Zdeněk Kala

Design characteristics of structural steels based on statistical analysis of metallurgical products

Abstract The results of experimental research of material and geometrical characteristics of Czech steel are given in the present paper. The yield strength, tensile strength and ductility were evaluated statistically. For hot-rolled steel IPE profiles, the geometrical characteristics of cross-section dimensions were evaluated statistically too. It has been proved that both material and geometrical characteristics of plates and hot-rolled IPE profiles are satisfactory. The problems are discussed also in connection with application of stochastic computations. For this purpose, correlation coefficients among the quantities measured were also investigated.

Material and geometrical characteristics of structural steels based on statistical analysis of metallurgical products

Abstract The experimental research results of material and geometrical characteristics of Czech steel are given in the presented paper. Measurements are carried out for the yield strength of plates made of steel grade S355. The values measured are used to compute axial resistances which are compared with the resistance resulting from standard (nominal) values. In this paper, there was used a statistical information for evaluating the results of strength measurements on a series of plates and hot‐rolled profiles under tension to determine the adequate partial γM0 safety factor.

Fuzzy probability analysis of the fatigue resistance of steel structural members under bending

Abstract The paper is aimed at the fuzzy probabilistic analysis of fatigue resistance due to uncertainty of input parameters. The fatigue resistance of the steel member is evaluated by linear fracture mechanics as the number of cycles leading to the propagation of initial cracks into a critical crack resulting in brittle fracture. When the histogram of stress range is known, the fatigue resistance is a random variable. In the event that the histogram is unknown or was acquired from a small number of experiments, another source of uncertainty is of an epistemic origin. Two basic approaches, which make provision for uncertainty of input histograms of stress range, are illustrated in the paper. Uncertainty of histograms of stress range is taken into account by the variability of equivalent stress range in the first stochastic approach. Input histograms as considered as members of a fuzzy set in the second approach.

Geometrically Non-linear Finite Element Reliability Analysis of Steel Plane Frames With Initial Imperfections

Abstract The random load carrying capacity of steel plane frames with bracing stiffness is studied. The load carrying capacity is evaluated using the geometrically non-linear FEM analysis. The incremental stiffness matrix of a slightly curved element utilized in the non-linear incremental analysis is listed. Initial imperfections are considered as random variables. Statistical analysis and Sobol sensitivity analysis are performed using the Latin Hypercube Sampling method. The effect of initial random imperfections on the load carrying capacity is studied, whilst assuming constant slenderness of the columns. The evaluation parameters are the pair of non-random values of elastic bracing stiffness, and system length of the columns. The paper illustrates that the load carrying capacity is very sensitive to initial crookedness of the columns in the event that the non-sway (symmetric) and sway (anti-symmetric) buckling modes coincide. In this case, the design load carrying capacity obtained from statistical ana...

Solving Civil Engineering Problems by Means of Fuzzy and Stochastic MCDM Methods: Current State and Future Research

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.

Reliability analysis of the lateral torsional buckling resistance and the ultimate limit state of steel beams with random imperfections

Abstract.The paper deals with the analysis of reliability of a hot-rolled steel IPE-beam designed according to Eurocodes. A beam at its ultimate limit state is considered. The load acting on the beam consists of permanent and long-term single variation actions. The beam is loaded with end bending moments about the major principal axis. The beam is susceptible to lateral torsional buckling between the end supports. Reliability of the beam is assessed using probabilistic analysis based on the Monte Carlo method. Failure probability is a function of the random variability of the loadcarrying capacity and the random variability of load effects. The variability of the load-carrying capacity is influenced by the variability of initial imperfections. Imperfections are considered according to experimental research. Numerical studies showed that the failure probability is significantly misaligned. High values of failure probability were obtained for slender beams, for beams loaded only by permanent load action, an...

Global sensitivity analysis in stability problems of steel frame structures

AbstractSlender steel frame structures are characterised by a number of imperfections which may reduce their load carrying capacity drastically. This article studies the effects of these imperfections on the load carrying capacity of a single storey steel plane frame using global sensitivity analysis and geometrically nonlinear (second-order) elastic finite element analysis. Imperfections are considered as random variables. Statistical load carrying capacities needed for the evaluation of sensitivity analysis are processed using classical statistical methods upon the emulation of Latin Hypercube Sampling simulation methods. The main interaction effects of random imperfections on the load carrying capacity are identified using global sensitivity analysis. It is illustrated that the effects of imperfections on the load carrying capacity varies dramatically depending on the height of the columns and the boundary conditions of the end conditions of the columns.

Sensitivity analysis of tangential digging forces of the bucket wheel excavator SchRs 1320 for different terraces

Abstract Researches in the field of economy of control of mining processes of minerals are continually met with a number of unsolved and newly arising problems. New deposits of brown coal are located at greater depths than before and are more difficult to mine. Problems in the field of rock mining stem from the greater diversity of rocks in mining, and it results in more difficult mining conditions. On the other hand, even greater demands are made to decrease the economic demand of mining. Current research is aimed at the most optimal utilization of energy provided on the bucket wheel of excavators, such that the energy demand of the mining process decreases, whilst preserving maximum performance. These requirements place greater demands on the precision of planning of mining and maximum economic efficiency. The presented article illustrates the possibilities of the utilization of Sobol sensitivity analysis during the investigation of the influence of the parameters of mining processes on tangential diggi...

Sensitivity Analysis of Stability Problems of Steel Structures using Shell Finite Elements and Nonlinear Computation Methods

The main focus of the paper is the analysis of the influence of residual stress on the ultimate limit state of a hot‐rolled member in compression. The member was modelled using thin‐walled elements of type SHELL 181 and meshed in the programme ANSYS. Geometrical and material non‐linear analysis was used. The influence of residual stress was studied using variance‐based sensitivity analysis. In order to obtain more general results, the non‐dimensional slenderness was selected as a study parameter. Comparison of the influence of the residual stress with the influence of other dominant imperfections is illustrated in the conclusion of the paper. All input random variables were considered according to results of experimental research.

Large‐deflection‐theory Analysis of the Effect of Web Initial Curvature on the Ultimate Strength of Steel Plate Girder

The objective of the paper is to analyze the influence of initial imperfections on the behaviour of thin‐walled girders welded of slender plate elements. In parallel with experiments, one of the ultimate load tests was computer modelled. In so doing, the girder was modelled, using the geometrically and materially non‐linear variant of the shell finite element method, by the ANSYS program. The shape changing during loading process is often accompanying with sudden “snap‐through” i. e. rapid curvature change.