Laminated Glass Units Research Articles

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.

NEWMARK ALGORITHM FOR DYNAMIC ANALYSIS WITH MAXWELL CHAIN MODEL

This paper investigates a time-stepping procedure of the Newmark type for dynamic analyses of viscoelastic structures characterized by a generalized Maxwell model. We depart from a scheme developed for a three-parameter model by Hatada et al. [1], which we extend to a generic Maxwell chain and demonstrate that the resulting algorithm can be derived from a suitably discretized Hamilton variational principle. This variational structure manifests itself in an excellent stability and a low artificial damping of the integrator, as we confirm with a mass-spring-dashpot example. After a straightforward generalization to distributed systems, the integrator may find use in, e.g., fracture simulations of laminated glass units, once combined with variationally-based fracture models.

Glass Entrance Van Gogh Museum Amsterdam

In September 2015 the Van Gogh Museum in Amsterdam has opened its new Glass Entrance to accommodate a growing number of visitors more comfortably. The architectural design is drawn by Kisho Kurokawa Architect & Associates and the detailed design by Hans van Heeswijk Architects and Octatube, complementing the curved and elliptical shape of the Kurokawa wing. The project fits in a trend of underground museum extensions enhanced by prominent structural glass geometries, such as the Louvre Pyramids in Paris, the Mauritshuis in The Hague and the Joanneum Quarter in Graz. The Van Gogh Museum Glass Entrance is featured by a spheroidal glass roof with glass fins stabilising the steel structure, a cold bent glass facade and a 1.5 m cantilevering glass canopy. Inside there are glass balustrades and a glass staircase supported by structural glass arches which are site-bonded to the stringers. All glass in the project is composed of low iron glass to create a high degree of transparency without discolouring. The shape of the glass roof is defined by mirroring the spheroidal surface of the existing wing. The so created roof consists of insulated and laminated glass units all different in width and supported by 30 triple laminated glass fins with SentryGlas $$^{\circledR }$$ (SG) interlayers. All glass fins are optimised and unique in length and height, the largest fin being 12 m long and 700 mm in height. The glass beams are supported by steel shoes connected to the main steel structure consisting of 400 mm circular hollow sections. This detail allows the glass fins to act like beams while stiffening the steel structure and supporting and stabilising the double glass units in the roof. Due to the complex geometry, the many glass fin connections and extremely tight tolerances, the entire steel structure of 60 m $$\times $$ 15 m $$\times $$ 10 m was pre-assembled, surveyed and checked in the factory scale 1:1. The IGU’s in the roof’s outer 1.3 m wide perimeter are cold-twisted to fit in between the roof surface and facade perimeter. The curved outer facade consists of cold-bent insulated glass units fixed to 20 unique triple laminated glass fins with SG, the longest being 9.4 m. The smallest bending radius of the elliptical curvature is 11.5 m.

Experimental and numerical treatment of delamination in laminated glass plate structures

This paper aims to investigate the delamination issues of laminated glass plates and the effect of boundary conditions on the delamination of laminated glass plates. Delamination of laminated glass which may be defined as reduction or total loss in the perfect bond between the glass sheets and the PVB interlayer is one of the most important failure modes. Due to delamination, the load-carrying capacity and structural stiffness of laminated glass unit can change significantly. The author conducted experimental and numerical studies about the delamination of laminated glass plate problem based on the results of digital image processing.

Numerical Modeling of Laminated Glass Units

Laminated glass has been developed to improve the impact resistance of brittle glass sheets and to prevent injuries and collapse of glass members. The goal of this contribution is to briefly introduce a finite element model based on the refined plate theory by Mau that can describe the response of laminated glass plates without the need for fully resolved three-dimensional simulations. Each layer is considered to behave according to the Reissner-Mindlin kinematics, complemented with membrane effects and the von Karman assumptions. The compatibility of independent layers is enforced by nodal Lagrange multipliers. Predictions of the finite element model, obtained with a MATLAB-based program LaPla (Laminated Plates) developed by the authors, are compared with simplified monolithic and layered limits and a semi-analytical solution.

