Integrated performance-based design of building-foundation systems.

Research papers, University of Canterbury Library

The effects of soil-foundation-structure interaction (SFSI) have been a topic of discussion amongst the structural and geotechnical community for many decades. The complexity of the mechanisms, as well as the need for inter-disciplinary knowledge of geotechnical and structural dynamics has plagued the advancement and the consequent inclusion of SFSI effects in design. A rigorous performance-based design methodology should not just consider the performance of the superstructure but the supporting foundation system as well. Case studies throughout history (eg. Kobe 1995, Kocaeli 1999 and Christchurch earthquakes 2010-2011) have demonstrated that a poor performance at the foundation level can result in a full demolition of the structure and, in general terms, that the extent of damage to, and repairability of, the building system as a whole, is given by the combination of the damage to the soil, foundation and superstructure. The lack of consideration of the modifying factors of SFSI and an absence of intuitive performance levels for controlling foundation and soil behaviour under seismic loads has resulted in inadequate designs for buildings sited on soft soil. For engineers to be satisfied that their designs meet the given performance levels they must first, understand how SFSI affects the overall system performance and secondly have tools available to adequately account for it in their design/assessment. This dissertation presents an integrated performance-based design procedure for buildingfoundation systems that considers all of the major mechanisms of SFSI. A new soil-foundation macro-element model was implemented into a nonlinear finite element software and validated against several experimental tests. The numerical model was used to provide insights in to the mechanisms of SFSI and statistical analysis on the results yielded simple expressions that allow the behaviour to be quantified. Particular attention was paid to the effects of shear force on the foundation response and the quantification of the rocking mode of response. The residual deformations of the superstructure and distribution of forces up the structure were also investigated. All of the major SFSI mechanisms are discussed in detail and targeted numerical studies are used to explain and demonstrate concepts. The design procedure was validated through the design and assessment of a series of concrete buildings that were designed to account for the effects of SFSI.

Less Talk, More Action; The integration of small figures in a solution-foc…

Research papers, University of Canterbury Library

This thesis seeks to examine how the integration of play, small toys specifically, and the use of solution-focused brief therapy techniques can affect the outcomes for primary school aged children undergoing counselling. The setting is a counselling agency in Christchurch, New Zealand. A qualitative research approach is used and the data analysed using a narrative inquiry approach. The context of this study is the counselling service of an agency where young children, adolescents and their families are helped and supported through a variety of life issues. The counselling the participants are offered uses a combination of a solution-focused and play therapy where the purpose is to encourage clients to find exceptions to their presenting problems and identify their preferred future. The aim of this study is to help the children navigate their problem through a better understanding of and the gaining of personal skills and strengths. Participants were invited to be part of this study through the agency waiting list. The four included presented with a variety of reasons for coming to counselling yet these proved similar to that which the agency has been routinely presented with in the aftermath of the Canterbury earthquakes from 2011 to present day. Each participant had the consent of their parents or caregivers to engage in this project. The participants themselves separately agreed to engage in a solution- focused counselling process where the counsellor also integrated the use of small toys as part of the course. Counselling sessions were audiotaped, aspects photographed and analysed with a specific focus on client engagement. Four key themes emerged as the participants explored their personal narrative. Firstly, the “I’m OK” theme depicted in their first scaling activity, secondly a recognition that things could indeed be better and they needed help. Thirdly, a realisation of their own strengths and skills and finally that the future was an optimistic place to look forward to. These themes are described and explained through descriptions of the participant’s stories as well as self-reflection by the researcher. Transcriptions of sessions are included as are excerpts from the research journal and photographs of the use of the small toys by the children.

Planning for resilient communities: and every other day: learning from the…

Research papers, University of Canterbury Library

After a disaster, cities experience profound social and environmental upheaval. Current research on disasters describes this social disruption along with collective community action to provide support. Pre-existing social capital is recognised as fundamental to this observed support. This research examines the relationship between sense of place for neighbourhood, social connectedness and resilience. Canterbury residents experienced considerable and continued disruption following a large and protracted sequence of earthquakes starting in September 2010. A major aftershock on 22 February 2011 caused significant loss of life, destruction of buildings and infrastructure. Following this earthquake some suburbs of Christchurch showed strong collective action. This research examines the features of the built environment that helped to form this cooperative support. Data were collected through semi-structured interviews with 20 key informants followed by 38 participants from four case study suburbs. The objectives were to describe the community response of suburbs, to identify the key features of the built environment and the role of social infrastructure in fostering social connectedness. The last objective was to contribute to future planning for community resilience. The findings from this research indicated that social capital and community competence are significant resources to be called upon after a disaster. Features of the local environment facilitated the formation of neighbourhood connections that enabled participants to cope, manage and to collectively solve problems. These features also strengthened a sense of belonging and attachment to the home territory. Propinquity was important; the bumping and gathering places such as schools, small local shops and parks provided the common ground for meaningful pre-existing local interaction. Well-defined geography, intimate street typology, access to quality natural space and social infrastructure helped to build the local social connections and develop a sense of place. Resourceful individuals and groups were also a factor, and many are drawn to live near the inner city or more natural places. The features are the same well understood attributes that contribute to health and wellbeing. The policy and planning framework needs to consider broader social outcomes, including resilience in new and existing urban developments. The socio-political structures that provide access to secure and stable housing and local education should also be recognised and incorporated into local planning for resilience and the everyday.

Innovation in Construction: An innovation Framework for Infrastructure rec…

Research papers, The University of Auckland Library

This thesis describes the management process of innovation through construction infrastructure projects. This research focuses on the innovation management process at the project level from four views. These are categorised into the separate yet related areas of: “innovation definition”, “Project time”, “project team motivation” and “Project temporary organisation”. A practical knowledge is developed for each of these research areas that enables project practitioners to make the best decision for the right type of innovation at the right phase of projects, through a capable project organisation. The research developed a holistic view on both innovation and the construction infrastructure project as two complex phenomena. An infrastructure project is a long-term capital investment, highly risky and an uncertain. Infrastructure projects can play a key role in innovation and performance improvement throughout the construction industry. The delivery of an infrastructure project is affected in most cases by critical issues of budget constraint, programme delays and safety Where the business climate is characterized by uncertainty, risk and a high level of technological change, construction infrastructure projects are unable to cope with the requirement to develop innovation. Innovation in infrastructure projects, as one of the key performance indicators (KPI) has been identified as a critical capability for performance improvement through the industry. However, in spite of the importance of infrastructure projects in improving innovation, there are a few research efforts that have developed a comprehensive view on the project context and its drivers and inhibitors for innovation in the construction industry. Two main reasons are given as the inhibitors through the process of comprehensive research on innovation management in construction. The first reason is the absence of an understanding of innovation itself. The second is a bias towards research at a firm and individual level, so a comprehensive assessment of project-related factors and their effects on innovation in infrastructure projects has not been undertaken. This study overcomes these issues by adopting as a case study approach of a successful infrastructure project. This research examines more than 500 construction innovations generated by a unique infrastructure alliance. SCIRT (Stronger Christchurch Infrastructure Rebuild Team) is a temporary alliancing organisation that was created to rebuild and recover the damaged infrastructure after the Christchurch 2011 earthquake. Researchers were given full access to the innovation project information and innovation systems under a contract with SCIRT Learning Legacy, provided the research with material which is critical for understanding innovations in large, complex alliancing infrastructure organisation. In this research, an innovation classification model was first constructed. Clear definitions have been developed for six types of construction innovation with a variety of level of novelties and benefits. The innovation classification model was applied on the SCIRT innovation database and the resultant trends and behaviours of different types of innovation are presented. The trends and behaviours through different types of SCIRT innovations developed a unique opportunity to research the projectrelated factors and their effect on the behaviour of different classified types of innovation throughout the project’s lifecycle. The result was the identification of specific characteristics of an infrastructure project that affect the innovation management process at the project level. These were categorised in four separate chapters. The first study presents the relationship between six classified types of innovation, the level of novelty and the benefit they come up with, by applying the innovation classification model on SCIRT innovation database. The second study focused on the innovation potential and limitations in different project lifecycle phases by using a logic relationship between the six classified types of innovation and the three classified phases of the SCIRT project. The third study result develops a holistic view of different elements of the SCIRT motivation system and results in a relationship between the maturity level of definition developed for innovation as one of the KPIs and a desire though the SCIRT innovation incentive system to motivate more important innovations throughout the project. The fourth study is about the role of the project’s temporary organisation that finally results in a multiple-view innovation model being developed for project organisation capability assessment in the construction industry. The result of this thesis provides practical and instrumental knowledge to be used by a project practitioner. Benefits of the current thesis could be categorized in four groups. The first group is the innovation classification model that provides a clear definition for six classified types of innovation with four levels of novelty and specifically defined outcomes and the relationship between the innovation types, novelty and benefit. The second is the ability that is provided for the project practitioner to make the best decision for the right type of innovation at the right phases of a project’s lifecycle. The third is an optimisation that is applied on the SCIRT innovation motivation system that enables the project practitioner to incentivize the right type of innovation with the right level of financial gain. This drives the project teams to develop a more important innovation instead of a simple problemsolving one. Finally, the last and probably more important benefit is the recommended multiple-view innovation model. This is a tool that could be used by a project practitioner in order to empower the project team to support innovation throughout the project.

