Performance of Flat Roofs Made of Wooden Beams and Straw-Mud Mixture in the 2012 Twin Earthquakes of Ahar and Varzaghan, East Azarbaijan, Iran

Abstract

Roofs covering buildings in the rural areas in Ahar and Varzaghan regions, prior to the August 11, 2012, twin earthquakes, can be categorized into three main groups: flat roofs composed of wooden beams together with a plaster of straw-mud/clay mixture, traditional masonry dome or vault, and rarely, a steel I-beam jack-arch system. Similar to other earthquakes such as the 2003 Bam, Iran, earthquake, the collapse of nonengineered masonry roofs and floor slabs during the earthquakes was the most important factor causing a large number of fatalities. The observed behavior and the performance of the first group of roofs after the earthquakes are demonstrated here, some matters of interest are discussed, and some aspects of the existing construction methods in rural areas are assessed. The poor seismic performance of traditional building roofs made of wooden beams and mud is noted.