ER3 Seismic improvement of loadbearing unreinforced masonry cavity walls (April 2015)

The main objectives of the reported research were to develop a background understanding of unreinforced masonry (URM) cavity wall type construction, to identify typically occurring failure modes and to establish seismic retrofit solutions for URM cavity wall construction.

An informative background to URM cavity walls is presented in sequence of historical development, typical construction details and observed damage in major past earthquakes.

From URM building surveys it was found that cavity walls in their original state make up approximately 40% of URM construction in New Zealand, with the remainder having solid interconnected multi-leaf walls.

Based on a detailed review of 125 URM cavity wall buildings that were damaged during the 2010/11 Canterbury earthquakes, it was concluded that unretrofitted URM cavity walls generally suffered irreparable damage due to weak mortar strength and lack of effective wall restraints.