This thesis addresses the topic of local bond behaviour in RC structures. The mechanism of bond refers to the composite action between deformed steel reinforcing bars and the surrounding concrete. Bond behaviour is an open research topic with a wide scope, particularly because bond it is such a fundamental concept to structural engineers. However, despite many bond-related research findings having wide applications, the primary contribution of this research is an experimental evaluation of the prominent features of local bond behaviour and the associated implications for the seismic performance of RC structures. The findings presented in this thesis attempt to address some structural engineering recommendations made by the Canterbury Earthquakes Royal Commission following the 2010-2011 Canterbury (New Zealand) earthquake sequence. A chapter of this thesis discusses the structural behaviour of flexure-dominated RC wall structures with an insufficient quantity of longitudinal reinforcement, among other in situ conditions, that causes material damage to predominantly occur at a single crack plane. In this particular case, the extent of concrete damage and bond deterioration adjacent to the crack plane will influence the ductility capacity that is effectively provided by the reinforcing steel. As a consequence of these in situ conditions, some lightly reinforced wall buildings in Christchurch lost their structural integrity due to brittle fracture of the longitudinal reinforcement. With these concerning post-earthquake observations in mind, there is the underlying intention that this thesis presents experimental evidence of bond behaviour that allows structural engineers to re-assess their confidence levels for the ability of lightly reinforced concrete structures to achieve the life-safety seismic performance objective the ultimate limit state. Three chapters of this thesis are devoted to the experimental work that was conducted as the main contribution of this research. Critical details of the experimental design, bond testing method and test programme are reported. The bond stress-slip relationship was studied through 75 bond pull-out tests. In order to measure the maximum local bond strength, all bond tests were carried out on deformed reinforcing bars that did not yield as the embedded bond length was relatively short. Bond test results have been presented in two separate chapters in which 48 monotonic bond tests and 27 cyclic bond tests are presented. Permutations of the experiments include the loading rate, cyclic loading history, concrete strength (25 to 70 MPa), concrete age, cover thickness, bar diameter (16 and 20 mm), embedded length, and position of the embedded bond region within the specimen (close or far away to the free surface). The parametric study showed that the concrete strength significantly influences the maximum bond strength and that it is reasonable to normalise the bond stress by the square-root of the concrete compressive strength, √(f'c). The generalised monotonic bond behaviour is described within. An important outcome of the research is that the measured bond strength and stiffness was higher than stated by the bond stress-slip relationship in the fib Model Code 2010. To account for these observed differences, an alternative model is proposed for the local monotonic bond stress-slip relationship. Cyclic bond tests showed a significant proportion of the total bond degradation occurs after the loading cycle in the peak bond strength range, which is when bond slip has exceeded 0.5 mm. Subsequent loading to constant slip values showed a linear relationship between the amount of bond strength degradation and the log of the number of cycles that were applied. To a greater extent, the cyclic bond deterioration depends on the bond slip range, regardless of whether the applied load cycling is half- or fully-reversed. The observed bond deterioration and hysteretic energy dissipated during cyclic loading was found to agree reasonably well between these cyclic tests with different loading protocols. The cyclic bond deterioration was also found to be reasonably consistent exponential damage models found in the literature. This research concluded that the deformed reinforcing bars used in NZ construction, embedded in moderate to high strength concrete, are able to develop high local bond stresses that are mobilised by a small amount of local bond slip. Although the relative rib geometry was not varied within this experimental programme, a general conclusion of this thesis is that deformed bars currently available in NZ have a relative rib bearing area that is comparatively higher than the test bars used in previous international research. From the parametric study it was found that the maximum monotonic bond strength is significant enhanced by dynamic loading rates. Experimental evidence of high bond strength and initial bond stiffness generally suggests that only a small amount of local bond slip that can occur when the deformed test bar was subjected to large tension forces. Minimal bond slip and bond damage limits the effective yielding length that is available for the reinforcing steel to distribute inelastic material strains. Consequently, the potential for brittle fracture of the reinforcement may be a more problematic and widespread issue than is apparent to structural engineers. This research has provided information that improve the reliability of engineering predictions (with respect to ductility capacity) of maximum crack widths and the extent of bond deterioration that might occur in RC structures during seismic actions.
Post-tensioned timber technology was originally developed and researched at the University of Canterbury (UC) in New Zealand in 2005. It can provide a low-damage seismic design solution for multi-storey mass timber buildings. Since mass timber products, such as cross-laminated timber (CLT), have high in-plane stiffness, a post-tensioned timber shear wall will deform mainly in a rocking mechanism. The moment capacity of the wall at the base is commonly determined using the elastic form of the Modified Monolithic Beam Analogy (MMBA). In the calculation of the moment capacity at the wall base, it is critical to accurately predict the location of the neutral axis and the timber compressive stress distribution. Three 2/3 scale 8.6m tall post-tensioned CLT walls were experimentally tested under quasi-static cyclic loading – both uni-directional and bi-directional- in this study. These specimens included a single wall, a coupled wall, and a C-shaped core-wall. The main objective was to develop post-tensioned C-shaped timber core-walls for tall timber buildings with enhanced lateral strength and stiffness. To better understand the timber compressive stress distributions at the wall base, particle tracking technology (PTT) technology was applied for the first time to investigate the behaviour of the compression toe. Previous post-tensioned timber testing primarily used the displacement measurements to determine the timber compressive behavior at the wall base or rocking interfaces. However, by using PTT technology, the timber strain measurements in the compression zone can be much more accurate as PTT is able to track the movement of many particles on the timber surface. This paper presents experimental testing results of post-tensioned CLT walls with a focus on capturing timber compressive behavior using PTT. The PTT measurements were able to better capture small base rotations which occurred at the onset of gap opening and capture unexpected phenomena in core-wall tests. The single wall test result herein presented indicates that while the MMBA could predict the moment rotation behavior with reasonable accuracy, the peak strain response was under predicted in the compression toe. Further detailed study is required to better understand the complex strain fields generated reflective of the inherent cross-thickness inhomogeneity and material variability of CLT.
This study investigates the uncertainty of simulated earthquake ground motions for smallmagnitude events (Mw 3.5 – 5) in Canterbury, New Zealand. 148 events were simulated with specified uncertainties in: event magnitude, hypocentre location, focal mechanism, high frequency rupture velocity, Brune stress parameter, the site 30-m time-averaged shear wave velocity (Vs30), anelastic attenuation (Q) and high frequency path duration. In order to capture these uncertainties, 25 realisations for each event were generated using the Graves and Pitarka (2015) hybrid broadband simulation approach. Monte-Carlo realisations were drawn from distributions for each uncertainty, to generate a suite of simulation realisations for each event and site. The fit of the multiple simulation realisations to observations were assessed using linear mixed effects regression to generate the systematic source, path and site effects components across all ground motion intensity measure residuals. Findings show that additional uncertainties are required in each of the three source, path, and site components, however the level of output uncertainty is promising considering the input uncertainties included.
