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The present review examines decision-making methods developed for dealing with uncertainties and applied to solve problems of civil engineering. Several methodological difficulties emerging from uncertainty quantification in decision-making are identified. The review is focused on formal methods of multiple criteria decision-making (MCDM). Handling of uncertainty by means of fuzzy logic and probabilistic modelling is analysed in light of MCDM. A sensitivity analysis of MCDM problems with uncertainties is discussed. An application of stochastic MCDM methods to a design of safety critical objects of civil engineering is considered. Prospects of using MCDM under uncertainty in developing areas of civil engineering are discussed in brief. These areas are design of sustainable and energy efficient buildings, building information modelling, and assurance of security and safety of built property. It is stated that before long the decision-making in civil engineering may face several methodological problems: the need to combine fuzzy and probabilistic representations of uncertainties in one decision-making matrix, the necessity to extend a global sensitivity analysis to all input elements of a MCDM problem with uncertainties, and an application of MCDM methods in the areas of civil engineering where decision-making under uncertainty is presently not common.

Failures of sprinklers to extinguish fires generate a basic need for the assessment and increase of reliability of these crucial safety systems. This in turn creates a demand for input data used for reliability assessment. Broadly speaking, data on sprinkler failures are available in large amounts and some countries have well-established systems of data collection and reporting. Data are accumulated in the sprinklered environments of conventional buildings and some industrial facilities. The compilation of data sets necessary for reliability assessment may face several problems: differences in definition and naming failure modes; differences in the failure of data reporting; the prevalence of a human factor among the causes of sprinkler failures in a conventional building; the influence of ageing, modifications and repairs on sprinkler reliability. The size of data sets can be limited by such factors as limited relevance of data collected in different sprinklered environments, differences in operation conditions and components, ageing of data collected in the past, the concealment of data and/or a high cost of data, poor documentation and explanation of data in available databases. Data on sprinkler component failure rates necessary for fault tree models can be extracted from generic databases. However, databases containing information on the failure rates of sprinkler-specific components do not seem to exist in literature or on the Internet. Scarce data on sprinkler failures can be utilised within the Bayesian format. The potentially critical issue of reliability dependence on sprinkler aging and other changes in time remains unsolved from the standpoint of both theoretical modelling and data collection. Trumpa duomenų apie įprastiniuose pastatuose įrengtų sprinklerių patikimumą apžvalga Santrauka.Nereti sprinklerių atsakai, gesinant gaisrus, verčia vertinti šių kritinių saugos sistemų patikimumą. Dėl to reikia kaupti ir apdoroti duomenis, kurių reikia vertinant patikimumą. Duomenų apie sprinklerių atsakus yra daug. Kai kurios šalys turi gerai sudarytas sprinklerių patikimumo duomenų rinkimo ir skelbimo sistemas. Duomenys renkami apie sprinklerius, įrengtus tiek įprastiniuose pastatuose, tiek pramoniniuose objektuose. Tačiau duomenų patikimumui vertinti rinkimas susiduria ir su kai kuriais sunkumais. Nėra sutartinės sprinklerių atsakų apibrėžimo ir įvardijimo praktikos, ataskaitos apie atsakus dažnai labai skiriasi, patikimumo vertinimą sunkina ir tai, kad vyraujanti įprastinių pastatų sprinklerių atsakų priežastis yra žmonių klaidos. Patikimumo vertinimą apsunkina ir sprinklerių senėjimo reiškinys, sistemų modifikavimai ir remontai. Patikimumo duomenų kiekį riboja ir tai, kad duomenys, gauti skirtingose eksploatavimo aplinkose, tinka tik toms aplinkoms. Sprinklerių eksploatacija ir aplinkos sąlygos gali būti skirtingos. Duomenų kiekį riboja ir jų kaina, senėjimas bei slėpimas. Duomenys, kaupiami kai kuriose bazėse, būna nepakankamai paaiškinti ir netinkamai dokumentuoti. Kai sprinklerių sistemos patikimumas vertinamas taikant atsakų medžio analizę, įvesties duomenys gali būti gauti ir iš bendrųjų patikimumo duomenų bazių. Tačiau literatūroje ir internete negalima rasti duomenų bazės, kurioje būtų sukaupti duomenys būtent apie sprinklerių sistemų komponentų patikimumą. Kai patikimumo duomenų trūksta, jį galima vertinti taikant Bajeso metodus. Tiek teorinis modeliavimas, tiek duomenų rinkimas šiandien dar neleidžia atsižvelgti į fizinį sprinklerių senėjimą bei modifikacijas, kurios gali labai paveikti šių sistemų patikimumą. Reikšminiai žodžiai: sprinkleriai,gaisras,duomenų šaltinis,duomenų bazė,patikimumas,atsako dažnis,senėjimas,žmogaus klaida.