Finite element model based on refined plate theories for laminated glass units

Laminated glass units exhibit complex response as a result of different mechanical behavior and properties of glass and polymer foil. We aim to develop a finite element model for elastic laminated glass plates based on the refined plate theory by Mau. For a geometrically nonlinear description of the behavior of units, each layer behaves according to the Reissner-Mindlin kinematics, complemented with membrane effects and the von K\'{a}rm\'{a}n assumptions. Nodal Lagrange multipliers enforce the compatibility of independent layers in this approach. We have derived the discretized model by the energy-minimization arguments, assuming that the unknown fields are approximated by bi-linear functions at the element level, and solved the resulting system by the Newton method with consistent linearization. We have demonstrated through verification and validation examples that the proposed formulation is reliable and accurately reproduces the behavior of laminated glass units. This study represents a first step to the development of a comprehensive, mechanics-based model for laminated glass systems that is suitable for implementation in common engineering finite element solvers.

Effect of Delamination on the Strength of Laminated Glass Plate Structures

Laminated glass which consists of two glass sheets connected to each other with PVB interlayer is used in many engineering applications for years. Despite the long history of the use of laminated glass in buildings there are serious problems about delamination of laminated glass units. This paper provides information about delamination issues of laminated glass plate structures. Delamination of laminated glass unit may be due to the thinning of PVB (Polyvinyl Butyral) interlayer or the folds which occur during the manufacturing process. Laminated glass behaves in a complex manner due to the effect of geometry that undergoes large deflection even under their own weight and the order difference between the elastic modulus of glass and interlayer. Because of the mentioned reasons large deflection analysis has to be performed in the determination of the effect of delamination on the strength of laminated glasses.

The mechanical performance of laminated hybrid-glass units

Conventional laminated glass has a relatively low post-fracture strength and stiffness, which imposes several constraints on the structural use of glass in buildings. This paper proposes a new generation of laminated hybrid-glass units, built-up from plies of chemically strengthened glass, conventional polymer interlayers and heat treated/annealed glass, that aim to outperform conventional laminated glass units. The paper describes the experimental investigations on the novel laminated hybrid-glass units subjected to quasi-static out-of-plane loads and presents the corresponding analytical models developed to characterise the load–deflection response of the units, both in the unfractured and post-fractured states. The experimental data shows that laminated hybrid-glass units can achieve significant post-fracture stiffness and their post-fracture strength can equal or exceed the strength at first fracture. The analytical models are successfully validated and the equivalent shear modulus approach developed in this paper facilitates future numerical analysis and optimisation of these units.

Effect of Support Conditions on the Vibration of Laminated Composite Beams

Laminated glass plate or beam used in the building industry is an architectural unit of the building formed by two or more thin glass plates or beams bonded together by an interlayer PVB (polyvinyl butyral). The behavior of laminated glass beams is complicated because the different materials have different elastic modulus. Laminated glass is very thin and can easily undergo large displacements, therefore, the equilibrium equations governing their behavior should be based on large deflection theory. In the present study, the effect of boundary conditions on the vibration of a laminated glass unit is investigated by considering the cases of simply supported and fixed supported laminated glass beams. Glass units considered in this study have two thin glass beams and an interlayer PVB. A mathematical model for the dynamic behavior of a laminated glass beam is developed using variational principles. The assumptions of the classical beam theory are valid. Three coupled partial differential equations which express the dynamic behavior are obtained for lateral and axial displacements. By solving these equations, the effect of boundary conditions on the natural frequencies is observed in figures depicting displacement versus angular frequency.

Laminated glass beams: Strength factor and temperature effect

Glass design charts are available for annealed, monolithic glasses. In order to use these design charts, strength of a laminated glass unit needs to be adjusted by a strength factor. This paper presents a study on strength factor and the effect of various factors on the strength factor, like ambient temperature, width and length of the beam. The effect of nonlinearity on the strength factor is also investigated by considering the nonlinear behavior of fixed end laminated glass beams since the simply supported glass plates behaves nonlinearly. From the study, two factors are crucial in the estimation of relative strength of laminated glass with respect to monolithic glass: one of two factors is the plasticizer content and therefore the transition temperature of the PVB layer used in the manufacture of laminated glass unit, and the other is the effect of nonlinearity as observed in the analysis conducted with fixed end beams in this study.

