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Wellington, New Zealand

Bothara J.K.,Beca Carter Hollings and Ferner Ltd | Dhakal R.P.,University of Canterbury | Mander J.B.,Texas A&M University
Earthquake Engineering and Structural Dynamics | Year: 2010

This paper presents the results of an experimental investigation carried out to investigate the seismic performance of a two storey brick masonry house with one room in each floor. A half-scale building constructed using single wythe clay brick masonry laid in cement sand mortar and a conventional timber floor and timber roof clad with clay tiles was tested under earthquake ground motions on a shaking table, first in the longitudinal direction and then in the transverse direction. In each direction, the building was subjected to different ground motions with gradually increasing intensity. Dynamic properties of the system were assessed through white-noise tests after each ground motion. The building suffered increasing levels of damage as the excitations became more severe. The damage ranged from cracking to global/local rocking of different piers and partial out-of-plane failure of the walls. Nevertheless, the building did not collapse under base excitations with peak ground acceleration up to 0.8g. General behaviour of the tested building model during the tests is discussed, and fragility curves are developed for unreinforced masonry buildings based on the experimental results. Copyright © 2009 John Wiley & Sons, Ltd. Source

Kam W.Y.,Beca Carter Hollings and Ferner Ltd | Kam W.Y.,University of Canterbury | Pampanin S.,University of Canterbury
Structural Concrete | Year: 2011

The 22 February 2011 M w 6.2 Christchurch (Lyttelton) earthquake was a particularly severe test for both modern seismically designed and existing non-ductile reinforced concrete (RC) buildings. Some 16.2 % of 833 buildings with RC systems within the Christchurch central business district (CBD) were severely damaged. There were 182 fatalities, 135 of which were the unfortunate consequences of the complete collapse of two medium-rise RC buildings. As with the post-Northridge 1994 earthquake, the design performance of "modern" structures is being scrutinized - with the inevitable question: is "life safety" but irreparable damage still a valid performance target? This brief paper presents a summary of RC building damage from a broad performance-based earthquake engineering perspective. Several preliminary lessons, not all of them surprising, and the issues that have arisen will be discussed using case study buildings, with suggestions for urgently needed research areas. © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

Pender M.,University of Auckland | Ramsay G.,Beca Carter Hollings and Ferner Ltd | Lynne B.,University of Auckland | Bromley C.,Institute of Geological & Nuclear Sciences
Proceedings of the Institution of Civil Engineers: Geotechnical Engineering | Year: 2013

Geothermal fluid has been extracted from the Wairakei field in New Zealand since the mid-1950s for electricity generation. This has induced regional subsidence of more than 1 m; in addition, there are a few localised bowls with much greater subsidence. A comprehensive geotechnical investigation with recovery of undisturbed samples from depths of up to 774 m was undertaken with testing of samples from within and outside subsidence bowls to determine material properties, with the aim of improved understanding of subsidence within the Wairakei-Tauhara geothermal system. Results from more than 130 K0 triaxial compression tests on core samples are discussed. Given the volcanic origins of most of the material present, a wide variation in the measured constrained modulus values is not surprising. Scanning electron microscope images reveal differences between the texture of the soft materials and the very stiff materials; these correlate with the constrained modulus values. The applicability of the Terzaghi effective stress equation is considered in relation to the measured property values; the conventional equation remains valid even for the least compressible materials tested. Source

Leon R.T.,Virginia Polytechnic Institute and State University | Kam W.Y.,Beca Carter Hollings and Ferner Ltd | Pampanin S.,University of Canterbury
American Concrete Institute, ACI Special Publication | Year: 2012

The design of beam-column joints in reinforced concrete moment frames is an area where USA and New Zealand standards have diverged for many years. USA design guidelines, and ACI 352 in particular, implicitly accept damage in the form of shear cracking, bar slip and possible column hinging for joints subjected to large lateral load reversals. Since the 1980's, the New Zealand approach has been to minimize that type of damage and to concentrate the deformations in plastic hinges in the beams by careful detailing of the joint and adjacent beam regions, thus keeping columns essentially elastic. The recent February 22, 2011 Christchurch earthquake and its associated swarm present an excellent opportunity to contrast these approaches in terms of visual performance for a variety of New Zealand structures detailed and built before and after the newer, more stringent joint design guidelines came into effect. The main lesson from the Christchurch experience is the importance of providing both some degree of lateral resistance, e.g. via beam-column joint moment-resisting capacity, and an increased level of displacement capacity in secondary or gravity-frames in order to improve the overall building's robustness and seismic resilience in response to earthquake demands beyond the code design level. Source

Bothara J.,Beca Carter Hollings and Ferner Ltd | Beetham D.,Institute of Geological & Nuclear Sciences | Brunsdon D.,Kestrel Group | Brown R.,CAL Engineering | And 5 more authors.
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2010

The Mw 7.5 Padang earthquake struck at 17:16 local time on 30th September 2009 with an epicentre offshore about 60 km west-northwest of Padang, capital of West Sumatra Province. More than 1,100 people were killed, and over 2,900 injured. The earthquake caused significant damage to public buildings and offices as well as to about 140,000 houses. It affected 250,000 families through the total or partial loss of their homes and livelihoods. More than half the earthquake fatalities occurred when several villages inland from Pariaman were buried by landslides. However, the damage and destruction of building structures was a major cause behind human and property losses. In addition to landslides, the earthquake triggered extensive liquefaction and lateral spreading in the region. A ten-member team from New Zealand visited the area under the auspices of NZAid and New Zealand Society for Earthquake Engineering to undertake building safety evaluations. The team spent most of their time in Padang city and other nearby earthquake-affected areas. This paper presents their observations and explores causes behind the damage and destruction of buildings by the moderate to strong earthquake shaking. Source

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