Performance of unreinforced masonry buildings against natural disasters – review study

Abstract

Un-Reinforced Masonry (URM) buildings are popular due to their durability, low cost, construction easiness and architectural character, need of less skilled labour, eco-friendly and use of locally available materials such as ashlar or rubble, adobe and brick. URM buildings have a higher probability of failing under natural disasters such as earthquakes, tsunamis and storm surges, floods, cyclones and landslides. In Sri Lanka, landslides and floods have frequently occurred. Massive tsunami adversely affected the people in 2004 and its effect to islands on the Indian Ocean has been continued since December, 2004. Minor earthquakes have come off recently with experiences of only wall cracks. Besides, it is believed there is a defused plate boundary in the making some 500 km south of the southern tip of Sri Lanka as the cause of these tremors or minor quakes. Investigation on performance of URM buildings against these natural disasters is increasingly important. In this review study an attempt was made to summarize types of damages on URM structures caused by natural disasters, different kind of retrofitting methods for URM structures to be seismic resistant. Common failure mechanisms for URM structures consist of separation of walls at corners, diagonal cracking in walls, separation of roofing from walls, vertical cracking in walls, out-of-plane wall failure, in-plane failure, shear cracks and de-lamination. These damages on a wall lead to diminish the service life of building. Simple technologies with low cost to strengthen the existing structures and damaged structures to resist dynamic loads are also discussed in this paper.