The paper considers the problem of fire safety assurance by means of fire risk indexing and fire risk assessment. The attention in focused on the comparison of these two principal approaches and possibilities of their application in a combined set. The paper aims to define, compare and analyse fire safety assessment by applying the aforementioned approaches. The practicability of both approaches is compared by means of an example which considers fire safety of an existing office building. It is stated that it makes sense to combine the merits both fire risk indexing and assessment in order to apply them to a comprehensive decision-making concerning fire safety assurance. The paper also states that this can be done within the framework of a multi-attribute decision-making methodology.

Natural fires occurring in buildings and damage to structures caused by these fires have always been uncertain phenomena. Failure of a structure exposed to a natural fire cannot be predicted with certainty. The present paper describes an approach to an estimation of failure probability by developing a fragility function for a timber structure exposed to the hazard of fire. The fragility function is used to relate results of a probabilistic computer simulation of a potential fire to the probability that an exposed structure will fail during this fire. The developing of the fragility function utilizes the fact that fire damage to an unprotected timber structure can be expressed through the depth of char front. This depth is used as a key demand variable of the fragility function. The estimate of the failure probability is calculated as a mean of fragility function values.

Prediction of dynamic mechanical properties of concrete and reinforcing steel is considered. The attention is focussed on dynamic loading imposed on reinforced concrete structures by large distant explosions. The prediction is made by a combined application of mathematical models describing explosive loading, straining of concrete and steel under this loading and dynamic enhancement of static mechanical properties of these materials. Problems arising at coupling these models in a combined set are discussed. The main finding is that prediction of dynamic properties is to a large extent a problem of structural analysis for explosive loading. The prediction on material level consists mainly in an application of enhancement factors relating static and dynamic properties. The intricacy of these factors lies in the input information required for their calculation. This information is obtained by a structural analysis for explosive loading. Such an analysis can be a complicated task for complex, real world structural sys-tems.and thickness of the layer.

Accidental (abnormal) actions are among the main causes of structural failures. In this paper an estimation of probability of structural failure of tank with flammable liquid due to an accidental action is considered. Two sources of evidence are applied to this estimation: a small-size statistical sample and a fragility function. This function expresses aleatory and epistemic uncertainties related to the potential failure. The estimation of the failure probability is based on Bayesian reasoning. Bayesian prior and posterior distributions are applied to express the epistemic uncertainty in the failure probability. The prior distribution is developed by propagating epistemic uncertainty inherent in the fragility function and, if necessary, values of demand variables. The posterior distribution is estimated by carrying out Bayesian updating with uncertain (imprecise) data. Such updating is considered a sort of uncertainty propagation. The uncertain data is expressed by a set of continuous epistemic probability distributions of fragility function values. The distributions are generated by inserting elements of the small-size sample into the fragility function which is uncertain in the epistemic sense. The Bayesian updating with the new data represented by the set of continuous distributions is carried out by discretizing these distributions. The discretization yields a new sample which is entered into the Bayes theorem through likelihood function. The sample created by the discretization consists of fragility function values which have equal epistemic weights. The proposed scheme of discretization is considered an alternative to a posterior averaging approach. This approach is suitable for Bayesian updating with uncertain data; however, it is applicable to the case where data uncertainty is modeled by discrete distributions of epistemic uncertainty. Several aspects of numerical implementation of the proposed discretization approach and subsequent updating are discussed and illustrated by an example.

