Martina Eliášová

Material properties of adhesives for shear bonded connections of structural glass

Thanks to intensive research in the field of polymer adhesives in the last few years, there is a possibility of using a glued joint with a real load bearing role. The reliability of adhesive in the connection during the lifetime of a structure is affected by many factors, but the initial choice of a proper adhesive material is the most crucial one. The article deals with the experimental analysis focused on the determination of material characteristics of adhesives in planar connections, it describes the effect of various factors on the behavior of an adhesive joint under increasing loads, its ultimate bearing capacity and its failure modes. The main investigated factors are the type of adhesive, the type of connected materials (material of substrate), surface treatment and the thickness of the adhesive layer. A special part of the article describes numerical models of a glued joint with respect to different types of adhesive.

Shear Adhesive Connections for Glass Structures

Unique aesthetical properties of glass - not only transparency but also smooth, glossy and primarily reflective surface - give this material special importance in the contemporary architecture. In every structural application of glass it is necessary to solve the problem associated with connections between glass pane and other part from a different material or between two glass elements. Moreover, there are many types of hybrid structures that combine glass and different materials to achieve safe failure behaviour and high degree of transparency at the same time. Connection of brittle glass and reinforcing material is an essential part of these structures, where composite action between two parts is beneficially ensured by a glued joint. The current paper deals with the experimental analysis focused on the determination of mechanical characteristics of adhesives applied in planar connections under shear loading.

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.

Glass Columns under Impact - Experimental and Numerical Analyses

Compared to traditional construction materials, structural glass members subjected to main compression are relatively unusual in buildings, despite a substantially high material compressive strength. The major limit for the use of glass columns is in fact represented by an overall residual load-bearing capacity highly affected by the tensile brittle fracture of glass. An optimal and fail-safe design approach, in this regard, should take care of a multitude of geometrical and mechanical aspects, including boundary details and possible defects, as well as accidental loading scenarios. Aiming to assess the feasibility and vulnerability of structural glass members, based on earlier research efforts, the paper deals on the load-bearing performance of a reference set of full-scale glass columns. Careful consideration is in fact paid for the experimental investigation of glass members with square hollow cross-section and subjected to dynamic impacts, being representative of an accidental loading scenario. Full-scale experimental results are presented, as well as further considered for validation and calibration of Finite Element (FE) numerical models accounting for possible damage propagation in all the structural components, hence allowing to assess the residual load-bearing capacity of the examined structural typology.

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.

Environmental Conditions Effect for Adhesive Connections in Glass Structures

Load-bearing joints of glass structures belong to the one of new applications of adhesive connections in civil engineering. They provide several important benefits particularly even stress distribution along the contact depending on geometry and stiffness of the glue joint, which is crucial for brittle glass. There is a lack of knowledge about semi-flexible or semi-rigid adhesive connections in the structural glass field and durability is one of the essential properties that have to be assessed during design-process of bonded connection. An extensive research focused on shear glued joints in glass structures was performed at CTU in Prague, which also comprised environmental effect simulation on the glued specimens in laboratory accelerated conditions. The paper is dedicated to impact of ageing to the specimens and their mechanical properties together with brief overview of available laboratory ageing methods.

Stability of Glass Structural Elements Subjected to Bending

Glass has got important role in modern architecture not only because of its transparency, interior lighting and for aesthetical function but nowadays also more often for its load bearing function. Design of structural glass elements is limited by the lack of knowledge and standards, especially in case of stability problems of beams or columns. Slender glass beams with rectangular cross-section tend to fail because of instability.

Behavior of Glued Connections under Shear Loading

An intensive research in load-bearing glass structures leads to the requirement for performing glass-to-glass or glass-to-different material connections. Glued shear connection is suitable for these applications mainly due to its uniform stress distribution in larger area in comparison with bolted connections. The reliability of adhesive in the connection during the life time of a structure is affected by many factors, [1], [2], [3], [4]. The article deals with the experimental analysis focused on the determination of material characteristics of adhesives in planar connections, it describes the effect of various factors on the behavior of an adhesive joint under increasing shear loads, its ultimate load-bearing capacity and its failure modes. The main investigated factors are the type of adhesive, the type of connected materials (material of substrate), surface treatment and the thickness of the adhesive layer. Due to importance of adhesive layer thickness especially in rigid and semi-rigid glues, numerical models responding to the effect of thickness was carried out.

Flexural Strength of Float Glass

A series of simple and laminated glass tests were carried out under laboratory conditions at the Klokner Institute. The test specimens comprised panes made from float glass with dimensions of 1.1 x 0.36 m. The paper contains experimentally determined characteristic values of flexural strength and estimated design values related to commonly used glass.

Experimental Investigation of Transparent Glazed Noise Reducing Traffic Barrier against Impact of Flying Stones

Number of experimental tests was carried out to simulate a flying stone at road noise barriers under laboratory conditions in the Klokner Institute laboratory. Prefabricated modules made in the Czech Republic were used for these experiments. It was designed testing system consisting of a toughened steel pin, the guiding device and the supporting scaffolding. This system allows to simulate the impact of the steel hammer with kinetic energy of 30 Nm in accordance with the requirements of the standard ČSN EN 1974-1 [.