Increased security needs have led to a demand in enhanced curtain wall facade 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 facade ductility by accounting for elasto-plastic deformations. This approach considers global dynamic interaction between the major components of the facade. The key elements within a blast facade include, but are not limited to, laminated glass, structural silicone, catenary clips, shear blocks and thoughtfully designed framing members. Therefore a blast enhanced dissipative facade compared to a facade 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.
Applied Research Associates Inc. Window glazing analysis response & design – WINGARD – Technical manual, ARA-TR-05-16462-2, US General Services Administration, Washington DC, July 2005.
BS EN 1063 2000, Glass in Building. Security Glazing. Testing and Classifications of Resistance Against Bullet Attack
Charles N. Kingery and Gerald Bulmash. Airblast parameters from TNT spherical air burst and hemispherical surface burst.Technical report, Defence Technical Information Center, Ballistic Research Laboratory, Aberdeen Proving Ground, Maryland, 1984.
GSA Security Criteria, Building Technologies Division Office of Property Development Public Building Service Administration, 1997.
ISO 16933:2007, Glass in Building - Explosion Resistant Security Glazing. Test And Classification For Arena Air-Blast Loading.
Le Gall – Zobec, A. Balanced Design of Blast Enhanced Glass Curtain Wall Facades. June 2016.
Lori G., Zobec M., Franceschet A., Manara G., “The behavior of facades due to blast loads – A single degree of freedom performance evaluation approach”, Glass Processing Days, 2009.
Morison, C., Zobec, M., Franceschet, A.: “The measurement of PVB properties at high strain rates and their application in the design of laminated glass under bomb blast”, International Symposium on the Interaction of the Effects of munitions with structures, 2007.
Newmark N M. “An engineering approach to blast resistant design”, American Society of Civil Engineers Transactions, Paper No 2786, Vol 121 p45, 1956. (Noted as published “essentially as printed here” as proceedings –Separate No 506, October 1953.)
Norville, H.S., Harville, N., Conrath, E.J., Shariat, S., and Mallone, S.: “Glass-Related Injuries in Oklahoma City Bombing”, Journal of Performance of Constructed Facilities 13(2), 1999.
PSDB Notes on Design for Glazing Protection, Current UK Design Philosophy. Home Office, Police Scientific Development Branch, 2004.
DoD, UFC 3-340-02 Structures to resist the effects of accidental explosions, US Army Corps of Engineers/Naval Facilities Engineering Command/ Air Force Civil Engineer Support Agency, 2014.
UL 752 Underwriters Laboratories, Inc. Standard for Safety, Bullet-Resisting Equipment and the U.S. Department of Justice Standard for Ballistic Resistant Protective Materials (NIJ Standard 0108.01).
Zobec, M. “Blast Enhanced Glass Facades: an integrated and holistic design approach”, PhD Thesis at University of Technology, Sydney, 2013.
Zobec, M., Lori, G., Lumantarna, R., Ngo, T., Nguyen, C. (2014) “Innovative design tool for optimization of blast enhanced facades”, Journal for Facade Design & Engineering.