Earthquake-Damaged Unreinforced Masonry Building Tested In-Situ

Abstract

In December 2007 a magnitude 6.8 earthquake had an epicentre located approximately 50 km from the city of Gisborne, New Zealand. This earthquake caused damage to a number of buildings in Gisborne, and in particular, to numerous unreinforced masonry buildings. One such building was damaged to the extent that significant post-earthquake repairs were necessary, and partial removal of two of the building’s gable ended walls was required. This reconstruction provided an opportunity for a team of researchers from the University of Auckland to conduct field tests on the building, allowing comparison with companion testing that had previously been undertaken in a laboratory setting. This field testing involved the extraction of clay brick and mortar samples, in-situ bed joint shear tests, diagonal shear tests on samples extracted from the gabled walls, an in-situ in-plane shear test and out-of-plane testing of a gable ended wall both in the as-built condition and after the installation of a near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) retrofit solution. Testing confirmed that the boundary conditions in real buildings can significantly affect experimental response, with vertical restraint resulting in a large increase in out-of-plane load capacity, and also confirmed that the near-surface mounted FRP solution is an excellent low invasive option for seismic strengthening of unreinforced masonry walls. Details of the history of the building, and the methods used to undertake the field testing are reported, and experimental results are presented.