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Seismic events on both sides of the Tasman

Location:

New Zealand

Some masonry structures in Gisborne demonstrate greater seismic resilience than others.

A collaborative project investigating the seismic retrofitting of masonry buildings, involving researchers from both sides of the Tasman, continues to make headway.

Led by engineers at the University of Auckland and Canterbury in New Zealand, in conjunction with colleagues at the University of Newcastle and Adelaide in Australia, the Seismic Retrofit Solutions project has targeted the development of cost-effective guidelines and solutions to retrofit unreinforced masonry (URM) structures.The wording and implementation of a full list of solutions and formal provisions has yet to reach fruition, but the research, which is now at an advanced stage, has produced compelling results and there is a growing expectation that a suite of technical seismic manuals will result. As part of the project, researchers have investigated the performance of a number of different retrofitting systems. Shotcrete, fibre-reinforced polymer (FRP) sheeting and shear truss systems, among others, have received attention. Helifix has also supported a coordinated series of studies into its own Helibeam System of masonry reinforcement.

Unreinforced masonry panels, cut from condemned buildings in Gisborne (pictured), the site of a significant earthquake in 2007, provided the raw material for Helifix testing in New Zealand. In Australia, tests conducted using newly constructed masonry panels reinforced with HeliBar and HeliBond grout have fuelled research at the University of Newcastle. Results to the date of publication (November 2009) confirm much of what is already known about the Helibeam System, and which has been confirmed previously at numerous different sites and laboratories around the world. That is, the Helibeam System can be used to provide tremendous strength and greatly enhanced seismic performance to existing masonry structures.The Helibeam System, which builds around the bonding of specially formed stainless steel HeliBars into existing masonry with a specially formulated cementitious grout, HeliBond, also offers great versatility.Available in a range of different diameters and cross-sectional areas, different combinations of HeliBars and installation patterns may be used in pursuit of a variety of different solutions. Their unique helical profile ensures that HeliBars can be bonded into slots and clearance holes cut and drilled into masonry without workmanship difficulty.Complete results of the tests will be published through a series of papers presented at various international seismic and engineering conferences and symposiums in the new year. Current results confirm that, critical to the performance of the Helibeam System is the high quality and strength of the bond created between the HeliBar reinforcement, the HeliBond, and the masonry itself.Further, results indicate a significant increase in the performance of the tested masonry ‘wallettes’ when subjected to simulated seismic loads.