This analysis employs both qualitative and quantitative approaches to identify how young adults in New Zealand aged 18-25 years old have engaged with All Right? campaign material. A survey targeting young adults returned 51 viable out of 117 responses due to participation prerequisites. From the survey, five participants elaborated on their thoughts in an in-depth interview voluntarily. Interviews were conducted with key personnel from All Right? to craft broader understanding of the initiative whilst enhancing knowledge of mental health frameworks and their application. Ciaran Fox, Lucy Daeth and Sara Epperson, who have been imperative to the success of the campaign, shared their working experience in the community and public health sector and how this intertwines to their current roles at All Right?. Discussions of key frameworks, community conversations, the development of communication strategies and how All Right? approached Canterbury publics in a post-earthquake setting provided insight to the importance of understanding community circumstance in initial crisis and the correlated secondary stressors.
In 2010 and 2011 Christchurch, New Zealand experienced a series of earthquakes that caused extensive damage across the city, but primarily to the Central Business District (CBD) and eastern suburbs. A major feature of the observed damage was extensive and severe soil liquefaction and associated ground damage, affecting buildings and infrastructure. The behaviour of soil during earthquake loading is a complex phenomena that can be most comprehensively analysed through advanced numerical simulations to aid engineers in the design of important buildings and critical facilities. These numerical simulations are highly dependent on the capabilities of the constitutive soil model to replicate the salient features of sand behaviour during cyclic loading, including liquefaction and cyclic mobility, such as the Stress-Density model. For robust analyses advanced soil models require extensive testing to derive engineering parameters under varying loading conditions for calibration. Prior to this research project little testing on Christchurch sands had been completed, and none from natural samples containing important features such as fabric and structure of the sand that may be influenced by the unique stress-history of the deposit. This research programme is focussed on the characterisation of Christchurch sands, as typically found in the CBD, to facilitate advanced soil modelling in both res earch and engineering practice - to simulate earthquake loading on proposed foundation design solutions including expensive ground improvement treatments. This has involved the use of a new Gel Push (GP) sampler to obtain undisturbed samples from below the ground-water table. Due to the variable nature of fluvial deposition, samples with a wide range of soil gradations, and accordingly soil index properties, were obtained from the sampling sites. The quality of the samples is comprehensively examined using available data from the ground investigation and laboratory testing. A meta-quality assessment was considered whereby a each method of evaluation contributed to the final quality index assigned to the specimen. The sampling sites were characterised with available geotechnical field-based test data, primarily the Cone Penetrometer Test (CPT), supported by borehole sampling and shear-wave velocity testing. This characterisation provides a geo- logical context to the sampling sites and samples obtained for element testing. It also facilitated the evaluation of sample quality. The sampling sites were evaluated for liquefaction hazard using the industry standard empirical procedures, and showed good correlation to observations made following the 22 February 2011 earthquake. However, the empirical method over-predicted liquefaction occurrence during the preceding 4 September 2010 event, and under-predicted for the subsequent 13 June 2011 event. The reasons for these discrepancies are discussed. The response of the GP samples to monotonic and cyclic loading was measured in the laboratory through triaxial testing at the University of Canterbury geomechanics laboratory. The undisturbed samples were compared to reconstituted specimens formed in the lab in an attempt to quantify the effect of fabric and structure in the Christchurch sands. Further testing of moist tamped re- constituted specimens (MT) was conducted to define important state parameters and state-dependent properties including the Critical State Line (CSL), and the stress-strain curve for varying state index. To account for the wide-ranging soil gradations, selected representative specimens were used to define four distinct CSL. The input parameters for the Stress-Density Model (S-D) were derived from a suite of tests performed on each representative soil, and with reference to available GP sample data. The results of testing were scrutinised by comparing the data against expected trends. The influence of fabric and structure of the GP samples was observed to result in similar cyclic strength curves at 5 % Double Amplitude (DA) strain criteria, however on close inspection of the test data, clear differences emerged. The natural samples exhibited higher compressibility during initial loading cycles, but thereafter typically exhibited steady growth of plastic strain and excess pore water pressure towards and beyond the strain criteria and initial liquefaction, and no flow was observed. By contrast the reconstituted specimens exhibited a stiffer response during initial loading cycles, but exponential growth in strains and associated excess pore water pressure beyond phase-transformation, and particularly after initial liquefaction where large strains were mobilised in subsequent cycles. These behavioural differences were not well characterised by the cyclic strength curve at 5 % DA strain level, which showed a similar strength for both GP samples and MT specimens. A preliminary calibration of the S-D model for a range of soil gradations is derived from the suite of laboratory test data. Issues encountered include the influence of natural structure on the peak-strength–state index relationship, resulting in much higher peak strengths than typically observed for sands in the literature. For the S-D model this resulted in excessive stiffness to be modelled during cyclic mobility, when the state index becomes large momentarily, causing strain development to halt. This behaviour prevented modelling the observed re- sponse of silty sands to large strains, synonymous with “liquefaction”. Efforts to reduce this effect within the current formulation are proposed as well as future research to address this issue.
Well-validated liquefaction constitutive models are increasingly important as non-linear time history analyses become relatively more common in industry for key projects. Previous validation efforts of PM4Sand, a plasticity model specifically for liquefaction, have generally focused on centrifuge tests; however, pore pressure transducers installed at several free-field sites during the Canterbury Earthquake Sequence (CES) in Christchurch, New Zealand provide a relatively unique dataset to validate against. This study presents effective stress site response analyses performed in the finite difference software FLAC to examine the capability of PM4Sand to capture the generation of excess pore pressures during earthquakes. The characterization of the subsurface is primarily based on extensive cone penetration tests (CPT) carried out in Christchurch. Correlations based on penetration resistances are used to estimate soil parameters, such as relative density and shear wave velocity, which affect liquefaction behaviour. The resulting free-field FLAC model is used to estimate time histories of excess pore pressure, which are compared with records during several earthquakes in the CES to assess the suitability of PM4Sand.
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.
