Miroslav Vokáč

Experimental Investigation of Mechanical Properties of Textile Glass Reinforcement

Mechanical tests were performed at the Klokner Institute on samples of a textile glass reinforcement. These tests will be used for determining the modulus of elasticity of textile glass reinforcements and for assessing the maximal stress that the samples will withstand. Both of these quantities are required for further modeling of the structures and for designing elements made from textile reinforced concrete (TRC). The tests were carried out on a total of 10 samples made from a single piece of 2D net (produced by V. FRAAS, GmbH, Germany). The tests were carried out on AR-glass reinforcement (alkali - resistant glass) textile glass with 2400 TEX [g/km] fineness, which is often supplied with dimensions of 1 x 2 m. The first 5 samples were prepared in the direction of the warp (the direction of the load-bearing reinforcement), and the remaining 5 samples were prepared from the transverse direction (the direction of the weft). These samples were loaded by a constant force increasing up to collapse. Then the modulus of elasticity of the textile glass reinforcement and the stress at the strength limit were determined from the monitored data.

Use of Textile Reinforced Concrete – Especially for Facade Panels

In recent years, textile reinforced concrete (TRC) is at the beginning of industrial production mainly in Germany and relates especially to facade panels and concrete footbridges. The subtle panels with a minimum thickness of coverage layer can be designed due to the textile reinforcement, which is resistant to corrosion. Furthermore, a long durability is expected in case of these structures. The textile reinforcement with the fine-grained ultra-high performance concrete (UHPC) enables to produce concrete elements with a minimum thickness. Therefore, the concrete element with up to 70 % lower weight compared to element with conventional reinforcement can be produced and significant environmental savings can be achieved (reducing the consumption of non-renewable raw materials, transport energy, reduced dead load acting on the supporting structure, etc.).

The Behaviour of the Embedded Rail in Interaction with Bridges

Since the introduction of the direct fastening system, Embedded Rail System (ERS) is probably one of the most spectacular and innovative developments in railway engineering. The development has become more rapid, especially in the last decade due to competitive advantages in comparison toother systems with respect to higher speed, cost effectiveness, environmental-material sustainability and others. But still there is a lack of specific interaction model, especially when it comes to bridges equipped with ERS system. Previous studies on ERS by Estzer Ludvigh2 found out some important coefficients (vertical and longitudinal bedding coefficient) and compared the longitudinal resistance of ERS with flexible fastening systems. Other studies on ERS do not specifically deal with the evaluation of longitudinal resistance of such a system. With a view to establish the typical behaviour pattern of ERS, this paper is dedicated to find out the interaction of a specific Embedded Rail System with bridges. A small scale test was conducted on a sample of ERS in the laboratory under different combinations of vertical and longitudinal track loads and subsequently a Finite Element Model (FEM) was developed to simulate the test. The paper presents the FEA result validation with test results, the interaction pattern, longitudinal resistance of ERS track for both loaded and unloaded conditions, design load distribution for such systems and some specific influences of ERS on simply supported bridge systems.

Degradation of Laminated Glass as Result of Increased Temperature

The degradation of laminated glass as a result of increased temperature has become one of the important problem of reconstructions and designs of new glass structures, for instance high-rise buildings that are exposed to the impacts of an intensive heating caused e. g. by sunshine. The temperatures during heating can reach very high values, commonly from 60 to 70 °C. The effect of heating was simulated using the thermal chamber where the glass panes with the size of 120 x 1100 mm were heated. The deformation course under the increase of temperature was continually monitored by a measuring unit. In total six types of foils joining particular layers of glass were examined. In this paper the experimentally gained results are compared with a numeric computer analysis and the particular kinds of interlayers are evaluated using the loss of shear interaction.

Thermal and load rate-dependent interaction between embedded rail system and bridge

Recent developments in the technology of a modern embedded rail system grant many new possibilities for improving the railway infrastructure. An embedded rail system significantly reduces noise and the dynamical impact affecting both the infrastructure and the rolling stock itself. An embedded rail system may be used for constructing any type of railway infrastructure including high-speed railways. Its attributes are also suitable for modernization of the current steel railway bridges or constructing new structures, where slender bridge decks are required. However, in a railway track equipped with an embedded rail system, stress increments rise due to its restricted expansion movement. This effect is naturally higher when the embedded rail system is placed on a bridge, because of their different deformation possibilities. For a wider use of embedded rail system, examining the interaction behavior between the embedded rail system and the substructure is a matter of essential importance. Furthermore, the nonlinear character of embedded rail system polymer-based components needs to be considered when examining their interaction behavior. Therefore, this paper aims at investigating the nonlinear coupling functions of an embedded rail system under the effects of temperature and load rate. For this purpose, a comprehensive analysis consisting of laboratory experiments, material tests of the embedded rail system components and subsequent numerical validation was performed. Results are concluded in the paper.

