Safety Issues in the Seismic Design of Secondary Frameless Glass Structures

Abstract

Glass is largely used in buildings, in the form of an innovative and versatile material. Both for novel and existing constructions, secondary glass systems are frequently realized to interact with primary components of different materials. In most cases, the structural challenge deriving from the intrinsic brittleness and vulnerability of glass is efficiently controlled via laminated (LG) multi-layer sections. However, further potential risks for people should be properly minimized, like for example, in the presence of extreme loads. This is the case of seismic regions, where dedicated calculation methods are required to accommodate displacement and resistance demands, but design specifications are rarely provided by existing standards for earthquake resistant buildings. Even more attention is needed for frameless glass systems in which the bracing members (i.e., continuous frames, cable-nets, etc.,) are reduced to a minimum, in favour of metal point connections (i.e., bolts and mechanical fixings, friction clamps, etc.). This paper aims at discussing the current design requirements for the seismic performance assessment of these relatively simple but challenging structural solutions, with careful consideration for the Italian scenario, where a practical support for design can be found in the CNR-DT 210/2013 technical document. Based on a case-study system, major issues, open questions and uncertainties or critical aspects for the seismic analysis and design of secondary frameless glass assemblies are thus emphasized.

Analytical Fragility Curves for Seismic Design of Glass Systems Based on Cloud Analysis

“…For glass, the mechanical properties were described as for CS#1. In case of PVB film, for the assigned seismic action, the material behaviour was described in the form of equivalent secant stiffness for shortterm duration load (30 s, see also [19]). Finally, the adhesive layers were described with a set of equally spaced axial connectors, so as to allow in-plane displacements (u x and u y ) for the glass panel.…”

“…The first critical step to define fragility curves with the herein adopted analytical method is to identify the performance variables for the examined structural systems, and thus to establish damage thresholds. For glass structures, such a step may involve major uncertainties for design proposals, given that typical damage and failure mechanisms are affected by unsymmetrical (and brittle in tension) behaviour of glass or special restraint systems [19,54].…”

“…However, major safety issues in design relate to robustness, redundancy, ductility, durability, and even comfort [15]. Given the characteristic brittle behaviour of this material, when designing structural glass system, it is necessary to identify all the aspects involved in the response which results in an expensive calculation model, especially in case of seismic action [16][17][18][19].…”

Building Design Rule for Glass Structures by Persian Curve

“…Experimental results were compared with lateral torsional buckling resistance calculated according to the buckling curve approach. Analysis and design of glass structural members is an active area of study in this days (Bedon and Amadio, 2018;Bedon, 2019;Bedon et al, 2019;Koca, 2019;Santo et al, 2020).…”

On the Use of Cloud Analysis for Structural Glass Members under Seismic Events

“…In addition to intrinsic mechanical features of the involved load-bearing materials [1,2], careful consideration should be paid in earthquake-prone regions to satisfy rigid resistance and displacement demands. This is the case of primary, stand-alone glass structures, but also secondary glass systems belonging to different primary buildings and constructional assemblies [3][4][5][6][7][8].…”