The Screw Driving Sounding (SDS) method developed in Japan is a relatively new insitu testing technique to characterise soft shallow sites, typically those required for residential house construction. An SDS machine drills a rod into the ground in several loading steps while the rod is continuously rotated. Several parameters, such as torque, load and speed of penetration, are recorded at every rotation of the rod. The SDS method has been introduced in New Zealand, and the results of its application for characterising local sites are discussed in this study. A total of 164 SDS tests were conducted in Christchurch, Wellington and Auckland to validate/adjust the methodologies originally developed based on the Japanese practice. Most of the tests were conducted at sites where cone penetration tests (CPT), standard penetration tests (SPT) and borehole logs were available; the comparison of SDS results with existing information showed that the SDS method has great potential as an in-situ testing method for classifying the soils. By compiling the SDS data from 3 different cities and comparing them with the borehole logs, a soil classification chart was generated for identifying the soil type based on SDS parameters. Also, a correlation between fines content and SDS parameters was developed and a procedure for estimating angle of internal friction of sand using SDS parameters was investigated. Furthermore, a correlation was made between the tip resistance of the CPT and the SDS data for different percentages of fines content. The relationship between the SPT N value and a SDS parameter was also proposed. This thesis also presents a methodology for identifying the liquefiable layers of soil using SDS data. SDS tests were performed in both liquefied and non-liquefied areas in Christchurch to find a representative parameter and relationship for predicting the liquefaction potential of soil. Plots were drawn of the cyclic shear stress ratios (CSR) induced by the earthquakes and the corresponding energy of penetration during SDS tests. By identifying liquefied or unliquefied layers using three different popular CPT-based methods, boundary lines corresponding to the various probabilities of liquefaction happening were developed for different ranges of fines contents using logistic regression analysis, these could then be used for estimating the liquefaction potential of soil directly from the SDS data. Finally, the drilling process involved in screw driving sounding was simulated using Abaqus software. Analysis results proved that the model successfully captured the drilling process of the SDS machine in sand. In addition, a chart to predict peak friction angles of sandy sites based on measured SDS parameters for various vertical effective stresses was formulated. As a simple, fast and economical test, the SDS method can be a reliable alternative insitu test for soil and site characterisation, especially for residential house construction.
Natural hazard disasters often have large area-wide impacts, which can cause adverse stress-related mental health outcomes in exposed populations. As a result, increased treatment-seeking may be observed, which puts a strain on the limited public health care resources particularly in the aftermath of a disaster. It is therefore important for public health care planners to know whom to target, but also where and when to initiate intervention programs that promote emotional wellbeing and prevent the development of mental disorders after catastrophic events. A large body of literature assesses factors that predict and mitigate disaster-related mental disorders at various time periods, but the spatial component has rarely been investigated in disaster mental health research. This thesis uses spatial and spatio-temporal analysis techniques to examine when and where higher and lower than expected mood and anxiety symptom treatments occurred in the severely affected Christchurch urban area (New Zealand) after the 2010/11 Canterbury earthquakes. High-risk groups are identified and a possible relationship between exposure to the earthquakes and their physical impacts and mood and anxiety symptom treatments is assessed. The main research aim is to test the hypothesis that more severely affected Christchurch residents were more likely to show mood and anxiety symptoms when seeking treatment than less affected ones, in essence, testing for a dose-response relationship. The data consisted of mood and anxiety symptom treatment information from the New Zealand Ministry of Health’s administrative databases and demographic information from the National Health Index (NHI) register, when combined built a unique and rich source for identifying publically funded stress-related treatments for mood and anxiety symptoms in almost the whole population of the study area. The Christchurch urban area within the Christchurch City Council (CCC) boundary was the area of interest in which spatial variations in these treatments were assessed. Spatial and spatio-temporal analyses were done by applying retrospective space-time and spatial variation in temporal trends analysis using SaTScan™ software, and Bayesian hierarchical modelling techniques for disease mapping using WinBUGS software. The thesis identified an overall earthquake-exposure effect on mood and anxiety symptom treatments among Christchurch residents in the context of the earthquakes as they experienced stronger increases in the risk of being treated especially shortly after the catastrophic 2011 Christchurch earthquake compared to the rest of New Zealand. High-risk groups included females, elderly, children and those with a pre-existing mental illness with elderly and children especially at-risk in the context of the earthquakes. Looking at the spatio-temporal distribution of mood and anxiety symptom treatments in the Christchurch urban area, a high rates cluster ranging from the severely affected central city to the southeast was found post-disaster. Analysing residential exposure to various earthquake impacts found that living in closer proximity to more affected areas was identified as a risk factor for mood and anxiety symptom treatments, which largely confirms a dose-response relationship between level of affectedness and mood and anxiety symptom treatments. However, little changes in the spatial distribution of mood and anxiety symptom treatments occurred in the Christchurch urban area over time indicating that these results may have been biased by pre-existing spatial disparities. Additionally, the post-disaster mobility activity from severely affected eastern to the generally less affected western and northern parts of the city seemed to have played an important role as the strongest increases in treatment rates occurred in less affected northern areas of the city, whereas the severely affected eastern areas tended to show the lowest increases. An investigation into the different effects of mobility confirmed that within-city movers and temporary relocatees were generally more likely to receive care or treatment for mood or anxiety symptoms, but moving within the city was identified as a protective factor over time. In contrast, moving out of the city from minor, moderately or severely damaged plain areas of the city, which are generally less affluent than Port Hills areas, was identified as a risk factor in the second year post-disaster. Moreover, residents from less damaged plain areas of the city showed a decrease in the likelihood of receiving care or treatment for mood or anxiety symptoms compared to those from undamaged plain areas over time, which also contradicts a possible dose-response relationship. Finally, the effects of the social and physical environment, as well as community resilience on mood and anxiety symptom treatments among long-term stayers from Christchurch communities indicate an exacerbation of pre-existing mood and anxiety symptom treatment disparities in the city, whereas exposure to ‘felt’ earthquake intensities did not show a statistically significant effect. The findings of this thesis highlight the complex relationship between different levels of exposure to a severe natural disaster and adverse mental health outcomes in a severely affected region. It is one of the few studies that have access to area-wide health and impact information, are able to do a pre-disaster / post-disaster comparison and track their sample population to apply spatial and spatio-temporal analysis techniques for exposure assessment. Thus, this thesis enhances knowledge about the spatio-temporal distribution of adverse mental health outcomes in the context of a severe natural disaster and informs public health care planners, not only about high-risk groups, but also where and when to target health interventions. The results indicate that such programs should broadly target residents living in more affected areas as they are likely to face daily hardship by living in a disrupted environment and may have already been the most vulnerable ones before the disaster. Special attention should be focussed on women, elderly, children and people with pre-existing mental illnesses as they are most likely to receive care or treatment for stress-related mental health symptoms. Moreover, permanent relocatees from affected areas and temporarily relocatees shortly after the disaster may need special attention as they face additional stressors due to the relocation that may lead to the development of adverse mental health outcomes needing treatment.
<b>New Zealand has experienced several strong earthquakes in its history. While an earthquake cannot be prevented from occurring, planning can reduce its consequences when it does occur. This dissertation research examines various aspects of disaster risk management policy in Aotearoa New Zealand.</b>
Chapter 2 develops a method to rank and prioritise high-rise buildings for seismic retrofitting in Wellington, the earthquake-prone capital city of New Zealand. These buildings pose risks to Wellington’s long-term seismic resilience that are of clear concern to current and future policymakers. The prioritization strategy we propose, based on multi-criteria decision analysis (MCDA) methods, considers a variety of data on each building, including not only its structural characteristics, but also its location, its economic value to the city, and its social importance to the community around it. The study demonstrates how different measures, within four general criteria – life safety, geo-spatial location of the building, its economic role, and its socio-cultural role – can be operationalized into a viable framework for determining retrofitting/demolition policy priorities.