Influence of the adhesive type and metal substrate on adhesion of bonded joints after salt spray test

Abstract This article was focused on the evaluation of neutral salt spray test effect (according to ISO 9124), procedure E4, on mechanical properties of load-bearing adhesive joints. The study also comprises the influence of substrate material (mild steel, aluminum alloys) and substrate surface roughness (verified by optical confocal microscopy). The experimental program contained acrylate-based adhesive and hybrid silicone polyurethane based adhesive which were applied in double lap joints loaded by shear.

Textile Concrete in Adverse Conditions

Textile concrete (TRC) is a modern material that has been the subject of many scientific studies over the past two decades. It is a material based on a fine-grained cement-based matrix, fiber reinforced, fabric of acrylic-resistant glass, basalt or carbon reinforcement. The products from this material are thin-walled elements, which can be used, for example, for facade claddings elements, lost formwork, shell structures, garden architecture or for strengthening or repair of existing structural elements. This paper presents some examples of the behavior of glass reinforced textile concrete during exposure to road salts, under load of bending moment, at long-term loading at elevated temperatures, and assessment of glass fiber resistance during exposure simulating concrete pore solution.

Effect of Temperature Increasing on Deformation Properties of TRC

This paper presents a description of the changes in the deformation properties of TRC under a gradual increase in temperature. TRC [1, 2] is a composite material consisting of a fine-grained UHPC matrix and textile glass fibres, known as AR-Glass. A very high load-bearing composite can be produced by combining the high compressive strength of UHPC (approximately 150 MPa) and the high tensile strength of textile glass fibres (about 2200 MPa). Samples 1100 x 120 x 20 mm in size were produced for the experiment. The samples were placed in a thermal chamber and were submitted to a constant load. In the next step, a gradual increase in temperature up to 75oC was simulated using heating cables located on the bottom of the chamber. We monitored the changes in bending in the middle of the span. Since the experiments are very time-consuming, the experiment was also simulated using a numerical model. Finally, there is a qualitative comparison of the two methods.

Safety Design of Laminated Glass Regarding PVB Interlayer Stiffness for Large Glass Facades and Shop Windows

When looking at current architecture, we can notice large glass facades and shop windows. These elements are usually made of laminated glass panes with polymeric interlayer between and the task of shear forces transfer is the subject of a current survey especially in case of accidental load cases. It essentially depends on polymer material stiffness, which is temperature, load duration and loading rate dependent. A lot of different polymeric interlayers with different properties are available on a market but their experimentally determined material properties with respect to the load duration and temperature are not mostly specified. Structural engineers tend to design laminated glass structural elements on the safe side and do not take the interlayer stiffness into account. This leads to uneconomical and robust glass bearing members. In case of accidental load verification, shear stiffness of used interlayers plays a significant role. This paper is focused on two types of PVB (polyvinyl-buthyral interlayers) experimental investigation under various temperature and loading rate conditions.

Determination of PVB interlayer’s shear modulus and its effect on normal stress distribution in laminated glass panels

Noticing the current architecture, there are many examples of glass bearing members such as beams, panes, ribs stairs or even columns. Most of these elements are made of laminated glass from panes bonded by polymer interlayer so the task of transferring shear forces between the glass panes needs to be investigated due to the lack of knowledge. This transfer depends on stiffness of polymer material, which is affected by temperature and load duration. It is essential to catch the safe side with limit cases when designing these members if the exact material behaviour is not specified. There are lots of interlayers for structural laminated glass applications available on a market. Most of them exhibit different properties, which need to be experimentally verified. This paper is focused on tangent shear modulus of PVB (polyvinyl-buthyral) interlayer and its effect on the stress distribution in glass panes when loaded. This distribution may be determined experimentally or numerically, respectively. This enables to design structural laminated glass members more effectively regarding price and safety. Furthermore, this is the way, how to extend the use of laminated glass in architectural design.