structure for its purpose.
Key performance requirements (KPRs)Requirements set for the primary function(s) of an asset that further specify the functional requirement(s), usually in terms of reliability, availability, maintainability, safety, security, health, environment, economics and politics, aiming at meeting a specified functional requirement(s during the service life at appropriate service level.
Level of riskMagnitude of a risk or a combination of risks, expressed qualitatively- or quantitatively in terms of a combination of consequences and their likelihood.
LikelihoodChance of something happening in a specific time period.
MaintenanceCombination of all technical, administrative and managerial actions performed during the service life of the structure in order to retain at or restore its performance and future serviceability at/to the level at which it can perform the required function.1,2,3,4
1 Maintenance provides an essential contribution to the dependability of the structure.
2 Maintenance is one of the intervention options.
3 Activities to restore the structure after an accidental or seismic event are normally outside the scope of maintenance.
4 Technical maintenance actions include observation and analyses of the item state (e.g. inspection, monitoring, testing, diagnosis, prognosis, etc.) and active maintenance actions (e.g. repair, refurbishment).
Meta dataDiscrete and objective observations, facts and/or records of events with a potential to be transformation into applicable information
MonitoringFrequent or continuous, normally long-term, observation or measurement of structural conditions or actions or structural response
Monitoring and reviewProcedure related to continual observing, determining the status (e.g. structural conditions or actions or structural response), checking and supervising in order to identify change from the performance level required or expected.1
1 Monitoring mat involve similar activities to inspection and testing, but with measurements being undertaken on an ongoing and possibly quasi-continuous basis.
NetworkAggregate of interconnected objects that collectively fulfil a function.
ObjectIndividually identifiable part of a network with specific functions, e.g. tunnels, locks, weirs, bridges, viaducts, sound barriers.
ObservationA datum from a primary source, which may be acquired by human senses or via adequate instruments, . that is regarded as relevant within the context of the inquiry
PerformanceEfficiency of a system; indicating how well the system works.1
1 Efficiency of a system with regard to structural behaviour is referred to as structural performance
Predetermined maintenancePreventive maintenance carried out in accordance with established intervals of time or number of units of use but without previous condition investigation, and entails a component being replaced after a certain calendar time, period of use or number of times being put into use.
Predictive maintenanceAn expansion of the condition based maintenance which includes a combination of condition monitoring and/or inspection and/or testing, analysis and the ensuing maintenance actions, and entails prescribed criteria related to one (or more) condition thresholds to enable decisions about interventions based on a forecast derived from repeated analysis or known characteristics and evaluation of the significant parameters of the degradation of the item.
Preventive maintenanceMaintenance carried out either at predetermined intervals or according to prescribed criteria, which is intended to reduce the probability of failure and/or the degradation of the functioning of an item.
ProbabilityQuantitative measure of likelihood (i.e. the chance of occurrence in a specific time period) expressed as a number between 0 and1, where 0 is impossibility and1 is absolute certain.
Qualitative risk analysisEstimation of level of risk in a descriptive manner, where probabilities and consequences of undesired events are based on subjective experience and/or expert opinion, with both probabilities and consequences being categorized instead of quantified.
Quantitative risk analysisEstimation of level of risk based on calculated values of probabilities of hazards, effects and consequences of undesirable events, which are quantified using data and mathematical analyses.
RehabilitationStructural intervention such as repair and/or upgrading of an existing structure to reach compliance with required structural performance, generally without restriction upon the materials or methods employed.
Reliability-based performance assessmentAssessment executed by full-probabilistic approach (e.g. FORM or Monte Carlo) where reliability of a structure is be verified in terms of failure probability Pf (or the reliability index β).1
1 I context of limit state approach, when using the reliability-based assessment, the verification of a structure with respect to a particular limit state is carried out via estimation of the probability of occurrence of failure in a specified reference period and its verification against reliability requirements.
RepairIntervention taken to improve the condition of a structure by restoring or replacing existing components or elements that have been damaged or deteriorated.
RiskThe effect of uncertainty on objectives, realized as the expected value of all undesirable consequences, combining the probability of event and related consequences.
Risk analysisProcess aimed at determining the level of risk by comprehending the nature of risk and considering the likelihood and the consequences of an undesired event, which involves determination of hazard scenarios, determination of effects and consequences and risk estimation.
Risk assessmentOverall process, aimed at helping to understand uncertainty and the associated risk, which involves establishment of structural engineering context, system definition, hazard and consequence identification, risk analysis, risk evaluation and evaluation of risk treatment options.