Chapter 3 and chapter 4 analyse the Residential Red Zone (RRR) program that was implemented in Christchurch after the 2011 earthquake. In the program, approximately 8,000 homeowners were told that their homes were no longer permittable, and they were bought by the government (through the Canterbury Earthquake Recovery Authority).
Chapter 3 examines the subjective wellbeing of the RRR residents (around 16000 people) after they were forced to move. We consider three indicators of subjective wellbeing: quality of life, stress, and emotional wellbeing. We found that demographic factors, health conditions, and the type of government compensation the residents accepted, were all significant determinants of the wellbeing of the Red Zone residents. More social relations, better financial circumstances, and the perception of better government communication were also all associated positively with a higher quality of life, less stress, and higher emotional wellbeing.
Chapter 4 concentrates on the impact of this managed retreat program on RRR residents’ income. We use individual-level comprehensive, administrative, panel data from Canterbury, and difference in difference evaluation method to explore the effects of displacement on Red Zone residential residents. We found that compared to non-relocated neighbours, the displaced people experience a significant initial decrease in their wages and salaries, and their total income. The impacts vary with time spent in the Red Zone and when they moved away. Wages and salaries of those who were red-zoned and moved in 2011 were reduced by 8%, and 5.4% for those who moved in 2012. Females faced greater decreases in wages and salaries, and total income, than males. There were no discernible impacts of the relocation on people’s self-employment income.
As part of the Canterbury Earthquake Digital Archive, this thesis documents the effects of the earthquakes on the musical life of Christchurch. It concentrates, primarily, on the classical music scene. The thesis examines the difficulties experienced by musical organisations, individual musicians, and teachers as they sought to bring music to the broken city, together with the measures that were necessary in order to overcome those difficulties. It examines how those organisations have worked to re-establish themselves in their particular musical fields. It charts the progress made, to date, along the path to recovery and offers suggestions regarding precautionary measures which, if instituted, could reduce the after-effects of a future disaster. Recognising that not all of the difficulties encountered were directly related to the earthquakes, this thesis also examines the effects on music and musicians, of decision making associated with the recovery effort. The thesis also demonstrates how a destructive event can provide the inspiration for creativity. It recognises the importance of music in maintaining a sense of normality for people, whether they realise it or not, as well as its influences in providing emotional relief in times of stress. Hopefully, it may become a useful guide to which other cities that may be faced with some natural disaster, could refer.
The Eastern Humps and Leader faults, situated in the Mount Stewart Range in North Canterbury, are two of the ≥17 faults which ruptured during the 2016 MW7.8 Kaikōura Earthquake. The earthquake produced complex, intersecting ground ruptures of these faults and the co-seismic uplift of the Mount Stewart Range. This thesis aims to determine how these two faults accommodated deformation during the 2016 earthquake and how they interact with each other and with pre-existing geological structures. In addition, it aims to establish the most likely subsurface geometry of the fault complex across the Mount Stewart Range, and to investigate the paleoseismic history of the Leader Fault. The Eastern Humps Fault strikes ~240° and dips 80° to 60° to the northwest and accommodated right- lateral – reverse-slip, with up to 4 m horizontal and 2 m vertical displacement in the 2016 earthquake. The strike of the Leader Fault varies from ~155 to ~300°, and dips ~30 to ~80° to the west/northwest, and mainly accommodated left-lateral – reverse-slip of up to 3.5 m horizontal and 3.5 m vertical slip in the 2016 earthquake. On both the Eastern Humps and Leader faults the slip is variable along strike, with areas of low total displacement and areas where horizontal and vertical displacement are negatively correlated. Fault traces with low total displacement reflect the presence of off-fault (distributed) displacement which is not being captured with field measurements. The negative correlation of horizontal and vertical displacement likely indicates a degree of slip partitioning during the 2016 earthquake on both the Eastern Humps and Leader faults. The Eastern Humps and Leader faults have a complex, interdependent relationship with the local bedrock geology. The Humps Fault appears to be a primary driver of ongoing folding and deformation of the local Mendip Syncline and folding of the Mount Stewart Range, which probably began prior to, or synchronous with, initial rupture of The Humps Fault. The Leader Fault appears to use existing lithological weaknesses in the Cretaceous-Cenozoic bedrock stratigraphy to rupture to the surface. This largely accounts for the strong variability on the strike and dip of the Leader Fault, as the geometry of the surface ruptures tend to reflect the strike and dip of the geological strata which it is rupturing through. The Leader Fault may also accommodate some degree of flexural slip in the Cenozoic cover sequence of the Mendip Syncline, contributing to the ongoing growth of the fold. The similarity between topography and uplift profiles from the 2016 earthquake suggest that growth of the Mount Stewart Range has been primarily driven by multiple (>500) discrete earthquakes that rupture The Humps and Leader faults. The spatial distribution of surface displacements across the Mount Stewart Range is more symmetrical than would be expected if uplift is driven primarily by The Humps and Leader faults alone. Elastic dislocation forward models were used to model potential sub-surface geometries and the resulting patterns of deformation compared to photogrammetry-derived surface displacements. Results show a slight preference for models with a steeply southeast-dipping blind fault, coincident with a zone of seismicity at depth, as a ‘backthrust’ to The Humps and Leader faults. This inferred Mount Stewart Fault accommodated contractional strain during the 2016 earthquake and contributes to the ongoing uplift of the Mount Stewart Range with a component of folding. Right-lateral and reverse shear stress change on the Hope Fault was also modelled using Coulomb 3.3 software to examine whether slip on The Humps and Leader faults could transfer enough stress onto the Hope Fault to trigger through-going rupture. Results indicate that during the 2016 earthquake right-lateral shear and reverse stress only increased on the Hope Fault in small areas to the west of the Leader Fault, and similar ruptures would be unlikely to trigger eastward propagating rupture unless the Hope Fault was close to failure prior to the earthquake. Paleoseismic trenches were excavated on the Leader Fault at four locations from 2018 to 2020, revealing near surface (< 4m depth) contractional deformation of Holocene stratigraphy. Three of the trench locations uncovered clear evidence for rupture of the Leader Fault prior to 2016, with fault displacement of near surface stratigraphy being greater than displacement recorded during the 2016 earthquake. Radiocarbon dating of in-situ organic material from two trenches indicate a date of the penultimate earthquake on the Leader Fault within the past 1000 years. This date is consistent with The Humps and Leader faults having ruptured simultaneously in the past, and with multi-fault ruptures involving The Humps, Leader, Hundalee and Stone Jug faults having occurred prior to the 2016 Kaikōura earthquake. Overall, the results contribute to an improved understanding of the Kaikōura earthquake and highlight the importance of detailed structural and paleoseismic investigations in determining controls on earthquake ‘complexity’.