Engineering geology assessment of Slovens Creek Viaduct, Midland Line, Can…

Research papers, University of Canterbury Library

This project was initiated by ENGEO Limited and KiwiRail Holdings Limited to assess the stability of Slovens Creek Viaduct (specifically its western abutment) and a 3km section of rail corridor between Slovens Creek Viaduct and Avoca on the Midland Line (MDL). Commonly known as the scenic TranzAlpine rail journey (through Arthurs Pass National Park) the MDL connects Greymouth to Christchurch via Rolleston, where the MDL meets the Main South Line into Christchurch. The project area is approximately 40km southeast of Arthurs Pass Township, in the eastern extension of the Castle Hill Basin which is part of the Waimakariri Catchment and Canterbury Foothills. The field area is underlain by Rakaia Terrane, which is part of the Torlesse Composite Terrane forming the basement rock unit for the field area. Cretaceous-Tertiary rocks of the Castle Hill Basin overlie the basement strata and record a transgression-regression sequence, as well as mid-Oligocene submarine volcanism. The stratigraphic sequence in the Castle Hill Basin, and its eastern extension to Avoca, comprises two formations of the Eyre group, the older Broken River Formation and the younger Iron Creek Formation. Deep marine Porter Group limestones, marls, and tuffs of Oligocene age succeed the Iron Creek Formation of the Eyre Group, and probably records the maximum of the transgression. The Enys Formation lies disconformably on the Porter Group and is overlain unconformably by Late Pleistocene glacifluvial and glacial deposits. The Tertiary strata in the Slovens-Avoca rail corridor are weak, and the clay-rich tuff derived from mid-Oligocene volcanism is particularly prone to slaking. Extensive mapping carried out for this project has identified that some 90 percent of the surface along the length of the Slovens-Avoca corridor has been subject to mass movement. The landslides of the Slovens-Avoca rail corridor are clearly younger than the Last Glaciation, and Slovens Creek has been downcutting, with associated faulting and uplift, to form the present day geomorphology of the rail corridor. Deep-seated landslides in the rail corridor extend to Slovens Creek, locally deflecting the stream course, and a generic ground failure model for the rail corridor has been developed. Exploratory geotechnical investigations, including core drilling, installation of an inclinometer and a piezometer, enabled the construction of a simple ground model and cross section for the Slovens Creek Viaduct western abutment. Limit-equilibrium and pseudo-static slope stability analyses using both circular and block critical slip surface search methods were applied to the ground model for the western abutment of Slovens Creek Viaduct. Piezometric and strength data obtained during laboratory testing of core material have been used to constrain the western abutment stability assessment for one representative section line (C-C’). Prior to pseudo-static sensitivity analyses peak ground acceleration (PGA) for various Ultimate Limit State (ULS) design return periods, defined by an equation given in NZS1170.5:2004, were calculated and have been used as a calibration technique to find and compare specific PGA values for pseudo-static analyses in the Slovens Creek Viaduct area. The main purpose has been to provide an indication of how railway infrastructure could be affected by seismic events of various return periods defined by ULS design standards for the area. Limit equilibrium circular slip surface search methods, both grid search and auto refine search, indicated the slope is stable with a FoS greater than 1.0 returned from each, although one particular surface returned the lowest FoS in each. This surface is in the lower portion of the slope, adjacent to Slovens Stream and northeast of the MDL. As expected, pseudo-static analyses returned a lower FoS overall when compared to limit equilibrium analyses. The PGA analyses suggest that partial ground failure at the Slovens Creek Viaduct western abutment could occur in a 1 in 25-year return period event within materials on the slower slope beyond the immediate rail corridor. A ULS (1 in 500-year) event in the Slovens Creek Viaduct area would likely produce a PGA of ~0.9g, and the effects on the western abutment and rail infrastructure would most likely be catastrophic. Observed ground conditions for the western abutment of the Slovens Creek Viaduct suggest there is no movement within the landslide at depth within the monitoring timeframe of this project (22 May 2015 – 4 August 2015). Slope stability monitoring is recommended to be continued in two parts: (1) the inclinometer in BH1 is to be monitored on a six monthly basis for one year following completion of this thesis, and then annually unless ground movements become evident; and (2) surface movement monitoring should be installed using a fixed datum on the stable eastern abutment. Long-term stability management strategies for the Slovens Creek Viaduct western abutment are dependent upon future observed changes and ongoing monitoring. Hazard and risk assessment using the KiwiRail Qualitative Risk Assessment Framework (QRA) is recommended, and if slope stability becomes problematic for operation of the Midland Line consideration should be given to deep slope drainage. In the event of a large magnitude or high PGA earthquake all monitoring should be reviewed.

Seismic Behaviour of Grouted Connections in Precast Concrete Panels

Research papers, The University of Auckland Library

Following the 2010/2011 Canterbury (New Zealand) earthquakes the seismic design of buildings with precast concrete panels has received significant attention. Although this form of construction generally performed adequately in Christchurch, there were a considerable number of precast concrete panel connection failures. This observation prompted a review of more than 4700 panel details to establish representative details used in both existing and new multi-storey and low rise industrial precast concrete buildings. The detailing and quantity of each reviewed connection type in the sampled data is reported, and advantages and potential deficiencies of each connection type are discussed. Following the Canterbury earthquakes, it was observed that brittle failure had occurred in some grouted metal duct connections used for precast concrete wall panels, resulting in recommendations for more robust detailing of this connection type. A set of experimental tests was subsequently performed to investigate the in-plane seismic behaviour of precast concrete wall panel connections. This testing comprised of seven reversed cyclic in-plane tests of fullscale precast concrete wall panels having wall-to-foundation grouted metal duct connections. Walls with existing connection detailing were found to perform adequately when carrying low axial loads, but performance was found to be less satisfactory as the axial load and wall panel length increased. The use of new recommended detailing was observed to prevent brittle connection response and to improve the robustness of the reinforcement splice. A parametric investigation was conducted using the finite element method to predict the failure mode of metal duct connections. From the results of the parametric study on metal duct connections it was identified that there were three possible failure modes, being reinforcement fracture, concrete spalling without metal duct pull out, and concrete spalling with metal duct pull-out. An alternative simple analytical method was proposed in order to determine the type of connection failure without using a time-consuming finite element method. Grouted sleeves inserts are an alternative connector that is widely used to connect wall panels to the foundations. The two full-scale wall panels were subjected to reversed cyclic in-plane demands until failure of either the connection or the wall panel. Wall panel failure was due to a combination of connection reinforcement pulling-out from the coupler and reinforcement fracture. In addition, non-embedded grouted sleeve tests filled with different quality of grout were conducted by subjecting these coupler assemblages to cyclic and monotonic forces.

Holocene surface-faulting earthquakes along the Porters Pass fault

Research papers, University of Canterbury Library

The Porters Pass fault (PPF) is a prominent element of the Porters Pass-Amberley Fault Zone (PPAFZ) which forms a broad zone of active earth deformation ca 100 km long, 60-90 km west and north of Christchurch. For a distance of ca 40 km the PPF is defined by a series of discontinuous Holocene active traces between the Rakaia and Waimakariri Rivers. The amount of slip/event and the timing of paleoearthquakes are crucial components needed to estimate the earthquake potential of a fault. Movement was assumed to be, coseismic and was quantified by measuring displaced geomorphic features using either tape measure or surveying equipment. Clustering of offset data suggests that four to five earthquakes occurred on the PPF during the Holocene and these range between ca 5-7 m/event. Timing information was obtained from four trenches excavated across the fault and an auger adjacent to the fault. Organic samples from these sites were radiocarbon dated and used in conjunction with data from previous studies to identify the occurrence of at least four earthquakes at 8500 ± 200, 5300 ± 700, 2500 ± 200 and 1000 ± 100 years B.P. Evidence suggests that an additional event is also possible at 6200 ± 500 years B.P. The ~1000, 5300 and 6200 years B.P. paleoearthquakes were previously unrecognised, while the 500 year event previously inferred from rock-avalanche data has been discarded. The present data set produces recurrence intervals of ~2000-2500 years for the Holocene. The identification of only one Holocene PPF rupture to the west of Red Lakes indicates the presence of a segment boundary that prevents the propagation of rupture beyond this point. This is consistent with displacement data and results in slip rates of 0.5-0.7 mm/yr and 2.5-3.4 mm/yr to the west and east of Red Lakes respectively. It is possible that the nearby extensional Red Hill Fault influences PPF rupture propagation. The combination of geometric, slip rate and timing data has enabled the magnitude of prehistoric earthquakes on the PPF to be estimated. These magnitudes range from an average of between 6.9 for a fault rupture from Waimakariri River to Red Lakes, to a maximum of 7.4 that ruptures the entire length of the PPAFZ, including the full length of the PPF. These estimates are approximately consistent with previous magnitude estimates along the full length of the PPAFZ of between 7.0 and 7.5.

Cross-sectoral suicide prevention implementation post-disasters in Canterb…

Research papers, University of Canterbury Library

From 2010, Canterbury, a province of Aotearoa New Zealand, experienced three major disaster events. This study considers the socio-ecological impacts on cross-sectoral suicide prevention agencies and their service users of the 2010 – 2016 Canterbury earthquake sequence, the 2019 Christchurch mosque attacks and the COVID-19 pandemic in Canterbury. This study found the prolonged stress caused by these events contributed to a rise in suicide risk factors including anxiety, fear, trauma, distress, alcohol misuse, relationship breakdown, childhood adversity, economic loss and deprivation. The prolonged negative comment by the media on wellbeing in Canterbury was also unhelpful and affected morale. The legacy of these impacts was a rise in referrals to mental health services that has not diminished. This adversity in the socio-ecological system also produced post-traumatic growth, allowing Cantabrians to acquire resilience and help-seeking abilities to support them psychologically through the COVID-19 pandemic. Supporting parental and teacher responses, intergenerational support and targeted public health campaigns, as well as Māori family-centred programmes, strengthened wellbeing. The rise in suicide risk led to the question of what services were required and being delivered in Canterbury and how to enable effective cross-sectoral suicide prevention in Canterbury, deemed essential in all international and national suicide prevention strategies. Components from both the World Health Organisation Suicide Prevention Framework (WHO, 2012; WHO 2021) and the Collective Impact model (Hanleybrown et al., 2012) were considered by participants. The effectiveness of dynamic leadership and the essential conditions of resourcing a supporting agency were found as were the importance of processes that supported equity, lived experience and the partnership of Māori and non-Māori stakeholders. Cross-sectoral suicide prevention was found to enhance the wellbeing of participants, hastening learning, supporting innovation and raising awareness across sectors which might lower stigma. Effective communication was essential in all areas of cross-sectoral suicide prevention and clear action plans enabled measurement of progress. Identified components were combined to create a Collective Impact Suicide Prevention framework that strengthens suicide prevention implementation and can be applied at a local, regional and national level. This study contributes to cross-sectoral suicide prevention planning by considering the socio- ecological, policy and practice mitigations required to lower suicide risk and to increase wellbeing and post-traumatic growth, post-disaster. This study also adds to the growing awareness of the contribution that social work can provide to suicide prevention and conceptualises an alternative governance framework and practice and policy suggestions to support effective cross-sectoral suicide prevention.

