Laminated Glass Panels Research Articles

Natural frequencies and damping ratios of multi-layered laminated glass beams using a dynamic effective thickness

Multi-layered laminated glass panels are those with at least three monolithic glass layers and two viscoelastic interlayers. Multi-layered laminated glass panels are commonly used in floors, roofs and other horizontal glazing accessible to the public where a high level of security is required. Although the glass can be consider as a linear-elastic material, the viscoelastic interlayers determine a non-linear behavior of the laminated structure that must be taken into consideration. In this paper, a dynamic effective thickness is proposed to predict the natural frequencies and damping ratios of multi-layered laminated glass beam-like structures with different boundary conditions and at different temperatures. Furthermore, the presented dynamic effective thickness can be also used to any frequency domain calculations such as displacements and stresses. To validate the proposed model, operational modal analysis was carried out on a multi-layered laminated glass beam to obtain the experimental natural frequencies and damping ratios at 20, 25, 30 and 35℃. Moreover, a finite element model of the beam was also assembly for the sake of comparison. The proposed model predicts the natural frequencies with errors less than 5%, whereas the discrepancies in damping ratios are less than 50%.

Material characterization for laminated glass composite panel

Purpose: Laminated glass composite panel (LGCP) with at least one flexible plastic/ viscoelastic interlayer is considered. The purpose of this paper is to determine the material properties of the constituents of LGCP required for accurate modelling of the laminated glass structures. Design/methodology/approach: The proposed approach includes the following three type of tests: non-destructive tests for determining mechanical properties of the glass layers (based on wave propagation), mechanical tests and finite element simulations for determining properties of the interlayers, measuring residual stresses in glass layers using novel methods and equipment (non-destructive, wave propagation based). Findings: Methodology and procedures for determining material properties of the LGCP. Research limitations/implications: Due to fact that the shear moduli of the viscoelastic interlayers and glass skin layers differs up to thousands times, the direct application of the classical sandwich theory may lead to inaccurate results. The layer wise plate theory with viscoelastic interlayer should be applied. In the case of layer wise theory, the material properties should be determined for each layer (not averaged properties for laminate only). Practical implications: The proposed approach allows to determine the properties of the LGCP components with high accuracy and form base for development of accurate plate model for modelling vibration, buckling and bending of the LGCP. The effect of the residual stresses is most commonly omitted in engineering applications. However, in the case of tempered glass the residual stresses are significant and have obviously impact on stress- strain behaviour of the laminated glass panel. Originality/value: Study consists of valuable parts, i.e. determining residual stresses in glass performed in cooperation with private company GlasStress Ltd. Special software and measuring equipment are developed. Further LGCP interlayer mechanical properties are tested experimentally and using simulation tools for design optimization purposes.

Correlation between Numerical and Experimental Tests of Laminated Glass Panels with Visco-elastic Interlayer

Present research is focused on numerical and experimental investigation of glass laminate structure consolidated with ethylene vinyl acetate film. The European wide industry standard for laminate glass panels is considered polyvinyl butyral interlayer film where ethylene vinyl acetate layer is particular out of autoclave manufacturing process related. Conducted numerical and experimental research worldwide rarely consider this type of polymer in lamination process even though in Baltic‘s this is industry standard. So far such glass laminate products are not mechanically characterised to the level that experimental results correlation with numerical predictions to give an engineers required confidence. Therefore current research initially characterise post cured ethylene vinyl acetate film then integration of viscoelastic material properties in numerical four point bending analysis and finally verification with non-contact measurements of natural frequencies to assess mechanical response of laminate glass panels. It was shown that by introducing non-linear viscoelastic behaviour of ethylene vinyl acetate film for depicting mechanical behaviour in 4-point bending the discrepancy between numerical and experimental results was less than 5% whereas assuming the interlayer as isotropic material only obtained discrepancy reached up to 50%.

