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.
In September 2010 and February 2011, the Canterbury region experienced devastating earthquakes with an estimated economic cost of over NZ$40 billion (Parker and Steenkamp, 2012; Timar et al., 2014; Potter et al., 2015). The insurance market played an important role in rebuilding the Canterbury region after the earthquakes. Homeowners, insurance and reinsurance markets and New Zealand government agencies faced a difficult task to manage the rebuild process. From an empirical and theoretic research viewpoint, the Christchurch disaster calls for an assessment of how the insurance market deals with such disasters in the future. Previous studies have investigated market responses to losses in global catastrophes by focusing on the insurance supply-side. This study investigates both demand-side and supply-side insurance market responses to the Christchurch earthquakes. Despite the fact that New Zealand is prone to seismic activities, there are scant previous studies in the area of earthquake insurance. This study does offer a unique opportunity to examine and document the New Zealand insurance market response to catastrophe risk, providing results critical for understanding market responses after major loss events in general. A review of previous studies shows higher premiums suppress demand, but how higher premiums and a higher probability of risk affect demand is still largely unknown. According to previous studies, the supply of disaster coverage is curtailed unless the market is subsidised, however, there is still unsettled discussion on why demand decreases with time from the previous disaster even when the supply of coverage is subsidised by the government. Natural disaster risks pose a set of challenges for insurance market players because of substantial ambiguity associated with the probability of such events occurring and high spatial correlation of catastrophe losses. Private insurance market inefficiencies due to high premiums and spatially concentrated risks calls for government intervention in the provision of natural disaster insurance to avert situations of noninsurance and underinsurance. Political economy considerations make it more likely for government support to be called for if many people are uninsured than if few people are uninsured. However, emergency assistance for property owners after catastrophe events can encourage most property owners to not buy insurance against natural disaster and develop adverse selection behaviour, generating larger future risks for homeowners and governments. On the demand-side, this study has developed an intertemporal model to examine how demand for insurance changes post-catastrophe, and how to model it theoretically. In this intertemporal model, insurance can be sought in two sequential periods of time, and at the second period, it is known whether or not a loss event happened in period one. The results show that period one demand for insurance increases relative to the standard single period model when the second period is taken into consideration, period two insurance demand is higher post-loss, higher than both the period one demand and the period two demand without a period one loss. To investigate policyholders experience from the demand-side perspective, a total of 1600 survey questionnaires were administered, and responses from 254 participants received representing a 16 percent response rate. Survey data was gathered from four institutions in Canterbury and is probably not representative of the entire population. The results of the survey show that the change from full replacement value policy to nominated replacement value policy is a key determinant of the direction of change in the level of insurance coverage after the earthquakes. The earthquakes also highlighted the plight of those who were underinsured, prompting policyholders to update their insurance coverage to reflect the estimated cost of re-building their property. The survey has added further evidence to the existing literature, such as those who have had a recent experience with disaster loss report increased risk perception if a similar event happens in future with females reporting a higher risk perception than males. Of the demographic variables, only gender has a relationship with changes in household cover. On the supply-side, this study has built a risk-based pricing model suitable to generate a competitive premium rate for natural disaster insurance cover. Using illustrative data from the Christchurch Red-zone suburbs, the model generates competitive premium rates for catastrophe risk. When the proposed model incorporates the new RMS high-definition New Zealand Earthquake Model, for example, insurers can find the model useful to identify losses at a granular level so as to calculate the competitive premium. This study observes that the key to the success of the New Zealand dual insurance system despite the high prevalence of catastrophe losses are; firstly the EQC’s flat-rate pricing structure keeps private insurance premiums affordable and very high nationwide homeowner take-up rates of natural disaster insurance. Secondly, private insurers and the EQC have an elaborate reinsurance arrangement in place. By efficiently transferring risk to the reinsurer, the cost of writing primary insurance is considerably reduced ultimately expanding primary insurance capacity and supply of insurance coverage.