A dramatic consequence of the Christchurch, New Zealand, earthquakes of 2010 and 2011 was the widespread liquefaction in the city. Part of the central business district (CBD) was badly affected by liquefaction but elsewhere large volumes of ejecta were not evident for those parts of the CBD where the upper layers in the soil profile are sandy gravel and gravelly sand. The purpose of the paper is to investigate the effect of the gravel permeability on the rise and dissipation of excess pore water pressure during cyclic loading of a soil profile idealised from Christchurch data. The Cyclic1D software, which performs one-dimensional non-linear effective stress site response analysis, was used. Permeability values associated with gravel were found to suppress the cyclic accumulation of excess pore water pressure in gravel layers. Given that there has not been any systematic measurement of the in situ permeability of the gravels in Christchurch, the modelling in the paper suggests that likely values for the bulk permeability of the gravel layers are within the range suggested in the geotechnical literature. However, the work reported is of wider application than Christchurch and emphasises the controlling influence of permeability on the accumulation and dissipation of cyclic pore pressures. VoR - Version of Record
The majority of current procedures used to deduce liquefaction potential of soils rely on empirical methods. These methods have been proven to work in the past, but these methods are known to overestimate the liquefaction potential in certain regions of Christchurch due to a whole range of factors, and the theoretical basis behind these methods cannot be explained scientifically. Critical state soil mechanics theory was chosen to provide an explanation for the soil's behaviour during the undrained shearing. Soils from two sites in Christchurch were characterised at regular intervals for the critical layers and tested for the critical state lines (CSL). Various models and relationships were then used to predict the CSL and compared with the actual CSL. However none of the methods used managed to predict the CSL accurately, and a separate Christchurch exclusive relationship was proposed. The resultant state parameter values could be obtained from shear-wave velocity plots and were then developed into cyclic resistance ratios (CRR). These were subsequently compared with cyclic stress ratios (CSR) from recent Christchurch earthquakes to obtain the factor of safety. This CSL-based approach was compared with other empirical methods and was shown to yield a favourable relationship with visual observations at the sites' locations following the earthquake.
At 4.35am on Saturday 4 September 2010, a magnitude 7.1 earthquake struck near the township of Darfield in Canterbury leading to widespread damage in Christchurch and the wider central Canterbury region. Though it was reported no lives were lost, that was not entirely correct. Over 3,000 animals perished as a result of the earthquake and 99% of these deaths would have been avoidable if appropriate mitigation measures had been in place. Deaths were predominantly due to zoological vulnerability of birds in captive production farms. Other problems included lack of provision of animal welfare at evacuation centres, issues associated with multiple lost and found pet services, evacuation failure due to pet separation and stress impact on dairy herds and associated milk production. The Canterbury Earthquake has highlighted concerns over a lack of animal emergency welfare planning and capacity in New Zealand, an issue that is being progressed by the National Animal Welfare Emergency Management Group. As animal emergency management becomes better understood by emergency management and veterinary professionals, it is more likely that both sectors will have greater demands placed upon them by national guidelines and community expectations to ensure provisions are made to afford protection of animals in times of disaster. A subsequent and more devastating earthquake struck the region on Monday 22 February 2011; this article however is primarily focused on the events pertaining to the September 4 event.
This study sought to investigate employee burnout within a post-disaster context by exploring teachers’ burnout perceptions and workplace attitudes in the aftermath of the 2010-2011 Christchurch earthquakes. The study hypothesised that burnout dimensions (emotional exhaustion and cynicism) would be related with the extent to which individuals and schools were impacted by the earthquakes, and with the quality of school support for staff and students (i.e., personal disaster impact, school disaster impact and school responsiveness to the disaster), with perceptions of role conflict and role overload, and with turnover intentions. Additionally, a Teacher Burnout Model was proposed whereby emotional exhaustion and cynicism were hypothesised to mediate the relationships between the independent variables (i.e., the disaster-related and role-related variables) and turnover intentions. 125 primary, intermediate and secondary school teachers from the city of Christchurch completed an online survey. Results revealed that high role overload, high role conflict, high school disaster impact, and schools’ ineffective disaster coping responses, were associated with increased levels of emotional exhaustion and cynicism. Although greater impact of earthquakes on teachers’ personal lives was related to higher levels of emotional exhaustion, results revealed a non-significant relationship between personal disaster impact and cynicism. In the Teacher Burnout Model, the relationships between both role stress variables and turnover intentions were mediated by perceptions of emotional exhaustion. This study contributes novel findings to the burnout literature, and provides implications for schools and organisations operating within a disaster context.
The self-regulation approach to educating parents focusses on promoting parenting confidence, independence, and the ability to solve future problems. As parents learn the skills to modify their own behaviour, in turn, they aim to foster self-regulation in their children/adolescents. A need had been identified by Christchurch school principals for the Ministry of Education to respond to the post-earthquake stress in local families. The aim of this study was to investigate if a parenting programme was effective in promoting parental self-management skills and adolescent behaviour change in Christchurch families affected by earthquakes between 2010 and 2012. A single case research design was used to follow five families with adolescents (12-16 years old) as they participated in a Group Teen Triple P – Positive Parenting Programme. Measures of self-management skill acquisition were taken during three family discussions (pre-intervention, mid-intervention, and post-intervention) and during the three telephone consultations (Sessions 5-7). Adolescent target behaviour tallies were also analysed for change. The main findings showed that parental self-management skill acquisition increased over-time accompanied by positive change in adolescent behaviour. Additionally, the results suggested that higher rates and levels of self-management skill acquisition in the parents were associated with greater improvements in adolescent behaviour. This study demonstrated that Group Teen Triple P – Positive Parenting Programme was effective in promoting self-management competencies in parents and behaviour change in adolescents.
Background: Earthquakes are found to have lingering post-disaster effects on children that can be present for months or years after the disaster, including hyperarousal symptoms. Young children have the most difficulties in regulating their emotions, especially when they are highly aroused. Colouring-in mandala designs have been found to reduce hyperarousal symptoms of stress in young adults. The purpose of this study was to determine if the same effects of colouring-in mandalas would be seen with children showing signs of hyperarousal. Research Question: To identify what effect colouring-in mandala designs would have on the heart rate in a young child showing signs of hyperarousal. Method: Following approved procedures for informed consent, two 6-year-old girls from a Christchurch primary school were chosen for the study. Heart rate was measured using a Fitbit in a single subject design. The baseline, colouring-in and a second baseline phase were conducted during mathematics. The participants and their teacher reported on arousal, enjoyment, and positive and problem behaviours. The study took 26 school days to complete. Results: Compared with baseline, the average heart rate data showed no decrease in heart rate (i.e., calming effect) during the mandala colouring-in task phase. Conclusions: The participants enjoyed colouring-in the mandalas, but the average heart rate data did not show that colouring-in pre-drawn designs reduced heart rate, a measure of arousal. Major study limitations included; not having suitable participants or a suitable setting for the colouring-in task, and not being able to observe both participants.