Effects of stiffening sealant thickness on the structural performance of structural silicone glazing (SSG) sealant connections in curtain wall systems

This paper describes the experimental results of tests of the structural behavior of structural silicone glazing (SSG) sealant connections in a curtain wall system in which structural sealant is placed between an aluminum frame and laminated glass panel. Cases often have been found where the structural sealant has been applied at a 45° angle from the inside of the curtain wall. Thus, assessment of the structural behavior of the SSG connections between the aluminum frame and glass panel in a curtain wall system is required. The tests conducted in this research include variables such as the use of Norton tape, the application (or omission) of end sealant, the thickness of the stiffening sealant applied on top of the structural sealant, and the span length of the glass panel. The test results indicate that the use of Norton tape directly affects the initial stiffness and strength values of the SSG connection and that the application of end sealant improves the strength and ductility of the SSG connection. However, the change in the maximum load per unit length caused by the application of stiffening sealant on the existing structural sealant was found to be insignificant.

Blast test and numerical simulation of point-supported glazing

The blast resistance of point-supported laminated glass curtain wall has been investigated by means of field blast tests and numerical simulation. Nine site blast tests were carried out, considering two types of glass thickness and six TNT charges ranging from 0.4 to 30 kg. The overpressure and displacement time histories were measured and the failure modes were observed. The overpressure obtained from the measurement panel exhibited a typical pattern of near-field blast with a steep increase followed by a rapid decay within a few milliseconds. The displacement response of the laminated glass panels increased with the increase in the TNT charge almost linearly in the smaller tests (scaled distance ranging 4.5–7 m/kg1/3), which was in line with the increase in the blast impulse in these tests. The failure mode of the point-supported laminated glass panels was featured by tearing off of the polyvinyl butyral layer around the support area, while the glass shards still adhered to the polyvinyl butyral interlayer. Nonlinear dynamic finite element simulation agrees reasonably well with the results from the blast tests. Severe stress concentration has been predicted to occur at the rim of the support holes, leading to initiation of failure at these supports, and this also agrees with the failure mode observed from the blast test. Finally, parametric studies are carried out to investigate the influence of TNT charge weight and the geometric parameters of the panel on the blast response of the glass curtain wall.

Numerical simulation of the EN 12600 Pendulum Test for Structural Glass

In modern-day architecture, transparent glass units are omnipresent as large facades, windows, floors and balustrades. To ensure safety in an accident, glass panels must successfully pass the 'human impact' test, described by the international standard EN 12600. This test setup consists of a steel frame in which the test plate is clamped with prescribed force; and the pendulum impactor, hanging from a steel cable. The impactor weighs a total 50 kg and is built up from a rigid steel core to which two small tyres are mounted. The window panels are assigned a qualification number as they remain intact, fracture without losing integrity or fragment completely in impacts from different drop heights. As experimental testing is expensive and time-consuming, there is an interest in numerical modelling to predict a qualifying glass panel, which is already allowed by the German standard DIN 18008-4. Several modelling approaches allow the impact simulation for intact glass panels. This paper presents a detailed numerical model for the pendulum impact which enables realistic simulation of impactor, frame and test plate, to be valid also for the post-breakage safety assessment of laminated glass. The model shows good correspondence for static compression of the tyres and for impact against a pressure plate. Further comparison is made for the impact on a laminated glass panel that remains intact. Although less suited for structural design qualification, the detailed model can be used for future simulation of the post-breakage response of laminated glass panels.

FE Exploratory Investigation on the Performance of SMA‐Reinforced Laminated Glass Panels

Shape‐Memory Alloys (SMAs) are a class of metal materials that exhibit two outstanding properties, the superelastic and the shape‐memory effects. Taking advantage of these properties, several SMA actuator wires and plates have been proposed over the last years in robotic, automotive, and biomedical engineering. In this paper, the feasibility of a novel design concept of SMA‐reinforced laminated glass panels is proposed, based on an adaptive embedded system built up of SMA wires. Glass panels used as cladding walls in facades have in fact typically high size‐to‐thickness ratios, hence, major restrictions in design are represented by prevention of glass failure and large deflections. It is expected, based on the current investigation, that useful design recommendations can be derived for this novel design concept.

