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The Leonardo da Vinci Project, “Innovation Transfer in Risk Assessment and Management of Aging Infrastructures”, CZ/13/LLP-LdV/TOI/134014, addresses the urgent need to train students, young engineers and professionals in the assessment of existing infrastructures. The future of the construction industry lies in moving from new constructions towards the maintenance, repair and rehabilitation of existing structures, particularly of aging infrastructures. Risk management consisting of risk assessment and risk control of existing structure therefore plays thereby an important role. The assessment of existing infrastructures is an imperative issue of great economic significance in most countries around the world, as more than 50 % of all construction activities concerns existing buildings, bridges and other civil engineering works. At present, the Eurocodes which will be used in all CEN Member countries are primarily focused on the design of new structures. Additional operational rules for existing structures are still missing. The international standard ISO 13822 provides only general principles for the assessment of existing structures which should be further developed for their effective operational use in practice. The overall procedure of risk management of aging infrastructures is therefore an urgent issue of great economic significance in most countries around the world. This is primarily caused due to the fact that many infrastructures are affected by action effects, fatigue and environmental influences, and inevitably deteriorate. Moreover, available resources for the maintenance, repair or possible replacement of infrastructures are always limited. Typical questions and problems which must be solved in this context can be summarized as follows: • What is the current state of a particular infrastructure? • What is an acceptable level of the relevant risk? • Which aspects are critical to sustainable performance? • What is the optimum life-cycle cost? • What is the best long-term funding strategy? The proposed project highlights the above problems and focusses also on vocational training in risk management and assessment of aging infrastructure in the partner countries (CZ, DE, ES, IT and TR). The current project addresses the urgent need for practical implementation of principles of the management and risk assessment of existing infrastructures in all the partner countries. The project is supported by the Czech Chamber of Chartered Engineers (ČKAIT). The project consortium, under the leadership of the Klokner Institute of the Czech Technical University in Prague (KI CTU), consists of five other partners, including research institutions and universities from three EU Member States (DE, ES, IT) as well as one associated country (TR), and also the Secondary Technical School of Civil Engineering in Ceske Budejovice (CZ). All researchers within the partnership are involved in research projects dealing with reliability assessment of existing structures. They participate in the national and international standardization activities within the international organizations CEN (European Committee for Standardisation) and ISO (International Standardization Organisation). The project outcomes consist of vocational training materials based on international research and relevant standard committee’s activities, and on the significant experience gained from case studies, and on selected results obtained from the previous projects of the Leonardo da Vinci programme. In particular, the experience gained by the partners of the present consortium from the completed project on vocational training related to assessment of existing structures is utilized. Available innovations are transferred to undergraduate and graduate students, practising engineers and local government representatives. The developed training materials are of practical use in offering illustrative examples and several case studies. All the project outcomes are based on documents of the international research organization, Joint Committee on Structural Safety JCSS and international research projects, selected outcomes of the previous project of the Leonardo da Vinci programme (developed by five partners of the present consortium in 2013-2015) and also on background documents to the new European and international standards. Particular outcomes of the proposed project include practical handbooks, software tools, web-sites, e-learning, courses and seminars organized in the partners´ home countries. The project outcomes will also be offered to other European countries through code committees work, lectures and the project web-sites. It is foreseen that the outcomes being used by engineers, designers, technicians, and representatives of public authorities involved in planning and management will have an impact on the risk-based management of infrastructures. One of the important project outcomes is the present Handbook 2 “Operational Methods for the Assessment and Management of Aging Infrastructure”, which is focussed on operational techniques for the assessment of aging infrastructures supplemented by illustrative case studies developed according to ISO 13822 and Eurocodes for different structures and materials. From the mentioned project also result Handbook 1, where general procedures of risk-management and assessment of aging infrastructures are presented, and Handbook 3, where operational techniques for the assessment of aging infrastructures supplemented by illustrative case studies are presented with a more basic approach. Handbook 2 consists of eleven chapters. Chapter 1 gives a brief introduction. Chapter 2 summarizes current applicable standards and codes for existing structures. Chapter 3 reviews survey methods. The remaining chapters are devoted to the illustration of relevant case studies, referring to the assessment of different existing infrastructures. In particular, chapter 4 refers to a commercial building, chapter 5 to a r.c. building damaged by corrosion, chapter 6 to silos, chapter 7 to pipelines and water supply systems, chapter 8 to tanks, chapter 9 to historical aqueducts, chapter 10 to bridges and chapter 11 to dams and flood protection systems. In each case studies the entire procedure of the assessment is illustrated step by step emphasizing references to relevant Codes and in particular to ISO 13822. It is believed that the material of this handbook is presented in an understandable way, referring to several case studies. A number of references mentioned in each chapter provide additional background materials, further guidance and information useful to widen the significance and the field of application of the assessment methods illustrated for each case study. Pisa and Prague, 2015
