Linear dynamic properties in curved laminated glasses

The study presents the results of linear dynamics of laminated glass panels with different curvatures. This is an actual task in the field of mechanical engineering, aviation, shipbuilding, energy, architecture, etc. Such composites are durable, easy to care for and have a wide range of design options. The aim of the work is to study the influence of the curvature parameter on the frequencies and modes of composites. The paper considers the linear characteristics for laminated glass with polyvinyl butyral interlayer. The article considers behavior of the triplex and the propagation of elastic waves in the linear state. The paper performs calculations using the finite element method in the framework of modal analysis in a three-dimensional formulation in the framework of a physical linear-elastic formulation. The study uses hexagonal finite element with 8 nodes with 3 degrees of freedom in each. This work model laminated glass with a curvature parameter ranging from 0 mm to 250 mm. The composite consisted of three layers: two glass layers thickness of each was 3 mm, and a polyvinyl butyral interlayer with 0.38 mm thickness. The size of the plates was 500×500 mm. As a boundary condition, the laminate was fixed on two opposite sides. The article performs mesh size convergence analysis. The results of natural frequencies in accordance with the curvature parameter are derived. The graphs of natural vibration modes are also shown, that give a clear view about the state of composites.

Structural performance of a novel liquid-laminated embedded connection for glass

Connections between load-bearing glass components play a major role in terms of the structural integrity and aesthetics of glass applications. Recently, a new type of adhesive connection, known as embedded laminated glass connections, has been developed where a metallic insert is embedded within a laminated glass unit by means of transparent polymeric foil interlayers and assembled through an autoclave lamination process. In this study, a novel variant of this connection, consisting of a thin steel insert encapsulated by a transparent cold-poured resin, is proposed and examined. In particular, the axial tensile mechanical response of this connection is assessed via numerical (FE) analyses and destructive pull-out tests performed on physical prototypes at different displacement rates in order to assess the effect of the strain rate-dependent behaviour of the resin interlayer. It was found that the pull-out stiffness, the maximum load-bearing capacity and the failure mode of the connection are significantly affected by the imposed displacement rate. The numerical (FE) analysis of the pull-out tests, performed in Abaqus, showed that the complex state of stress in the vicinity of the connection is the result of two load-transfer mechanisms and that the relative contribution of these mechanisms depends on the insert geometry and the relative stiffnesses of the constituent materials. Overall, it is concluded that the prototypes are promising in terms of manufacturability, aesthetics and structural performance and thus the novel variant connection considered in this study offers a promising alternative to existing load-bearing connections for laminated glass structures, but further investigations are required to ascertain its suitability for real-world applications.

Proposal for a Safety Qualification Program for Vehicle-Integrated PV Modules

We propose a safety qualification program for vehicle-integrated photovoltaic (VIPV) modules, which could serve as a simplification, thereby accelerating the homologation process of new vehicle designs. The basis is the current photovoltaic (PV) module safety qualification, as defined in IEC 61730:2016, which is compared to automotive norms and regulations because additional safety requirements have to be considered for PV modules used in this application. Therefore, testing based on regulations that concern electrical and electronic equipment in vehicles (ISO 16750), rupture safety of glass and laminated glass in vehicles (ECE R43), and pedestrian safety (ECE R127) are assessed and compared in terms of severity. Additionally, optional testing concerning the long-term stability of VIPV modules is recommended, as a guideline for vehicle manufacturers. If assessed to be necessary, the qualification program of IEC 61730 is complemented by the respective tests to finally present a conclusive safety qualification program for VIPV modules in new vehicle designs.

Post-Breakage Vibration Frequency Analysis of In-Service Pedestrian Laminated Glass Modular Units

The vibration performance of pedestrian structures has attracted the attention of several studies, especially with respect to unfavourable operational conditions or possible damage scenarios. Specific vibration comfort levels must be commonly satisfied in addition to basic safety requirements, depending on the class of use, the structural typology and the materials involved. Careful consideration could be thus needed at the design stage (in terms of serviceability and ultimate limit state requirements), but also during the service life of a given pedestrian system. As for structural health monitoring purposes, early damage detection and maintenance interventions on constructed facilities, vibration frequency estimates are also known to represent a preliminary but rather important diagnostic parameter. In this paper, the attention is focused on the post-breakage vibration analysis of in-service triple laminated glass (LG) modular units that are part of a case-study indoor walkway in Italy. On-site non-destructive experimental methods and dynamic identification techniques are used for the vibration performance assessment of a partially cracked LG panel (LGF), compared to an uncracked modular unit (LGU). Equivalent material properties are derived to account for the fractured glass layer, and compared with literature data for post-breakage calculations. The derivation of experimental dynamic parameters for the post-breakage mechanical characterization of the structural system is supported by finite element (FE) numerical models and parametric frequency analyses.

Simple Laminated Glass Panels with Embedded Point Connection under Short-Term Load

Glass is a very attractive material for contemporary architecture. The trend is to achieve a maximum transparency of structures; therefore it becomes common to use glass as a material for load-bearing structural elements. Glass facades, roofs, beams or columns are widely used in buildings. The problematic part of a glass structure design is the connection between the glass pieces or between the glass elements and substructures from another material (e.g. steel, concrete etc.). The connection must be capable of bearing the stresses performing during the lifetime period and it should be as unobtrusive as possible at the same time. The ongoing research at the Faculty of Civil Engineering of the Czech Technical University in Prague is focused on an embedded laminated point connection for glass structures. Within this research, the real-scale glass panels were tested. The samples consisted of two glass plies bonded with the EVA foil. For the undrilled ply, the float glass was used in all cases. The thermally toughened or the heat strengthened glass was used for the pre-drilled ply. There was one embedded steel countersunk bolt with HDPE liners placed in each corner of the sample. During the experiment, the samples were horizontally placed using the embedded bolts. The load-bearing capacity of the six tested specimens was determined. The load was applied in several loading and unloading cycles until the collapse of the first embedded connection. If the glass panel failed before the connection, the sample was completely unloaded and then the load was gradually increasing until the collapse of the connection. Vertical deflection and the stresses at two different points were measured during the loading cycles. The humidity and the temperature were also monitored. The experiment showed the way of collapse and a short-term load-bearing capacity of a laminated glass panel with four embedded point connections.