Access to clean and safe drinking water is a fundamental human requirement. However, in many areas of the world natural water sources have been impacted by a variety of biological and chemical contaminants. The ingestion of these contaminants may cause acute or chronic health problems. To prevent such illnesses, many technologies have been developed to treat, disinfect and supply safe drinking water quality. However, despite these advancements, water supply distribution systems can adversely affect the drinking water quality before it is delivered to consumers. The primary aim of this research was to investigate the effect that water distribution systems may have on household drinking water quality in Christchurch, New Zealand and Addis Ababa, Ethiopia. Water samples were collected from the source water and household taps in both cities. The samples were then tested for various physical, chemical and biological water quality parameters. The data collected was also used to determine if water samples complied with national drinking water quality standards in both countries. Independent samples t-test statistical analyses were also performed to determine if water quality measured in the samples collected from the source and household taps was significantly different. Water quality did not vary considerably between the source and tap water samples collected in Christchurch City. No bacteria were detected in any sample. However, the pH and total iron concentrations measured in source and tap water samples were found to be significantly different. The lower pH values measured in tap water samples suggests that corrosion may be taking place in the distribution system. No water samples transgressed the Drinking Water Standards for New Zealand (DWSNZ) MAVs. Monitoring data collected by the Christchurch City Council (CCC) was also used for comparison. A number of pH, turbidity and total iron concentration measurements collected by the CCC in 2011 were found to exceed the guideline values. This is likely due to structural damage to the source wells and pump-stations that occurred during the 2011 earthquake events. Overall, it was concluded that the distribution system does not adversely affect the quality of Christchurch City’s household drinking water. The water quality measured in samples collected from the source (LTP) and household taps in Addis Ababa was found to vary considerably. The water collected from the source complied with the Ethiopian (WHO) drinking water quality standards. However, tap water samples were often found to have degraded water quality for the physical and chemical parameters tested. This was especially the case after supply interruption and reinstatement events. Bacteria were also often detected in household tap water samples. The results from this study indicate that water supply disruptions may result in degraded water quality. This may be due to a drop in pipeline pressure and the intrusion of contaminants through the leaky and cross-connected pipes in the distribution network. This adversely affects the drinking water quality in Addis Ababa.
In recent years, significant research has been undertaken into the development of lead-extrusion damping technology. The high force-to-volume (HF2V) devices developed at the University of Canterbury have been the subject of much of this research. However, while these devices have undergone a limited range of velocity testing, limitations in test equipment has meant that they have never been tested at representative earthquake velocities. Such testing is important as the peak resistive force provided by the dampers under large velocity spikes is an important design input that must be known for structural applications. This manuscript presents the high-speed testing of HF2V devices with quasi-static force capacities of 250-300kN. These devices have been subjected to peak input velocities of approximately 200mm/s, producing peak resistive forces of approximately 350kN. The devices show stable hysteretic performance, with slight force reduction during high-speed testing due to heat build-up and softening of the lead working material. This force reduction is recovered following cyclic loading as heat is dissipated and the lead hardens again. The devices are shown to be only weakly velocity dependent, an advantage in that they do not deliver large forces to the connecting elements and surrounding structure if larger than expected response velocities occur. This high-speed testing is an important step towards uptake as it provides important information to designers.
In recent years, significant research has been undertaken into the development of lead-extrusion damping technology. The high force-to-volume (HF2V) devices developed at the University of Canterbury have been the subject of much of this research. However, while these devices have undergone a limited range of velocity testing, limitations in test equipment has meant that they have never been tested at representative earthquake velocities. Such testing is important as the peak resistive force provided by the dampers under large velocity spikes is an important design input that must be known for structural applications. This manuscript presents the high-speed testing of HF2V devices with quasi-static force capacities of 250-300kN. These devices have been subjected to peak input velocities of approximately 200mm/s, producing peak resistive forces of approximately 350kN. The devices show stable hysteretic performance, with slight force reduction during high-speed testing due to heat build-up and softening of the lead working material. This force reduction is recovered following cyclic loading as heat is dissipated and the lead hardens again. The devices are shown to be only weakly velocity dependent, an advantage in that they do not deliver large forces to the connecting elements and surrounding structure if larger than expected response velocities occur. This high-speed testing is an important step towards uptake as it provides important information to designers.
