Auckland, New Zealand
Auckland, New Zealand

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Giongo I.,University of Trento | Wilson A.,Holmes Consulting Group | Dizhur D.Y.,University of Auckland | Derakhshan H.,University of Adelaide | And 4 more authors.
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2014

Currently there is little guidance available on an experimentally-validated detailed seismic assessment procedure for vintage flexible timber diaphragms such as are routinely encountered in New Zealand unreinforced masonry buildings. The results from recent testing of full-scale diaphragms are presented and interpreted with particular attention given to the definition of shear stiffness and shear strength values, whilst acknowledging that the recommendations derive from a small data set. References are provided to information previously published elsewhere to justify the theoretical framework adopted, and the procedure is linked to ASCE 41-13 for guidance regarding diaphragm scenarios that have not been studied by the authors. A procedure is provided to account for the effects on diaphragm response of supplementary stiffness due to masonry end walls. The performance of several diaphragms that were improved with either overlays or underlays is reported as potential proof-tested standard solutions. The assessment procedure is demonstrated by providing a mock worked example of a detailed diaphragm assessment.


Wijanto S.,Holmes Consulting Group | Clifton G.C.,University of Auckland
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2014

The recent series of damaging earthquakes in Christchurch, New Zealand has encouraged greater recognition of the post-earthquake economic impacts on New Zealand society and higher emphasis on low-damage earthquake resisting systems. Braced frames incorporating Buckling Restrained Braces (BRB) are seen as a significant contender for such a system. This research project focuses on the development of a reliable design procedure and detailing requirements for a generic BRB system. To gauge the performance of the designed system and to ascertain the reliability of the developed procedure, a series of static and dynamic sub-assemblage tests on the BRB frame with two different brace connection configurations were performed. The results are presented and discussed herein. The experimental tests generated stable and near symmetrical hysteresis loops, which is a principal characteristic of a well performing BRB system, albeit with the occurrence of slack in the connections. The experimental test results shows that several improvements need to be made to the proposed design procedure and detailing as outlined throughout the paper; especially the procedural modification to prevent slack from occurring in the two different connection systems. It is envisaged that applications will typically involve use of proprietary braces, however these need to be applied in accordance with the New Zealand design procedure; and determining the appropriate procedure was a key part of this project.


Morris G.J.,Holmes Consulting Group | Bull D.K.,Holmes Consulting Group | Bull D.K.,University of Canterbury | Bradley B.A.,University of Canterbury
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2015

Following the 2010-2011 Canterbury (New Zealand) earthquake sequence, lightly reinforced wall structures in the Christchurch central business district were observed to form undesirable crack patterns in the plastic hinge region, while yield penetration either side of cracks and into development zones was less than predicted using empirical expressions. To some extent this structural behaviour was unexpected and has therefore demonstrated that there may be less confidence in the seismic performance of conventionally designed reinforced concrete (RC) structures than previously anticipated. This paper provides an observation-based comparison between the behaviour of RC structural components in laboratory testing and the unexpected structural behaviour of some case study buildings in Christchurch that formed concentrated inelastic deformations. The unexpected behaviour and poor overall seismic performance of 'real' buildings (compared to the behaviour of laboratory test specimens) was due to the localization of peak inelastic strains, which in some cases has arguably led to: (i) significantly less ductility capacity; (ii) less hysteretic energy dissipation; and (iii) the fracture of the longitudinal reinforcement. These observations have raised concerns about whether lightly reinforced wall structures can satisfy the performance objective of "Life Safety" at the Ultimate Limit State. The significance of these issues and potential consequences has prompted a review of potential problems with the testing conditions and procedures that are commonly used in seismic experimentations on RC structures. This paper attempts to revisit the principles of RC mechanics, in particular, the influence of loading history, concrete tensile strength, and the quantity of longitudinal reinforcement on the performance of real RC structures. Consideration of these issues in future research on the seismic performance of RC might improve the current confidence levels in newly designed conventional RC structures.