The impact of repeated earthquakes on the cognition of Canterbury’s elderl…

Research papers, University of Canterbury Library

Objective: The nature of disaster research makes it difficult to adequately measure the impact that significant events have on a population. Large, representative samples are required, ideally with comparable data collected before the event. When Christchurch, New Zealand, was struck by multiple, devastating earthquakes, there presented an opportunity to investigate the effects of dose-related quakes (none, one, two or three over a 9-month period) on the cognition of Canterbury’s elderly population through the New Zealand Brain Research Institute’s (NZBRI’s) cognitive screening study. The related effects of having a concomitant medical condition, sex, age and estimated- full scale IQ (Est-FSIQ) on cognition were also investigated. Method: 609 participants were tested on various neuropsychological tests and a self-rated dementia scale in a one hour interview at the NZBRI. Four groups were established, based on the number of major earthquakes experienced at the time of testing: “EQ-dose: None” (N = 51) had experienced no quakes; “EQ-dose: One” (N = 193) had experienced the initial quake in September 2010; “EQ-dose: Two” (N = 82) also experienced the most devastating February 2011 quake; and “EQ-dose: Three” (N = 265) also the June 2011 quake at testing. Results: Two neuropsychological variables of Trail A and the AD8 were impacted by an EQ-dose effect, while having a medical condition was associated with poorer function on the MoCA, Rey Copy and Recall, Trail A, and AD8. Having a major medical condition led to worse performance on the Rey Copy and Recall following the major February earthquake. Males performed significantly better on Trail A and Rey Planning, while females better on the MoCA. Older participants (>73) had significantly lower scores on the MoCA than younger participants (<74), while those with a higher Est-FSIQ (>111) had better scores on the MoCA and Rey Recall than participants with a lower Est-FSIQ. Finally, predicted variable analysis (based on calculated, sample-specific Z-scores) failed to find a significant earthquake effect when variables of age, sex and Est-FSIQ were controlled for, while there was a significant effect of medical condition on each measure. Conclusion: The current thesis provides evidence suggesting resilience amongst Canterbury’s elderly population in the face of the sequence of significant quakes that struck the region over a year from September 2010. By contrast, having a major medical condition was a ‘more significant life event’ in terms of impact on cognition in this group.

The doctrine of frustration, commercial leases and the Canterbury earthqua…

Research papers, University of Canterbury Library

The Canterbury earthquakes in 2010 and 2011 had a significant impact on landlords and tenants of commercial buildings in the city of Christchurch. The devastation wrought on the city was so severe that in an unprecedented response to this disaster a cordon was erected around the central business district for nearly two and half years while demolition, repairs and rebuilding took place. Despite the destruction, not all buildings were damaged. Many could have been occupied and used immediately if they had not been within the cordoned area. Others had only minor damage but repairs to them could not be commenced, let alone completed, owing to restrictions on access caused by the cordon. Tenants were faced with a major problem in that they could not access their buildings and it was likely to be a long time before they would be allowed access again. The other problem was uncertainty about the legal position as neither the standard form leases in use, nor any statute, provided for issues arising from an inaccessible building. The parties were therefore uncertain about their legal rights and obligations in this situation. Landlords and tenants were unsure whether tenants were required to pay rent for a building that could not be accessed or whether they could terminate their leases on the basis that the building was inaccessible. This thesis looks at whether the common law doctrine of frustration could apply to leases in these circumstances, where the lease had made no provision. It analyses the history of the doctrine and how it applies to a lease, the standard form leases in use at the time of the earthquakes and the unexpected and extraordinary nature of the earthquakes. It then reports on the findings of the qualitative empirical research undertaken to look at the experiences of landlords and tenants after the earthquakes. It is argued that the circumstances of landlords and tenants met the test for the doctrine of frustration. Therefore, the doctrine could have applied to leases to enable the parties to terminate them. It concludes with a suggestion for reform in the form of a new Act to govern the special relationship between commercial landlords and tenants, similar to legislation already in place covering other types of relationships like those in residential tenancies and employment. Such legislation could provide dispute resolution services to enable landlords and tenants to have access to justice to determine their legal rights at all times, and in particular, in times of crisis.

When the shaking stops, the thinking starts : a grounded theory of turnove…

Research papers, University of Canterbury Library

Voluntary turnover has been the subject of scholarly inquiry for more than 100 years and much is understood about the drivers of turnover, and the decision-making processes involved. To date most models of voluntary turnover have assumed a rational and sequential decision process, initiated primarily by dissatisfaction with the job and the perceived availability of alternatives. Operating within a strong predictive research agenda, countless studies have sought to validate, extend and refine these traditional models through the addition of distal antecedents, mediators, moderators, and proximal antecedents of turnover. The net result of this research is a large body of empirical support for a somewhat modest relationship between job dissatisfaction, perceived alternatives, turnover intentions, job search behaviour and actual turnover. Far less scholarly attention has been directed at understanding shock-induced turnover that is not necessarily derived from dissatisfaction. Moreover, almost no consideration has been given to understanding how a significant and commonly experienced extra-organisational shock, such as natural disaster, might impact turnover decision making. Additionally, the dynamic and cumulative impacts of multiple shocks on turnover decision making have to date not been examined by turnover researchers. In addressing these gaps this thesis presents a leaver-centric theory of employee turnover decision making that is grounded in the post-disaster context. Data for the study were collected from in-depth interviews with 31 leavers in four large organisations in Christchurch, New Zealand; an area that experienced a major natural disaster in the form of the Canterbury earthquake sequence. This context provided a unique setting in which to study turnover as the primary shock was followed by a series of smaller shocks, resulting in a period of sustained disruption to the pre-shock status quo. Grounded theory methods are used to develop a typology of leaving which describes four distinct patterns of turnover decision making that follow a significant extra-organisational shock. The proposed typology not only addresses the heterogeneous and complex nature of turnover decision making, but also provides a more nuanced explanation of the turnover process explicating how the choice of decision path followed is influenced by four contextual factors which emerged from the data: (1) pre-shock motivational state; (2) decision difficulty; (3) experienced shock magnitude; and (4) the availability of resources. The research findings address several shortcomings in the extant literature on employee turnover, and offer practical recommendations for managers seeking to retain employees in a post-disaster setting.

Upper and lower bounds of device force capacity in high force to volume (H…

Research papers, University of Canterbury Library

To reduce seismic vulnerability and the economic impact of seismic structural damage, it is important to protect structures using supplemental energy dissipation devices. Several types of supplemental damping systems can limit loads transferred to structures and absorb significant response energy without sacrificial structural damage. Lead extrusion dampers are one type of supplemental energy dissipation devices. A smaller volumetric size with high force capacities, called high force to volume (HF2V) devices, have been employed in a large series of scaled and full-scaled experiments, as well as in three new structures in Christchurch and San Francisco. HF2V devices have previously been designed using very simple models with limited precision. They are then manufactured, and tested to ensure force capacities match design goals, potentially necessitating reassembly or redesign if there is large error. In particular, devices with a force capacity well above or below a design range can require more testing and redesign, leading to increased economic and time cost. Thus, there is a major need for a modelling methodology to accurately estimate the range of possible device force capacity values in the design phase – upper and lower bounds. Upper and lower bound force capacity estimates are developed from equations in the metal extrusion literature. These equations consider both friction and extrusion forces between the lead and the bulged shaft in HF2V devices. The equations for the lower and upper bounds are strictly functions of device design parameters ensuring easy use in the design phase. Two different sets of estimates are created, leading to estimates for the lower and upper bounds denoted FLB,1, FUB,1, FUB,2, respectively. The models are validated by comparing the bounds with experimental force capacity data from 15 experimental HF2V device tests. All lower bound estimates are below or almost equal to the experimental device forces, and all upper bound estimates are above. Per the derivation, the (FLB,1, FUB,1) pair provide narrower bounds. The (FLB,1, FUB,1) pair also had a mean lower bound gap of -34%, meaning the lower bound was 74% of device force on average, while the mean upper bound gap for FUB,1 was +23%. These are relatively tight bounds, within ~±2 SE of device manufacture, and can be used as a guide to ensure device forces are in range for the actual design use when manufactured. Therefore, they provide a useful design tool.

Post-Earthquake Residual Capacity of Reinforced Concrete Plastic Hinges

Research papers, The University of Auckland Library

Reinforced concrete buildings that satisfied modern seismic design criteria generally behaved as expected during the recent Canterbury and Kaikoura earthquakes in New Zealand, forming plastic hinges in intended locations. While this meant that life-safety performance objectives were met, widespread demolition and heavy economic losses took place in the aftermath of the earthquakes.The Christchurch central business district was particularly hard hit, with over 60% of the multistorey reinforced concrete buildings being demolished. A lack of knowledge on the post-earthquake residual capacity of reinforced concrete buildings was a contributing factor to the mass demolition.Many aspects related to the assessment of earthquake-damaged reinforced concrete buildings require further research. This thesis focusses on improving the state of knowledge on the post earthquakeresidual capacity and reparability of moderately damaged plastic hinges, with an emphasis on plastic hinges typical of modern moment frame structures. The repair method focussed on is epoxy injection of cracks and patching of spalled concrete. A targeted test program on seventeen nominally identical large-scale ductile reinforced concrete beams, three of which were repaired by epoxy injection following initial damaging loadings, was conducted to support these objectives. Test variables included the loading protocol, the loading rate, and the level of restraint to axial elongation.The information that can be gleaned from post-earthquake damage surveys is investigated. It is shown that residual crack widths are dependent on residual deformations, and are not necessarily indicative of the maximum rotation demands or the plastic hinge residual capacity. The implications of various other types of damage typical of beam and column plastic hinges are also discussed.Experimental data are used to demonstrate that the strength and deformation capacity of plastic hinges with modern seismic detailing are often unreduced as a result of moderate earthquake induced damage, albeit with certain exceptions. Special attention is given to the effects of prior yielding of the longitudinal reinforcement, accounting for the low-cycle fatigue and strain ageing phenomena. A material-level testing program on the low-cycle fatigue behaviour of grade 300E reinforcing steel was conducted to supplement the data available in the literature.A reduction in stiffness, relative to the initial secant stiffness to yield, occurs due to moderate plastic hinging damage. This reduction in stiffness is shown to be correlated with the ductility demand,and a proposed model gives a conservative lower-bound estimate of the residual stiffness following an arbitrary earthquake-type loading. Repair by epoxy injection is shown to be effective in restoring the majority of stiffness to plastic hinges in beams. Epoxy injection is also shown to have implications for the residual strength and elongation characteristics of repaired plastic hinges.

