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On September 4, 2010 a M 7.1 earthquake occurred with an epicentre near the town of Darfield 30-40 km west of the Christchurch CBD. In the days following the earthquake inspections were carried out on highway, road City Council and pedestrian bridges in the Canterbury area. This paper details the preliminary findings based on visual inspection of about fifty five bridges. The paper comprises information supplied by consulting engineering firms which were also directly involved in the inspections soon after the earthquake.
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This paper describes the performance of (or damage to) non-structural components and contents in buildings during the 4th September 2010 Darfield (Canterbury) earthquake and the subsequent aftershocks. Even in buildings with little damage to their structural systems, non-structural and content damages were significant; and these damages were reported to have increased during the aftershocks (especially those of magnitude 5 and higher). Most commonly damaged non-structural components were brick chimneys, parapets, ceilings, facades, internal walls and windows. The nature and extent of damages in each of these components are discussed in this paper with the help of typical damage photos taken after the earthquake. The extent of content damage in a building was dependent on its usage; typically buildings using racks/shelves for displaying commodities (such as library, departmental stores, liquor shops etc) suffered significantly greater loss from content damage than residential houses, office buildings and other types of commercial buildings.
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A reconnaissance survey of earth walled buildings in the Canterbury area was carried out in mid October 2010 following the Darfield Earthquake. Fifteen earth walled buildings were inspected during the survey including historic earthbuildings and recently constructed reinforced earthbuildings.
Reinforced earth houses constructed since the 1990s performed well provided the overall wall bracing was adequate and detailing of the reinforcement and connections was generally in accordance with the NZ Earth Building Standards. Several unreinforced earth buildings constructed before 1930 (or reconstructed historic buildings) suffered significant structural damage and will require reconstruction or substantial repair. Unreinforced rammed earth buildings, and reinforced cinva ram brick buildings, constructed between 1930 and 1990 with reinforced concrete foundations and bond beams and adequate overall wall bracing generally performed moderately well given the level of shaking they experienced.
Minor cracking was observed in all but one of modern houses, performance was good where reinforcement and construction complied with the New Zealand Standards. Where buildings did not comply the damage could have been prevented by following the Standards.
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This paper focuses on the observed seismic performance of residential houses (mainly single-storey and two-storey houses) in the Darfield earthquake on 4 September 2010 and identifies potential research areas for remediation and resilience.
Overall the residential building stock, consisting predominately of light timber frame construction, performed very well, with very little structural damage due to ground shaking. The most significant structural damage to houses was from differential settlement of foundations, induced by soil liquefaction and/or lateral spreading. Many older buildings (more than 20 years old) suffered damage due to falling chimneys. Close to the fault rupture, in areas such as West Melton and Rolleston, there was significant damage to building contents due to strong shaking, and a few broken windows. Away from the fault zone, very few windows were broken in any buildings, indicating limited inter-storey drift.
Research needs were identified associated mainly with the design and repair of houses on liquefaction-prone soils.
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Five days after the Darfield earthquake, a street survey of buildings with pounding damage was performed in Christchurch Central Business District (CBD). Pounding damage did not occur very often, and the level of damage observed was generally low. Moderate to severe pounding damage was observed only in some unreinforced masonry buildings. Outside the CBD one collapsed storey can be attributed to pounding.
The majority of pounding damage occurred in vertical structural elements. Adjacent stepped façades were also found to be susceptible. The damage patterns associated with pounding could have led to building collapse in more severe/longer duration shaking or major aftershocks. Pounding damage remains a serious concern for future strong earthquakes in New Zealand.
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This paper focuses on the structural behaviour and types of failure of churches located in the general Canterbury area following the Darfield earthquake of September 04, 2010. Given the variability in architectural styles, structural systems and properties of underlying soils, different patterns of damage were identified including out-of-plane gable failures, collapse of bell towers and cracking due to liquefaction and ground settlement.
An architectural and historical landmark of Christchurch, the Christchurch Cathedral, suffered insignificant damage during the earthquake mainly because of its seismic retrofitting during 2006-2007. However many other church structures required retrofitting and supporting measures to avoid additional damage.
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The University of Canterbury campus on the west side of Christchurch has a range of building types built since the late 1950s. The building stock is predominantly 3-12 storey concrete construction. About one third of campus buildings had some secondary and non-structural damage during the earthquake, while about three quarters had contents damaged; filing cabinets overturned, books off shelves, shelves overturned, fallen lab equipment, broken glassware. The secondary structural damage was primarily to stairs, finishes at seismic joints, ceilings and elevators. This paper outlines the impacts the earthquake had on the campus buildings, in terms of structural, secondary structural and contents damage. It also outlines the post-earthquake recovery process and downtime.
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The Christchurch Women's Hospital, completed in March 2005, is the only base-isolated building in the South Island of New Zealand. The displacement capacity of the base-isolation system and the super-structure ductility capacity are designed to meet 2000-year return-period demands. Detailed structural evaluations after the 2010 Darfield Earthquake revealed damage only to sacrificial non-structural components at the seismic gaps. Because the structure is not instrumented, basic design information and ground motion records from nearby sites are used to estimate the responses to the main shock and a large after-shock. Results from this modelling effort are used to corroborate reports of structural response from staff present at the time of the main shock and aftershocks. Issues meriting further investigation are related to the local site conditions, soil-structure interaction, super-structure dynamics, interaction with the adjacent structures, and large-deformation effects.
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This paper presents preliminary findings based on the performance of various steel structures during the Darfield earthquake of September 4, 2010, including concentrically braced frames, eccentrically braced frames, steel tanks, and steel houses. With a few exceptions, steel structures performed well during this earthquake, but much of this is attributed to the fact that seismic demands from the Darfield earthquake were generally lower than considered in their design.
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This paper describes observations of damage to reinforced concrete buildings from the September 2010 Darfield (Canterbury) earthquakes. Data was collated from first-hand earthquake reconnaissance observations by the authors, post-earthquake surveys, and communications and meetings with structural engineers in Christchurch. The paper discusses the general performance of several reinforced concrete building classes: pre-1976 low-rise, pre-1976 medium rise, modern low- and mid-rise, modern high-rise, industrial tilt-up buildings, advanced seismic systems and ground-failure induced damaged and retrofitted RC buildings. Preliminary lessons are highlighted and discussed. In general, reinforced concrete buildings behaved well and as expected, given the intensity of this event.
