Design Base for a Frameless Glass Structure Using Structural PVB Interlayers and Stainless-Steel Fittings

Abstract

Minimizing metallic primary structures in directly glazed grid shells is key to increasing transparency. Complete renunciation to a substructure results in the glass itself bearing the loads, with thin glass shells, for example, that support loads mainly via membrane forces. A 4.20 m tall, double-curved, frame-less modular glass shell with stainless steel fittings laminated into the thin interstice of two-ply laminated safety glass has been developed and built as a demonstrator to validate the concept. The fittings used to structurally join the glass modules transfer all translation loads and provide a certain rotational stiffness. They are geometrically designed to reduce stress peaks inside the laminate and feature a laminated contact surface at the edge of the glass. For lamination, an interlayer stack was applied comprising exterior layers of structural PVB to bond the fitting with the glass and translucent PVB as interior core layer for aesthetic reasons. The design of this structure initially relied on generic values for designing and finite element modelling of the fitting-interlayer bond, particularly in tensile “pull-out” mode. The present paper undertakes a review of basic interlayer stack data with regards to viscoelastic properties and adhesion, and the engineering hypotheses using recent preliminary fitting test results for various loading schemes (bending, shear, tensile).

Development and behavior of a thin fitting connection for lamination with structural PVB

“…As also shown in (Stevels 2022), the bending test show very high rotational capacity. The stacked interlayer samples were bent to about 127°and 111°(starting at plane 180°), see Figure 20.…”

“…In addition, the tests were intended to deliver additional data for the calibration of the spring models used in the joints of the demonstrator. An overview of the key numbers and figures has been published in the paper (Stevels 2022). The test results and the FE-analyses currently allow only partial comparison for the case of the tensile tests because of the different boundary conditions (Fig.…”

“…The data on the shear modulus of various interlayer compositions (Fig. 26) depending on temperature and on the surface adhesion provided by the manufacturer (Stevels 2022) show that increased indoor temperature up to 30 °C still provides high shear moduli especially for the pure structural PVB interlayer, which is the decisive material regarding the bond between the fitting and glass laminate. However, for outdoor applications or high temperature from direct solar radiation impact, relevant studies and tests on the laminated fitting connections yet must be made.…”

“…Detailed results are provided below. A summary of the global test results and the underlying interlayer properties are presented in a paper by Stevels (2022).…”

Zum Potential unterschiedlicher Methoden beim Einlaminieren struktureller Metallverbinder

“…Weitere Fügemöglichkeiten sind mit Ionomer-Interlayer [24], Gießharz [25] oder strukturellem PVB [26,27,28] in die dünne Zwischenschicht laminierte Blechstreifen. Eine für eine modulare Schale realisierte Anwendung, die im Rahmen des vorliegenden Beitrags behandelt wird, wird in [29][30][31][32][33] behandelt.…”