Laminated glass plates: revealing of nonlinear behavior

A laminated glass unit which consists of two glass plies and an interlayer polyvinyl butyral (PVB) shows very complex behavior in the range of service loads. Complex behavior is due to the effect of geometry that undergoes large deflection and order difference in modulus of elasticity of glass and PVB. The nonlinear behavior of laminated glass plate is represented by five coupled nonlinear partial differential equations for lateral and in-plane displacements obtained through the variational approach. Linear algebraic equations are obtained by writing the differential equations at discrete points of glass plates by using finite difference method with central differences. Since the algebraic equations are nonlinear, the iterative technique is employed to predict the displacements through the banded matrix solver for lateral displacement and strongly implicit method for in-plane displacements. Solution will only be reached when variable underrelaxation parameter is used; otherwise solution diverges. Results denote that complex stress fields develop, and maximum stress is traveling; starting at the center, following x-axis, then moving on the diagonal and settling at the region closer to the corner at high nonlinearity level.

Seismic Behavior of Curtain Walls Containing Insulating Glass Units

In-plane dynamic racking crescendo tests were performed on full-scale curtain wall mock-ups dry glazed with six different insulating glass unit (IGU) configurations and one laminated glass unit configuration. The tests were conducted to determine the serviceability and ultimate limit state behaviors of these configurations tested under simulated earthquake-induced lateral drifts. All IGU configurations tested were manufactured with an annealed monolithic pane and a laminated pane with an argon fill and an anodized aluminum spacer between the panes. Several parameters were varied in the laminated pane of each configuration including glass lite thickness and glass type in the laminated pane (annealed, heat strengthened, and fully tempered), and PVB interlayer thickness for the laminated pane. Properties of the annealed inside pane were not varied. For each configuration, average drift values for the occurrence of glass cracking in each IGU pane, glass fallout from the monolithic pane, and pullout and fallout of the entire glass unit are reported. Relevant damage to the aluminum framing is also reported. Results of these tests can be used to assess the seismic resistance of similarly glazed architectural glass panels in practice and to improve the design of asymmetric IGU configurations for use in seismic regions.

Impact Resistance of Laminated Glass Using “Sacrificial Ply” Design Concept

Experimental results of low velocity, small steel ball impact tests on laminated architectural glass units are presented. These tests are part of an ongoing effort to develop a design method for laminated architectural glass units to resist windborne debris from sources such as roof gravel, as required in several current and proposed U.S. building codes and standards. A design concept known as “sacrificial ply” permits the exterior-facing, outer glass ply of a laminated glass unit to fracture during windborne debris impacts, but prevents fracture of the inner glass ply. This concept also depends on an inner glass ply designed to resist lateral wind pressures for the remainder of the windstorm so that the integrity of the building envelope is preserved. In these experiments, inner and outer glass ply thicknesses and polyvinyl butyral interlayer thickness were varied to determine their effects on the impact resistance of the inner glass ply of laminated architectural glass when impacted on the outer glass ply. Results show that inner glass ply thickness and PVB interlayer thickness have stronger effects on the impact resistance of the inner glass ply than does outer glass ply thickness.

Dynamic strains in architectural laminated glass subjected to low velocity impacts from small projectiles

An experimental validation of a mechanics-based finite element model for architectural laminated glass units subjected to low velocity, two gram projectile impacts is described. The impact situation models a scenario commonly observed during severe windstorms, in which small, hard projectiles, such as roof gravel, impact windows. Controlled experiments were conducted using a calibrated air gun to propel a steel ball against simply supported rectangular laminated glass specimens. Dynamic strains on the inner glass ply were measured using foil strain gages and a high speed data acquisition system. Impact speed, interlayer thickness, glass ply thickness, and glass heat treatment conditions were varied. Dynamic strains predicted by the finite element model were in close agreement with those measured in the laboratory.

Damage probability in laminated glass subjected to low velocity small missile impacts

The probability of damage at the impact site in the outer glass ply of laminated glass units subjected to low velocity small missile impacts is investigated. A dynamic, non-linear finite element analysis is applied to compute the stress response on impacts. Based on the cumulative damage theory, a damage factor is introduced and related to Weibull's distribution of probability to characterize the probability of damage. In conjunction with the finite element analysis, controlled experiments are conducted to determine the material constants appearing in the damage model and Weibull's distribution of probability. A parametric study involving impact velocity, glass ply thickness and interlayer thickness is presented.

