A wide range of reinforced concrete (RC) wall performance was observed following the 2010/2011 Canterbury earthquakes, with most walls performing as expected, but some exhibiting undesirable and unexpected damage and failure characteristics. A comprehensive research programme, funded by the Building Performance Branch of the New Zealand Ministry of Business, Innovation and Employment, and involving both numerical and experimental studies, was developed to investigate the unexpected damage observed in the earthquakes and provide recommendations for the design and assessment procedures for RC walls. In particular, the studies focused on the performance of lightly reinforced walls; precast walls and connections; ductile walls; walls subjected to bi-directional loading; and walls prone to out-of-plane instability. This paper summarises each research programme and provides practical recommendations for the design and assessment of RC walls based on key findings, including recommended changes to NZS 3101 and the NZ Seismic Assessment Guidelines.
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.
On 22 February 2011 the Mw6.2 Christchurch earthquake occurred with an epicentre less than 10 km from the Christchurch Central Business District (CBD) on an unknown buried fault at the edge of the city. The majority of damage was a result of lateral spreading along the Avon and Heathcote Rivers, with few bridges damaged due to ground shaking only. The most significant damage was to bridges along the Avon River, coinciding with the areas of the most severe liquefaction, with less severe liquefaction damage developing along the Heathcote River. Most affected were bridge approaches, abutments and piers, with a range of damage levels identified across the bridge stock. In the days following the earthquake, teams from various organizations performed inspections on over 800 bridges throughout the affected Canterbury region. This paper details the preliminary findings based on visual inspections and some preliminary analyses of highway and road bridges. The paper comprises information supplied by consulting engineering firms which were also directly involved in the inspections soon after the earthquake.
Due to the extrusion manufacturing process, hollow‐core units in New Zealand do not have transverse shear reinforcement. The prestressing strands will not be fully developed near the ends of the hollow‐core units, which significantly affects the shear capacity and makes them prone to transverse and web cracking under deformation demands. In addition, initial end slip of the strands caused during cutting of the units in the production process may exacerbate this effect. This vulnerability of hollow‐core slabs was remarked during the 2016 Kaikōura earthquake, where an estimated 22% of the damaged buildings presented transverse cracking to hollow‐core units, sometimes accompanied by evident web cracking. The observed damaged, produced by earthquake‐imposed deformations, highlighted the urgency to advance the understanding of the behavior of hollow‐core floors. Subsequently, an experimental testing program was initiated to investigate the properties of extruded concrete and the shear strength of hollow‐core units under different shear span‐to‐depth or aspect ratios. The 200 mm deep specimens were loaded well beyond the peak shear force to study the postpeak behavior of the hollow‐core units. Additionally, the present study evaluates the effect of initial end slip of the prestressing strands on the pre and postpeak capacity of the units. The results obtained are compared against the formulations provided by commonly used design standards such as the New Zealand concrete standard NZS3101:2006, the ACI 318‐19, as well as the fib Model Code 2010 and the BS EN 1168:2005.
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