Sustainable development can be restricted by major accidents which occur in hazardous industries. Almost every major accident may have negative influence on each of the three constituents of the sustainable development: social, environmental and economic part. A characteristic feature of the most of major accidents is severe damage to the structural systems built inside and outside of the industrial facility in which the accident happens. To avoid such accidents or at least to reduce their consequences, structural systems should be designed using a risk‐based approach. On the level of detailed structural design, a formal measure of risk should be introduced and applied to express the effectiveness of the structural solution in terms of accident mitigation and minimization of potential consequences. The structural design should involve the consideration of possible accident scenarios and positive or negative contribution of structures and structural failures to the escalation or de‐escalation of the accident. This can be done by applying the risk‐oriented structural design. A well‐established methodological framework for such a design is provided by the quantitative risk assessment. A consequent application of a risk‐based approach can be one of the risk management tools which will reduce the number of major accidents and thus their negative influence on sustainable development. Rizika grindžiamos konstrukcijų inžinerijos įtaka mažinant sunkių pramonių avarijų poveikį darniam vystymuisi Santrauka.Darnus vystymasis gali būti stabdomas sunkių pramoninių avarijų, kurių kartkartėmis nutinka pavojingosepramonės įmonėse. Beveik kiekviena sunki avarija gali turėti neigiamą įtaką vienam iš trijų darnausvystymosi komponentų: socialiniam, gamtiniam ir ekonominiam. Būdingas beveik kiekvienos sunkiosavarijos bruožas yra rimti konstrukcijų, stovinčių tiek avariją patyrusioj gamykloj, tiek ir už jos, pažeidimai.Norint išvengti tokių avarijų ar bent mažinti jų pasekmes, konstrukcines sistemas reikia projektuoti taikantrizika grindžiamą požiūrį. Rengiant detalų projektą reikia naudoti matematinį rizikos matą, kuriuo galimaišreikšti konstrukcinių sprendimų efektyvumą, užkertant avariją ar mažinant jos pasekmes. Projektavimasturėtų aprėpti galimų avarijos scenarijų analizę bei teigiamą ar neigiamą konstrukcijos įtaką potencialiamavarijos eskalavimui ar deeskalavimui. Tai galima atlikti pasitelkiant projektavimą, kuris yra orientuotasį riziką. Metodologinis tokio projektavimo pagrindas yra kiekybinis rizikos vertinimas. Sistemingas jotaikymas yra vienas iš rizikos valdymo būdų, leidžiančių sumažinti sunkių avarijų skaičių ir neigiamą jųįtaką darniajam vystymuisi. Reikšminiai žodžiai: darnusis vystymasis, pramoninė avarija, rizika, mechaninė pažaida, pasekmės, gaisras, sprogimas, susidūrimas. First published online:21 Oct 2010

The managerial problem of the choice among alternative protective equipment used to prevent industrial (technological) accidents is considered. The choice takes into account potential failures of the equipment or, conversely, the equipment reliability. Such failures can substantiate contributors to escalations of industrial accidents. The problem of the choice is formulated in the form of a multi-attribute selection. The probability of failure of alternative equipment sets is used as an attribute of the selection problem. An estimation of this probability by means of Bayesian statistical theory is considered. Bayesian prior and posterior distributions are applied as an estimate of failure probability. These distributions are incorporated in the selection problem as uncertain attributes. Development of prior distributions of individual alternatives is discussed in detail. The prior and posterior distributions are treated as measures of the epistemic uncertainty (state-of-knowledge) related to unknown values of failure probabilities. The modelling of uncertainty related to the failure probability corresponds to the classical Bayesian approach to risk assessment. It is suggested to apply the uncertain failure probabilities to developing risk profile for each of the alternative equipments and to incorporate the risk profile to the multi-attribute decision making. The epistemic uncertainty in the failure probabilities and elements of risk profile is quantified by means of Bayesian statistical theory. It is shown that this uncertainty can be reduced by applying Bayesian updating procedure when new data on equipment failures is obtained. Probable cases of the application of this procedure are discussed. This discussion relates the acquisition of the new statistical evidence used for Bayesian updating to the moments, at which managerial decisions are made. It is suggested to solve the problem of the multiattribute selection with uncertain attributes by means of uncertainty propagation. This propagation is accomplished by means of Monte Carlo simulation. The epistemic uncertainty related to the attributes is transformed into a discrete distribution of epistemic uncertainty. Probability masses of this distribution express the chance of individual alternatives to be selected as the best one. The result of this selection will be the alternative with the largest epistemic weight. The potential field of the application of the proposed approach is the management of technological risks present in many industrial facilities and non-industrial installations (dwellings, offices, public places) which are subjected to the hazard of accidents. The approach proposed in the paper allows to make managerial decisions which take into account the reliability of protective equipment. In addition, this approach will allow to utilize data on equipment failures encountered in the past. Such data is usually scarce and expensive. The Bayesian framework is best suited for the application of such data.

