Blast and Impact Loading and Response of Structures
Full Session with Abstracts
Blast-resistant criteria and design specifications frequently require a balanced design for window system. The principle of balanced design was developed to control the manner of failure in window systems such that the glass would fail before supporting framing, the framing would fail prior to connections, which in turn fail prior to the supporting structure. When static loads are considered, the capacity of a pane of glass is fairly simple to evaluate. However, when dynamic loads are considered the capacity of the glass is a function of the dynamic pressure, load duration, and shape. All of these parameters vary with charge weight and standoff. The typical approach is for design specifications to provide a dynamic pressure and impulse that are the design basis for the windows. The capacity of the glass would then be determined for the equivalent linear duration of the load, normally resulting in a higher pressure than the design pressure. It has been noted that due to the complex dynamic nature of window systems the response of the system can change significantly depending on how the capacity load of the window system is determined. Changing the load duration, charge weight, or standoff can all change both the design-basis capacity of the system as well as the peak reactions associated with the glass capacity. A review of representative window systems is made, comparing the impact of the spatial distribution of blast loads over a building with the capacity of the windows. Based on this review, key factors are provided for consideration by designers and specification writers to improve balanced design of window systems while maintaining the level of protection required for blast-resistant projects.