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Remedial Wall Tie Review, Canterbury

Results from an independent report into the performance of Helifix ties installed as part of seismic strengthening projects in Christchurch can be found below. Based on visits to four case study sites around Christchurch following the 2010 Darfield earthquake, the 2011 February earthquake and the June 2011 aftershock, the report concludes:

(1) the DryFix system is “effective in improving the out-of-plane performance” of the external masonry veneer in cavity brick construction; and

(2) HeliBar and HeliBond used together are “effective in repairing in-plane cracks and corner cracks in earthquake damaged unreinforced masonry buildings.”

The field-based report follows seismic laboratory testing of masonry panels reinforced with HeliBar reinforcement in 2010 and 2011 at Auckland and Newcastle Universities, and remedial and new build wall tie testing to AS/NZS2699.1 conducted at Newcastle University in 2011 and 2012.

Not unexpected, the positive findings provide a welcome confirmation of outcomes witnessed at many other sites around the city and regions where similar Helifix techniques have been used and seismic jarring occurred.

Among the techniques and buildings surveyed were crack stitching repairs conducted at the above Manchester Street site. Repairs were carried out following the Darfield event. One metre lengths of HeliBar were bonded using HeliBond grout into slots cut into the masonry at regular intervals across both vertical and horizontal cracks found at the ground floor level.The repairs and building were surveyed again in April and July, following the two major aftershocks of 11 February and 13 June. Although damage to other parts of the building was so severe that the building had to later be demolished, the cracks in the repaired masonry showed no signs of re-opening – indicating that strength had been restored to the previously damaged area.