Natural fires occurring in buildings and damage to structures caused by these fires have always been uncertain phenomena. Failure of a structure exposed to a natural fire can not be predicted with certainty. The present paper de-scribes an approach to an estimation of failure probability by developing a fragility function for a timber structure exposed to the hazard of fire. The fragility function is used to relate results of a probabilistic computer simulation of a potential fire to the probability that an exposed structure will fail during this fire. The developing of the fragility function utilizes the fact that fire damage to an unprotected timber structure can be expressed through the depth of char front. This depth is used as a key demand variable of the fragility function. The estimate of the failure probability is calculated as a mean of fragility function values.

A procedure for estimating potential damage to buildings induced by accidental explosions on railway is developed. By the damage are meant failures of nearby structures due to actions generated by the accidental explosions. This damage is measured in terms of probabilities of potential failures caused by the explosions. The estimation of the damage probabilities is based on a stochastic simulation of railway accident involving an explosion. The proposed simulation-based procedure quantifies epistemic (state-of-knowledge) uncertainties in the damage probabilities. These uncertainties are expressed in terms of Bayesian prior and posterior distributions. A foundation of the procedure is a computer intensive method known as a Bayesian bootstrap. It is used for approximating the posterior distributions of damage probabilities. An application of the Bayesian bootstrap makes the proposed procedure highly automatic and convenient for assessing structures subjected to the hazard of the accidental actions. In addition, it can be used for specifying safe distances between the railway and nearby buildings. Structures of these buildings can be designed for tolerable probabilities of failures induced by the accidental explosions.

The dissertation presents an approach to decreasing the risk of transportation of hazardous materials (hazmat transportation) by applying construction-related solutions. They consist in deploying safety barriers between transportation routes and vulnerable property built in the roadside territory. The attention is focussed on the hazmat transportation accidents known as boiling liquid expanding vapour explosions (BLEVEs). It is considered how to predict thermal and mechanical effects of BLEVEs on potential barriers or roadside property. It is suggested to interlink results of this prediction with the conventional structural response techniques used for estimating the susceptibility of safety barriers to the effects of BLEVEs. The dissertation consists of introduction, three chapters, conclusions, list of references and papers published by the author as well as four annexes. The first chapter presents a review and evaluation of the published work on the risk posed by the hazmat transportation. In addition, existing approaches to the design of safety barriers suitable to protect roadside property against fires and explosions on road and rail are discussed. In the second chapter, BLEVEs are recognised as relatively frequent and highly damaging accidents on road and rail. The attention is focussed on predicting two main effects by BLEVE: thermal radiation and projectile impact. Three computational procedures are proposed for assessing thermal and mechanical effects generated of BLEVEs. The first procedure was developed to predict the position of road tanker vessel sustaining a BLEVE with respect to a potential target. The second procedure deals with assessing the thermal radiation of a BLEVE fireball. The third procedure was developed for forecasting the impact of road tanker vessel fragments on roadside object or possible safety barrier. The third chapter formulates a series of proposals to the design of safety barriers aimed at protection of roadside objects against thermal and mechanical effects of BLEVEs on road and rail. The first proposal considers the sitting of barriers in the area of potential deployment. The second proposal deals with a design of a steel barrier intended for a protection of blast loading from a railway tanker BLEVE. The third proposal consists in recommendations of how to design a reinforced concrete barrier capable to sustain impact by fragments from a tanker vessel. All proposals have the form of preliminary, conceptual designs. The main statements of the dissertation were published in twelve scientific articles: four articles – in the Thomson ISI Web of Science register.