Perfect Imperfection: Finding Beauty in the Broken

Research papers, The University of Auckland Library

While societal messages can encourage an unhealthy strive for perfection, the notion of embracing individual flaws and openly displaying vulnerabilities can appear foreign and outlandish. However, when fallibility is acknowledged and imperfection embraced, intimate relationships built on foundations of acceptance, trust and understanding can be established. In an architectural context, similar deep-rooted connections can be formed between a people and a place through the retention of layers of historical identity. When a building is allowed to age with blemishes laid bare for all to see, an architectural work can exhibit a sense of 'humanising vulnerability' where the bruises and scars it bears are able to visually communicate its contextual narrative. This thesis explores the notion of designing to capitalise on past decay through revitalisation of the former Wood Brothers Flour Mill in Addington, Christchurch (1891). Known as one of the city's last great industrial buildings, the 130-year-old structure remains hugely impressive due to its sheer size and scale despite being abandoned and subject to vandalism for a number of years. Its condition of obsolescence ensured the retention of visible signs of wear and tear in addition to the extensive damage caused by the 2010-12 Canterbury earthquakes. In offering a challenge to renovation and reconstruction as a means of conservation, this thesis asks if 'doing less' has the potential to 'do more'. How can an understanding of architecture as an ongoing process inform a design approach to celebrate ageing and patina? While the complex is undergoing redevelopment at the time of writing, the design project embraces the condition of the historic buildings in the immediate aftermath of the earthquakes and builds upon the patina of the mill and adjacent flour and grain store in developing a design for their adaptation as a micro-distillery. Research into the traditional Japanese ideology of wabi-sabi and its practical applications form the basis for a regenerative design approach which finds value in imperfection, impermanence and incompleteness. The thesis combines a literature review, precedent review and site analysis together with a design proposal. This thesis shows that adaptive reuse projects can benefit from an active collaboration with the processes of decay. Instead of a mindset where an architectural work is considered the finished article upon completion of construction, an empathetic and sensitive design philosophy is employed in which careful thought is given to the continued preservation and evolution of a structure with the recognition that evidence of past wear, tear, patina and weathering can all contribute positively to a building's future. In this fashion, rather than simply remaining as relics of the past, buildings can allow the landscape of their urban context to shape and mould them to ensure that their architectural experience can continue to be enjoyed by generations to come.

Restoration opportunities assessment for the Avon Ōtākaro Red Zone using a…

Research papers, University of Canterbury Library

Following the Canterbury earthquake sequence of 2010-11, a large and contiguous tract of vacated ‘red zoned’ land lies alongside the lower Ōtākaro / Avon River and is known as the Avon-Ōtākaro Red Zone (AORZ). This is the second report in the Ecological Regeneration Options (ERO) project that addresses future land uses in the AORZ. The purpose of this report is to present results from an assessment of restoration opportunities conducted in April 2017. The objectives of the assessment were to identify potential benefits of ecological restoration activities across both land and water systems in the AORZ and characterise the key options for their implementation. The focus of this report is not to provide specific advice on the methods for achieving specific restoration endpoints per se. This will vary at different sites and scales with a large number of combinations possible. Rather, the emphasis is on providing an overview of the many restoration and regeneration options in their totality across the AORZ. An additional objective is to support their adequate assessment in the identification of optimum land uses and adaptive management practices for the AORZ. Participatory processes may play a useful role in assessment and stakeholder engagement by providing opportunities for social learning and the co-creation of new knowledge. We used a facilitated local knowledge based approach that generated a large quantity of reliable and site specific data in a short period of time. By inviting participation from a wide knowledge-holder network inclusivity is improved in comparison to small-group expert panel approaches. Similar approaches could be applied to other information gathering and assessment needs in the regeneration planning process. Findings from this study represent the most comprehensive set of concepts available to date to address the potential benefits of ecological regeneration in the AORZ. This is a core topic for planning to avoid missed opportunities and opportunity costs. The results identify a wide range of activities that may be applied to generate benefits for Christchurch and beyond, all involving aspects of a potential new ecology in the AORZ. These may be combined at a range of scales to create scenarios, quantify benefits, and explore the potential for synergies between different land use options. A particular challenge is acquiring the information needed within relatively short time frames. Early attention to gathering baseline data, addressing technical knowledge gaps, and developing conceptual frameworks to account for the many spatio-temporal aspects are all key activities that will assist in delivering the best outcomes. Methodologies by which these many facets can be pulled together in quantitative and comparative assessments are the focus of the final report in the ERO series.

Lived experiences of Bhutanese former refugee youth : coping, resilience a…

Research papers, University of Canterbury Library

This thesis explores the lived experiences of a group of young Bhutanese former refugees between the ages of 18 to 24 years who were resettled in Christchurch between 2008 and 2010 – prior to the first major earthquake. The main goal of the thesis was to gain an understanding of their ways of coping and a second goal was to explore whether their participation in up to five mindfulness infused counselling sessions had influenced their ways of coping. A qualitative research methodology was used to guide the thesis. Participants were interviewed about the major events in their life and how they coped with them. They were then invited to participate in five sessions of mindfulness infused counselling. Approximately five weeks after their final session had ended they were invited to one final interview to explore the influence of the sessions on their ways of coping. Interviews were recorded and transcribed and research notes were taken of the mindfulness infused counselling sessions. Max van Manen’s method of phenomenology was adopted to interpret the narratives of the youth. Three main themes emerged from the data analysis and these are described as essences of lived coping experiences. The first captures their strong sense of community back in the refugee camp. The second presents the sense of resilience that exists among the Bhutanese former refugees. The third essence indicated the inner strengths of the participants which they said helped them deal with the challenging circumstances that life cast in their direction. This meant that their first experience of an earthquake was not considered the biggest event in their lives. After attending the mindfulness infused counselling sessions’ participants reported positive benefits from giving non-judgemental attention to their thoughts and feelings and they found themselves dealing with their issues proactively. For some participants their ‘accepting’ attitude facilitated better control over their emotions while others reported being able to form deeper connections with nature and other people as a result of being mindful. Other participants reported being able to make peace with the events in their past and even found that they were able to forgive those who tormented their community. However, in the absence of any major event in any of the participants’ lives in the time period following their final counselling session, the research was not able to definitely conclude that using mindful-based counselling facilitates better coping in the face extremely stressful events. There is currently very little research that focuses on the experiences of former refugee youth within New Zealand and how they utilize their capacities to deal with adversities. When this thesis commenced, the Bhutanese were the newest refugee community to be accepted for resettlement in New Zealand. This research partly addresses the limited voice of this community.

Generalisable nonlinear finite element modeling for high force to volume (…

Research papers, University of Canterbury Library

Supplemental energy dissipation devices are increasingly used to protect structures, limit loads transferred to structural elements and absorbing significant response energy without sacrificial structural damage. Lead extrusion dampers are supplemental energy dissipation devices, where recent development of smaller volumetric size with high force capacities, called high force to volume (HF2V) devices, has seen deployment in a large series of scaled and full-scaled experiments, as well as in three new structures in Christchurch, NZ and San Francisco, USA. HF2V devices have previously been designed using limited precision models, so there is variation in force prediction capability. Further, while the overall resistive force is predicted, the knowledge of the relative contributions of the different internal reaction mechanisms to these overall resistive forces is lacking, limiting insight and predictive accuracy in device design. There is thus a major need for detailed design models to better understand force generation, and to aid precision device design. These outcomes would speed the overall design and implementation process for uptake and use, reducing the need for iterative experimental testing. Design parameters from 17 experimental HF2V device tests are used to create finite element models using ABAQUS. The analysis is run using ABAQUS Explicit, in multiple step times of 1 second with automatic increments, to balance higher accuracy and computational time. The output is obtained from the time- history output of the contact pressure forces including the normal and friction forces on the lead along the shaft. These values are used to calculate the resistive force on the shaft as it moves through the lead, and thus the device force. Results of these highly nonlinear, high strain analyses are compared to experimental device force results. Model errors compared to experimental results for all 17 devices ranged from 0% to 20% with a mean absolute error of 6.4%, indicating most errors were small. In particular, the standard error in manufacturing is SE = ±14%. In this case, 15 of 17 devices (88%) are within ±1SE (±14%) and 2 of 17 devices (12%) are within ±2SE (±28). These results show low errors and a distribution of errors compared to experimental results that are within experimental device construction variability. The overall modelling methodology is objective and repeatable, and thus generalizable. The exact same modelling approach is applied to all devices with only the device geometry changing. The results validate the overall approach with relatively low error, providing a general modelling methodology for accurate design of HF2V devices.

Self-Management of Disaster Risk and Uncertainty: The Role of Preventive H…

Research papers, University of Canterbury Library

One of the great challenges facing human systems today is how to prepare for, manage, and adapt successfully to the profound and rapid changes wreaked by disasters. Wellington, New Zealand, is a capital city at significant risk of devastating earthquake and tsunami, potentially requiring mass evacuations with little or short notice. Subsequent hardship and suffering due to widespread property damage and infrastructure failure could cause large areas of the Wellington Region to become uninhabitable for weeks to months. Previous research has shown that positive health and well-being are associated with disaster-resilient outcomes. Preventing adverse outcomes before disaster strikes, through developing strengths-based skill sets in health-protective attitudes and behaviours, is increasingly advocated in disaster research, practise, and management. This study hypothesised that well-being constructs involving an affective heuristic play vital roles in pathways to resilience as proximal determinants of health-protective behaviours. Specifically, this study examined the importance of health-related quality of life and subjective well-being in motivating evacuation preparedness, measured in a community sample (n=695) drawn from the general adult population of Wellington’s isolated eastern suburbs. Using a quantitative epidemiological approach, the study measured the prevalence of key quality of life indicators (physical and mental health, emotional well-being or “Sense of Coherence”, spiritual well-being, social well-being, and life satisfaction) using validated psychometric scales; analysed the strengths of association between these indicators and the level of evacuation preparedness at categorical and continuous levels of measurement; and tested the predictive power of the model to explain the variance in evacuation preparedness activity. This is the first study known to examine multi-dimensional positive health and global well-being as resilient processes for engaging in evacuation preparedness behaviour. A cross-sectional study design and quantitative survey were used to collect self-report data on the study variables; a postal questionnaire was fielded between November 2008 and March 2009 to a sampling frame developed through multi-stage cluster randomisation. The survey response rate was 28.5%, yielding a margin of error of +/- 3.8% with 95% confidence and 80% statistical power to detect a true correlation coefficient of 0.11 or greater. In addition to the primary study variables, data were collected on demographic and ancillary variables relating to contextual factors in the physical environment (risk perception of physical and personal vulnerability to disaster) and the social environment (through the construct of self-determination), and other measures of disaster preparedness. These data are reserved for future analyses. Results of correlational and regression analyses for the primary study variables show that Wellingtonians are highly individualistic in how their well-being influences their preparedness, and a majority are taking inadequate action to build their resilience to future disaster from earthquake- or tsunami-triggered evacuation. At a population level, the conceptual multi-dimensional model of health-related quality of life and global well-being tested in this study shows a positive association with evacuation preparedness at statistically significant levels. However, it must be emphasised that the strength of this relationship is weak, accounting for only 5-7% of the variability in evacuation preparedness. No single dimension of health-related quality of life or well-being stands out as a strong predictor of preparedness. The strongest associations for preparedness are in a positive direction for spiritual well-being, emotional well-being, and life satisfaction; all involve a sense of existential meaningfulness. Spiritual well-being is the only quality of life variable making a statistically significant unique contribution to explaining the variance observed in the regression models. Physical health status is weakly associated with preparedness in a negative direction at a continuous level of measurement. No association was found at statistically significant levels for mental health status and social well-being. These findings indicate that engaging in evacuation preparedness is a very complex, holistic, yet individualised decision-making process, and likely involves highly subjective considerations for what is personally relevant. Gender is not a factor. Those 18-24 years of age are least likely to prepare and evacuation preparedness increases with age. Multidimensional health and global well-being are important constructs to consider in disaster resilience for both pre-event and post-event timeframes. This work indicates a need for promoting self-management of risk and building resilience by incorporating a sense of personal meaning and importance into preparedness actions, and for future research into further understanding preparedness motivations.

