Performance Evaluation of Brick Masonry Building Against Blast Loading

Abstract

primary school buildings are fabricated from unreinforced burnt clay brick masonry in Khyber Pakhtunkhwa Pakistan. These school buildings are being targeted with improvised explosive devices in the terrorist activities after 9/11 continuously. Consequently, several hundred schools were partially damaged or fully collapsed due to improvised explosive devices detonated in close vicinity. These school buildings are reconstructed again by the government agencies without proper scientific knowledge of blast loading phenomenon and the expected response of masonry buildings. Consequently, this research study is carried out to evaluate response of brick masonry against blast loading. In this report, response of burnt clay brick masonry against blast loading is investigated experimentally. A representative primary school full scale unreinforced brick masonry building and three different masonry systems (unreinforced, ferrocement overlay and confined masonry) were fabricated in the field from typical burnt clay bricks with cement-sand (1:6) mortar commonly used in Khyber Pakhtunkhwa Pakistan. All the four test specimens were placed on an equal spacing on the perimeter of circle with a 3.66 m radius. The shock waves were generated at the centre of the circle by igniting cylindrical shaped explosive charges placed at 0.91m height from the ground surface. The test specimens were subjected to similar blast scenario in the eight successive events with increasing explosive charge weights but fixed stand-off distances. The recorded pressure data was processed and an empirical model predicting peak over pressure for the cylindrical shaped explosives was developed. The damage level in test specimens was evaluated after each successive blast event. Weak zones in masonry room were identified and safe scaled distance for masonry room before collapse was experimentally acquired. Scaled distances for different damage levels in the masonry system of walls were obtained. The relative response of different masonry systems subjected to similar blast loading environment was evaluated. The confined masonry, ferrocement overlay masonry and unreinforced masonry walls were found in an increasing order of their responses against blast loading.