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.

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

Sensitivity assessment of steel members under compression

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.

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

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

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

The paper is aimed at the analysis of the influence of partial safety factors on the reliability of designing steel members. The reliability assessment of a steel member is based on extensive experimental research on real material and geometric characteristics evaluated by samples obtained from frequently manufactured products. Material and geometric characteristics are random variables represented by histograms during the probabilistic assessment of reliability. The random variability of structural dimensions and of material characteristics does not present the only source of uncertainty present during design according to standards. The reliability of steel structures design is also dependent on the partial safety factor values, which are specified by the design standards. Partial safety factors are basic indicators, which determine structural dimensions in relation to loading. The probabilistic assessment of reliability is performed as a parametric study in the first part of the numerical analy...

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Influence of partial safety factors on design reliability of steel structures ‐ probability and fuzzy probability assessments

An actual structural design, especially that of lightweight structures, must evaluate strength, stiffness and stability constraints. A designed structure must satisfy optimality criteria. One faces known difficulties when trying to implement several from above mentioned requirements into optimization problem for further successful numerical realisation. A method to formulate the optimization problem, incorporating all above described criterions, mathematical model and algorithm to solve it numerically, taking into account the geometrically non‐linear structural behaviour are presented for truss type structure. In each optimization cycle the member forces obtained in the previous optimization cycle via elastic‐plastic non‐linear analysis procedure are employed to obtain the new optimal design values. During the optimization procedures, the tension members are assumed to be loaded up to the yield limit, compression members are assumed to be stressed up to their critical limits, the nodal displaceme...

Optimization of elastic‐plastic geometrically non‐linear lightweight structures under stiffness and stability constraints

Truss optimization under stiffness, stability constraints and random loading

A mathematical model and calculation algorithm for geometrically non‐linear structure cross‐sectional optimisation are developed. Inelastic strains in the state prior to plastic collapse are evaluated. The algorithm is obtained combining the extreme energy principle for minimum value dissipated power and mathematical programming theory in concert with a large displacement analysis. An evaluation of dissipative features by employing inelastic strains finally results in a significant reducement of structure carrying capacity resource versus accounting its elastic response only. The safety requirements of structure involve stability conditions in addition to the strength ones. Stability conditions define the minimum cross‐sectional and slenderness values of structural members. An evaluation of the above‐mentioned factors restrict a free development of plastic strains, thus an optimal structure generally is in a state prior to plastic failure. The problem is solved iteratively, as the employed values...

Optimisation of geometrically non‐linear elastic‐plastic structures in the state prior to plastic collapse

Optimization of geometrically nonlinear elastic-plastic structures under stiffness constraints

Straipsnyje plėtojamas tampriosios plastinės rėminės konstrukcijos optimizacijos ir analizės uždavinių sprendimo algoritmas, įvertinant geometrinį netiesiskumą. Konstrukcija diskretizuojama baigtiniais strypiniais elementais, kurie yra tempiami arba gniuždomi ir kartu lenkiami. Pateikiamas tokios konstrukcijos elementų tangentinės standumo matricos sudarymo algoritmas, pritaikius matematinio programavimo paketo MatLab simbolinius skaiciavimus. Atliktas pasirinktos konfigūracijos rėminės konstrukcijos skaitinis eksperimentas. Netiesinės tamprios analizės rezultatai gauti taikant iteracinį apkrovos kontrolės Newtono ir Raphsono metodą. Nustatytas minimalus tūris konstrukcijos, kuri dar nėra pasiekusi visisko plastiskojo suirimo, taciau atskiri jos elementai jau deformuojasi plastiskai. Sudaryta konstrukcijos plastiskojo deformavimosi trajektorija.

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Romanas Karkauskas

Papers

Optimization of elastic‐plastic geometrically non‐linear lightweight structures under stiffness and stability constraints

Truss optimization under stiffness, stability constraints and random loading

Optimisation of geometrically non‐linear elastic‐plastic structures in the state prior to plastic collapse

Optimization of geometrically nonlinear elastic-plastic structures under stiffness constraints

Calculation of Elastic-Plastic Geometrically Nonlinear Frames