Seismic response of adjacent structures on dry and saturated sand

Research papers, The University of Auckland Library

Soil-structure interaction (SSI) has been widely studied during the last decades. The influence of the properties of the ground motion, the structure and the soil have been addressed. However, most of the studies in this field consider a stand-alone structure. This assumption is rarely justifiable in dense urban areas where structures are built close to one another. The dynamic interaction between adjacent structures has been studied since the early 1970s, mainly using numerical and analytical models. Even though the early works in this field have significantly contributed to understanding this problem, they commonly consider important simplifications such as assuming a linear behaviour of the structure and the soil. Some experimental works addressing adjacent structures have recently been conducted using geotechnical centrifuges and 1g shake tables. However, further research is needed to enhance the understanding of this complex phenomenon. A particular case of SSI is that of structures founded in fine loose saturated sandy soil. An iconic example was the devastating effects of liquefaction in Christchurch, New Zealand, during the Canterbury earthquake in 2011. In the case of adjacent structures on liquefiable soil, the experimental evidence is even scarcer. The present work addresses the dynamic interaction between adjacent structures by performing multiple experimental studies. The work starts with two-adjacent structures on a small soil container to expose the basics of the problem. Later, results from tests considering a more significant number of structures on a big laminar box filled with sand are presented. Finally, the response of adjacent structures on saturated sandy soil is addressed using a geotechnical centrifuge and a large 1g shake table. This research shows that the acceleration, lateral displacement, foundation rocking, damping ratio, and fundamental frequency of the structure of focus are considerably affected by the presence of neighbouring buildings. In general, adjacent buildings reduced the dynamic response of the structure of focus on dry sand. However, the acceleration was amplified when the structures had a similar fundamental frequency. In the case of structures on saturated sand, the presence of adjacent structures reduced the liquefaction potential. Neighbouring structures on saturated sand also presented larger rotation of the footing and lateral displacement of the top mass than that of the stand-alone case.

People in Disasters Conference - Land Use Recovery Plan: How an impact ass…

Videos, UC QuakeStudies

A video of a presentation by Jane Murray and Stephen Timms during the Social Recovery Stream of the 2016 People in Disasters Conference. The presentation is titled, "Land Use Recovery Plan: How an impact assessment process engaged communities in recovery planning".The abstract for this presentation reads as follows: In response to the Canterbury earthquakes, the Minister for Canterbury Earthquake Recovery directed Environment Canterbury (Canterbury's regional council) to prepare a Land Use Recovery Plan that would provide a spatial planning framework for Greater Christchurch and aid recovery from the Canterbury earthquakes. The Land Use Recovery Plan sets a policy and planning framework necessary to rebuild existing communities and develop new communities. As part of preparing the plan, an integrated assessment was undertaken to address wellbeing and sustainability concerns. This ensured that social impacts of the plan were likely to achieve better outcomes for communities. The process enabled a wide range of community and sector stakeholders to provide input at the very early stages of drafting the document. The integrated assessment considered the treatment of major land use issues in the plan, e.g. overall distribution of activities across the city, integrated transport routes, housing typography, social housing, employment and urban design, all of which have a key impact on health and wellbeing. Representatives from the Canterbury Health in All Policies Partnership were involved in designing a three-part assessment process that would provide a framework for the Land Use Recovery Plan writers to assess and improve the plan in terms of wellbeing and sustainability concerns. The detail of these assessment stages, and the influence that they had on the draft plan, will be outlined in the presentation. In summary, the three stages involved: developing key wellbeing and sustainability concerns that could form a set of criteria, analysing the preliminary draft of the Land Use Recovery Plan against the criteria in a broad sector workshop, and analysing the content and recommendations of the Draft Plan. This demonstrates the importance of integrated assessment influencing the Land Use Recovery Plan that in turn influences other key planning documents such as the District Plan. This process enabled a very complex document with wide-ranging implications to be broken down, enabling many groups, individuals and organisations to have their say in the recovery process. There is also a range of important lessons for recovery that can be applied to other projects and actions in a disaster recovery situation.

Building the Carbon Case for Resilient Design

Research papers, The University of Auckland Library

The research presented in this thesis investigated the environmental impacts of structural design decisions across the life of buildings located in seismic regions. In particular, the impacts of expected earthquake damage were incorporated into a traditional life cycle assessment (LCA) using a probabilistic method, and links between sustainable and resilient design were established for a range of case-study buildings designed for different seismic performance objectives. These links were quantified using a metric herein referred to as the seismic carbon risk, which represents the expected environmental impacts and resource use indicators associated with earthquake damage during buildings’ life. The research was broken into three distinct parts: (1) a city-level evaluation of the environmental impacts of demolitions following the 2010/2011 Canterbury earthquake sequence in New Zealand, (2) the development of a probabilistic framework to incorporate earthquake damage into LCA, and (3) using case-study buildings to establish links between sustainable and resilient design. The first phase of the research focused on the environmental impacts of demolitions in Christchurch, New Zealand following the 2010/2011 Canterbury Earthquake Sequence. This large case study was used to investigate the environmental impact of the demolition of concrete buildings considering the embodied carbon and waste stream distribution. The embodied carbon was considered here as kilograms of CO2 equivalent that occurs on production, construction, and waste management stage. The results clearly demonstrated the significant environmental impacts that can result from moderate and large earthquakes in urban areas, and the importance of including environmental considerations when making post-earthquake demolition decisions. The next phase of the work introduced a framework for incorporating the impacts of expected earthquake damage based on a probabilistic approach into traditional LCA to allow for a comparison of seismic design decisions using a carbon lens. Here, in addition to initial construction impacts, the seismic carbon risk was quantified, including the impacts of seismic repair activities and total loss scenarios assuming reconstruction in case of non-reparability. A process-based LCA was performed to obtain the environmental consequence functions associated with structural and non-structural repair activities for multiple environmental indicators. In the final phase of the work, multiple case-study buildings were used to investigate the seismic consequences of different structural design decisions for buildings in seismic regions. Here, two case-study buildings were designed to multiple performance objectives, and the upfront carbon costs, and well as the seismic carbon risk across the building life were compared. The buildings were evaluated using the framework established in phase 2, and the results demonstrated that the seismic carbon risk can significantly be reduced with only minimal changes to the upfront carbon for buildings designed for a higher base shear or with seismic protective systems. This provided valuable insight into the links between resilient and sustainable design decisions. Finally, the results and observations from the work across the three phases of research described above were used to inform a discussion on important assumptions and topics that need to be considered when quantifying the environmental impacts of earthquake damage on buildings. These include: selection of a non-repairable threshold (e.g. a value beyond which a building would be demolished rather than repaired), the time value of carbon (e.g. when in the building life the carbon is released), the changing carbon intensity of structural materials over time, and the consideration of deterministic vs. probabilistic results. Each of these topics was explored in some detail to provide a clear pathway for future work in this area.