Martin Krejsa

The paper is focused on the static analysis of the cone, which is one of the basic shapes used for membrane structures. These structures are specific by their ability to transmit only tensile forces. Pressure forces in the membrane construction may cause unwanted wrinkling of the used textile materials. When designing membranes, one of the variable parameters can be the height of cone and the radius of the circular profile at the top of the cone, which affects the resulting stress and internal forces. This paper aims to analyze the reliability of the cone in terms of the extreme stress and internal forces while maintaining the same ground plan.

The paper deals with evaluation of possible fatigue damage of existing steel crane structure. It is possible to use the some traditional methods to solve the problem - a concept of fatigue S-N curves (which are mainly used for designing of a new structures) or the procedures based on linear fracture mechanics utilizing the Paris-Erdogan’s law (which are suitable for estimation of remaining lifetime). For the resistance assessment the relevant data of load effects caused by cyclically loaded structure operation are necessary for both concepts. For the prediction of fatigue damage over time, calibration functions for short edge cracks were derived based on the results of the experiment, and the acceptable size of the fatigue crack in damaged structural component under analysis was determined. Using the derived relationships, a stochastic analysis of the selected element was performed and the results are discussed.

Reliability and security of a power transmission depends on the state of the power grid and mainly on the state of the Extra-High Voltage pylons. The paper deals with deformation analysis of existing steel structure of selected Extra-High Voltage pylons which showed excessive differences comparing to the original design. In the assessment of the situation, geodetic survey of selected pylons of power grid that showed the greatest deformation was performed. On taken images, deformation of steel structures by using the FOTOMNG system was also analyzed. The proposed method allows a modeling of the structure of the object based on precisely obtained photographic documentation of the current state. It also represents a very effective method which allows to quickly and efficiently analyze the deformation in the structure of Extra-High Voltage pylons in the critical position of the power grid. Other benefits include the possibility of repeatable and safe measurement.

The closed steel supports of different shapes are used in mining and underground constructions. The yielding and unyielding supports are prefabricated from rolled, usually robust steel profiles. The load carrying capacity of the support is considerably influenced by the active loading and passive forces. The passive forces are induced by the interactions of support with the surrounding rock massif [1]. The user-friendly software was processed for the operational determination of load carrying capacity. The analysis has three parts: the first part consists of the structural geometry processing. The second part includes the numerical solution of statically indeterminate structure for the specified load. The third part is the calculation of load carrying capacity, components of internal forces and deformations. The force method and the numerical integration were used for solution. The Winkler model is applied when the support is in interaction with the surrounding environment. The load...

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.

ABSTRACT The paper briefly reviews the proposed non-traditional numerical tool, PPDV, applicable in the framework of the probabilistic structural reliability assessment method SBRA which allows for checking the reliability by comparing the calculated probability of failure Pf and the target probability Pd defined in specifications. The numerical tool PPDV was developed using Borland Delphi platform. It allows exploring reliability function SF using analytical form in string expression or in DLL (dynamic link library) function. Results are compared with solution based on the application of the direct Monte Carlo simulation, or Importance sampling and some other numerical tools.

ABSTRACT The probabilistic methods find its application in engineering practice at solving of tasks when variables with random character enter in the computational model. The newly developed method, Direct Optimised Probabilistic Calculation -DOProC, appears as a very effective one for a line of tasks considering either computing time, either obtained solution accuracy. The computing procedure does not use any simulation technique and works in purely numerical way. The described algorithm has already been implemented in several applications which were successfully used at solution of probabilistic tasks and probabilistic reliability evaluations.

To determine dynamic response of mechanical system is always a complex issue. One of the core inputs for such a task is a coefficient of logarithmic damping decrement. There is no way how to determine this coefficient analytically; it needs to be measured on the final product. There has been a large amount of dynamic tests carried out on common structures and the results have been incorporated in design codes. Nevertheless, power plant boiler structure differs significantly from common structures. To provide a large number of dynamic tests on real facility is very difficult for many reasons. Using a scaled model is a way how to achieve relevant data based on repeatable experiment.