Developing a holistic understanding of social, cultural, and economic impacts of disasters can help in building disaster risk knowledge for policy making and planning. Many methods can help in developing an understanding of the impacts of a disaster, including interviews and surveys with people who have experienced disaster, which may be invasive at times and create stress for the participants to relive their experiences. In the past decade, social media, blog posts, video blogs (i.e. “vlogs”), and crowdsourcing mechanisms such as Humanitarian OpenStreetMap and Ushahidi, have become prominent platforms for people to share their experiences and impacts of an event from the ground. These platforms allow for the discovery of a range of impact information, from physical impacts, to social, cultural, and psychological impacts. It can also reveal interesting behavioural information such as their decision to heed a warning or not, as people tend to share their experiences and their reactions online. This information can help researchers and authorities understand both the impacts as well as behavioural responses to hazards, which can then shape how early warning systems are designed and delivered. It can also help to identify gaps in desired behavioural responses. This poster presents a selection of cases identified from the literature and grey literature, such as the Haiti earthquake, the Christchurch earthquake, Hurricane Sandy, and Hurricane Harvey, where online platforms were widely used during and after a disaster to document impacts, experiences, and behavioural responses. A summary of key learnings and areas for future research is provided.
This study explicitly investigates uncertainties in physics-based ground motion simulation validation for earthquakes in the Canterbury region. The simulations utilise the Graves and Pitarka (2015) hybrid methodology, with separately quantified parametric uncertainties in the comprehensive physics and simplified physics components of the model. The study is limited to the simulation of 148 small magnitude (Mw 3.5 – 5) earthquakes, with a point source approximation for the source rupture representations, which also enables a focus on a small number of relevant uncertainties. The parametric uncertainties under consideration were selected through sensitivity analysis, and specifically include: magnitude, Brune stress parameter and high frequency rupture velocity. Twenty Monte Carlo realisations were used to sample parameter uncertainties for each of the 148 events. Residuals associated with the following intensity measures: spectral acceleration, peak ground velocity, arias intensity and significant duration, were ascertained. Using these residuals, validation was performed through assessment of systematic biases in site and source terms from mixed-effects regression. Based on the results to date, initial standard deviation recommendations for parameter uncertainties, based on the Canterbury simulations have been obtained. This work ultimately provides an initial step toward explicit incorporation of modelling uncertainty in simulated ground motion predictions for future events, which will improve the use of simulation models in seismic hazard analysis. We plan to subsequently assess uncertainties for larger magnitude events with more complex ruptures, and events across a larger geographic region, as well as uncertainties due to path attenuation, site effects, and more general model epistemic uncertainties.
Recent major earthquakes such as Northridge 1994 and Izmit Kocaeli 1999 highlighted the poor performance of existing buildings constructed prior to the early 1970’s. Low lateral seismic design coefficients and the adopted “working stress design” methodology (essentially an elastic design) lacked any inelastic design considerations, thus leading to inadequate detailing. Insufficient development lengths, lapping within potential plastic hinge regions, lack, or total absence of joint transverse reinforcement, and the use of plain round reinforcement and hooked end anchorages were common throughout the structure. The behaviour is generally dominated by brittle local failure mechanisms (e.g. joint or element shear failures) as well as possible soft-storey mechanisms at a global level. Amongst several possible retrofit interventions, a typical solution is to provide the structure with additional structural walls i.e. external buttressing or column in-fills. Extensive developments on precast, post-tensioned, dissipative systems have shown promise for the use of rocking wall systems to retrofit existing poorly detailed frame structures. In this contribution, the feasibility of such a retrofit intervention is investigated. A displacement-based retrofit procedure is developed and proposed, based on targeting pre-defined performance criteria, such as joint shear and/or column curvature deformation limits. A design example, using the proposed retrofit strategy on a prototype frame is presented. A brief overview on experimental work ongoing at the University of Canterbury investigating the dynamic response of advanced rocking walls for retrofit purposes will be provided.
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.
This dissertation addresses a diverse range of topics in the physics-based broadband ground motion simulation, with a focus on New Zealand applications. In particular the following topics are addressed: the methodology and computational implementation of a New Zealand Velocity Model for broadband ground motion simulation; generalised parametric functions and spatial correlations for seismic velocities in the Canterbury, New Zealand region from surface-wave-based site characterisation; and ground motion simulations of Hope Fault earthquakes. The paragraphs below outline each contribution in more detail. A necessary component in physics-based ground motion simulation is a 3D model which details the seismic velocities in the region of interest. Here a velocity model construction methodology, its computational implementation, and application in the construction of a New Zealand velocity model for use in physics-based broadband ground motion simulation are presented. The methodology utilises multiple datasets spanning different length scales, which is enabled via the use of modular sub-regions, geologic surfaces, and parametric representations of crustal velocity. A number of efficiency-related workflows to decrease the overall computational construction time are employed, while maintaining the flexibility and extensibility to incorporate additional datasets and re- fined velocity parameterizations as they become available. The model comprises explicit representations of the Canterbury, Wellington, Nelson-Tasman, Kaikoura, Marlborough, Waiau, Hanmer and Cheviot sedimentary basins embedded within a regional travel-time tomography-based velocity model for the shallow crust and provides the means to conduct ground motion simulations throughout New Zealand for the first time. Recently developed deep shear-wave velocity profiles in Canterbury enabled models that better characterise the velocity structure within geologic layers of the Canterbury sedimentary basin to be developed. Here the development of depth- and Vs30-dependent para-metric velocity and spatial correlation models to characterise shear-wave velocities within the geologic layers of the Canterbury sedimentary basin are presented. The models utilise data from 22 shear-wave velocity profiles of up to 2.5km depth (derived from surface wave analysis) juxtaposed with models which detail the three-dimensional structure of the geologic formations in the Canterbury sedimentary basin. Parametric velocity equations are presented for Fine Grained Sediments, Gravels, and Tertiary layer groupings. Spatial correlations were developed and applied to generate three-dimensional stochastic velocity perturbations. Collectively, these models enable seismic velocities to be realistically represented for applications such as 3D ground motion and site response simulations. Lastly the New Zealand velocity model is applied to simulate ground motions for a Mw7.51 rupture of the Hope Fault using a physics-based simulation methodology and a 3D crustal velocity model of New Zealand. The simulation methodology was validated for use in the region through comparison with observations for a suite of historic small magnitude earthquakes located proximal to the Hope Fault. Simulations are compared with conventionally utilised empirical ground motion models, with simulated peak ground velocities being notably higher in regions with modelled sedimentary basins. A sensitivity analysis was undertaken where the source characteristics of magnitude, stress parameter, hypocentre location and kinematic slip distribution were varied and an analysis of their effect on ground motion intensities is presented. It was found that the magnitude and stress parameter strongly influenced long and short period ground motion amplitudes, respectively. Ground motion intensities for the Hope Fault scenario are compared with the 2016 Kaikoura Mw7.8 earthquake, it was found that the Kaikoura earthquake produced stronger motions along the eastern South Island, while the Hope Fault scenario resulted in stronger motions immediately West of the near-fault region. The simulated ground motions for this scenario complement prior empirically-based estimates and are informative for mitigation and emergency planning purposes.