Improvement in impact properties of laminated glass panels through surface treatment and silane coupling agent

Improvement in impact properties of laminated glass panels through surface treatment and silane coupling agent

Adaptive glass panels using shape-memory alloys

Due to the growing application of laminated glass panels in building facades and roofs, tending towards the minimization of frameworks, substructures and supports, technological solutions based on the use of glass panels with increasingly wide dimensions and modern design principles are becoming more frequent. The growing use of structural glass applications is leading to “lighter” and “smarter” optimized design solutions. The design of such applications greatly depends on the material mechanical properties of their structural elements and on their sensitivity to ambient and loading conditions. This is the specific case of laminated glass, where a temperature and time loading sensitive interlayer is generally used to bond together two (or more) glass panes with brittle behavior and rather limited tensile resistance. In this research paper, a novel adaptive glass panel concept is developed by using shape-memory alloy (SMA) cables, and assessed by means of Finite-element numerical studies and experimental validation. Based on the case study of an existing laminated glass roof panel, several geometrical configurations of practical interest are investigated. A key role in the proposed approach is the application of external pre-stressing based on the Joule heating of the SMA bracing system. The structural efficiency of the cable system is emphasized by taking into account the effects of ordinary wind pressures and temperature variations. Due to the innovative adaptive control system, as shown, the structural performance of traditional laminated glass panels can be enhanced, e.g. optimized in terms of maximum displacements and stresses in the glass, as well as in the overall dimensions and thicknesses of the glass panes.

보강두께 및 방법에 따른 실리콘 폴리머 구조용 실링재의 부착성능 평가

This paper describes the adhesion performance of silicone polymer structural sealant in aluminum curtain wall system. There is marked contrast between standard details and actual details of structural sealant in south Korea. Therefore, this paper explores the capacity of actual detail and repaired system. Test variables included the construction of norton tape and boundary sealant, repaired method and thickness of sealant. The one-way laminated glass panels were supported on two sides and subjected lateral load for condition of wind load applied. The test results indicated that norton tape affects the stiffness and strength of connection between glass and aluminum frame. On the other hand, the boundary sealant affects the ductility of that. There is are no significant effects of sealant thickness and repaired method on strength of connection, and observed the difference between measured capacity of specimens and design capacity of those. Therefore, the proposed reduction ratio based on measured results to reflect the actual construction details.

Low Velocity Impact Behaviors of a Laminated Glass

Dynamic behaviors of a laminated glass subjected to foreign object impact are studied by the use of the developed finite element program. A finite element simulation based on a higher-order beam finite element and a PVB interlayer model is applied to compute the dynamic responses of laminated glass panel. In this analysis, the glass plies and PVB interlayer are modeled as linear elastic. The results such as the histories of contact force and deflection, and the distribution for strains, stresses through the beam thickness during impact are obtained. The impact behaviors of laminated glass panel are compared with those of the monolithic glass of the same total thickness. It shows that PVB interlayer can be prevented inner glass ply of LG beam from damage by reducing the stress to zero. Specially, stress distribution through the thickness except PVB interlayer in impact analysis shows nearly linear unlike that of static analysis in spite of its discontinuity of the short time shear modulus of PVB in a laminated glass.

Exploratory Finite-Element investigation and assessment of standardized design buckling criteria for two-side linear adhesively supported glass panels under in-plane shear loads

In this paper, the buckling response of glass panels linearly supported along the top and bottom edges, under the action of in-plane shear loads, is investigated by means of analytical and Finite-Element (FE) methods.The typical buckling behaviour is first assessed in the hypothesis of fully neglecting the possible deformability contribution of adhesive linear supports, while successively the effects of linear, flexible sealant joints on the overall structural response of the same panels are also properly taken into account and highlighted. Based on extended parametric FE linear buckling and nonlinear incremental simulations, the influence of initial geometrical imperfections with various shapes and amplitudes, adhesive stiffnesses and glass types is investigated, both for monolithic and laminated glass panels. In the latter case, the accuracy of an equivalent thickness approach derived from early contributions is also demonstrated. Analytical approximating curves are proposed for the fitting of numerically derived buckling coefficients, so that they could represent a practical tool in the calculation of the expected Euler’s critical load. A normalized buckling curve for ideally simply supported glass panels under in-plane shear loads is finally recalled from past research projects and proposed as a rational design method for the examined loading and boundary condition.