A Bayesian network is applied in this contribution in order to assess the risks of a selected production unit in a fossil power station. A general framework for the risk assessment of production units of a power station is presented first by implementing statistical methods and Bayesian networks. Special emphasis is given to the input data consisting of failure rates which are obtained on the basis of recorded data and expert judgements. The consequences of failure are divided into economical and human (societal): economic consequences include outages of key technological devices, societal consequences cover potential injuries and fatalities. Probabilistic risk assessment methods are applied to the selected production unit of a power station. The influence of the uncertainties in the considered technical parameters on the availability of the unit is assessed and the acceptance of the calculated availability represented through the mean value and the standard deviation is discussed. Societal risks given in terms of weighted injuries and fatalities are obtained and respective risk acceptance criteria are presented. Uncertainties affecting the risks are discussed. It appears that the proposed framework provides a valuable assessment of the influence individual devices and their components on availability and societal risk. For that purpose the used methodology, intentionally simplified for operational applications, includes important factors affecting risks of production units. It is concluded that Bayesian networks are a transparent method for the probabilistic risk assessment of complex technological systems. The results of the performed analyses can be easily updated when additional information becomes available as illustrated in characteristic examples.
The assessment of existing infrastructures in the energy sector is of great economic significance worldwide. Fossil power stations are reaching their design service life and rational decisions concerning extensions of service life, maintenance and replacements of devices should be based on updated information of the actual conditions of the energy devices and their components, and on cost-benefit analysis using risk analysis and probabilistic optimisation procedures.
The contribution provides an integrated framework for probabilistic reliability and risk assessment of existing energy production units considering availability and human safety criteria. An extensive case study focused on risks of an energy production unit in a fossil power station is provided to support practical applications. A Bayesian network is thereby implemented to assess the risks of the selected production unit. Special emphasis is given to the input data consisting of failure rates obtained from recorded data and expert judgements. The influence of uncertainties in the considered performance indicators on the availability of the unit is analysed. It is shown that a reasonably simplified framework can provide a valuable assessment of the influence of individual devices and their components on availability and societal risk, identifying thus the major risk contributors. (C) 2017 Elsevier Ltd. All rights reserved.
Environmental and climate change is a global issue that will and has already impacted the frequency and intensity of natural hazards in many regions throughout the world. Consequently, the actions on structures will be changing and present design practices will need to be adapted to provide for reliable structures with service lifetimes spanning over decades and centuries. A submitted review of present environmental and climate change information is focused on the distinct, but complementary climatic conditions of Central Europe and South Africa. An outline of the basis of structural design accounting for extreme wind and snow loads is presented and recommendations for future risk-based design procedures are discussed.
Issues to consider include:
a) use of extreme value models;
b) implementation of changes in distribution parameters to obtain extremes with long return periods;
c) consideration of the rate of the change.
The example of a representative structure illustrates the effects of climatic actions on structural reliability. It appears that uncertainties related to the lack of observations hinder drawing strong conclusions concerning appropriate modifications of design procedures due to environmental and climate change. Uncertainties in the prediction of environmental and climate change have a direct bearing on optimal levels of reliability and the subsequent derivation of design values.
Specification of the target reliability levels is one of the key issues of the assessment of existing structures. ISO 13822:2010 and ISO 2394:1998 indicate procedures for deriving the target reliability levels by optimisation of the total cost related to an assumed remaining working life of a structure. In the submitted study this approach is applied to estimate the target reliability levels of an existing structural member in conjunction with the human safety criteria. Obtained results are critically compared with the recommendations given in present standards. It appears that the requirement on the same target reliability levels for existing structures as for new structures is uneconomical. Further, the cost optimisation seems to yield rather low reliability levels and human safety criteria become commonly decisive for specification of the target reliabilities of existing structures.