The development of cheap, whilst effective and relatively non-invasive structural retrofit techniques for existing non-ductile reinforced concrete (RC) structures still remains the most challenging issue for a wide implementation on a macro scale. Seismic retrofit is too often being confused as purely structural strengthening. As part of a six-years national project on “Seismic retrofit solutions for NZ multi-storey building”, focus has been given at the University of Canterbury on the development of a counter-intuitive retrofit strategy for earthquake vulnerable existing rc frame, based on a “selective weakening” (SW) approach. After an overview of the SW concept, this paper presents the experimental and numerical validation of a SW retrofit strategy for earthquake vulnerable existing RC frame with particular focus on the exterior beam-column (b-c) joints. The exterior b-c joint is a critically vulnerable region in many existing pre-1970s RC frames. By selectively weakening the beam by cutting the bottom longitudinal reinforcements and/or adding external pre-stressing to the b-c joint, a more desirable inelastic mechanism can be attained, leading to improved global seismic performance. The so-called SW retrofit is implemented on four 2/3-scaled exterior RC b-c joint subassemblies, tested under quasi-static cyclic loading at the University of Canterbury. Complemented by refined 3D Finite Element (FE) models and dynamic time-history analyses results, the experimental results have shown the potential of a simple and cost-effective yet structurally efficient structural rehabilitation technique. The research also demonstrated the potential of advanced 3D fracture-mechanics-based microplane concrete modelling for refined FE analysis of non-ductile RC b-c joints.
While it is well known that challenging and distressing events can negatively impact people’s psychological and physical state, increasingly researchers have investigated how challenging or stressful life circumstances can lead to the phenomenon of posttraumatic growth: positive psychological or life changes that can emerge from potentially traumatic events. Posttraumatic growth has been investigated primarily with people displaying varying levels of posttraumatic stress symptoms and other psychopathology due to theories suggesting that resilience would prohibit posttraumatic growth. Few studies have examined growth amongst resilient people. The current study examined posttraumatic growth in a sample of sixty psychologically healthy people who experienced the Canterbury earthquake sequence of 2010-2011. The current study is a follow-up study that used thematic analysis to explore: (1) Whether posttraumatic growth is evident nine years after the Canterbury earthquake sequence and approximately six years after baseline assessment; and (2) What themes may facilitate the posttraumatic growth process in psychologically healthy people. Data were collected using semi-structured interviews. Thematic analysis revealed four themes describing participants’ experiences of growth: New possibilities, reappraisal of life and priorities, positive changes in self-perception and closer more meaningful relationships. Themes describing posttraumatic growth provide evidence for research question one. Thematic analysis revealed three main themes and multiple subthemes that may facilitate the process of growth in psychologically healthy people: Hardship, optimistic positive appraisal and people helping people. Themes describing processes that may lead to growth provide evidence for research question two. Results of the current study provide insights about the experience of growth in psychologically healthy people and cognitive and psychosocial factors that may facilitate growth in resilient individuals.
Semi-empirical models based on in-situ geotechnical tests have become the standard of practice for predicting soil liquefaction. Since the inception of the “simplified” cyclic-stress model in 1971, variants based on various in-situ tests have been developed, including the Cone Penetration Test (CPT). More recently, prediction models based soley on remotely-sensed data were developed. Similar to systems that provide automated content on earthquake impacts, these “geospatial” models aim to predict liquefaction for rapid response and loss estimation using readily-available data. This data includes (i) common ground-motion intensity measures (e.g., PGA), which can either be provided in near-real-time following an earthquake, or predicted for a future event; and (ii) geospatial parameters derived from digital elevation models, which are used to infer characteristics of the subsurface relevent to liquefaction. However, the predictive capabilities of geospatial and geotechnical models have not been directly compared, which could elucidate techniques for improving the geospatial models, and which would provide a baseline for measuring improvements. Accordingly, this study assesses the realtive efficacy of liquefaction models based on geospatial vs. CPT data using 9,908 case-studies from the 2010-2016 Canterbury earthquakes. While the top-performing models are CPT-based, the geospatial models perform relatively well given their simplicity and low cost. Although further research is needed (e.g., to improve upon the performance of current models), the findings of this study suggest that geospatial models have the potential to provide valuable first-order predictions of liquefaction occurence and consequence. Towards this end, performance assessments of geospatial vs. geotechnical models are ongoing for more than 20 additional global earthquakes.
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.