Galloway B.,Holmes Consulting Group | Ingham J.M.,University of Auckland
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2015

The South Napa earthquake occurred on Sunday, 24 August 2014 at 3.20 am local time at a depth of 10.7 km, having MW 6.0 and causing significant damage to unreinforced masonry (URM) buildings in the City of Napa and generating strong ground shaking in a region well known for its wine production. Parallels exist between the damage in past New Zealand earthquakes, particularly to unreinforced masonry buildings, and the disruption in the Marlborough region following the recent 2013 MW 6.5 Seddon earthquake. Furthermore, the event was the largest to have occurred in Northern California since the 1989 Loma Prieta earthquake 25 years earlier, and hence was an important event for the local community of earthquake researchers and professionals regarding the use of a physical and virtual clearinghouse for data archiving of damage observations. Because numerous URM buildings in the City of Napa had been retrofitted, there was significant interest regarding the observed performance of different retrofitting methods. Following a brief overview of the earthquake affected area and previous earthquakes to have caused damage in the Napa Valley region, details are provided regarding the characteristics of the 2014 South Napa earthquake, the response to the earthquake including placarding procedures and barricading, and more specific details of observed building and non-structural damage. Aspects of business continuity following the South Napa earthquake are also considered. One conclusion is that in general the seismic retrofitting of URM buildings in the Napa region proved to be very successful, and provides an important benchmark as New Zealand begins to more actively undertake seismic assessment and retrofitting of its earthquake prone building stock. It is also concluded that there are sufficient similarities between New Zealand and California, and a rich network of contacts that has developed following the hosting of many US visitors to New Zealand in conjunction with the 2010/2011 Canterbury earthquakes, that it is sensible for the New Zealand earthquake engineering community to maintain a close focus on ongoing earthquake preparedness and mitigation methods used and being developed in USA, and particularly in California.


Galloway B.,Holmes Consulting Group | Hare J.,Holmes Consulting Group | Brunsdon D.,Kestrel Group | Wood P.,Ministry of Civil Defence and Emergency Management | And 2 more authors.
Earthquake Spectra | Year: 2014

The New Zealand Society for Earthquake Engineering (NZSEE) building safety evaluation process was implemented in several earthquakes that occurred as part of the 2010-2011 Canterbury earthquake sequence. This provided an opportunity to evaluate the effectiveness of the current processes across a range of issues. In addition to the established rapid assessments, guidelines have been developed for the detailed engineering evaluation of damaged buildings. Lessons have been drawn from these experiences relating to the effectiveness of placards and the rapid visual assessment of damage, requirements for a full spectrum of assessment processes, and training needs. Improvements to the current building safety evaluation processes are proposed and further considerations for reoccupation of damaged buildings are outlined. While this paper is based on the authors' experiences in New Zealand, the findings are expected to have wider applications. © 2014, Earthquake Engineering Research Institute.


Peng B.H.H.,Holmes Consulting Group | Dhakal R.P.,University of Canterbury | Fenwick R.C.,University of Canterbury | Carr A.J.,University of Canterbury | Bull D.K.,University of Canterbury
Journal of Structural Engineering (United States) | Year: 2013

This paper describes the development and validation of an analytical multispring plastic hinge element that can predict elongation of ductile RC plastic hinges together with its flexural and shear responses. The element consists of layers of longitudinal and diagonal springs that represent the behavior of concrete, reinforcing bars, and diagonal compression struts. Beam tests reported in the literature, for which elongation of plastic hinges was measured at different stages of the lateral cyclic loading, were used to validate the effectiveness of the newly developed plastic hinge element. Comparisons of the analytical predictions with experimental results show that the proposed element predicts elongation of plastic hinges satisfactorily. The ability of the model to predict elongation of a plastic hinge together with its flexural and shear deformations offers a significant advancement in seismic performance assessment of RC structures. © 2013 American Society of Civil Engineers.