Assessment of seismic behavior of full-scale instrumented buildings using …

Research papers, The University of Auckland Library

The full scale, in-situ investigations of instrumented buildings present an excellent opportunity to observe their dynamic response in as-built environment, which includes all the real physical properties of a structure under study and its surroundings. The recorded responses can be used for better understanding of behavior of structures by extracting their dynamic characteristics. It is significantly valuable to examine the behavior of buildings under different excitation scenarios. The trends in dynamic characteristics, such as modal frequencies and damping ratios, thus developed can provide quantitative data for the variations in the behavior of buildings. Moreover, such studies provide invaluable information for the development and calibration of realistic models for the prediction of seismic response of structures in model updating and structural health monitoring studies. This thesis comprises two parts. The first part presents an evaluation of seismic responses of two instrumented three storey RC buildings under a selection of 50 earthquakes and behavioral changes after Ms=7.1 Darfield (2010) and Ms=6.3 Christchurch (2011) earthquakes for an instrumented eight story RC building. The dynamic characteristics of the instrumented buildings were identified using state-of-the-art N4SID system identification technique. Seismic response trends were developed for the three storey instrumented buildings in light of the identified frequencies and the peak response accelerations (PRA). Frequencies were observed to decrease with excitation level while no trends are discernible for the damping ratios. Soil-structure interaction (SSI) effects were also determined to ascertain their contribution in the seismic response. For the eight storey building, it was found through system identification that strong nonlinearities in the structural response occurred and manifested themselves in all identified natural frequencies of the building that exhibited a marked decrease during the strong motion duration compared to the pre-Darfield earthquakes. Evidence of foundation rocking was also found that led to a slight decrease in the identified modal frequencies. Permanent stiffness loss was also observed after the strong motion events. The second part constitutes developing and calibrating finite element model (FEM) of the instrumented three storey RC building with a shear core. A three dimensional FEM of the building is developed in stages to analyze the effect of structural, non-structural components (NSCs) and SSI on the building dynamics. Further to accurately replicate the response of the building following the response trends developed in the first part of the thesis, sensitivity based model updating technique was applied. The FEMs were calibrated by tuning the updating parameters which are stiffnesses of concrete, NSCs and soil. The updating parameters were found to generally follow decreasing trends with the excitation level. Finally, the updated FEM was used in time history analyses to assess the building seismic performance at the serviceability limit state shaking. Overall, this research will contribute towards better understanding and prediction of the behavior of structures subjected to ground motion.

Performance of precast cladding panels with rocking connections under late…

Research papers, University of Canterbury Library

Several concrete cladding panels were damaged during the 2011 Christchurch Earthquakes in New Zealand. Damage included partial collapse of panels, rupture of joint sealants, cracking and corner crushing. Installation errors, faulty connections and inadequate detailing were also contributing factors to the damage. In New Zealand, two main issues are considered in order to accommodate story drifts in the design of precast cladding panels: 1) drift compatibility of tieback or push-pull connections and 2) drift compatibility of corner joints. Tieback connections restrain the panels in the out-of-plane direction while allowing in-plane translation with respect to the building frame. Tieback connections are either in the form of slots or oversized holes or ductile rods usually located at the top of the panels. Bearing connections are also provided at the bottom of panels to transfer gravity loads. At the corners of a building, a vertical joint gap, usually filled with sealants, is provided between the two panels on the two orthogonal sides to accommodate the relative movement. In cases where the joint gap is not sufficient to accommodate the relative movements, panels can collide, generating large forces and the likely failure of the connections. On the other hand, large gaps are aesthetically unpleasing. The current design standards appear to recognize these issues but then leave most of the design and detailing to the discretion of the designers. In the installation phase, the alignment of panels is one of the main challenges faced by installers (and/or contractors). Many prefer temporary props to guide, adjust and hold the panels in place whilst the bearing connections are welded. Moreover, heat generated from extensive welding can twist the steel components inducing undesirable local stresses in the panels. Therefore, the installation phase itself is time-consuming, costly and prone to errors. This paper investigates the performance of a novel panel system that is designed to accommodate lateral inter-story drift through a ‘rocking’ motion. In order to gauge the feasibility of the system, six 2m high precast concrete panels within a single-story steel frame structure have been tested under increasing levels of lateral cyclic drift at the University of Canterbury, New Zealand. Three different panel configurations are tested: 1) a panel with return cover and a flat panel at a corner under unidirectional loading, 2) Two adjacent flat panels under unidirectional loading, and 3) Two flat panels at another oblique corner under bidirectional loading. A vertical seismic joint of 25 mm, filled with one-stage joint sealant, is provided between two of the panels. The test results show the ability of the panels with ‘rocking’ connection details to accommodate larger lateral drifts whilst allowing for smaller vertical joints between panels at corners, quick alignment and easy placement of panels without involving extensive welding on site.

Post-earthquake assessment of damaged and repaired reinforced concrete wal…

Research papers, The University of Auckland Library

High demolition rates were observed in New Zealand after the 2010-2011 Canterbury Earthquake Sequence despite the success of modern seismic design standards to achieve required performance objectives such as life safety and collapse prevention. Approximately 60% of the multi-storey reinforced concrete (RC) buildings in the Christchurch Central Business District were demolished after these earthquakes, even when only minor structural damage was present. Several factors influenced the decision of demolition instead of repair, one of them being the uncertainty of the seismic capacity of a damaged structure. To provide more insight into this topic, the investigation conducted in this thesis evaluated the residual capacity of moderately damaged RC walls and the effectiveness of repair techniques to restore the seismic performance of heavily damaged RC walls. The research outcome provided insights for developing guidelines for post-earthquake assessment of earthquake-damaged RC structures. The methodology used to conduct the investigation was through an experimental program divided into two phases. During the first phase, two walls were subjected to different types of pre-cyclic loading to represent the damaged condition from a prior earthquake, and a third wall represented a repair scenario with the damaged wall being repaired using epoxy injection and repair mortar after the pre-cyclic loading. Comparisons of these test walls to a control undamaged wall identified significant reductions in the stiffness of the damaged walls and a partial recovery in the wall stiffness achieved following epoxy injection. Visual damage that included distributed horizontal and diagonal cracks and spalling of the cover concrete did not affect the residual strength or displacement capacity of the walls. However, evidence of buckling of the longitudinal reinforcement during the pre-cyclic loading resulted in a slight reduction in strength recovery and a significant reduction in the displacement capacity of the damaged walls. Additional experimental programs from the literature were used to provide recommendations for modelling the response of moderately damaged RC walls and to identify a threshold that represented a potential reduction in the residual strength and displacement capacity of damaged RC walls in future earthquakes. The second phase of the experimental program conducted in this thesis addressed the replacement of concrete and reinforcing steel as repair techniques for heavily damaged RC walls. Two walls were repaired by replacing the damaged concrete and using welded connections to connect new reinforcing bars with existing bars. Different locations of the welded connections were investigated in the repaired walls to study the impact of these discontinuities at the critical section. No significant changes were observed in the stiffness, strength, and displacement capacity of the repaired walls compared to the benchmark undamaged wall. Differences in the local behaviour at the critical section were observed in one of the walls but did not impact the global response. The results of these two repaired walls were combined with other experimental programs found in the literature to assemble a database of repaired RC walls. Qualitative and quantitative analyses identified trends across various parameters, including wall types, damage before repair, and repair techniques implemented. The primary outcome of the database analysis was recommendations for concrete and reinforcing steel replacement to restore the strength and displacement capacity of heavily damaged RC walls.