The 4th of September 2010 Mw 7.1 Darfield (Canterbury) earthquake had generated significant ground shaking within the Christchurch Central Business District (CBD). Despite the apparently significant shaking, the observed structural damage for pre-1970s reinforced concrete (RC) buildings was indeed limited and lower than what was expected for such typology of buildings. This paper explores analytically and qualitatively the different aspects of the "apparent‟ good seismic performance of the pre-1970s RC buildings in the Christchurch CBD, following the earthquake reconnaissance survey by the authors. Damage and building parameters survey result, based on a previously established inventory of building stock of these non-ductile RC buildings, is briefly reported. From an inventory of 75 buildings, one building was selected as a numerical case-study to correlate the observed damage with the non-linear analyses. The result shows that the pre-1970s RC frame buildings performed as expected given the intensity of the ground motion shaking during the Canterbury earthquake. Given the brittle nature of this type of structure, it was demonstrated that more significant structural damage and higher probability of collapse could occur when the buildings were subjected to alternative input signals with different frequency content and duration characteristics and still compatible to the seismicity hazard for Christchurch CBD.
Over 900 buildings in the Christchurch central business district and 10,000 residential homes were demolished following the 22nd of February 2011 Canterbury earthquake, significantly disrupting the rebuild progress. This study looks to quantify the time required for demolitions during this event which will be useful for future earthquake recovery planning. This was done using the Canterbury Earthquake Recovery Authority (CERA) demolition database, which allowed an in-depth look into the duration of each phase of the demolition process. The effect of building location, building height, and the stakeholder which initiated the demolition process (i.e. building owner or CERA) was investigated. The demolition process comprises of five phases; (i) decision making, (ii) procurement and planning, (iii) demolition, (iv) site clean-up, and (v) completion certification. It was found that the time required to decide to demolish the building made up majority of the total demolition duration. Demolition projects initiated by CERA had longer procurement and planning durations, but was quicker in other phases. Demolished buildings in the suburbs had a longer decision making duration, but had little effect on other phases of the demolition process. The decision making and procurement and planning phases of the demolition process were shorter for taller buildings, though the other phases took longer. Fragility functions for the duration of each phase in the demolition process are provided for the various categories of buildings for use in future studies.
Recent earthquakes in New Zealand proved that a shift is necessary in the current design practice of structures to achieve better seismic performance. Following such events, the number of new buildings using innovative technical solutions (e.g. base isolation, controlled rocking systems, damping devices, etc.), has increased, especially in Christchurch. However, the application of these innovative technologies is often restricted to medium-high rise buildings due to the maximum benefit to cost ratio. In this context, to address this issue, a multi-disciplinary geo-structural-environmental engineering project funded by the Ministry of Business Innovation and Employment (MBIE) is being carried out at the University of Canterbury. The project aims at developing a foundation system which will improve the seismic performance of medium-density low-rise buildings. Such foundation is characterized by two main elements: 1) granulated tyre rubber mixed with gravelly soils to be placed beneath the structure, with the goal of damping part of the seismic energy before it reaches the superstructure; and 2) a basement raft made of steel-fibre rubberised concrete to enhance the flexibility of the foundation under differential displacement demand. In the first part of this paper, the overarching objectives, scope and methodology of the project will be briefly described. Then, preliminary findings on the materials characterization, i.e., the gravel-rubber mixtures and steel-fibre rubberised concrete mixes, will be presented and discussed with focus on the mechanical behaviour.
Liquefaction of sandy soil has been observed to cause significant damage to infrastructure during major earthquakes. Historical cases of liquefaction have typically occurred in sands containing some portion of fines particles, which are defined as 75μm or smaller in diameter. The effects of fines on the undrained behaviour of sand are not however fully understood, and this study therefore attempts to quantify these effects through the undrained testing of sand mixed with non-plastic fines sourced from Christchurch, New Zealand. The experimental program carried out during this study consisted of undrained monotonic and cyclic triaxial tests performed on three different mixtures of sand and fines: the Fitzgerald Bridge mixture (FBM), and two Pinnacles Sand mixtures (PSM1 and PSM2). The fines content of each host sand was systematically varied up to a maximum of 30%, with all test specimens being reconstituted using moist tamping deposition. The undrained test results from the FBM soils were interpreted using a range of different measures of initial state. When using void ratio and relative density, the addition of fines to the FBM sand caused more contractive behaviour for both monotonic and cyclic loadings. This resulted in lower strengths at the steady state of deformation, and lower liquefaction resistances. When the intergranular void ratio was used for the interpretation, the