Marcela Karmazínová

Thin-Walled Cold-Formed Steel Beams with Holes in Lateral Flexural-Torsional Buckling

In this paper the study on lateral flexural-torsional buckling of steel sigma-cross-section beams with web holes will be presented. The analysis of corresponding stability problem is based on general approach derived for a group of beams including at least mono-symmetric sections loaded transversally to their plane of symmetry. The effective flexural and torsional stiffness of steel beams with holes has been verified by tests. The results of theoretical analysis were compared with specification design procedure and also with actual behaviour of set of beams investigated by experiments. The study conclusions aim to become the background of the supplements to specified provisions for the design of steel structures.

Material Testing and Evaluation of Steel Mechanical Properties for Classification of Steel Grade of Existing Civil Engineering Structure

The paper is generally focused on the determination and evaluation of yield and ultimate strengths of structural steels, not only current materials but also materials of existing steel structures when the properties are unknown and no material certificates exist. The attention is paid i.a. to the testing and evaluation of steel strengths, especially from the viewpoint of the statistical elaboration of material test results aimed to obtain strength values leading to the reliable structural design [3], in the meaning of general rules according to the European Standards for structural design of civil engineering constructions. The paper deals with actual yield and ultimate strengths obtained using material tests and with characteristic and design strengths based on the test results evaluation versus nominal and design strengths given by European Standards which are used for the structural design in the usual cases when steel grade is known. But in the case of existing structures, very often no information about the material exist that actual values of steel properties shall be determined using material tests and their statistical elaboration to obtain such values of steel properties which lead to the reliable structural design [3], [6], [7]. However, approaches of the derivation of characteristic and design steel strengths using actual test results are principally different from the consideration of nominal and design steel strengths covered by the rules of the European Standards. This paper illustrates the evaluation of the results of material tests performed on the test specimens taken from the steel roof structure of the sport stadium almost 50 years aged, within the diagnostics of load-carrying steel structures of this building [1] aimed to the evaluation of the existing construction [2].

Experimental Verification of Glass-Fibre-Concrete Covers of Footbridge Deck Cornice, Subjected to Wind Loading Actions

The paper summarizes the results and evaluation of tests of the resistance of glass-fibre-concrete components used for footbridge deck cover subjected to wind loading actions. The main aims of this research was not only to verify the objective load-carrying capacity and serviceability of covering panels, but also to verify the use of glass-fibre-concrete and its properties, if applied for non-typical product. The tests also show the usage of the unique and effective method of the vacuum loading. The research has been elaborated based on the requirements of DAKO Brno Ltd. Company.

Classification of Structural Steel of Existing Civil Engineering Structure Based on Testing and Evaluation of Yield and Ultimate Strengths

The paper is generally focused on yield and ultimate strengths of structural steels. The attention is mainly paid to the testing and subsequent determination of steel strengths, especially from the viewpoint of the statistical evaluation aimed to obtain the strength values leading to the reliable structural design, in the meaning of general rules given by the European Standard for the structural design of civil engineering constructions. The presented paper deals with the actual yield and ultimate strengths obtained from material tests and their characteristic and design values based on the test results evaluation, versus nominal and design values considered according to European Standard rules and used for the structural design in the usual cases if the steel grade is known. But in the case of existing constructions, sometimes there are no information about the material that the actual steel properties shall be determined using the material tests and their statistical evaluation to obtain such steel properties values which can lead to the reliable structural design. However, approaches of the determination of characteristic and design steel strengths using actual test results are different from the determination of the nominal and design steel strengths given by standard rules. As an illustration the paper summaries the results and evaluations of tests of structural steel performed on the specimens taken from the load-carrying roof structure of the sport stadium aged about 40 years, within the steel construction diagnostics.

