2009 NZSEE
Conference
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2009 NZSEE Conference |
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Contents |
Keynote Address Session 1 Session 2 Session 3A Session 3B Session 4A Session 4B Session 5A Session 5B Session 6 Session 7 Poster Session Experience from California, USA on Seismic Retrofit of Unreinforced Masonry BuildingsDmytro Dizhur, Alistair Russell, Jason Ingham and Peter Laursen It is well known that New Zealand’s seismicity poses a considerable hazard on its structures. Unreinforced masonry (URM) buildings are acknowledged to be the structures most susceptible to damage during an earthquake. URM buildings have insufficient strength to resist lateral earthquake forces and lack the ability to dissipate energy. It becomes apparent that when the next earthquake strikes, New Zealand is at risk of sustaining many deaths and injuries, loss of heritage buildings, as well as incurring great damage and reconstruction costs. The recently introduced Building Act 2004 requires all earthquake prone structures to be retrofitted to improve their seismic performance, or otherwise be demolished. New Zealand is currently in the initial stages of systematically assessing and retrofitting its earthquake prone buildings, whilst California has had many years of experience in retrofitting their building stock. To develop a thorough understanding of current practices and lessons learned, meetings were arranged in California with engineers, building officials and architects, with the particular aim to establish the most sensible, efficient and economical methods of seismic retrofit, and what areas of research could be further developed to enhance the understanding of seismic retrofit to be applied in a New Zealand context. The information gathered from this set of meetings will be presented here.
Seismic Retrofit of Government HouseMatthew Ireland, Jason Milburn and John Trowsdale Government House in Wellington is listed as a Category 1 historic building and is one of the most historically significant buildings in New Zealand. The building was constructed in 1910 and is a large two-three storey timber framed structure with a clay tile roof and is founded on unreinforced masonry walls. The external walls are typically clad in Jarrah weatherboards on the ground floor and stucco on the first floor. The internal walls are typically lined in fibrous plaster and have stud heights of up to 4.8m. As part of the Government House Conservation project, which is currently underway, a seismic retrofit is to be performed. The retrofit is a voluntary upgrade with the aim of improving the seismic performance to as near as reasonably practical to current code levels. An integral constraint on the nature of the retrofit was to minimise the impact and damage to the historic fabric of the building. The retrofit scheme was developed in collaboration with the Heritage Advisory Team which indicated the areas of most historical importance and appropriate locations for the retrofit works. The retrofit largely consists of a series of steel cross braces that are distributed throughout the building on the ground and first floors. However, reinforced masonry walls and various other elements/fixings were used to complete critical load paths. The steel cross braces were designed to be installed by removing the lining from only one face of the existing walls and to be concealed once the lining is replaced. As part of the design process the seismic performance was assessed pre and post retrofit using non-linear time history analysis. The analyses incorporated information from FEMA-356 and the NZSEE Red Book for Assessing and Strengthening Earthquake Risk Buildings, in addition to a series of in-situ experimental tests.
Reconstruction Project after Devastating 2005 Pakistan EarthquakeNajif Ismail and Jason Ingham The pre-2005 earthquake seismic zonation map of Pakistan was developed based on limited earthquake data. In comparison, the recently upgraded Pakistan seismic zonation, based on probabilistic hazard analysis, has identified the northern areas and south western areas of Pakistan as high seismic hazard zones. In Pakistan no area is completely safe from earthquakes and the areas adjacent to the active Karakoram fault line are more susceptible to high intensities. An earthquake of magnitude 7.6 on Richter scale rattled Pakistan on 8th October 2005, when energy released from the linear strike slip fault between Indian and Eurasian plates. This earthquake caused 80,000 fatalities and destruction to many communal and dwelling structures. The largest destruction was reported in the capital territory and northern areas. In response to these devastating effects a reconstruction and recovery project was initiated in North West Frontier Province and Azad Jammu and Kashmir. The initial challenges were the scarce number of technical personnel, inclement weather conditions and difficult terrain for logistics. This presentation covers a brief introduction to the project background, different types of constructions being used in the project and a discussion on relative merits and demerits. A brief of the design concept for different prototypes is also discussed. An overview of the embedded quality control procedures and project management is focused in the execution part with a brief of construction bottle necks from the writer’s personal experience.