Dynamic response of a novel laminated glass panel using a transparent glass fiber-reinforced composite interlayer under blast loading

The novel laminated glass-composite panel consists of a transparent glass fiber-reinforced polymer composite interlayer bonded to glass sheets. A numerical model has been developed to simulate the dynamic response of the laminated glass-composite panel under blast loading. The simulated dynamic response, in terms of the midpoint deflection, correlates well with the experiments conducted in a blast load simulator. Stress analysis of the laminated glass shows that it can survive under both medium intensity (peak pressure ≈ 4 psi) and high intensity (peak pressure ≈ 10 psi or higher) blast.

Enhanced Effective Thickness (EET) of curved laminated glass

Approximate methods for calculating laminated glass (LG), a composite where thin polymeric layers are sandwiched by glass plies, are very useful in the design practice. The most common approach relies upon the definition of the effective thickness, i.e., the thickness of a glass monolith that, under the same boundary and load conditions, presents the same maximal stress or deflection of the laminate. Different alternative formulations have been proposed, but for flat glass only. Meeting the increasing interest for curved glazing in modern architecture, here the recent “Enhanced Effective Thickness” method is extended to the case of single-curvature LG panels. Under the assumption that the curvature is moderate, usually met in the practice, simple formulae for the effective thickness are proposed. A practical method is presented to calculate the relevant coefficients, which depend upon the geometry, load and boundary conditions. Comparison with numerical experiments in paradigmatic examples confirms the accuracy of the proposed approach.

Response of Coated Laminated Glass Panels Subjected to Combined Blast and Temperature Loadings

An experimental study was conducted to investigate the performance of coated laminated safety glass panels under extreme temperatures and blast loading. Using a shock tube apparatus, specimens were evaluated under room temperature (25 °C), low temperatures (−10 and 0 °C), and high temperatures (50, 80, 110 °C). Special environmental chambers were designed to heat up and cool down the panels to the required temperatures prior to blast loading. To mimic real applications for glass windows, specimens were clamped fully along the boundaries during experimentation. For each experiment, the incident and reflected shock wave pressure profiles were recorded using pressure transducers located on the muzzle of the shock tube. The real-time deformation of the sandwich specimens was recorded using two high-speed cameras. Three-dimensional digital image correlation was used to analyze the high-speed images and compute the full-field deformation, in-plane strains, and velocities during the blast-loading event. A post-mortem study of the sandwich specimen was performed to investigate the effectiveness of such materials under different temperatures to withstand these shock loads. Experiments were conducted to characterize the tensile behavior of the coating material as a function of temperature. The mechanisms of failure of the panel are in agreement with the failure mechanisms outlined for laminated safety glass (LSG) in previous studies. The results indicated that polymeric thin sheet coating on both outer faces of the LSG panel had major influence on mitigating the blast loading and containing the glass fragments. The composite panel showed great endurance during the blast loading for temperatures from 0 to 80 °C. The failure of panel at −10 °C is attributed to the glass transition of the coating material and the failure at 110 °C is likely due tearing of the coating by the glass fragments.

Critical assessment of the post-breakage performance of blast loaded laminated glazing: Experiments and simulations

Glass windows are the most vulnerable building components when impacted by an air blast wave. For safety requirements, the customary choice for the window glazing is laminated glass, where two or more glass plies are bonded with a polymer interlayer to retain glass fragments upon breakage. With proper choice of interlayer material, the window can keep functioning as a shield to the blast wave even when fractured. Numerical simulation of the post-breakage response of a laminated glass panel can be a valuable tool for optimisation of the interlayer material and the glass panel configuration.This article presents the results of a blast testing campaign for laminated glazing, according to a standardised procedure, and subsequent numerical simulation thereof. The experiments show that laminated glass using a soft polyvinyl-butyral (PVB) interlayer with low adhesion properties achieves the best safety performance at higher loads with no interlayer tearing, while still efficiently retaining glass fragments. The numerical simulation of these experiments attempts to capture the fracture and post-breakage behaviour of laminated glass under the blast load. In the finite element model, glass elements are deleted upon reaching a fracture criterion. The model can globally reproduce crack formation and post-fracture deformation, but lacks prediction of ultimate failure, mainly because of a strong dependency on the element size for both glass and interlayer parts.

