Blast mitigation and design of laminated glass facades

Abstract

Laminated glass is an essential component for any building designed against blast loading. A polymer interlayer is sandwiched between glass layers in order to keep the cracked glass fragments intact. In successful design, the interlayer deforms and absorbs the blast load without tearing. A novel testing method was developed to capture the bending response of laminated glass under high rate uniform loading. Specimens with a dimension of 700 mm x 60 mm were tested. It was found that the failure mechanism of the laminated glass is controlled by the thickness of the interlayer. In addition, a new framing arrangement was tested which showed that the load on the laminated glass can be reduced by increasing the energy absorbing capacities within the frame. By allowing the frame to purposefully deform under loading, the chances of failure of the laminated glass are reduced. Tensile tests were conducted on cracked laminated glass in the temperature range of 0◦C−60◦C. Single-cracked and randomly-cracked specimens were tested. It was found that the optimum temperature for the greatest energy absorption of the cracked laminated varies between 10◦C − 40◦C depending on the interlayer thickness. The single-cracked results were further expanded to calculate a bond fracture toughness for the separation of the interlayer from the glass. A finite element model was developed to simulate the bond separation between the glass and the interlayer at different testing-rates and temperatures. It was found that the bond is testing-rate dependent in the range of 0.01 /s − 200 /s, but temperature independent in the range of 20◦C − 60◦C. The single-degree-of-freedom model is conventionally used for predicting the response of a laminated glass pane subject to blast loading. The single-degree-of- freedom model includes mass and load transformation factors, which vary with the deflected shape of the structure. In this thesis a finite element model was used to derive the deflected shapes and transformation factors for a range of loading conditions, boundary conditions and pane aspect ratios. The time-varying deflected shape was taken into account in this analysis, as this is currently not included in other single-degree-of-freedom models. The transformation factors were found to be insensitive to aspect ratio. In addition, at high loading rates, the deflected shape–time history proved to be important.