Experimental studies on the local damage and fragments of unreinforced masonry walls under close-in explosions

•Tests are carried out to investigate the local damage and fragments of unreinforced masonry walls under close-in explosions.•Mass proportion of the fragments induced by the close-in explosion with different sizes and splashed distances are analyzed.•Size distributions of the fine fragments from tests are analyzed, and the parameters of the distribution are determined. Most casualties and injuries resulting from a terrorist attack are caused by the fragments discharging from the failure structural components or building envelope systems. Unreinforced masonry wall, which is widely constructed as structural components or building envelope worldwide, tends to break into sharp fragments under terrorist explosions, especially when explosions are in the close range. Therefore, it is of great significance to study the local damage and fragments of unreinforced masonry walls under close-in explosions. In this paper, two unreinforced masonry walls were tested under blast loads generated by 1 kg and 6 kg of TNT charge separately to investigate their failure mechanism and fragment characteristics. The local damage such as spalling or punching damage of the masonry wall with fragments in different sizes and splash distances were observed, and the splashed fragments were categorized and weighted. The fragment size distribution was also analyzed and it was found that the size distribution of the fine portion of the fragments followed a Weibull distribution.