Disertacijoje nagrinėjama triukšmo sklaidos nuo vėjo jėgainių problema. Pagrindiniai tyrimo objektai yra vėjo jėgainių parkų skleidžiamas triukšmas ir aplinkai nekenksmingos, cilindrinę struktūrą turinčios, žemo dažnio triukšmą slopinančios medžiagos. Darbe sprendžiami keli pagrindiniai uždaviniai: nustatomas ir įvertinamas žemo dažnio triukšmo ir infragarso susidarymas ir sklaida pramoninių vėjo jėgainių parkuose ir jų išorėje, taip pat nustatomos efektyvios gyvenviečių apsaugos priemonės nuo vėjo jėgainių keliamo žemo dažnio triukšmo. Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, rekomendacijos, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmasis skyrius skirtas literatūros analizei. Jame pateikta vėjo jėgainių ir jų keliamo triukšmo apžvalga. Apžvelgtos vėjo energetikos būklė Lietuvoje, vėjo jėgainių konstrukcijos, vėjo jėgainių triukšmo formavimosi principas, triukšmo matavimo metodikos. Analizuojamos skleidžiamo aerodinaminio triukšmo mažinimo priemonės bei žemo dažnio triukšmo slopinimo būdai ir izoliuojančių medžiagų panaudojimas. Skyriaus... [toliau žr. visą tekstą] The dissertation examines the issue of noise emission from the wind farms. The objects of investigation are wind farm noise and environmentally friendly low-frequency noise-deadening materials with cylindrical structure. The paper addresses a number of key objectives: to determine and assess low frequency noise and infrasound emission and dispersion both inside and outside the industrial wind farms, as well as to establish effective measures for protection of settlements against low-frequency noise generated by wind turbines. The dissertation consists of an introduction, three chapters, conclusions, recommendations, list of references and the author's publications on the topics. The introductory chapter discusses the research problem, the relevance of the investigation, describes the object of the research, states the aims and objectives, presents the research methodology, scientific novelty, practical significance of the results, and the statements for defending. It also highlights practical significance of the dissertation presents the author's publications and presentations at conferences, and explains the structure of the thesis. The first chapter is devoted to literature review. It provides an overview of general problems related to wind and noise produced by wind turbines, an overview of the outlook on wind energy in Lithuania, and a discussion of wind turbine constructions. The chapter presents the analysis of aerodynamic noise emitted by means of low-frequency noise... [to full text]

Šio baigiamojo magistro darbo tikslas yra patobulinti kiekybinį pastatų gaisrinės saugos ir rizikos vertinimą, įtraukiant gaisrinės saugos (rizikos) rodiklius į daugiatikslės analizės uždavinius. Darbą sudaro dvi pagrindinės dalys. Pirmoje teorinėje darbo dalyje aprašomi kiekybinio gaisro rizikos vertinimo modeliai, gaisro rizikos privalumai ir trūkumai, daugiatikslės analizės modeliai, daugiatikslės analizės uždavinio sprendimas ir sprendimo kriterijai, aptariamas gaisrinės rizikos vertinimo ir daugiatikslės analizės derinimo poreikis. Antroje darbo dalyje yra sprendžiamas daugiatikslio pastato projektavimo uždavinys. Kaip uždavinio objektas pasirenkamas daugiaaukštis administracinis pastatas. Vertinamos trys skirtingos aukštų plano alternatyvos: atviro, koridorinio ir mišraus tipo. Taip pat šiame skyriuje yra apibrėžiami daugiatikslei analizei tinkantys gaisro rizikos rodikliai. Taikant kompiuterinį modeliavimą apskaičiuojami evakuacijos ir nepakeliamų sąlygų laikai, suskaičiuojami ekonominiai rodikliai ir apklausos būdu įvertinamas alternatyvių pastato aukštų patrauklumas. Visi šie rodikliai įtraukiami į daugiatikslės analizės uždavinį ir matematiniu būdu nustatoma geriausia alternatyva. Išsprendus uždavinį pateikiamos išvados ir pasiūlymai. Darbo pabaigoje pateikiamas literatūros šaltinių sąrašas. Darbo apimtis – 58 p. teksto be priedų, 22 iliustr., 11 lent., 52 biografiniai šaltiniai. The aim of this postgraduate thesis is to improve quantitative building fire safety and risk assessment, including fire safety (risk) indicators in the analysis of multi-criteria tasks. The work consists of two main parts. The first part is theoretical, it describes the quantitative fire risk assessment models, fire risk advantages and disadvantages, multi-criteria analytical models as well as the solution of multi-criteria analysis problem and solution parameters. The assessment of fire risk and the need for conformance of the multi-criteria analysis is also discussed. The second part of the work, focuses on the multi-criteria building design task. A multi-storey office building has been selected as the task object. Three different floor plan types are evaluated: open space, one with the corridor and the mixed type. In addition fire risk indicators suitable for the multi-criteria analysis are defined in this section. Using computer modeling times of evacuation, unbearable conditions and economic indicators are calculated, then the attractiveness of alternative building storey is assessed according to a survey. All these indicators are included in the task of multiple-criteria analysis and the best solution is determined using mathematical method. After solving the task at the end of the paper findings and recommendations are presented followed by references. Thesis consist of: 58 p. text without appendixes,22 pictures, 11 tables, 52 bibliographical entries.