Assessment of existing structures should be based on the actual as-built conditions concerning geometry, material properties, loading and environmental conditions. A crucial step of the assessment consists in updating of prior information by newly obtained measurements which may be conducted by Bayesian approach. Updating of probabilistic distributions of basic variables or direct updating of failure probability can be effectively used. Application of theoretical principles is illustrated by a case study of a historic factory built in 1900s. The paper is a tribute to Ton Vrouwenvelder for his essential contributions to developments of theory and promotion of practical applications of probabilistic assessment of existing structures.
Risk and reliability criteria are well established in many industrial sectors such as the offshore, chemi- cal or nuclear industries. Comparative risk thresholds have been specified to allow a responsible organization or regulator to identify activities, which impose an acceptable level of risk concerning the participating individuals, or society as a whole. The scope of this contribution is to present target reliability criteria based on acceptable human safety levels. Application of theoretical principles is illustrated by examples of railway engineering structures. Initially it is shown how civil engineering structures for which human safety criteria play a role are classified according to Eurocodes. Examples include bridges, tunnels or station buildings. The general concepts for risk acceptance are then briefly reviewed, particularly in their relation to the target reliability criteria. The distinction between the two types of criteria is made: group risk and the acceptance criterion based on the Life Quality Index LQI approach introduced by ISO 2394:2015. The differences between the criteria for new and existing structures are discussed. The application is illustrated by an example of a bridge crossing an important railway line. It appears that while benefits and costs of a private stakeholder or public authority are reflected by economic optimisation, the society should define the limits for human safety to achieve uniform risks for various daily-life activities and across different industrial sectors. Keywords: group risk, human safety, individual risk, Life Quality Index, railway, risk acceptance, structure, target reliability
Specification of the target reliability levels is one of the key issues of the assessment of existing systems. ISO 2394:2015 indicate procedures for specification of the target reliability levels by optimisation of the total cost related to an assumed remaining working life of a structural system. These approaches are critically compared with human safety criteria and with recommendations of present standards. It appears that the requirement on the same target reliability levels for existing civil engineering systems as for newly designed is uneconomical. Decisions in the assessment can result in the acceptance of the actual state or in upgrade of the existing structure, two reliability levels are thus needed - the minimum level below which the structure is unreliable and should be upgraded, and the target level indicating an optimum upgrade strategy. When reliability of a system or its key component is verified (as compared to design of a common component), the target reliability index should be increased by about 0.5.
Structural health monitoring (SHM) projects are mostly based on semi-empirical decisions, emphasising the importance of the structure and lacking a rational comparison of the benefits and costs. The present work offers guidance to overcome this, based on an objective framework using the quantification of the value of SHM in an engineering context. Firstly, procedures for practising engineers are outlined on the basis of the COST guidelines. Secondly, a case study, focused on the reliability of a historic masonry structure, demonstrates the optimisation of surveys based on non-destructive tests calibrated by destructive tests. Both the outlined procedures and case study are carefully prepared and in tune, so the reader can easily understand the feasibility of the framework. Decisions on the utilisation of SHM in practical applications can be effectively achieved based on the highest expected utility gained by SHM. For this, two scenarios are needed: (i) a scenario with at least one SHM strategy and (ii) a scenario without any SHM.
Masonry structures were built by means of various techniques, using materials whose properties exhibit a considerable scatter depending on the period of construction, region- specific soil resources and manufacturing procedures. Significant spatial variability within the structural system is often observed due to diverse deterioration mechanisms. Therefore, it is important to obtain case-specific information on the mechanical properties of existing masonry structures.
The case study of a historic building illustrates how the number of destructive tests (DTs) used to calibrate non-destructive tests (NDTs) can be optimised for the reliability assessment. Calibrated NDTs are used to establish the probabilistic model for compressive masonry strength. The specific focus is on compressive strength of masonry units; tests of mortar strength are only briefly discussed.
The preliminary assessment is based on non-calibrated NDTs. The number of DTs for calibration is then optimised by means of probabilistic cost optimisation, considering also possible subsequent actions – ‘do nothing’ or ‘strengthen the structure’. It appears that the estimates of masonry unit strength based on NDTs are associated with large dispersion and may be significantly biased. Consequently, it is often beneficial to conduct at least one DT. A practical tool is provided to determine optimum number of DTs for different outcomes of a NDT survey and different failure consequences.