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Research papers, University of Canterbury Library

In most design codes, infill walls are considered as non-structural elements and thus are typically neglected in the design process. The observations made after major earthquakes (Duzce 1999, L’Aquila 2009, Christchurch 2011) have shown that even though infill walls are considered to be non-structural elements, they interact with the structural system during seismic actions. In the case of heavy infill walls (i.e. clay brick infill walls), the whole behaviour of the structure may be affected by this interaction (i.e. local or global structural failures such as soft storey mechanism). In the case of light infill walls (i.e. non-structural drywalls), this may cause significant economical losses. To consider the interaction of the structural system with the ‘non-structural ’infill walls at design stage may not be a practical approach due to the complexity of the infill wall behaviour. Therefore, the purpose of the reported research is to develop innovative technological solutions and design recommendations for low damage non-structural wall systems for seismic actions by making use of alternative approaches. Light (steel/timber framed drywalls) and heavy (unreinforced clay brick) non-structural infill wall systems were studied by following an experimental/numerical research programme. Quasi-static reverse cyclic tests were carried out by utilizing a specially designed full scale reinforced concrete frame, which can be used as a re-usable bare frame. In this frame, two RC beams and two RC columns were connected by two un-bonded post tensioning bars, emulating a jointed ductile frame system (PRESSS technology). Due to the rocking behaviour at the beam-column joint interfaces, this frame was typically a low damage structural solution, with the post-tensioning guaranteeing a linear elastic behaviour. Therefore, this frame could be repeatedly used in all of the tests carried out by changing only the infill walls within this frame. Due to the linear elastic behaviour of this structural bare frame, it was possible to extract the exact behaviour of the infill walls from the global results. In other words, the only parameter that affected the global results was given by the infill walls. For the test specimens, the existing practice of construction (as built) for both light and heavy non-structural walls was implemented. In the light of the observations taken during these tests, modified low damage construction practices were proposed and tested. In total, seven tests were carried out: 1) Bare frame , in order to confirm its linear elastic behaviour. 2) As built steel framed drywall specimen FIF1-STFD (Light) 3) As built timber framed drywall specimen FIF2-TBFD (Light) 4) As built unreinforced clay brick infill wall specimen FIF3-UCBI (Heavy) 5) Low damage steel framed drywall specimen MIF1-STFD (Light) 6) Low damage timber framed drywall specimen MIF2-TBFD (Light) 7) Low damage unreinforced clay brick infill wall specimen MIF5-UCBI (Heavy) The tests of the as built practices showed that both drywalls and unreinforced clay brick infill walls have a low serviceability inter-storey drift limit (0.2-0.3%). Based on the observations, simple modifications and details were proposed for the low damage specimens. The details proved to be working effectively in lowering the damage and increasing the serviceability drift limits. For drywalls, the proposed low damage solutions do not introduce additional cost, material or labour and they are easily applicable in real buildings. For unreinforced clay brick infill walls, a light steel sub-frame system was suggested that divides the infill panel zone into smaller individual panels, which requires additional labour and some cost. However, both systems can be engineered for seismic actions and their behaviour can be controlled by implementing the proposed details. The performance of the developed details were also confirmed by the numerical case study analyses carried out using Ruaumoko 2D on a reinforced concrete building model designed according to the NZ codes/standards. The results have confirmed that the implementation of the proposed low damage solutions is expected to significantly reduce the non-structural infill wall damage throughout a building.

Images, UC QuakeStudies

Photograph captioned by Fairfax, "Gunyah homestead was badly damaged during the September 4th 2010 earthquake, but the Cotterill family are picking up the pieces and rebuilding. Builders repair the master bedroom where a large brick chimney came through the room narrowly missing the Cotterills and totally obliterating their bed".

Images, UC QuakeStudies

Photograph captioned by Fairfax, "Gunyah homestead was badly damaged during the September 4th 2010 earthquake, but the Cotterill family are picking up the pieces and rebuilding. Builders repair the master bedroom where a large brick chimney came through the room narrowly missing the Cotterills and totally obliterating their bed".

Images, UC QuakeStudies

The facade of the building housing the Daily Bagel and the Covent Fruit Centre has fallen away, leaving the building unstable and dangerous. The front wall has toppled onto the footpath leaving a pile of bricks. The front windows of this and surrounding buildings have been spray-painted with USAR codes 'No Go' and the times they were checked.

Images, UC QuakeStudies

Photograph captioned by Fairfax, "Gunyah homestead was badly damaged during the September 4th 2010 earthquake, but the Cottrell family are picking up the pieces and rebuilding. What remains of the master bedroom bed where a large brick chimney fell through the roof crushing the bed where William and Simonetta Cottrell had been sleeping moments before".

Images, eqnz.chch.2010

one of Christchurch's abandoned suburbs. The land moved - bricks and block walls everywhere collapsed - two multi story buildings folded - 184 people died. Wooden framed houses largely stayed up, many concrete slabs cracked, power poles leaned in liquid ground, surface bubbled, services ruptured .... damage to the cbd still gets the most cover...

Audio, Radio New Zealand

On the 10th anniversary of the devastating 2011 Christchurch quake we hear the first-hand story from Zara Potts, who describes how the brick cafe she was in caved in around her; we hear from Dr Caroline Bell on how the earthquakes impacted the mental health of Cantabrians and how things are looking a decade later; and our panellists share their own memories from that day.

Images, UC QuakeStudies

Photograph captioned by Fairfax, "Christchurch Earthquake. A massive 7.4 magnitude earthquake has hit Christchurch and the wider South Island, causing widespread damage, two serious injuries and power cuts to most of the city. Marsha Witehira had the bricks from the wall of her house fall onto her bed where she was sleeping. Both sides of her house have collapsed".

Images, UC QuakeStudies

Photograph captioned by Fairfax, "Christchurch Earthquake. A massive 7.4 magnitude earthquake has hit Christchurch and the wider South Island, causing widespread damage, two serious injuries and power cuts to most of the city. Marsha Witehira had the bricks from the wall of her house fall onto her bed where she was sleeping. Both sides of her house have collapsed".

Audio, Radio New Zealand

Four years ago Christchurch City Council vowed to get tough on the owners of 30 central city buildings left derelict since the 2011 earthquake. A wander through central Christchurch shows many of the buildings, nicknamed the dirty 30, still look unchanged. There are boarded up windows, tarps covering gaping holes, and containers keeping bricks from falling on passers by. But council says progress is finally being made on most Rachel Graham has more.

Audio, Radio New Zealand

The Aromaunga Baxters Flowers nursery in Heathcote, Christchurch sits right above the point where the earthquake struck on 22 February 2011. The greenhouses on the steep slopes of the Port Hills, as well as a big old villa and other brick buildings were badly damaged. Ten years on co-owner John Baxter says the earthquake damage is still being repaired, but sales have been boosted by a lack of imported flowers due to Covid-19 restrictions.

Images, UC QuakeStudies

Photograph captioned by Fairfax, "Christchurch Earthquake. A massive 7.4 magnitude earthquake has hit Christchurch and the wider South Island, causing widespread damage, two serious injuries and power cuts to most of the city. Marsha Witehira had the bricks from the wall of her house fall onto her bed where she was sleeping. Both sides of her house have collapsed. Witehira (L) is comforted by a friend".