Performance of confined masonry buildings in November 2017, Sarpole Zahab earthquake (Mw = 7.3), Iran.

Confined masonry buildings are common structural systems in many seismic-prone regions of the world. According to the building code provisions, an appropriate continuous tie system should be provided in these buildings to bind the structural elements together and stop separation and disintegration of these elements under ground shaking. Since usually prescriptive design provisions with minimum calculations are used for constructing confined masonry buildings, investigating their performance in real seismic events is of great importance. In this paper observations made on the performance of confined masonry buildings during the destructive Sarpole Zahab, Iran, earthquake of November 12, 2017 are reported. The earthquake had caused different types of damage in both the structural and non-structural elements of the buildings. Damages were found to be primarily due to large structural irregularities and poor workmanship. Nonetheless, it was noted that those buildings with no significant irregularities, in the construction of which all the code's main provisions had been followed, survived the earthquake and did not experience partial or total collapse. It is suggested that in the taller, two or three storey buildings, with the aim of enhancing the lateral deformation capacity of the load bearing walls, some modifications on the dimensions and reinforcement detailing of the vertical tie elements, particularly those located at the corners of the buildings, to be carried out. In addition, as it has been repeatedly observed in the past earthquakes that after the partial or total collapse of the load bearing walls the tie-beams and tie-columns have served as a secondary gravity load-resisting system and prevented collapse of floor and roof slabs, it is suggested that the adequacy of the current prescriptive detailing of the tie system in acting as a temporary secondary load-bearing system to be verified. [ABSTRACT FROM AUTHOR]