effect of additional fines was to cause less contractive response in the sand. The state parameter and state index were also used to interpret the undrained cyclic test results – these measures suggested that additional fines caused less contractive sand behaviour, the opposite to that observed when using the void ratio. This highlighted the dependency on the parameter chosen as a basis for the response comparison when determining the effects of fines, and pointed out a need to identify a measure that normalizes such effects. Based on the FBM undrained test results and interpretations, the equivalent granular void ratio, e*, was identified from the literature as a measure of initial state that normalizes the effects of fines on the undrained behaviour of sand up to a fines content of 30%. This is done through a parameter within the e* definition termed the fines influence factor, b, which quantifies the effects of fines from a value of zero (no effect) to one (same effect as sand particles). The value of b was also determined to be different when interpreting the steady state lines (bSSL) and cyclic resistance curves (bCR) respectively for a given mixture of sand and fines. The steady state lines and cyclic resistance curves of the FBM soils and a number of other sand-fines mixtures sourced from the literature were subsequently interpreted using the equivalent granular void ratio concept, with bSSL and bCR values being back-calculated from the respective test data sets. Based on these interpretations, it was concluded that e* was conceptually a useful parameter for characterizing and quantifying the effects of fines on the undrained behaviour of sand, assuming the fines influence factor value could be derived. To allow prediction of the fines influence factor values, bSSL and bCR were correlated with material and depositional properties of the presented sand-fines mixtures. It was found that as the size of the fines particles relative to the sand particles became smaller, the values of bSSL and bCR reduced, indicating lower effect of fines. The same trend was also observed as the angularity of the sand particles increased. The depositional method was found to influence the value of bCR, due to the sensitivity of cyclic loading to initial soil fabric. This led to bSSL being used as a reference for the effect of fines, with specimens prepared by moist tamping having bCR > bSSL, and specimens prepared by slurry deposition having bCR < bSSL. Finally the correlations of the fines influence factor values with material and depositional properties were used to define the simplified estimation method – a procedure capable of predicting the approximate steady state lines and cyclic resistance curves of a sand as the non-plastic fines content is increased up to 30%. The method was critically reviewed based on the undrained test results of the PSM1 and PSM2 soils. This review suggested the method could accurately predict undrained response curves as the fines content was raised, based on the PSM1 test results. It also however identified some key issues with the method, such as the inability to accurately predict the responses of highly non-uniform soils, a lack of consideration for the entire particle size distribution of a soil, and the fact the errors in the prediction of bSSL carry through into the prediction of bCR. Lastly some areas of further investigation relating to the method were highlighted, including the need to verify the method through testing of sandy soils sourced from outside the Christchurch area, and the need to correlate the value of bCR with additional soil fabrics / depositional methods.
Deformational properties of soil, in terms of modulus and damping, exert a great influence on seismic response of soil sites. However, these properties for sands containing some portion of fines particles have not been systematically addressed. In addition, simultaneous modelling of the modulus and damping behaviour of soils during cyclic loading is desirable. This study presents an experimental and computational investigation into the deformational properties of sands containing fines content in the context of site response analysis. The experimental investigation is carried on sandy soils sourced from Christchurch, New Zealand using a dynamic triaxial apparatus while the computational aspect is based on the framework of total-stress one-dimensional (1D) cyclic behaviour of soil. The experimental investigation focused on a systematic study on the deformational behaviour of sand with different amounts of fines content (particle diameter ≤ 75µm) under drained conditions. The silty sands were prepared by mixing clean sand with three different percentages of fines content. A series of bender element tests at small-strain range and stress-controlled dynamic triaxial tests at medium to high-strain ranges were conducted on samples of clean sand and silty sand. This allowed measurements of linear and nonlinear deformational properties of the same specimen for a wide strain range. The testing program was designed to quantify the effects of void ratio and fines content on the low-strain stiffness of the silty sand as well as on the nonlinear stress-strain relationship and corresponding shear modulus and damping properties as a function of cyclic shear strains. Shear wave velocity, Vs, and maximum shear modulus, Gmax, of silty sand was shown to be significantly smaller than the respective values for clean sands measured at the same void ratio, e, or same relative density, Dr. However, the test results showed that the difference in the level of nonlinearity between clean sand and silty sands was small. For loose samples prepared at an identical relative density, the behaviour of clean sand was slightly less nonlinear as compared to sandy soils with higher fines content. This difference in the nonlinear behaviour of clean sand and sandy soils was negligible for dense soils. Furthermore, no