Risk managementCoordinated activities to direct and control an organization towards the minimization of occurrence of potential risks.
Risk-based maintenancePreventive maintenance intended to reduce the probability of failure or noncompliance with the performance requirements, where maintenance resources are assigned to those items that carry the most risk in case of a failure or noncompliance.
Risk-informed performance assessmentAssessment executed with due consideration of the total risks, including loss of lives and injuries, damages to the qualities of the environment, and monetary losses, for the time horizon determined on the basis of the duration of the functionality which the structure shall provide.
Semi-probabilistic performance assessmentAssessment executed by semi-probabilistic approach (e.g. in partial safety factor format and in the global resistance format) where the compliance with the criterion that a design value of a resistance is larger than a design value of a corresponding load effect is verified.1
1 Design values for the load bearing capacity Rd are chosen to have a sufficiently low non-exceedance probability and design values for loads Sd are chosen to have a sufficiently low exceedance probability such that the design criterion in the limit (Rd = Sd) corresponds to the required level of reliability.
Semi-quantitative risk analysisEstimation of level of risk in a descriptive manner, where either probabilities or consequences of undesirable events are being categorized instead of quantified.
Structural componentComponents to be used as load-bearing part of works designed to provide mechanical resistance and stability to the works and/or fire resistance, including aspects of durability and serviceability.
Structural memberPhysically distinguishable part of a structure, e.g. column, beam, plate, foundation.
Structural performanceThe behaviour of a structure, a structural component, or a condition as a consequence of actions, usually classified by means of a quantitative parameters (e.g. reliability index, ratio between resistance capacity and action effect).
Structural performance assessmentSet of activities performed in order to verify the reliability of an existing structure, allowing a prognosis to be made of current and future performance, taking account of relevant deterioration mechanisms and, if appropriate, predictions of potential future damage.
Structural performance criteriaQuantitative limits, associated to a performance requirement, defining the border between desired and adverse behaviour.1
1 in context of limit state approach, performance criteria are the threshold values that describe for each limit state the conditions to be fulfilled.
Structural performance evaluationProcess undertaken after to performance assessment, that is concerned with evaluating whether any intervention is required to meet the specified performance requirements (original or revised) in order to allow the structure to remain in service during the specific period of time.
Structural performance requirementsA condition for design, or an actual, potential or intended option for intervention, aiming at meeting a specified performance criterion during the service life with appropriate reliability and in a sustainable way.1,2
1 Performance requirements are established by means of performance criteria and associated performance indicators and constraints related to service life and reliability.
2 Performance requirements refer to the fulfilment of the essential demands of the stakeholders (i.e. owners, users, contractors, society) during the intended lifetime of structures or structural elements. […..]
Structural safetyAbility (of a structure, structural component or structural member) to guarantee the overall stability as well as an adequate ultimate bearing resistance, corresponding to the assumed actions and the required reliability for the specified reference period1,2
1 Structural safety is usually expressed by the ratio (safety factor) between the actions that would cause collapse or other similar forms of structural failure and the actions that are imposed upon it in service.
2 In context of Limit State Approach Structural safety is defined as ability exceedance of the Ultimate Limit States.
StructureOrganized combination of connected structural components designed to fulfil specific functions with adequate reliability with regard to safety, serviceability and sustainability, for a defined period of time.
Surveying technologyTechnology applied to collect data during the survey process, which aims at gathering information about the shape and current condition for a network, structure, its components or elements and/or to about the relevant actions and hazards.
TestingTest of the structure (or part of it) aimed at obtaining information about the current condition or performance of a structure or/and its components or elements.
Upgrading (retrofitting)Intervention aimed to enhance functional or structural performance of existing structure by means of modifications of existing components and/or elements and/or addition of new components and/or elements, that are designed to act in combination with the retained parts of an existing structure.
Value of informationNumerical difference between the expected benefit (utility) estimated with the implementation of the information and the expected benefit without implementation of the information.
VulnerabilityIntrinsic property of an entity (e.g. network, object, component or element, or the parts thereof) resulting in its susceptibility to a risk, which may be quantified by the ratio between the risks due to direct consequences of an event and the total value of the considered entity, determined bearing in mind all relevant hazards for a specified time frame
Vulnerable zonesPhysically distinguishable part of an entity (e.g. network, object, component or element, or the parts thereof), for which change of its condition or other direct consequences of an hazardous event have the largest impact on its performance.1
1 One vulnerable zone may be related to several risks and failure modes.