Development of an assessment method for seismic damage to gravity waste wa…

Research papers, University of Canterbury Library

This thesis documents the development and demonstration of an assessment method for analysing earthquake-related damage to concrete waste water gravity pipes in Christchurch, New Zealand, following the 2010-2011 Canterbury Earthquake Sequence (CES). The method is intended to be internationally adaptable to assist territorial local authorities with improving lifelines infrastructure disaster impact assessment and improvements in resilience. This is achieved through the provision of high-resolution, localised damage data, which demonstrate earthquake impacts along the pipe length. The insights gained will assist decision making and the prioritisation of resources following earthquake events to quickly and efficiently restore network function and reduce community impacts. The method involved obtaining a selection of 55 reinforced concrete gravity waste water pipes with available Closed-Circuit Television (CCTV) inspection footage filmed before and after the CES. The pipes were assessed by reviewing the recordings, and damage was mapped to the nearest metre along the pipe length using Geographic Information Systems. An established, systematic coding process was used for reporting the nature and severity of the observed damage, and to differentiate between pre-existing and new damage resulting from the CES. The damage items were overlaid with geospatial data such as Light Detection and Ranging (LiDAR)-derived ground deformation data, Liquefaction Resistance Index data and seismic ground motion data (Peak Ground acceleration and Peak Ground Velocity) to identify potential relationships between these parameters and pipe performance. Initial assessment outcomes for the pipe selection revealed that main pipe joints and lateral connections were more vulnerable than the pipe body during a seismic event. Smaller diameter pipes may also be more vulnerable than larger pipes during a seismic event. Obvious differential ground movement resulted in increased local damage observations in many cases, however this was not obvious for all pipes. Pipes with older installation ages exhibited more overall damage prior to a seismic event, which is likely attributable to increased chemical and biological deterioration. However, no evidence was found relating pipe age to performance during a seismic event. No evidence was found linking levels of pre-CES damage in a pipe with subsequent seismic performance, and seismic performance with liquefaction resistance or magnitude of seismic ground motion. The results reported are of limited application due to the small demonstration sample size, but reveal the additional level of detail and insight possible using the method presented in this thesis over existing assessment methods, especially in relation to high resolution variations along the length of the pipe such as localised ground deformations evidenced by LiDAR. The results may be improved by studying a larger and more diverse sample pool, automating data collection and input processes in order to improve efficiency and consider additional input such as pipe dip and cumulative damage over a large distance. The method is dependent on comprehensive and accurate pre-event CCTV assessments and LIDAR data so that post-event data could be compared. It is proposed that local territorial authorities should prioritise acquiring this information as a first important step towards improving the seismic resilience of a gravity waste water pipe network.

Assessing seismic collapse of structures using digital cloning techniques.

Research papers, University of Canterbury Library

Rapid, reliable information on earthquake-affected structures' current damage/health conditions and predicting what would happen to these structures under future seismic events play a vital role in accelerating post-event evaluations, leading to optimized on-time decisions. Such rapid and informative post-event evaluations are crucial for earthquake-prone areas, where each earthquake can potentially trigger a series of significant aftershocks, endangering the community's health and wealth by further damaging the already-affected structures. Such reliable post-earthquake evaluations can provide information to decide whether an affected structure is safe to stay in operation, thus saving many lives. Furthermore, they can lead to more optimal recovery plans, thus saving costs and time. The inherent deficiency of visual-based post-earthquake evaluations and the importance of structural health monitoring (SHM) methods and SHM instrumentation have been highlighted within this thesis, using two earthquake-affected structures in New Zealand: 1) the Canterbury Television (CTV) building, Christchurch; 2) the Bank of New Zealand (BNZ) building, Wellington. For the first time, this thesis verifies the theoretically- and experimentally validated hysteresis loop analysis (HLA) SHM method for the real-world instrumented structure of the BNZ building, which was damaged severely due to three earthquakes. Results indicate the HLA-SHM method can accurately estimate elastic stiffness degradation for this reinforced concrete (RC) pinched structure across the three earthquakes, which remained unseen until after the third seismic event. Furthermore, the HLA results help investigate the pinching effects on the BNZ building's seismic response. This thesis introduces a novel digital clone modelling method based on the robust and accurate SHM results delivered by the HLA method for physical parameters of the monitored structure and basis functions predicting the changes of these physical parameters due to future earthquake excitations. Contrary to artificial intelligence (AI) based predictive methods with black-box designs, the proposed predictive method is entirely mechanics-based with an explicitly-understandable design, making them more trusted and explicable to stakeholders engaging in post-earthquake evaluations, such as building owners and insurance firms. The proposed digital clone modelling framework is validated using the BNZ building and an experimental RC test structure damaged severely due to three successive shake-table excitations. In both structures, structural damage intensifies the pinching effects in hysteresis responses. Results show the basis functions identified from the HLA-SHM results for both structures under Event 1 can online estimate structural damage due to subsequent Events 2-3 from the measured structural responses, making them valuable tool for rapid warning systems. Moreover, the digital twins derived for these two structures under Event 1 can successfully predict structural responses and damage under Events 2-3, which can be integrated with the incremental dynamic analysis (IDA) method to assess structural collapse and its financial risks. Furthermore, it enables multi-step IDA to evaluate earthquake series' impacts on structures. Overall, this thesis develops an efficient method for providing reliable information on earthquake-affected structures' current and future status during or immediately after an earthquake, considerably guaranteeing safety. Significant validation is implemented against both experimental and real data of RC structures, which thus clearly indicate the accurate predictive performance of this HLA-based method.

Development of an assessment method for seismic damage to gravity waste wa…

Research papers, University of Canterbury Library

This thesis documents the development and demonstration of an assessment method for analysing earthquake-related damage to concrete waste water gravity pipes in Christchurch, New Zealand, following the 2010-2011 Canterbury Earthquake Sequence (CES). The method is intended to be internationally adaptable to assist territorial local authorities with improving lifelines infrastructure disaster impact assessment and improvements in resilience. This is achieved through the provision of high-resolution, localised damage data, which demonstrate earthquake impacts along the pipe length. The insights gained will assist decision making and the prioritisation of resources following earthquake events to quickly and efficiently restore network function and reduce community impacts. The method involved obtaining a selection of 55 reinforced concrete gravity waste water pipes with available Closed-Circuit Television (CCTV) inspection footage filmed before and after the CES. The pipes were assessed by reviewing the recordings, and damage was mapped to the nearest metre along the pipe length using Geographic Information Systems. An established, systematic coding process was used for reporting the nature and severity of the observed damage, and to differentiate between pre-existing and new damage resulting from the CES. The damage items were overlaid with geospatial data such as Light Detection and Ranging (LiDAR)-derived ground deformation data, Liquefaction Resistance Index data and seismic ground motion data (Peak Ground acceleration and Peak Ground Velocity) to identify potential relationships between these parameters and pipe performance. Initial assessment outcomes for the pipe selection revealed that main pipe joints and lateral connections were more vulnerable than the pipe body during a seismic event. Smaller diameter pipes may also be more vulnerable than larger pipes during a seismic event. Obvious differential ground movement resulted in increased local damage observations in many cases, however this was not obvious for all pipes. Pipes with older installation ages exhibited more overall damage prior to a seismic event, which is likely attributable to increased chemical and biological deterioration. However, no evidence was found relating pipe age to performance during a seismic event. No evidence was found linking levels of pre-CES damage in a pipe with subsequent seismic performance, and seismic performance with liquefaction resistance or magnitude of seismic ground motion. The results reported are of limited application due to the small demonstration sample size, but reveal the additional level of detail and insight possible using the method presented in this thesis over existing assessment methods, especially in relation to high resolution variations along the length of the pipe such as localised ground deformations evidenced by LiDAR. The results may be improved by studying a larger and more diverse sample pool, automating data collection and input processes in order to improve efficiency and consider additional input such as pipe dip and cumulative damage over a large distance. The method is dependent on comprehensive and accurate pre-event CCTV assessments and LIDAR data so that post-event data could be compared. It is proposed that local territorial authorities should prioritise acquiring this information as a first important step towards improving the seismic resilience of a gravity waste water pipe network.

Invertebrate Responses to Large-Scale Change : Impacts of Eutrophication a…

Research papers, University of Canterbury Library

Environmental stress and disturbance can affect the structure and functioning of marine ecosystems by altering their physical, chemical and biological features. In estuaries, benthic invertebrate communities play important roles in structuring sediments, influencing primary production and biogeochemical flux, and occupying key food web positions. Stress and disturbance can reduce species diversity, richness and abundance, with ecological theory predicting that biodiversity will be at its lowest soon after a disturbance with assemblages dominated by opportunistic species. The Avon-Heathcote Estuary in Christchurch New Zealand has provided a novel opportunity to examine the effects of stress, in the form of eutrophication, and disturbance, in the form of cataclysmic earthquake events, on the structure and functioning of an estuarine ecosystem. For more than 50 years, large quantities (up to 500,000m3/day) of treated wastewater were released into this estuary but in March 2010 this was diverted to an ocean outfall, thereby reducing the nutrient loading by around 90% to the estuary. This study was therefore initially focussed on the reversal of eutrophication and consequent effects on food web structure in the estuary as it responded to lower nutrients. In 2011, however, Christchurch was struck with a series of large earthquakes that greatly changed the estuary. Massive amounts of liquefied sediments, covering up to 65% of the estuary floor, were forced up from deep below the estuary, the estuary was tilted by up to a 50cm rise on one side and a corresponding drop on the other, and large quantities of raw sewage from broken wastewater infrastructure entered the estuary for up to nine months. This study was therefore a test of the potentially synergistic effects of nutrient reduction and earthquake disturbance on invertebrate communities, associated habitats and food web dynamics. Because there was considerable site-to-site heterogeneity in the estuary, the sites in this study were selected to represent a eutrophication gradient from relatively “clean” (where the influence of tidal flows was high) to highly impacted (near the historical discharge site). The study was structured around these sites, with components before the wastewater diversion, after the diversion but before the earthquakes, and after the earthquakes. The eutrophication gradient was reflected in the composition and isotopic chemistry of primary producer and invertebrate communities and the characteristics of sediments across the sample sites. Sites closest to the former wastewater discharge pipe were the most eutrophic and had cohesive organic -rich, fine sediments and relatively depauperate communities dominated by the opportunistic taxa Capitellidae. The less-impacted sites had coarser, sandier sediments with fewer pollutants and far less organic matter than at the eutrophic sites, relatively high diversity and lower abundances of micro- and macro-algae. Sewage-derived nitrogen had became incorporated into the estuarine food web at the eutrophic sites, starting at the base of the food chain with benthic microalgae (BMA), which were found to use mostly sediment-derived nitrogen. Stable isotopic analysis showed that δ13C and δ15N values of most food sources and consumers varied spatially, temporally and in relation to the diversion of wastewater, whereas the earthquakes did not appear to affect the overall estuarine food web structure. This was seen particularly at the most eutrophic site, where isotopic signatures became more similar to the cleaner sites over two-and-a-half years after the diversion. New sediments (liquefaction) produced by the earthquakes were found to be coarser, have lower concentrations of heavy metals and less organic matter than old (existing) sediments. They also had fewer macroinvertebrate inhabitants initially after the earthquakes but most areas recovered to pre-earthquake abundance and diversity within two years. Field experiments showed that there were higher amounts of primary production and lower amounts of nutrient efflux from new sediments at the eutrophic sites after the earthquakes. Primary production was highest in new sediments due to the increased photosynthetic efficiency of BMA resulting from the increased permeability of new sediments allowing increased light penetration, enhanced vertical migration of BMA and the enhanced transport of oxygen and nutrients. The reduced efflux of NH4-N in new sediments indicated that the capping of a large portion of eutrophic old sediments with new sediments had reduced the release of legacy nutrients (originating from the historical discharge) from the sediments to the overlying water. Laboratory experiments using an array of species and old and new sediments showed that invertebrates altered levels of primary production and nutrient flux but effects varied among species. The mud snail Amphibola crenata and mud crab Austrohelice crassa were found to reduce primary production and BMA biomass through the consumption of BMA (both species) and its burial from bioturbation and the construction of burrows (Austrohelice). In contrast, the cockle Austrovenus stutchburyi did not significantly affect primary production and BMA biomass. These results show that changes in the structure of invertebrate communities resulting from disturbances can also have consequences for the functioning of the system. The major conclusions of this study were that the wastewater diversion had a major effect on food web dynamics and that the large quantities of clean and unpolluted new sediments introduced to the estuary during the earthquakes altered the recovery trajectory of the estuary, accelerating it at least throughout the duration of this study. This was largely through the ‘capping’ effect of the new liquefied, coarser-grained sediments as they dissipated across the estuary and covered much of the old organic-rich eutrophic sediments. For all aspects of this study, the largest changes occurred at the most eutrophic sites; however, the surrounding habitats were important as they provided the context for recovery of the estuary, particularly because of the very strong influence of sediments, their biogeochemistry, microalgal and macroalgal dynamics. There have been few studies documenting system level responses to eutrophication amelioration and to the best on my knowledge there are no other published studies examining the impacts of large earthquakes on benthic communities in an estuarine ecosystem. This research gives valuable insight and advancements in the scientific understanding of the effects that eutrophication recovery and large-scale disturbances can have on the ecology of a soft-sediment ecosystem.

