Tomáš Plachy

An Experiment Focused on Fans Behaviour and Induced Grandstand Vibrations during a Football Match

The sport fans behaviour has changed in recent decades, especially on football and ice hockey stadiums in the Czech Republic. Currently the fans more support their sport teams with more intensive cheering like as jumping or swaying. The main results of an experimental analysis that was focused on fans behaviour and simultaneously on the induced vibrations of a selected cantilever grandstand sector during a football match are mentioned in the paper. The actual types of fans cheering, the changes in fans behaviour during the match, relative proportion of active and passive spectators, the features and the levels of grandstand vibrations were investigated in detail.

Utilization of Recycled Fine-Ground Concrete from Railway Sleepers for Production of Cement-Based Binder

The environmental awareness and potential cost reduction have promoted the recycling of materials in civil engineering. This paper is dealing with the recycling and secondary use of old concrete railway sleepers for reconstruction of old railway lines. In particular, it is focused on the investigation of material properties of a binder prepared from finely crushed old concrete sleepers. This material could be used for strengthening of subsoil and embankments supporting the railway structures. The study shows that the compressive and bending strength of the investigated material is sufficient for this purpose and that the strength can be further increased by suitable curing conditions. These findings could contribute to the utilization of old concrete sleepers during railway reconstructions and safe money spent for the purchase of new materials and disposal of old sleepers.

Influence of Aggregate Stiffness on Fracture-Mechanical Properties of Lime-Based Mortars

Addition of relatively stiff aggregates into lime-based mortars is responsible for an increase of the effective mortar stiffness and stress concentrations around aggregates during mechanical loading. To observe the damage development during the three-point bending and splitting tests a 2D plane-stress nonlinear finite element analysis utilizing isotropic damage model was carried out and the results were validated against experimentally obtained data. The study revealed that the finite element model is able to capture the trends observed during the experimental investigation. The results of the numerical modeling and experimental investigation show the advantages of the use of relatively compliant crushed brick aggregates in ancient structures.

An Experimental Analysis of Grandstand Vibrations Caused by Crowd of Spectators during Two Football Matches

A significant dynamic load may be induced by synchronize movement of larger spectators group (like as jumping, bouncing, jouncing, swaying or abruptly rising) on a sport stadium during a sport event. This load could generate discomforting grandstand vibrations and in some extreme cases, the large grandstand vibrations are detectable by spectators even visually. A dynamic experiment is described in the paper which was realized on a steel cantilever grandstand during two football matches in the place where the most active spectators were concentrated. Vertical grandstand accelerations were observed in three points that were located at the ends of three grandstand main beams. The results of the experiment had shown predictably that the most excessive grandstand vibrations were induced by fans in the particular situations when the home team scored a goal and during the fans celebration after the matches especially. In these particular situations, the detected vibrations could be perceived by spectators as uncomfortable.

Experimental Evaluation of Tensile Forces in Short Steel Rods

There are a lot of structures in building and civil engineering where the significant structural elements are loaded by large tensile forces (e.g. tension bars of building structures). In many practical cases it is important to know the actual value of tensile forces in tensile structural elements for assessment of their reliability. The four experimental techniques are used for determination of tensile forces in practice most often. The vibration frequency method, which is one of them, is very suitable for experiments done only one time or sometimes, especially in cases when the examined structural elements are already activated and the application of an experimental method is necessary in this situation. The experiment described in this paper was focused on the tensile force determination in steel rods, which were very short and relatively stiff. The evaluated tensile forces of the investigated short steel rods were affected by a significant error when only the simplest models (the string model, the simply supported beam and the fixed beam) and measured natural frequencies were applied. In order to precise the determined tensile forces, the theoretical beam model supported by simple supports with torsion springs (“the elastically fixed beam”) and the measured natural modes of the rods had to be necessarily taken into account.

Non-Destructive Testing of Composite Gypsum Material Properties – Long Time Measurement

The paper presents results of long-time investigation of mechanical properties of composite gypsum material using nondestructive technique. The gypsum block was put to the façade of the building for four years. Then it was removed and cut to smaller specimens, which were investigated. The matrix of 6 × 4 specimens of dimensions 40 × 40 × 160 mm were cut from the block after its removal from the façade. After 6 and 9 years, the Young’s moduli and shear moduli of these specimens were determined from the transversal, longitudinal and torsional vibrations using the impulse excitation method.

The Experimental Observation of the Prestress Forces in the Structural Elements of a Tension Fabric Structure

The periodic experimental observation of the prestress forces in some selected structural elements of the tension fabric structure is mentioned in this paper. The described experiment was focused to the tension fabric roof which covers the tram stop K Barrandovu in Prague. So far the observation was performed three times and it was every time aimed on three types of basic structural elements support cables anchored to the ground, edge cables placed in a fabric pocket and fabric membranes. The used non-destructive experimental procedures are based on the geometrical nonlinearity and the frequency method, the applied measurement system was developed by authors. The dependence of cable forces on temperature changes can be found out from the obtained results.

Pulse Method Used for Non-Destructive Assessment of Glued Laminated Timber Beams

This text is focused on GLULAM (glued laminated timber) beams and determination of their properties. This text is mainly focused just on part of more complex research of glued laminated timber beams. This text is focused on pulse method, which is used to determine the dynamic modulus of elasticity of GLULAM beams. This text will describe how the pulse method works, with basic description, describes the tested material and compare the results of testing. In the conclusion we discuss the results, make conclusions and describe the way of our further research of glued laminated timber beams.

Destructive and Nondestructive Evaluation of Frost Resistance of Cement Pastes with Fly Ash

This paper is dedicated to the use of fly ash in cement and concrete. Using fly ash in cement and concrete has ecological and economic benefits. However, it is important to correctly apply the fly ash. If the substitution is close to 50% or more by weight of clinker (HVFAC - High-Volume Fly Ash Concrete), it is necessary to monitor the material and mechanical properties. This paper describes an analysis of a frost resistance of a cement paste with fly ash. The destructive and non-destructive tests were carried out.

Detection of Cracks on Small Specimens Based on Modal Analysis

The paper presents the detection and localization of the induced cracks on small specimens based on a modal analysis. The cracks were induced to cement specimens of dimensions 40 × 40 × 160 mm in three different positions. Their position was detected using different techniques based on natural mode shape changes between virgin and damage states of the specimen. The sensitivity of these techniques to the damage level and position was investigated, compared and then discussed in the conclusion.