Investigations of Cavity Pressure Behaviors of Double-Skin Facade Systems Subjected to Blast Loads

The main function of a facade system is to provide comfort and protection to occupants inside the building. Glass facades are susceptible to severe damage due to their direct exposure to extreme loading conditions, such as blast. There is increasing popularity in the application of double-skin facade systems (DSFSs) in modern facade construction practice due to their high energy efficiency. In addition, when designed correctly, DSFSs exhibit a potentially higher capacity for blast resistance as opposed to single-layer facade systems. However, due to the complex fluid-structure interaction (FSI) between DSFSs and blast waves, there is a lack of design codes that address the structural response of DSFSs subjected to blast pressures. Understanding the behavior of the pressure within the DSFS cavity will facilitate the analysis of the blast performance of DSFSs. This paper reports an experimental program on analogical DSFSs made of steel as opposed to glazing panels, subjected to 250-kg equivalent TNT explosives at a standoff distance of 52m. The test module contains three DSFS units. One of the DSFS units is sealed and the other two DSFS units are ventilated with a varying ventilation area. The computational fluid dynamics (CFD) code Air3D was used to simulate the cavity pressure behavior of the ventilated DSFS units. By analyzing the pressure time histories from the CFD analysis and the experimental results, the concepts of shock wave transfer and blast pressure ingress formed within the cavity were introduced to interpret the cavity pressure behaviors. A parametric study was conducted to investigate the influences of the ventilation area and the cavity volume on pressure changes within the cavity. (C) 2014 American Society of Civil Engineers.