Experimental study on the seismic performance of low damage systems for no…

Research papers, University of Canterbury Library

Field surveys and experimental studies have shown that light steel or timber framed plasterboard partition walls are particularly vulnerable to earthquake damage prompting the overarching objective of this research, which is to further the development of low damage seismic systems for non-structural partition walls in order to facilitate their adoption by industry to assist with reducing the losses associated with the maintenance and repair cost of buildings across their design life. In particular, this study focused on the behaviour of steel-framed partition walls systems with novel detailing that aim to be “low-damage” designed according to common practice for walls used in commercial and institutional buildings in New Zealand. This objective was investigated by (1) investigating the performance of a flexible track system proposed by researchers and industry by experimental testing of full-scale specimens; (2) investigating the performance of the seismic gap partition wall systems proposed in a number of studies, further developed in this study with input from industry, by experimental testing of full-scale specimens; and (3) investigating the potential implications of using these systems compared with traditionally detailed partition wall systems within multi-storey buildings using the Performance Based Earthquake Engineering loss assessment methodology. Three full-scale testing frames were designed in order to replicate, under controlled laboratory conditions, the effects of seismic shaking on partition walls within multi-storey buildings by the application of quasi-static uni-directional cyclic loading imposing an inter-storey drift. The typical configuration for test specimens was selected to be a unique “y-shape”, including one angled return wall, with typical dimensions of approximately 2400 mm along the main wall and 600 mm along (approximately) the returns walls with a height of 2405 mm from floor to ceiling. The specimens were aligned within test frames at an oblique angle to the direction of loading in order to investigate bi- directional effects. Three wall specimens with flexible track detailing, two identical plane specimens and the third including a doorway, were tested. The detailing involved removing top track anchors within the proximity of wall intersections, thus allowing the tracks to ‘bow’ out at these locations. Although the top track anchors were specified to be removed the proximity of wall intersections, a construction error was made whereby a single top track slab to concrete anchor was left in at the three-way wall junction. Despite this error, the experimental testing was deemed worthwhile since such errors will also occur in practice and because the behaviour of the wall can be examined with this fixing in mind. The specimens also included an acoustic/fire sealant at the top lining to floor boundary. In addition to providing drift capacities, the force-displacement behaviour is also reported, the dissipated energy was computed, and the parameters of the Wayne-Stewart hysteretic model were fitted to the results. The specimen with the door opening behaved significantly different to the plane specimens: damage to the doorway specimen began as cracking of the wallboard propagating from the corners of the doorway following which the L- and Y- shaped junctions behaved independently, whereas damage to the plane specimens began as cracking of the wallboard at the top of the L-junction and wall system deformed as a single unit. The results suggest that bi-directional behaviour is important even if its impact cannot be directly quantified by the experiments conducted. Damage to sealant implies that the bond between plasterboard and sealant is important for its seismic performance. Careful quality control is advised as defects in the bond may significantly impact its ability to withstand seismic movement. Two specimens with seismic gap detailing were tested: a steel stud specimen and a timber stud specimen. Observed drift capacities were significantly greater than traditional plasterboard partition systems. Equations were used to predict the drift at which damage state 1 (DS1) and damage state 2 (DS2) would initiate. The equation used to estimate the drift at the onset of DS1 accurately predicted the onset of plaster cracking but overestimated the drift at which the gap filling material was damaged. The equation used to predict the onset of DS2 provided a lower bound for both specimens and also when used to predict results of previous experimental tests on seismic gap systems. The gap-filling material reduced the drift at the onset of DS1, however, it had a beneficial effect on the re-centring behaviour of the linings. Out-of-plane displacements and return wall configuration did not appear to significantly impact the onset of plaster cracking in the specimens. A loss assessment according to the PBEE methodology was conducted on four steel MRF case study buildings: (1) a 4-storey building designed for the Christchurch region, (2) a 4-storey building designed for the Wellington region, (3) a 12-storey building designed for the Christchurch region, and (4) a 12- storey building designed for the Wellington region. The fragility parameters for a traditional partition system, the flexible track partition system, and the seismic gap steel stud and timber stud partition systems were included within the loss assessment. The order (lowest to highest) of each system in terms of the expected annual losses of each building when incorporating the system was, (1) the seismic gap timber stud system, (2) the seismic gap steel stud system, (3) the traditional/baseline system, and (4) the flexible track system. For the seismic gap timber stud system, which incurred the greatest reduction in expected annual losses for each case study building, the reduction in expected annual losses in comparison to the losses found when using the traditional system ranged from a 5% to a 30% reduction. This reinforces the fact that while there is a benefit to the using low damage partition systems in each building the extent of reduction in expected annual losses is significantly dependent on the particular building design and its location. The flexible track specimens had larger repair costs at small hazard levels compared to the traditional system but smaller repair costs at larger hazard levels. However, the resulting expected annual losses for the flexible track system was higher than the traditional system which reinforces findings from past studies which observed that the greatest contribution to expected annual losses arises from low to moderate intensity shaking seismic events (low hazard levels).

Development and Validation of Shear Links for LCF and EBF Seismic Systems …

Research papers, The University of Auckland Library

Eccentrically Braced Frames (EBFs) are a widely used seismic resisting structural steel system. Since their inception in the late 1970s, they have been a viable option with an available stiffness that is between simple braced systems and moment resisting systems. A similar concept, the linked column frame (LCF), uses shear links between two closely spaced columns. In both cases, the key component is the active link or the shear link, and this component is the objective of this study. The performance of high rise EBF buildings in the 2010 and 2011 Christchurch earthquakes was beyond that which was expected, especially considering the very high accelerations recorded. As the concrete high-rises were torn down, two EBF buildings remained standing and only required some structural repair. These events prompted a renewed interest in bolted shear links, as well as their performance. While some research into replaceable shear links had already been done (Mansour, 2011), the objectives of this study were to improve on the shear link itself, with the consideration that links built in the future are likely to be bolted. The main components of this study were to: 1. Reduce or eliminate the requirements for intermediate web stiffeners, as they were suspected of being detrimental to performance. Furthermore, any reduction in stiffening requirements is a direct fabrication cost saving. Links with low web aspect ratios were found to achieve exceptional ductilities when no stiffeners were included, prompting new design equations. 2. Ensure that the stresses in the ends of links are adequately transferred into the endplates without causing fractures. Although most of the experimental links had web doubler plates included, four had varied lengths of such doubler plates from 0.0 in. to 8.0 in. The link without any doubler plates performed to a similar level to its peers, and thus it is likely that links with quality end details may not need web doubler plates at all. 3. Evaluate the performance of a link with double sided stiffeners without the use of web welds, as opposed to conventional single sided, welded stiffeners. This link performed well, and web-weld-less double sided stiffeners may be an economical alternative to conventional stiffeners for deeper sections of links. 4. Evaluate the performance of a link with thin endplates that are made efficient with the use of gusset plates. This link performed to an acceptable level and provides evidence for a cost effective alternative to thick endplates, especially considering the high overstrength end moments in links, typically requiring 16-bolt connections. 5. Examine the potential use of an alternative EBF arrangement where the collector beam is over sized, and the link section is formed by cutting out parts of the beam's web. After running a series of finite element models each with a unique variation, a number of approximate design rules were derived such that future research could develop this idea further experimentally. 6. Ensure that during testing, the secondary elements (members that are not the shear link), do not yield and are not close to yielding. None of the instrumented elements experienced any unexpected yielding, however the concerns for high stresses in the collector beam panel zone during design were warranted. The use of an existing New Zealand design equation is recommended as an extra check for design codes worldwide. The above objectives were mainly conducted experimentally, except: the data set for item 1 was greatly expanded through the use of a calibrated numerical model which was then used in an extensive parametric study; item 5 was purely finite element based; and, a small parametric study was included for item 3 in an attempt to expand on the trends found there.