Ahmadi A.,University of Auckland | Mathieson C.,Holmes Consulting Group | Clifton G.C.,University of Auckland | Das R.,University of Auckland | Lim J.B.P.,University of Auckland
Journal of Constructional Steel Research | Year: 2016

This paper describes an experimental investigation on a novel hollow connector, to be referred to as the Howick Rivet Connector (HRC). The HRC is of diameter of 12.75 mm and thickness of 0.95 mm and can be used to connect cold-formed steel channel-sections with a gap, such as found in the connection arrangement of cold-formed steel trusses and seismic framing units. Laboratory tests on twenty-seven Tee-stub specimens that use the HRC are described; for comparison, another twenty-seven Tee-stub specimens are also tested that use standard bolts. In the laboratory tests, the effect of three different thicknesses of channel-sections and three different end distances are investigated. It is shown that the behaviour of the HRC Tee-stubs is similar to that of the bolted Tee-stubs, but possess a higher capacity and an improved ductility, as shown by a longer yield plateau once the connection becomes inelastic. It recommended that a minimum end distance of 1.5 times the diameter of the HRC is sufficient. Design equations that can be used to predict the bearing strength of the HRC Tee-stubs are proposed; for these equations, the index of reliability calculated was greater than the recommended 3.5. © 2016 Elsevier Ltd. All rights reserved.


Peng B.H.H.,Holmes Consulting Group | Dhakal R.P.,University of Canterbury | Fenwick R.C.,University of Canterbury | Carr A.J.,University of Canterbury | Bull D.K.,University of Canterbury
Journal of Advanced Concrete Technology | Year: 2011

This paper follows on from a companion paper which described the development of a plastic hinge element that can capture elongation of plastic hinges and its effect on other aspects of cyclic response of ductile RC members. In this paper, some experimental elongation data available in literature are used to verify the effectiveness of this newlydeveloped plastic hinge element. The experimental results compiled in this study are examined to determine the effect of axial force on the behavior of reinforced concrete members; especially on the amount of plastic hinge elongation. Comparisons of the analytical predictions with experimental results show that the proposed model predicts elongation of plastic hinges satisfactorily. The ability to predict elongation in plastic hinges is a significant advancement in assessing the seismic performance assessment of RC structures. Copyright © 2011 Japan Concrete Institute.


Galloway B.D.,Holmes Consulting Group | Hare H.J.,Holmes Consulting Group
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2012

The Canterbury earthquake sequence was particularly disruptive for building owners and businesses located within the CBD. The initial damage to buildings in the relatively moderate September 2010 earthquake was surpassed by the significantly more damaging February 2011 event, challenging the way in which engineers have traditionally considered earthquake recovery. Internationally, re-occupation of buildings following an earthquake has been based on the need to get businesses operating from buildings that are rapidly identified as having suffered minor structural damage. However, following the February 2011 earthquake, the shift in risk profile was reflected by limiting reoccupation unless it could be shown that the building also had a minimum capacity to resist earthquakes. This challenges the balance between continuing function and safety in the traditional post-earthquake evaluation process. The timeframe for commencement of repairs has a significant impact on the speed of recovery. The importance of well defined regulations was highlighted in the well insured Christchurch building market, where legal arguments halted repairs in many instances. There is also a clear need for a modified, streamlined building consent process for the repair of earthquake damaged buildings. This paper looks at the various building control policies enacted during the Canterbury earthquakes, and their effectiveness in aiding the recovery of the Christchurch CBD.


Hare J.,Holmes Consulting Group
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2013

The Canterbury earthquakes have afforded the author a unique opportunity to view the state of engineering from a different perspective. The development of the Detailed Engineering Evaluation (DEE) procedure and the related activities of the Engineering Advisory Group have required thorough consideration of structural engineering practice. This has extended to an overview of the outputs from the DEEs completed by a wide range of engineers, over a wide range of buildings. From these and more general observations of engineering practice in contrast with that of other countries, a view on the state of earthquake engineering in New Zealand is offered with some thoughts on future direction and development needs.

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