Martin Krejsa

Using DOProC Method in Structural Reliability Assessment

Reliability of load-carrying structures has been assessed by various calculation procedures based on probability theory and mathematic statistics, which have been becoming more and more popular. The calculation procedures are well-suited for the design of elements in load-carrying structures with the required level of reliability if at least some input parameters are random and contribute to a qualitatively higher level of the reliability assessment and, in turn, higher safety of those who use the buildings and facilities. This paper discusses application of the original and new probabilistic methods – the Direct Optimized Probabilistic Calculation (“DOProC”), which uses a purely numerical approach without any simulation techniques. This provides more accurate solutions to probabilistic tasks, and, in some cases, to considerably faster completion of computations.

Probabilistic computational methods in structural failure analysis

Probabilistic methods are used in engineering where a computational model contains random variables. Each random variable in the probabilistic calculations contains uncertainties. Typical sources of uncertainties are properties of the material and production and/or assembly inaccuracies in the geometry or the environment where the structure should be located. The paper is focused on methods for the calculations of failure probabilities in structural failure and reliability analysis with special attention on newly developed probabilistic method: Direct Optimized Probabilistic Calculation (DOProC), which is highly efficient in terms of calculation time and the accuracy of the solution. The novelty of the proposed method lies in an optimized numerical integration that does not require any simulation technique. The algorithm has been implemented in mentioned software applications, and has been used several times in probabilistic tasks and probabilistic reliability assessments.

Validating a Computational Model of a Rooflight Steel Structure by Means of a Load Test

During erection of a rooflight steel structure excessive deformation started appearing in the steel structure designed for a rooflight. After repairing the load-carrying system it was necessary to check whether the structure was free of permanent deformations. The situation was consulted with the investor and it was proposed to carry out a load test which should prove that the real structure was in accordance with the computational model.

The Use of the Direct Optimized Probabilistic Calculation Method in Design of Bolt Reinforcement for Underground and Mining Workings

The load-carrying system of each construction should fulfill several conditions which represent reliable criteria in the assessment procedure. It is the theory of structural reliability which determines probability of keeping required properties of constructions. Using this theory, it is possible to apply probabilistic computations based on the probability theory and mathematic statistics. Development of those methods has become more and more popular; it is used, in particular, in designs of load-carrying structures with the required level or reliability when at least some input variables in the design are random. The objective of this paper is to indicate the current scope which might be covered by the new method—Direct Optimized Probabilistic Calculation (DOProC) in assessments of reliability of load-carrying structures. DOProC uses a purely numerical approach without any simulation techniques. This provides more accurate solutions to probabilistic tasks, and, in some cases, such approach results in considerably faster completion of computations. DOProC can be used to solve efficiently a number of probabilistic computations. A very good sphere of application for DOProC is the assessment of the bolt reinforcement in the underground and mining workings. For the purposes above, a special software application—“Anchor”—has been developed.

Probabilistic Failure Analysis of Steel Structures Exposed to Fatigue

The paper is focuses on one of probabilistic methods which can be used for failure analysis and reliability assessment of steel structures which are subject to cyclic loads and exposed to fatigue. A particular attention is paid to creation and propagation of fatigue cracks from edges and surface. On the basis of the reliability assessment, a system of inspections is proposed for structural details which tend to be sensitive to fatigue damage. A new probabilistic method which is still under development - Direct Optimized Probabilistic Calculation (DOProC) was used for this probabilistic task. This method is the basis of the FCProbCalc code.

Measured Data Processing in Civil Structure Using the DOProC Method

This paper describes the use of measured values in the probabilistic tasks by means of the new method which is under development now - Direct Optimized Probabilistic Calculation (DOProC). This method has been used to solve a number of probabilistic tasks. DOProC has been applied in ProbCalc a part of this software is a module for entering and assessing the measured data. The software can read values saved in a text file and can create histograms with non-parametric (empirical) distribution of the probabilities. In case of the parametric distribution, it is possible to make selection from among 24 defined types and specify the best choice, using the coefficient of determination. This approach has been used, for instance, for modelling and experimental validation of reliability of an additionally prestressed masonry construction.

