Experimental approaches for assessing time and temperature dependent performances of fractured laminated safety glass

Laminated glass is for a few decades a well-known product in the construction industry for conferring safety performances to glazing units. Besides to the safeguarding of persons, laminated glass products are contributing to a variety of other safety performances, in case of accidental or attack situations leading to breakage of or crack propagation in the glass panes of a laminated glass unit. The ultimate residual load-bearing capacity of a damaged element can be resumed to one critical load-transfer mechanism, in the form of interlayer ligaments bridging the glass fragments. The characterization for design purposes of the mechanical properties of the interlayer involved in this load-transfer mechanism through the ligament appears however far from obvious. This results from specificities on the one hand of adhesive polymer components and on the other of design and control processes in the building industry. These specificities are mainly related to two aspects : firstly to the time- and temperature dependent behaviour of interlayer materials and their possible sensitivity to ageing effects, and secondly to initially vaguely defined intended fields of use, especially when non-conventional structural applications are within the considered application scope. The combination of these two aspects raises constraints for the development of experimental methods, test configurations and assessment strategies for laminated glass products. This research proposes analysis grids to get an overview of the constitutive elements of application scopes and of the possibilities and limitations for experimental assessment, with purpose to distinguish and estimate different types of border effects. These are used to evaluate the representativeness and the robustness of different test methods and test configurations, corresponding to different experimental scales. An incremental experimental approach has been developed for investigating the time- and temperature dependent performances of damaged laminated glass elements, on the basis of tests on pre-cracked specimens of small dimensions. The assessment of the residual load-bearing capacity of damaged elements used in structural applications was the main focus of these investigations. This research highlights the need for adapting experimental assessment approaches to characterize properties of laminated glass products for design purposes with respect to their post-fracture performances, in comparison with other construction materials. It also explains specific difficulties for obtaining quantitatively meaningful results and the challenges for harmonizing experimental assessment strategies for different applications and products made with a same type of interlayer material

A story about standardization for design of glass works

This contribution attempts to give an overview of the European standardization framework which is related to the design and calculation of glass works in buildings. The different work levels, institutions, technical committees and workgroups, and the various types of documents and their statute will be introduced, explaining the difference between draft, experimental and final standards, between harmonized, support and design standards, the general and particular meaning of harmonization and implementation. The standardization framework is explained firstly from the point of view of European standardization policy and history, and secondly regarding the standardization framework in Belgium. In particular, an attempt is made to highlight some particularities existing in harmonization efforts of design methods and codes for glass works

Post-breakage behaviour of laminated glass in structural applications

Firstly is introduced what the post-breakage behaviour of laminated safety glass is, and why it's important to can model it for designing structural glass elements. A general description of post-breakage behaviour and the different possible mechanisms leading to failure are presented. We then focus on the mechanical properties of the interlayer material, more specifically in the perspective to model its behaviour at large strain up to break. Typical results of standard uniaxial tensile tests on SGP samples (SentryGlas (R) Plus, interlayer of DuPont de Nemours) are shortly presented, and we then explain why those are insufficient to calibrate numeric material models to use in finite elements softwares. Finally perspectives for further experimental investigation with aiming to calibrate material models are presented

Failure behaviour of glass laminates with a "stiff" interlayer at room temperature

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Influence of temperature on post-breakage behaviour of laminated glass beams: experimental approach

The assessment of the post-breakage performances of laminated glass elements used in construction need to take into account the sensitivity to the temperature of the mechanical behaviour and properties of the product, in particular of the interlayer material. A general problem statement and an overview of different experimental approaches are firstly presented. Then results of specific orientation tests on pre-cracked laminated glass beams with a stiff interlayer of DuPont carried at three different temperatures (23, 45 and 60°C) are presented and commented. A comparison of the mechanical behaviour at the different temperatures is done, aiming to give a comprehensive order of magnitude of the sensitivity to temperature of the post-breakage behaviour observed during the tests