Performance of Laminated Glass Units under Simulated Windborne Debris Impacts

Severe windstorm events such as Hurricane Andrew in 1992 have underscored the vulnerability of building envelopes to breaching under the combined effects of windborne debris impacts and wind pressu...

Discussion of “ Strength of New Heat Treated Window Glass Lites and Laminated Glass Units ” by H. Scott Norville, Paul M. Bove, Darrel L. Sheridan, and Stacey L. Lawrence (March, 1993, Vol. 119, No. 3)

Discussion of “ <i>Strength of New Heat Treated Window Glass Lites and Laminated Glass Units</i> ” by H. Scott Norville, Paul M. Bove, Darrel L. Sheridan, and Stacey L. Lawrence (March, 1993, Vol. 119, No. 3)

Dynamic in‐plane racking tests of curtain wall glass elements

AbstractAttention has been paid recently to the potentially serious life safety and economic loss issues related to the seismic performance of ‘architectural,’ or ‘non‐structural’ building elements such as glass lites in curtain wall systems. In response, a pilot study was undertaken at the University of Missouri‐Rolla to investigate the dynamic racking performance of a 15·6 × 12·0 ft (4·56 × 3·68 m) section of curtain wall containing three 5 × 6 ft (1·52 × 1·84 m) glass panels. The curtain wall system was a ‘wide mullion’ design that had generous 1 in (25 mm) clearances between glass edges and the aluminium glazing pocket. Dynamic racking tests were performed totally in plane; no out‐of‐plane or torsional motions were included. Various types of glass specimens were tested, including annealed, heat‐strengthened and fully tempered glass in monolithic and laminated configurations. Dry glazed and two‐side structural silicone curtain walls were tested. Test results for dry glazed specimens showed that annealed and heat‐strengthened laminated glass experienced no fallout whatsoever. By contrast, annealed monolithic glass experienced frequent fallout in both small and large shards. Fully tempered monolithic glass experienced dicing, which resulted in occasional fallout of entire glass lites. Loss of rigidity in fully tempered laminated glass (when both glass plies were broken) occasionally caused entire lites to fall out. Polyester film (not anchored to the mullions) was applied to annealed monolithic glass; it prevented small shards from falling out, but sometimes contributed to entire lite fallout after the onset of severe glass cracking. Annealed laminated glass units with two‐side structural silicone glazing exhibited only very minor glass damage and no glass fallout.

Analysis of Laminated Glass Units

Laminated glass units for glazing buildings consist of two thin glass plates bonded together by a thin core material, called polyvinyl butyral (PVB). As the plates are usually thin and undergo large lateral displacements, the conventional thin plate theory cannot be applied; instead, a nonlinear theory of plates has to be employed. As well, the interlayer, though soft in material properties, provides significant change in the overall behavior of the composite. Variational calculus and minimum potential energy theorem are employed to obtain the five nonlinear differential equations with appropriate boundary conditions; these equations are solved numerically with iteration. Experiments were conducted at the Glass Research and Testing Laboratory at Texas Tech University, Lubbock, Tex., to validate the mathematical model. Laminated glass units 1.524 m × 1.524 m (60 in. × 60 in.) in size with two glass plates each 4.763 mm (0.1875 in.) thick with a PVB of thickness equal to 1.52 mm. (0.06 in.) were tested up to a lateral pressure of 6.895 kPa (1 psi). Lateral displacements and strains at four different locations at the top and bottom of the units were measured. The experimental results are compared with those from the mathematical model and presented in this paper.

Strength of New Heat Treated Window Glass Lites and Laminated Glass Units

The strengths of certain window glass types, window glass constructions, and window glass treatments are poorly understood by the window‐glass‐design community. Many assumptions are employed in defining the design strengths of various window‐glass types, constructions, and treatments such as laminated glass, heat‐strengthened glass, and insulating glass. As part of its ongoing research program into the strength of window glass, the Glass Research and Testing Laboratory at Texas Tech University conducted strength tests on fully tempered monolithic glass lites, heat‐strengthened monolithic glass lites, fully tempered laminated‐glass units, and heat‐strengthened laminated glass‐units. The objective of these tests was to determine the strengths of these glass types and constructions relative to monolithic annealed glass lites with the same nominal dimensions. The failure strength data resulting from these tests differ significantly compared to the assumptions underlying design strengths proposed by ASTM for these glass types and constructions.