Fixing Steel Braced Frames to Concrete Structures for Earthquake StrengtheningGilbert Balbuena and J. Kunz Steel braced frames are widely used to upgrade concrete structures for earthquake loads. They are used both to strengthen the structure and to increase its ductility. In order to transfer the horizontal shear loads from the concrete structure to the steel braced frame, a reliable connection between the two is essential. It must be able to transfer the full capacity of the steel frame with only limited displacements. The behavior of two different fixing methods has been investigated in research programs in Japan and in Europe. A device to ensure an evenly distributed load transfer to a long row of anchors has been developed to meet the requirements of such applications. Paper P15: [Read] [Presentation] Seismic Assessment of Existing Reinforced Concrete Buildings with Plain Round Reinforcing BarsAngela Liu Seismic assessment of reinforced concrete buildings designed to out-dated design codes has attracted more and more attention in recent years. There have been extensive research activities around the world, and most of the approaches have been developed based on the test evidence with deformed longitudinal reinforcing bars. However, the majority of the existing reinforced concrete building stock in New Zealand contains plain round reinforcing bars because deformed bars were not available before the 1960s. There has been testing on the cyclic behaviour of reinforced concrete members with plain round reinforcing bars. The tests, although limited number, revealed a very different mechanism compared to that in reinforced concrete members with deformed reinforcing bars. The assessment procedures currently available have not given any consideration to identify the proper mechanism for reinforced concrete members based on the type of the reinforcing bars. This paper addresses the issues associated with the type of the reinforcing bars by comparatively examining the observed cyclic behaviour of reinforced concrete members for different reinforcing bar types with respect to the current assessment procedures. This presentation may be viewed at www.nzsee.org.nz after the conference. Paper P16: [Read] [Presentation] New Zealand Representation at the 2008 Asia Pacific IDEERS Seismic Design CompetitionCharlotte Knox, Dmytro Dizhur, Ronald Lumantarna and Sam Green The Asia Pacific IDEERS competition (APEC IDEERS) is an international seismic resistant design competition with the aim of promoting earthquake engineering research to school and university students. The annual competition began in 2001 and is hosted by the National Center for Research on Earthquake Engineering (NCREE) in Taiwan. The competition involved designing and constructing the most efficient multi-storey model structures using the materials provided to resist artificial earthquakes as simulated on the NCREE shake table. In 2008, for the first time in the competition history, a New Zealand team competed in the the postgraduate divisions of the competition thanks to generous sponsorship from the Earthquake Commission and the Structural Engineering Society of New Zealand. This presentation presents the designs and testing process prior to the competition and documents the many lessons learnt from the trip.
A Tutorial on Stone Masonry Houses: A Compendium of Worldwide ExperiencesJitendra Bothera, Ali Qaisar, C.V.R. Murty, Marjana Lutman, Tom Schacher and Andrea Penna Stone masonry buildings are one of the most common housing types built across the world, and will continue to be so in the foreseeable future. It also represents the structural type of a large architectural heritage that needs to be preserved and inhabited. In general, they perform very poorly in even under minor earthquake shaking. Motivated by the associated colossal human and property loss, a team of the World Housing Encyclopedia project with experience in field work, testing and outreach are currently working on the development of a tutorial (i.e., easy to understand document) on Stone Masonry Houses. The tutorial is expected to fill the prevalent vacuum of practical advice on how to incorporate seismic resilience into such buildings. Because the construction of stone masonry houses is very informal, incremental, and broadly controlled by the local availability and affordability of construction materials, the tutorial is taking a sensitive approach towards such issues and emphasizes that the incorporating seismic safety in such construction is not only a technical issue but a socio-economic and cultural one. This tutorial presents concepts of incorporating incremental safety in this building type. It offers various alternatives that are suitable for diverse environmental conditions, cultural and habitual needs, local architecture and different socio-economic conditions. This paper presents the experience gained during the process of development of this tutorial by volunteer contributors from different backgrounds. It records the challenges and opportunities, its content, and its worthiness.
Keynote Address Session 1 Session 2 Session 3A Session 3B Session 4A Session 4B Session 5A Session 5B Session 6 Session 7 Poster Session |