The Direct Optimized Probabilistic Calculation (DOProC) is originally developed as one way of solving probabilistic problems which don't use any simulation technique. DOProC is based on general terms and procedures used in probabilistic theories. Input random quantities (such as the load, geometry, material properties, or imperfections) are in DOProC method expressed by the parametric or empirical distribution in histograms. DOProC applications are processed in ProbCalc software, in which the calculation model under analysis can be expressed analytically as a sign arithmetic expression or can be expressed using code from the dynamic library. The method requires high-performing information systems for complex tasks. Therefore, efforts have been made to optimize calculations in order to reduce the number of operations, keeping, at the same time, reliable calculation results. The paper will also focus on other special software applications that are able to assess the reliability of...

ABSTRACT Pravděpodobnostní metody nacházejí v inženýrské praxi uplatnění při řešení úloh, kdy do výpočetního modelu vstupují proměnné s nahodilým charakterem. Nově vyvíjená metoda Přímého Optimalizovaného Pravděpodobnostního Výpočtu -POPV, se pro řadu úloh jeví jako velmi efektivní jak z hlediska výpočetního času, tak dosažené přesnosti řešení. Výpočetní postup nevyužívá žádnou simulační techniku a pracuje čistě numerickým způsobem. Popisovaný algoritmus byl již implementován v několika aplikacích, které byly úspěšné využity při řešení pravděpodobnostních úloh a pravděpodobnostních posudků spolehlivosti.

Summary: The paper briefly reviews the proposed non-traditional numerical tool, direct determined probabilistic calculation (DDPC), applicable in the framework of the probabilistic structural reliability assessment method SBRA (4) which allows for checking the reliability by comparing the calculated probability of failure Pf and the target probability Pd defined in specifications. The procedure of the calculation above was published first in

ABSTRACT The paper briefly reviews the proposed non-traditional numerical tool, PPDV, applicable in the framework of the probabilistic structural reliability assessment method SBRA which allows for checking the reliability by comparing the calculated probability of failure Pf and the target probability Pd defined in specifications. The numerical tool PPDV was developed using Borland Delphi platform. It allows exploring reliability function SF using analytical form in string expression or in DLL (dynamic link library) function. Results are compared with solution based on the application of the direct Monte Carlo simulation, or Importance sampling and some other numerical tools.

... 103/01/1410 a 105/01/0783 a projekt Leonardo da Vinci EU Agency No.: CZ/98/1/82502/PI/I. 1.1.a ... ocelového nosníku namáhaného nárazem, Sborník konference "Dynamika v pozemních stavitelství a dopravních konstrukcích a větrné inženýrství", Vyhne, září 2000, Slovenská ...

In probabilistic tasks, input random variables are often statistically dependent. This fact should be considered in correct computational procedures. In case of the newly developed Direct Optimized Probabilistic Calculation (DOProC), the statistically dependent variables can be expressed by the socalled multidimensional histograms, which can be used e.g. for probabilistic calculations and reliability assessment in the software system ProbCalc.

The objective of this monograph is to illustrate the current scope of the original method - Direct Optimized Probabilistic Calculation – „DOProC“. The attention is paid especially to reliability assessment of load carrying structures. After the
introduction (chapter 1), chapters 2.1 and 2.2 provide necessary overviews of basic terms from the probability theory, mathematical statistics and reliability theory, respectively. Chapter 2.3 introduces detailed information about currently used probabilistic methods and procedures, which have been utilized so far for calculation of failure probability in the load carrying structures under investigation. Chapter 3 deals with the method of Direct Optimized Probabilistic Calculation
– „DOProC“, in detail. This probabilistic method presents a new computational tool for solving probability problems. This calculation procedure consists, in particular, in the optimized method of numerical integration using the basic knowledge
of probability theory. It uses a purely numerical approach without Monte Carlo method or any of the other simulation techniques or approximation methods. Applications
of the „DOProC“ method leads in many cases to more accurate solution of probabilistic tasks, and, in some cases, to considerably faster completion of computations. The input variables of calculations by „DOProC“ are particularly
statistically dependent and statistically independent random variables. The calculation algorithm was programmed in multiple software applications and has been successfully applied in solving a number of probabilistic tasks and
probabilistic reliability assessments of carrying structures. „DOProC“ method has proved to be a good solution, among others, in fatigue crack progression in
constructions subjected to cyclical loads. Chapter 4.1 describes in detail and gives examples of the probabilistic assessment of a construction subject to fatigue load. This information is used as a basis for proposing a system of inspections.
Application of „DOProC“ is also demonstrated by the probabilistic design methodology of anchorage reinforcement in long mining and underground workings (chapter 4.2).