A plate finite element for modelling of triplex laminated glass and comparison with other computational models

Laminated glass became a popular safety glass. The very soft interlayer of polymeric material impedes the slippage between glass layers, bending in parallel, by shear stress. The shear stress of the interlayer breaches the principle of straight normals remaining straight after deformation, on which is based the conventional shell elements in finite element (FE) analysis. As a result of this, the conventional finite elements are not capable to solve the laminated glass problems efficiently. Based on the assumption that the glass layers of a laminated glass obey Kirchoff’s plate theory and the interlayer transfer shear stress only, a finite element formulation is elaborated by introducing new degrees of freedom and implemented in a special rectangular triplex laminated glass plate FE. The element is validated by comparison with other computational FE models and experimental tests of a laminated glass strip in cylindrical bending and a laminated glass panel in transverse loading. The developed plate element or similar shell elements that could be developed on the same theory could solve the problem with laminated glass structures very efficiently and accurately, which is now usually solved by sacrificing the fidelity.

Influence of interlayer properties on the blast performance of laminated glass panels

This paper investigates the influence of interlayer properties on the blast performance of laminated glass (LG) panels. A parametric study is carried out by varying the thickness and Young’s modulus (E) of the interlayer under two different blast loads. Results indicate the existence of a critical interlayer thickness (or E) that causes the onset of interlayer failure. This should be achieved in the design to enhance energy absorption, reduce support reactions and initiate a safer failure mode. Present findings provide information to achieve such design targets and enable safe and efficient performance of LGs under credible blast loads.

A user-defined finite element for laminated glass panels and photovoltaic modules based on a layer-wise theory

Laminated plates with glass skin layers and a core layer from polyvinyl butyral are widely used in the civil engineering and automotive industry. Crystalline or thin film photovoltaic modules are composed from front and back glass or polymer layers and a solar cell layer embedded in a polymeric encapsulant. For the structural analysis of such laminates, layer-wise theories (LWTs) for plates have been introduced in literature. In this paper, an extended LWT is proposed to assure the C0 continuity. Based on this theory, a finite element formulation and a user-defined quadrilateral serendipity element with quadratic shape functions and nine degrees of freedom (DOFs) is presented. The element is implemented using the Abaqus subroutine “User Element”. Benchmark problems are developed to examine the accuracy and efficiency of the proposed element for a wide range of material properties including the limiting cases of shear compliant and shear rigid laminates. An emphasis is placed on the influence of boundary conditions with respect to additional degrees of freedom as well as on accurate representation of boundary layer effects.

Quasi-Static Performance of Interlayer Systems for Laminated Glass

AbstractTo be able to accurately predict the static resistance function of laminated glass subjected to blast loads using engineering analysis methods, it is critical to evaluate the static behavior of the polymer interlayer before and after breakage of the glass layers. Therefore, the main objective of this research is to experimentally evaluate the constitutive behavior of polymeric glass interlayers under quasi-static loading. Constitutive relation of virgin and extracted polyvinyl butyral (PVB) and UVEKOL-S extracted from laminated glass panels were evaluated, including the energy absorption capabilities for each material. Also, the postbreakage behavior of laminated glass was investigated. The experimental results of scored tensile samples carried out on UVEKOL-S glass laminates using different numbers of scores are presented, discussed, and compared with the results of the PVB glass laminates. The energy absorption of the PVB glass interlayer was found to be larger than that of the UVEKOL-S interlay...