Probabilistic Calculation of Fatigue Crack Progression Using Fcprobcalc Code

Probabilistic Calculation of Fatigue Crack Progression Using Fcprobcalc Code The paper gives examples of the probabilistic assessment of a steel cyclic loaded structure. Fatigue progression of the cracks from the edge and from the surface is used as a basis for proposing a system of inspections of details which tend to be damaged by fatigue. The newly developed method Direct Optimized Probabilistic Calculation (DOProC method) was used for solution. The method was applied in FCProbCalc software. Pravděpodobnostní Výpočet Šíření Únavové Trhliny s Využitím Programu Fcprobcalc Příspěvek je zaměřen na jeden z možných způsobů posouzení spolehlivosti cyklicky namáhané ocelové konstrukce s ohledem na vznik únavových trhlin z okraje a povrchu, které vede k návrhu systému prohlídek konstrukčních detailů náchylných na únavové poškození. Pro řešení pravděpodobnostní úlohy byla použita nově vyvíjená metoda Přímého Optimalizovaného Pravděpodobnostního Výpočtu (zkráceně POPV), implementovaná do programu FCProbCalc.

Probabilistic prediction of fatigue damage based on linear fracture mechanics

Paper describes in detail and gives example of the probabilistic assessment of a steel structural element subject to fatigue load, particular attention being paid to cracks from the edge and those from surface. Fatigue crack damage depends on a number of stress range cycles. Three sizes are important for the characteristics of the propagation of fatigue cracks - the initial size, detectable size and acceptable size. The theoretical model of fatigue crack progression in paper is based on a linear fracture mechanics. When determining the required degree of reliability, it is possible to specify the time of the first inspection of the construction which will focus on the fatigue damage. Using a conditional probability, times for subsequent inspections can be determined. For probabilistic calculation of fatigue crack progression was used the original and new probabilistic methods - the Direct Optimized Probabilistic Calculation (“DOProC”), which is based on optimized numerical integration. The algorithm of the probabilistic calculation was applied in the FCProbCalc code (“Fatigue Crack Probabilistic Calculation”), using which is possible to carry out the probabilistic modelling of propagation of fatigue cracks in a user friendly environment very effectively.

Material Study of a Short Seismic Link in a Dissipative Structure of a Vertical Industrial Boiler

Submitted paper presents brief information about structural dissipative design of a power plant boiler structure. The main attention is paid to the selection of material solution. Several material combinations of materials for dissipative members and other structural elements have been evaluated. As a measure of material combination effectiveness has been chosen a ratio between structural stiffness of primary and secondary lateral load resisting system. Probabilistic analysis of the structural sub-section has been carried-out for the most common material combination with steel S235 used for seismic links. Probabilistic analysis has been performed for the evaluation of the risk of material hardening in links and probabilistic distribution of material properties.

Determination of Inspections of Structures Subject to Fatigue

Determination of Inspections of Structures Subject to Fatigue The paper describes in detail and gives examples of the probabilistic assessment of a steel construction subject to fatigue load, particular attention being paid to cracks from the edge and those from surface. This information is used as a basis for proposing a system of inspections. The newly developed method Direct Optimized Probabilistic Calculation (DOProC) is used for solution. Stanovení Systému Prohlídek Konstrukcí Namáhaných Na Únavu V příspěvku je detailně zpracovaná a na příkladu demonstrovaná metodika pravděpodobnostního posouzení ocelové konstrukce namáhané únavou s ohledem na vznik únavových trhlin z okraje a povrchu, která vede k návrhu systému prohlídek konstrukce. K řešení je využita nově vyvíjená metoda Přímého Optimalizovaného Pravděpodobnostního Výpočtu - POPV.