(top) Steel frame testing setup includes strain gauges and hydraulic pump; (bottom) Overall anchor pullout testing setup includes on-site monitor and computer to record force and displacement results.
For centuries, structures in Europe have been built using the technique of securing timber diaphragms to the perimeter walls through the implementation of adhesive anchors. This structural component has proven to be beneficial in retrofitting buildings subject to the seismic frequencies of natural disasters by providing additional connections within the frame and therefore reducing the distance of which unsupported walls must span.
Decades ago, this application was adopted in New Zealand to help strengthen buildings along the Australian fault line with the use of external anchor plates. The technique has since evolved to a widespread use throughout the construction industry. After the devastating earthquake in Christchurch in 2011, these anchors came under examination as one of the main failures of the buildings subject to the natural disaster. It was discovered that prior to the implementation of the anchors in New Zealand’s unreinforced masonry buildings, few tests of the anchors had been conducted and little was actually known about the strength of these adhesive techniques. Motivation to test these retrofits came from both a significant lack of prior research as well as the severity of building failure in the Christchurch earthquake last year.
The focus of our research, performed in partnership with the University of Auckland was on the seismic response of anchors in unreinforced masonry buildings. Multiple tests were conducted to observe the seismic responses of different anchor parameters. Tests consisted of measuring the shear strength of masonry walls, learning the process of the anchors’ installation, measuring the displacements of anchors being pulled out of the masonry walls, and observing the tensile strengths of anchors that were either installed using epoxy or grout adhesives. Photographic interpretations were also collected and organized into a database that could be used for later analysis of several Christchurch buildings that had been affected by the Canterbury earthquake swarm in 2011.
In order to display the data that was collected, we created graphs to better illustrate our claims for the main causes of multiple levels of damage. Additional analysis of the effect of anchors in unreinforced masonry buildings is necessary and will add to our findings, analyses, and conclusions.
PARTICIPATING RESEARCHERS: University of Auckland: Dmytro Dizhar, Josiah Campbell, Brad Christie, Jason Ingham; UCSD: Lelli Van Den Einde