Increased security needs have led to a demand in enhanced curtain wall façade performance. In addition to thermal, acoustic, and structural requirements, the building envelope has to be designed to dissipate blast loads and protect against ballistics. The purpose is to minimize injuries, loss of lives, and reduce the risk of a global building collapse. These additional security considerations will have further impacts on pricing, design, engineering, testing, and other business functions.
Since ballistic glazing products are already “rated” when purchased from a manufacturer, the facade engineer is responsible for understanding the mechanics of projectile penetration. In terms of resisting projectile penetration, the measure of success is for the product to have a ballistic limit velocity greater than the impact velocity of the projectile. Therefore ballistic design aims to achieve local penetration resistance and as such greatly stiffens the overall glass and other facade components, thus negating the principle of a dissipative system.
On the contrary, to accomplish blast requirements, the designer will increase the façade ductility by accounting for elasto-plastic deformations. This approach considers global dynamic interaction between the major components of the façade. The key elements within a blast façade include, but are not limited to, laminated glass, structural silicone, catenary clips, shear blocks and thoughtfully designed framing members. Therefore a blast enhanced dissipative façade compared to a façade providing ballistic resistance results in somewhat of a design paradox.
This paper will focus on integrated ballistic and blast design, showing the possible shortcomings and design solutions to mitigate them.
A glass curtainwall serves many functions including structural integrity (wind, dead, snow, seismic, fire, live loads), accommodating building and tolerance movements (slab deflections, sway, shortening, creep) and acting as an
Two principal standards are used in North America to rate the performance of bullet resisting equipment [13; 2].
At projectile impact, two longitudinal waves (plastic and elastic) are formed in the
Blast load classes and hazard level specifications are based on performance conditions laid out in the General Services Administration Standard Test Method for Glazing and Window Systems Subject to Dynamic
When façade project specifications contain both ballistic and blast requirements, the starting point of the design is the ballistic glazing. In general the glazing necessary to achieve ballistic requirements will
The integrated ballistic-blast design can be affected due to the relatively large glazing stiffness. One possible solution to overcome this shortcoming is by the use of a dissipative bracket. The
A special thanks to the entire Permasteelisa Group team.
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