Is the Canterbury Partnership Community Health Worker project fulfilling i…

Research papers, University of Canterbury Library

Abstract The original intention for the Partnership Community Worker (PCW) project in 2006 was for it to be an extension of the Pegasus Health General Practice and furthermore to be a bridge between the community and primary healthcare. It was believed that a close working relationship between the Practice Nurse and the PCW would help the target population of Māori, Pacifica and low income people to address and overcome their perceived barriers to healthcare which included: finance, transport, anxiety, cultural issues, communication, or lack of knowledge. Seven years later although the PCW project has been deemed a success in the Canterbury District Health Board annual reports (2013-14) and community and government agencies, including the Christchurch Resettlement Service (2012), many of the Pegasus Health General Practices have not utilised the project to its full extent, hence the need for this research. I was interested in finding out in the first instance if the model had changed and, if so why, and in the second instance if the promotional material currently distributed by Pegasus Health Primary Health Organisation reflected the daily practice of the PCW. A combination of methods were used including: surveys to the Pegasus Health General Practices, interviews with PCWs, interviews with managers of both the PCW host organisations and referring agencies to the PCW project. All the questions asked of all the participants in this research were focussed on their own perception of the role of the PCW. Results showed that the model has changed and although the publications were not reflecting the original intention of the project they did reflect the daily practice of the PCWs who are now struggling to meet much wider community expectations and needs. Key Results: Partnership Community Worker (PCW) interviews: Seventeen PCWs of the 19 employed were interviewed face to face. A number expressed interest in more culturally specific training and some are pursuing qualifications in social work; for many pay parity is an issue. In addition, many felt overwhelmed by the expectations around clients with mental health issues and housing issues now, post-earthquakes. Medical Practice surveys: Surveys were sent to eighty-two Pegasus Health medical practices and of these twenty five were completed. Results showed the full capacity of the PCW role was not clearly understood by all with many believing it was mostly a transport service. Those who did understand the full complexity of the role were very satisfied with the outcomes. PCW Host Community Manager Interviews: Of the ten out of twelve managers interviewed, some wished for more communication with Pegasus Health management because they felt aspects of both the PCW role and their own role as managers had become blurred over time. Referring organisations: Fifteen of the fifty referring community or government organisations participated. The overall satisfaction of the service was high and some acknowledged the continuing need for PCWs to be placed in communities where they were well known and trusted. Moreover results also showed that both the Canterbury earthquakes 2010-2011 and the amalgamation of Partnership Health PHO and Pegasus Health Charitable Limited in 2013 have contributed to the change of the model. Further future research may also be needed to examine the long term effects on the people of Canterbury involved in community work during the 2011-2014 years.  

Post-earthquake damage assessment and residual capacity of concrete and RC…

Research papers, University of Canterbury Library

The assessment of damage and remaining capacity after an earthquake is an immediate measure to determine whether a reinforced concrete (RC) building is usable and safe for occupants. The recent Christchurch earthquake (22 February 2011) caused a uniquely severe level of structural damage to modern buildings, resulting in extensive damage to the building stock. About 60% of damaged multistorey concrete buildings (3 storeys and up) were demolished after the earthquake, and the cost of reconstruction amounted to 40 billion NZD. The aftermath disclosed issues of great complexities regarding the future of the RC buildings damaged by the earthquakes. This highlighted the importance of post-event decision-making, as the outcome will allow the appropriate course of action—demolition, repair or acceptance of the existing building—to be considered. To adopt the proper strategy, accurate assessment of the residual capacity and the level of damage is required. This doctoral dissertation aims to assess the damage and remaining capacity at constituent material and member level (i.e., concrete material and beams) through a systematic approach in an attempt to address part of an existing gap in the available literature. Since the residual capacity of RC members is not unique and depends on previously applied loading history, post-event residual capacity in this study was assessed in terms of fraction of fatigue life (i.e., the number of cycles required to failure). This research comprises three main parts: (1) residual capacity and damage assessment at material level (i.e., concrete), (2) post-yield bond deterioration and damage assessment at the interface of steel and concrete, and, finally, (3) residual capacity and damage assessment at member level (i.e., RC beam). The first part of this research focused on damage assessment and the remaining capacity of concrete from a material point of view. It aimed to employ appropriate and reliable durability-based testing and image-detection techniques to quantify deterioration in the mechanical properties of concrete on the basis that stress-induced damage occurred in the microstructural system of the concrete material. To this end, in the first phase, a feasibility study was conducted in which a combination of oxygen permeability, electrical resistivity and porosity tests were assessed to determine if they were robust and reliable enough to reveal damage which occurred in the microstructural system of concrete. The results, in terms of change in permeability, electrical resistivity and porosity features of disk samples taken from the middle third of damaged concrete cylinders (200 mm × 100 mm) monotonically pre-loaded to 50%, 70%, 90% and 95% of the ultimate strength (f′c), showed the permeability test is a reliable tool to identify the degree of damage, due to its high sensitivity to the load-induced microcracking. In parallel, to determine the residual capacity, the companion damaged concrete cylinders already loaded to the same level of compressive strength were reloaded up to failure. Comparing the stress–strain relationship of damaged concrete with intact material, it was also found that the strain capacity of the reloaded pre-damaged concrete cylinders decreases while strength remained virtually unchanged. In the second phase of the first part, a fluorescent microscopy technique was used to assess the damage and develop a correlation between material degradation, by virtue of the geometrical features, and damage to the concrete. To account for the effect of confinement and cyclic loading, in the third phase, the residual capacity and damage assessment of unconfined and GFRP confined concrete cylinders subjected to low-cycle fatigue loading, was investigated. Similar to the first phase, permeability testing technique was used to provide an indirect evaluation of fatigue damage. Finally, in the fourth phase of the first part, the suitability of permeability testing technique to assess damage was evaluated for cored concrete taken from three types of RC members: columns, beams and a beam-column joint. In view of the fact that the composite action of an RC member is highly dependent on the bond between reinforcement and surrounding concrete, understanding the deterioration of the bond in the post-yield range of strain in steel was crucial to assess damage at member level. Therefore, in the second phase of this research, a state-of-the- art distributed fibre optic strain sensor system (DFOSSS) system was used to evaluate bond deterioration in a cantilever RC beam subjected to monotonic lateral loading. The technology allowed the continuous capture of strain, every 2.6 mm along the length, in both reinforcing bars and cover concrete. The strain profile provided a basis by which the slip, axial stress and bond stress distributions were then established. In the third part, the study focused on the damage assessment and residual capacity of seven half-scale RC beams subjected to a constant-amplitude cyclic loading protocol. In the first stage, the structural performances of three specimens under constant-amplitude fatigue at 1%, 2% and 4% chord rotation (drift) were examined. In parallel, the number of cycles to failure, degradation in strength, stiffness and energy dissipation were characterized. In the second stage, four RC beams were subjected to loading up to 70% and 90% of their fatigue life, at 2% and 4% drift, and then monotonically pulled up to failure. To determine the residual flexural capacity, the lateral force–displacement results of pre-damaged specimens were compared with an undamaged specimen subjected to only monotonic loading. The study showed significant losses in strength, deformability, stiffness and energy dissipation capacity. A nonlinear finite element analysis (FEA) using concrete damage plasticity (CDP) model was also conducted in ABAQUS to numerically investigate the behaviour of the tested specimen. The results of the FE simulations indicated a reasonable response compared with the behaviour of the test specimen in terms of force–displacement and cracking pattern. During the Christchurch earthquake it was observed that the loading history has a significant influence on structural responses. While in conventional pseudo-static loading protocol, internal forces can be redistributed along the plastic length: there is little chance for structures undergoing high initial loading amplitude to redistribute pertinent stresses. As a result, in the third phase of this part, the effect of high rate of loading on the behaviour of seismically designed RC beams was investigated. Two half-scale cantilever RC beams were subjected to similar constant-amplitude cyclic loading at 2% and 4% drifts, but at a rate of 500 mm/s. Due to the incapability of conventional measuring techniques, a motion-tracking system was employed for data acquisition with the high-speed tests. The effect of rate of loading on the fatigue life of specimens (i.e., the number of cycles required to failure), secant stiffness, failure mode, cracking pattern, beam elongations and bar fracture surface were analysed. Integrating the results of all parts of this research has resulted in a better understanding of residual capacity and the development of damage at both the material and member level by using a low-cycle fatigue approach.

Development of a Non-Destructive Field Based Method to Determine the Relat…

Research papers, The University of Auckland Library

A non-destructive hardness testing method has been developed to investigate the amount of plastic strain demand in steel elements subjected to cyclic loading. The focus of this research is on application to the active links of eccentrically braced frames (EBFs), which are a commonly used seismic-resisting system in modern steel framed buildings. The 2010/2011 Christchurch earthquake series, especially the very intense February 22 shaking, which was the first earthquake worldwide to push complete EBF systems fully into their inelastic state, generating a moderate to high level of plastic strain in EBF active links, for a range of buildings from 3 to 23 storeys in height. This raised two important questions: 1) what was the extent of plastic deformation in active links; and 2) what effect does that have to post-earthquake steel properties? This project comprised determining a robust relationship between hardness and plastic strain in order to be able to answer the first question and provide the necessary input into answering the second question. A non-destructive Leeb (portable) hardness tester (model TH170) has been used to measure the hardness, in order to determine the plastic strain, in hot rolled steel universal sections and steel plates. A bench top Rockwell B was used to compare and validated the hardness measured by the portable hardness tester. Hardness was measured from monotonically strained tensile test specimens to identify the relationship between hardness and plastic strain demand. Test results confirmed a good relationship between hardness and the amount of monotonically induced plastic strain. Surface roughness was identified as an important parameter in obtaining reliable hardness readings from a portable hardness reader. A proper surface preparation method was established by using three different cleaning methods, finished with hand sanding to achieve surface roughness coefficients sufficiently low not to distort the results. This work showed that a test surface roughness (Ra) is not more than 1.6 micron meter (μm) is required for accurate readings from the TH170 tester. A case study on an earthquake affected building was carried out to identify the relationship between hardness and amount of plastic strain demand in cyclically deformed active links. Hardness was carried out from active links shown visually to have been the most affected during one of the major earthquake events. Onsite hardness test results were then compared with laboratory hardness test results. A good relationship between hardness from onsite and laboratory was observed between the test methods; Rockwell B bench top and portable Leeb tester TH170. Manufacturing induced plastic strain in the top and bottom of the webs of hot rolled sections were discovered from this research, an important result which explains why visual effects of earthquake induced active link yielding (eg cracked or flaking paint) was typically more prevalent over the middle half depth of the active link. The extent of this was quantified. It was also evident that the hardness readings from the portable hardness tester are influenced by geometry, mass effects and rigidity of the links. The final experimental stage was application of the method to full scale cyclic inelastic tested nominally identical active links subjected to loading regimes comprising constant and variable plastic strain demands. The links were cyclically loaded to achieve different plastic strain level. A novel Digital Image Correlation (DIC) technique was incorporated during the tests of this scale, to confirm the level of plastic strain achieved. Tensile test specimens were water jet cut from cyclically deformed webs to analyse the level of plastic strain. Test results show clear evidence that cyclically deformed structural steel elements show good correlation between hardness and the amount of plastic strain demand. DIC method was found to be reliable and accurate to check the level of plastic strain within cyclically deformed structural steel elements.