As for the film inserted between the panels
, it is a thin layer of transparent plastic that performs an important function. In fact, in the event of accidental impacts and consequent fractures, it will retain the glass fragments, guaranteeing safety and preserving the panel in place. For this purpose it is recommended to opt for a rigid plastic material, able to guarantee greater safety and strength in the remote case of breakage of all the panels. In addition, there are countless processes that provide glass for specific uses: an example are shatterproof, bulletproof and armored glass, used for banks, offices and prisons.
Thanks to the presence of diversified products on the market, it is also possible to choose colored, opaque films and sunshades that not only guarantee greater thermal comfort but also avoid unpleasant glare phenomena. Furthermore, the protective layer between the glass plates generates good sound insulation as it tends to dampen vibrations.
Composition and behavior of a laminated glass sheet in case of impact and consequent breakage
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All types of laminated glass are based on the processing of the so-called float
glass, produced starting from a compound of minerals and sand and then subjected to heat. Once solidified, the glass is cut into standardized panels or sheets made to measure to meet the most demanding and diversified needs.
The legislation relating to the installation of structural glass parapets
The Technical Standards for Construction, dated January 17, 2018, provide the provisions for the correct installation of structural glass parapets inside and outside the buildings. This legislation dictates the rules to be respected in terms of safety and resistance to loads typical of the different types of glass to be used. In fact, it is necessary to predict the behavior of the material with respect to linearly distributed static loads and dynamic loads.
The parapet is mandatory in the case of differences in height greater than 50 cm in order to prevent accidental falls and preserve individual safety. The minimum heights that the glass parapet must have and the presence of the handrail, necessary for a secure grip, are also established. Depending on the intended use of the building, the minimum height of the parapet, starting from the floor, must be equal to 1m for public and private buildings, while it can go down to 0.90m in the case of internal stairs to apartments. . In any case, each Municipality may be subject to specific variations regarding the minimum dimensions to be respected. As for the thickness of the glass panels, the choice depends on the function of the balustrade and the consequent loads that weigh on it.
The structural glass parapet has the great advantage of ensuring transparency and material continuity, without the need for interruptions generated by the insertion of load-bearing elements. However, some countries stipulate the obligation to insert a handrail or an element with a tubular profile (U-shaped) in the upper part of the glass. These elements in addition to ensuring greater safety, allow a better connection between the glass panels and the contiguous wall, making it possible to use thinner transparent sheets. If the glass structural elements do not adhere strictly to each other, the distance between them must be minimal, so as not to allow the passage of objects or human limbs that could get stuck, undermining personal safety.
The UNI 7997 Standard - Safety criteria in glass applications, establishes some essential directives for choosing the type of glass most suitable for transparent parapets. In addition to the high resistance to loads and accidental impacts, the external parapets must ensure durability with respect to the action of atmospheric agents. To this end, the panels undergo numerous resistance tests before being installed. Furthermore, it is good that the sheets are beveled, rounded on the edges and without protrusions or incongruent surface portions. Each glass must have a certificate of conformity
, drawn up after checking the loads, constraints and correct dimensions according to the specific need.
As regards the necessary permits before installing a structural glass parapet, it is necessary to report the start of the activity at the offices of the municipality concerned and proceed with scaffolding and auxiliary structures, where necessary, always according to current legislation and in compliance with full safety of workers and users.
It is therefore of fundamental importance to act in full awareness from the early design stages and carefully choose components, types and materials only after conducting a structural analysis of the building that will accommodate the parapet, be it internal or external.
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