Load-Carrying Capacity of Cantilevers of Anti-Flood Barriers Made of FRP Composite Structural Profiles

After the devastating floods in the Europe and Czech Republic especially, in 1997, 2002 and 2007 years, the need of the anti-flood protection was very actual and delicate. One of the ways, how to solve this problem in the case of usual or lower water level, is the usage of anti-flood barriers. The paper is focused on the experimental verification of the actual behaviour, load-carrying capacity and failure mechanisms of the cantilevers made of FRP composite profiles PREFEN, which are in reality used as columns of anti-flood barriers. The investigated water-proof profile of H-cross-section is composed of epoxy resin and glass fibres.

Fatigue Loading Tests and Acceptance Criteria of Reinforced Pre-Stressed Concrete Railway Sleepers

The paper is focused on the problems of the fatigue behaviour, failure and resistance of reinforced pre-stressed concrete railway sleepers, developed and verified continuously in the period of several last years. The results of fatigue loading tests are presented for the sleepers for both wide and narrow track gauge. Test results have been evaluated using the criteria for the acceptance based on the load corresponding to the prescribed crack width and the load at the moment of total fracture.

Failure Modes and Acceptance Criteria of Reinforced Prestressed Concrete Railway Sleepers Based on Dynamic Loading Tests

The paper is focused on the problems of the dynamic behaviour, failure and resistance of reinforced prestressed concrete railway sleepers, developed and verified continuously in the period of several last years. The results of dynamic loading tests are presented for the sleepers for both wide and narrow track gauge. The test results have been evaluated using the criteria for the acceptance based on the load corresponding to the prescribed crack width and the load at the moment of total fracture.

Experimental Verification of Atmospheric Physical Influence on Behaviour of Glass-Fibre-Concrete Façade Panels

The paper presents the brief information on particular results of experimental study focused to the problems of behaviour of structural plated components made of glass-fibre-concrete and used in building constructions, exposed to the atmospheric physical effects caused by the weather changes in the summer period. Weather changes represented namely by temperature and rain cause also the changes of the temperature and moisture of the investigated structural components. This can affect their static behaviour that means stresses and deformations, which have been monitored as the main outputs of tests performed. Experimental verification is based on the simulation of the influence of temperature and rain using the defined procedure of warming and water sprinkling with respect to the corresponding weather conditions during summer period in the South Moravian region at the Czech Republic, where the application of these structural components is mainly considered. Within this experimental programme glass-fibre-concrete panels used for building façades have been tested.

Static Loading Tests of New Type of Bolt Assembly Connection Developed for Perspective Temporary Steel Railway Bridges

The paper deals with the problems of the actual behaviour, failure mechanism and load-carrying capacity of the special bolt connection developed and intended for the assembly joints of the truss main girders chords of perspective railway steel temporary bridges. Within the framework of this problem solution, several types of structural details of assembly joints have been considered as the conceptual structural design. Based on the preliminary evaluation of advantages or disadvantages of these ones, in principle two basic structural configurations – so-called “tooth” and “splice plate” connections have been selected for the subsequent detailed investigation. This investigation is mainly based on the experimental verification of the actual behaviour, strain and failure mechanism and corresponding strength of the connection, and on its numerical modelling using FEM. This paper is focused only on the static loading tests results of the splice plate connections and their evaluation, which have already been finished. Simultaneously with the static tests, the fatigue loading tests are being realized, too, but they have not been finished so far, as well as the FEM numerical modelling.

Experimental Verification of Fatigue Resistance of Steel Expansion Anchors to Concrete Loaded by Cyclic Tensile Force with Regard to Particular Failure Modes

The paper deals with some questions of the actual behaviour of post-installed anchoring elements and it is oriented to the problems of the behaviour of steel expansion anchors to concrete under repeated tension loading, especially. In this connection, the paper is mainly directed towards the investigation of the strain and failure mechanism from the viewpoint of the possibilities of the resistance determination using experimental results. Specifically, this paper presents some brief information about the results of loading tests of expansion anchors loaded by the actions of cyclic tensile force, also in relation to the similar results referenced in literature.