Documenting earthquake-induced ground deformation is significant to assess the characteristics of past and contemporary earthquakes and provide insight into seismic hazard. This study uses airborne light detection and ranging (LiDAR) and conducts multi-disciplinary field techniques to document the surface rupture morphology and evaluate the paleoseismicity and seismic hazard parameters of the Hurunui segment of the Hope Fault in the northern South Island of New Zealand. It also documents and evaluates seismically induced features and ground motion characteristics of the 2010 Darfield and 2011 Christchurch earthquakes in the Port Hills, south of Christchurch. These two studies are linked in that they investigate the near-field coseismic features of large (Mw ~7.1) earthquakes in New Zealand and produce data for evaluating seismic hazards of future earthquakes. In the northern South Island of New Zealand, the Australian-Pacific plate boundary is characterised by strike-slip deformation across the Marlborough Fault System (MFS). The ENE-striking Hope Fault (length: ~230 km) is the youngest and southernmost fault in the MFS, and the second fastest slipping fault in New Zealand. The Hope Fault is a major source of seismic hazard in New Zealand and has ruptured (in-part) historically in the Mw 7.1 1888 Amuri earthquake. In the west, the Hurunui segment of the Hope Fault is covered by beech forest. Hence, its seismic hazard parameters and paleoearthquake chronology were poorly constrained and it was unknown whether the 1888 earthquake ruptured this segment or not and if so, to what extent. Utilising LiDAR and field data, a 29 km-long section of the Hurunui segment of the Hope Fault is mapped. LiDAR-mapping clearly reveals the principal slip zone (PSZ) of the fault and a suite of previously unrecognised structures that form the fault deformation zone (FDZ). FDZ width measurements from 415 locations reveal a spatially-variable, active FDZ up to ~500 m wide with an average width of 200 m. Kinematic analysis of the fault structures shows that the Hurunui segment strikes between 070° and 075° and is optimally oriented for dextral strike-slip within the regional stress field. This implies that the wide FDZ observed is unlikely to result from large-scale fault mis-orientation with respect to regional stresses. The analysis of FDZ width indicates that it increases with increased hanging wall topography and increased topographic relief suggesting that along-strike topographic perturbations to fault geometry and stress states increase fault zone complexity and width. FDZ width also increases where the tips of adjacent PSZ strands locally vary in strike, and where the thickness of alluvial deposits overlying bedrock increases. LiDAR- and photogrammetrically-derived topographic mapping indicates that the boundary between the Hurunui and Hope River segments is characterised by a ~850-m-wide right stepover and a 9º-14° fault bend. Paleoseismic trenching at Hope Shelter site reveals that 6 earthquakes occurred at A.D. 1888, 1740-1840, 1479-1623, 819-1092, 439-551, and 373- 419. These rupture events have a mean recurrence interval of ~298 ± 88 yr and inter-event times ranging from 98 to 595 yrs. The variation in the inter-event times is explained by (1) coalescing rupture overlap from the adjacent Hope River segment on to the Hurunui segment at the study site, (2) temporal clustering of large earthquakes on the Hurunui segment, and/or (3) ‘missing’ rupture events. It appears that the first two options are more plausible to explain the earthquake chronologies and rupture behaviour on the Hurunui segment, given the detailed nature of the geologic and chronologic investigations. This study provides first evidence for coseismic multi-segment ruptures on the Hope Fault by identifying a rupture length of 44-70 km for the 1888 earthquake, which was not confined to the Hope River segment (primary source for the 1888 earthquake). LiDAR data is also used to identify and measure dextral displacements and scarp heights from the PSZ and structures within the FDZ along the Hurunui segment. Reconstruction of large dextrally-offset geomorphic features shows that the vertical component of slip accounts for only ~1% of the horizontal displacements and confirms that the fault is predominantly strike-slip. A strong correlation exists between the dextral displacements and elevations of geomorphic features suggesting the possibility of age correlation between the geomorphic features. A mean single event displacement (SED) of 3.6 ± 0.7 m is determined from interpretation of sets of dextral displacements of ≤ 25 m. Using the available surface age data and the cumulative dextral displacements from Matagouri Flat, McKenzie Fan, Macs Knob and Hope River sites, and the mean SED, a mean slip rate of 12.2 ± 2.4 mm/yr, and a mean recurrence interval of ~320 ± 120 yr, and a potential earthquake magnitude of Mw 7.2 are determined for the Hurunui segment. This study suggests that the fault slip rate has been constant over the last ~15000 yr. Strong ground motions from the 2010 Darfield (Canterbury) earthquake displaced boulders and caused ground damage on some ridge crests in the Port Hills. However, the 2011 Christchurch earthquake neither displaced boulders nor caused ground damage at the same ridge crests. Documentation of locations (~400 m a.s.l.), lateral displacements (8-970 cm), displacement direction (250° ± 20°) of displaced boulders, in addition to their hosting socket geometries (< 1 cm to 50 cm depth), the orientation of the ridges (000°-015°) indicate that boulders have been displaced in the direction of instrumentally recorded transient peak ground horizontal displacements nearby and that the seismic waves have been amplified at the study sites. The co-existence of displaced and non-displaced boulders at proximal sites suggests small-scale ground motion variability and/or varying boulder-ground dynamic interactions relating to shallow phenomena such as variability in soil depth, bedrock fracture density and/or microtopography on the bedrock-soil interface. Shorter shaking duration of the 2011 Christchurch event, differing frequency contents and different source characteristics were all factors that may have contributed to generating circumstances less favourable to boulder displacement in this earthquake. Investigating seismically induced features, fault behaviour, site effects on the rupture behaviour, and site response to the seismic waves provides insights into fault rupture hazards.
Following the devastation of the Canterbury earthquake sequence a unique opportunity exists to rebuild and restructure the city of Christchurch, ensuring that its infrastructure is constructed better than before and is innovative. By installing an integrated grid of modern sensor technologies into concrete structures during the rebuild of the Christchurch CBD, the aim is to develop a network of self-monitored ‘digital buildings’. A diverse range of data will be recorded, potentially including parameters such as concrete stresses, strains, thermal deformations, acoustics and the monitoring of corrosion of reinforcement bars. This procedure will allow an on-going complete assessment of the structure’s performance and service life, both before and after seismic activity. The data generated from the embedded and surface mounted sensors will be analysed to allow an innovative and real-time health monitoring solution where structural integrity is continuously known. This indication of building performance will allow the structure to alert owners, engineers and asset managers of developing problems prior to failure thresholds being reached. A range of potential sensor technologies for monitoring the performance of existing and newly constructed concrete buildings is discussed. A description of monitoring work conducted on existing buildings during the July 2013 Cook Strait earthquake sequence is included, along with details of current work that investigates the performance of sensing technologies for detecting crack formation in concrete specimens. The potential market for managing the real-time health of installed infrastructure is huge. Civil structures all over the world require regular visual inspections in order to determine their structural integrity. The information recorded during the Christchurch rebuild will generate crucial data sets that will be beneficial in understanding the behaviour of concrete over the complete life cycle of the structure, from construction through to operation and building repairs until the time of failure. VoR - Version of Record
This study explored the effects of the Canterbury earthquakes of 2010 and 2011 on different areas of quality of life (QOL) for children and adolescents with disabilities. Using a survey developed from the Quality of Life Instrument for People with Developmental Disabilities – Short Version (QOL-PDD-SV) (Brown, Raphael & Renwick, 1997) and The World Health Organisation Quality of Life - (WHOQOL)-BREF, parents or caregivers were asked to identify what level of importance and satisfaction their child or adolescent placed on areas of QOL including physical health, psychological health - stress levels and coping ability, attachment to their neighbourhood, friends, family, leisure activities, community access and schooling. They were also asked to determine what level of impact the earthquakes had had on each area of their child or adolescent’s life and overall quality of life in the aftermath of the earthquakes. A total of 31 parents of 22 males and 9 females between the ages of 2.5 years to 19 years of age (mean age: 12.6 years) responded. The results were collated and analysis was run to measure for the effect of age, gender and geographical location. The results found that the earthquakes affected nearly every area of QOL for the children and adolescents. The biggest impact on the children’s psychological health and their ability to cope It was observed that younger children (<13) were more likely to record improved or lessened effects from the earthquakes in psychological health areas. However, the areas of social belonging and friendships were the least affected by the earthquakes. Female children were more likely to indicate higher scores for social belonging after the earthquakes. Many parents observed that their children developed improved coping skills over the earthquake period. The findings in this study offer a better understanding of how earthquakes can affect the quality of life children and adolescents with disabilities.