Disertacijoje aprašomas metodas, sukurtas vertinti ypatingųjų poveikių statiniams keliamą riziką. Darbe pateikti trys šio metodo taikymo pavyzdžiai. Disertaciją sudaro įvadas, penki skyriai, išvados, literatūros šaltiniai, autoriaus publikacijų sąrašas ir penki priedai. Pirmajame skyriuje apžvelgiama mokslinė literatūra, kurioje tiriami rizikos vertinimo metodai ir aptariama jų taikymo konstrukcijoms skaičiuoti galimybė. Pateikiama trumpa ypatingųjų poveikių klasifikacija bei konstrukcijų, kurias jie gali paveikti, pažeidžiamumo modeliavimas. Antrajame skyriuje aprašomas metodas, sukurtas ypatingųju poveikių keliamų konstrukcijų pažaidų tikimybėms vertinti. Metodas derina statybinių konstrukcijų patikimumo teorijos ir Bajeso statistinės teorijos priemones. Jis gali būti taikomas tiek projektuojant konstrukcijas, tiek vertinant pramoninių objektų riziką. Trečiajame skyriuje aprašoma, kaip taikyti siūlomą metodą vertinant medinėms konstrukcijoms keliamą gaisro riziką. Ta rizika išreiškiama gaisro pažeistos konstrukcijos suirimo tikimybe, kuri yra vertinama apriorine ir aposteriorine tankio funkcijomis, skaiciuojamomis Bajeso statistinės teorijos priemonėmis. Šiame skyriuje nagrinėjama medinė gaisro veikiama pramoninio pastato stogo konstrukcijos sija. Gaisro poveikis modeliuojamas maža statistine gaisro charakteristikų imtimi. Ketvirtajame skyriuje pateiktas siūlomo metodo taikymas projektuojant sprogimo veikiamą apsauginį barjerą. Atsižvelgiama i barjero elementų mechaninio... [toliau žr. visą tekstą] The dissertation presents a method developed for assessing the risk to constructed facilities posed by accidental actions. The proposed method is applied to the analysis of structures subjected to accidental actions induced by fire, explosion and extreme wind. The dissertation consists of introduction, five chapters, conclusions, lists of references and papers published by the author of the dissertation, as well as five annexes. Chapter 1 presents a review of published work on the assessment of risk to structures and non-structural property posed by accidental actions. The review covers general aspects of risk assessment and application of risk analysis tools to the analysis and design of structures. The core of the review is an application of Bayesian methods, which prevail in the field of risk assessment, to a risk-based structural analysis. Chapter 2 proposes a method developed for the assessment of damage to structures from accidental actions. This method combines structural analysis with Bayesian handling of information related to accidental actions and response of structures to these actions. The method allows to estimate probabilities of the damage to structures caused by accidental actions. Chapter 3 deals with an application of the proposed method to the estimation of fire risk to structures. It is shown how to apply this method to the estimation of failure probability of a timber beam damaged by fire in an industrial building. This chapter shows how to handle... [to full text]

Baigiamajame magistro darbe išnagrinėti STR ir EC 2 betono fizikinių ir mechaninių rodiklių nustatymo metodai bei šiose normose pateiktų įtempių nuostolių skaičiavimo modeliai. Aprašytas tikimybinis įtempių nuostolių vertinimo modelis. Atlikta atskirųjų ir suminių įtempių nuostolių analizė pagal STR ir EC 2 modelius, aprašyti šių modelių skirtumai. Išnagrinėta atskirų fizikinių faktorių lemiančių įtempių nuostolius įtaka. Atlikta iš anksto įtemptos gelžbetoninės sijos tikimybinė suminių įtempių nuostolių analizė. Darbe pateiktas kiaurymėtųjų perdangos plokščių suminių įtempių nuostolių skaičiavimo rezultatų pagal EC 2 ir STR modelius ir eksperimentinių įtempių nuostolių palyginimas. Evaluation of different physical and mechanical factors of concrete according to STR and EC 2 models is considered in this master thesis. Probabilistic model for prestress loss determination is presented in this paper. The analysis of separate and total losses according to STR and EC 2 models was carried out. Some differencies of these models were described. The influence of several factors to the value of separate prestress loss has been studied in this thesis. The probabilistic analysis of long-term losses of post-tensioned RC beam has been carried out. The comparison of total prestress loss values of hollow core slabs according to EC 2, STR and experimental results is subjected in this master thesis.