systematic influence of fines content on the material damping curve was observed for sands with fines content FC = 0 to 30%. In order to normalize the effects of fines on moduli of sands, equivalent granular void ratio, e*, was employed. This was done through quantifying the participation of fines content in the force transfer chain of the sand matrix. As such, a unified framework for modelling of the variability of shear wave velocity, Vs, (or shear modulus, Gmax) with void ratio was achieved for clean sands and sands with fines, irrespective of their fines content. Furthermore, modelling of the cyclic stress-strain behaviour based on this experimental program was investigated. The modelling effort focused on developing a simple constitutive model which simultaneously models the soil modulus and damping relationships with shear strains observed in laboratory tests. The backbone curve of the cyclic model was adopted based on a modified version of Kondner and Zelasko (MKZ) hyperbolic function, with a curvature coefficient, a. In order to simulate the hysteretic cycles, the conventional Masing rules (Pyke 1979) were revised. The parameter n, in the Masing’s criteria was assumed to be a function of material damping, h, measured in the laboratory. As such the modulus and damping produced by the numerical model could match the stress-strain behaviour observed in the laboratory over the course of this study. It was shown that the Masing parameter n, is strain-dependent and generally takes values of n ≤ 2. The model was then verified through element test simulations under different cyclic loadings. It was shown that the model could accurately simulate the modulus and the damping simultaneously. The model was then incorporated within the OpenSees computational platform and was used to scrutinize the effects of damping on one-dimensional seismic site response analysis. For this purpose, several strong motion stations which recorded the Canterbury earthquake sequence were selected. The soil profiles were modelled as semi-infinite horizontally layered deposits overlying a uniform half-space subjected to vertically propagating shear waves. The advantages and limitations of the nonlinear model in terms of simulating soil nonlinearity and associated material damping were further scrutinized. It was shown that generally, the conventional Masing criteria unconservatively may underestimate some response parameters such as spectral accelerations. This was shown to be due to larger hysteretic damping modelled by using conventional Masing criteria. In addition, maximum shear strains within the soil profiles were also computed smaller in comparison to the values calculated by the proposed model. Further analyses were performed to study the simulation of backbone curve beyond the strain ranges addressed in the experimental phase of this study. A key issue that was identified was that relying only on the modulus reduction curves to simulate the stress-strain behaviour of soil may not capture the actual soil strength at larger strains. Hence, strength properties of the soil layer should also be incorporated to accurately simulate the backbone curve.
As a consequence of the 2010 – 2011 Canterbury earthquake sequence, Christchurch experienced widespread liquefaction, vertical settlement and lateral spreading. These geological processes caused extensive damage to both housing and infrastructure, and increased the need for geotechnical investigation substantially. Cone Penetration Testing (CPT) has become the most common method for liquefaction assessment in Christchurch, and issues have been identified with the soil behaviour type, liquefaction potential and vertical settlement estimates, particularly in the north-western suburbs of Christchurch where soils consist mostly of silts, clayey silts and silty clays. The CPT soil behaviour type often appears to over-estimate the fines content within a soil, while the liquefaction potential and vertical settlement are often calculated higher than those measured after the Canterbury earthquake sequence. To investigate these issues, laboratory work was carried out on three adjacent CPT/borehole pairs from the Groynes Park subdivision in northern Christchurch. Boreholes were logged according to NZGS standards, separated into stratigraphic layers, and laboratory tests were conducted on representative samples. Comparison of these results with the CPT soil behaviour types provided valuable information, where 62% of soils on average were specified by the CPT at the Groynes Park subdivision as finer than what was actually present, 20% of soils on average were specified as coarser than what was actually present, and only 18% of soils on average were correctly classified by the CPT. Hence the CPT soil behaviour type is not accurately describing the stratigraphic profile at the Groynes Park subdivision, and it is understood that this is also the case in much of northwest Christchurch where similar soils are found. The computer software CLiq, by GeoLogismiki, uses assessment parameter constants which are able to be adjusted with each CPT file, in an attempt to make each more accurate. These parameter changes can in some cases substantially alter the results for liquefaction analysis. The sensitivity of the overall assessment method, raising and lowering the water table, lowering the soil behaviour type index, Ic, liquefaction cutoff value, the layer detection option, and the weighting factor option, were analysed by comparison with a set of ‘base settings’. The investigation confirmed that liquefaction analysis results can be very sensitive to the parameters selected, and demonstrated the dependency of the soil behaviour type on the soil behaviour type index, as the tested assessment parameters made very little to no changes to the soil behaviour type plots. The soil behaviour type index, Ic, developed by Robertson and Wride (1998) has been used to define a soil’s behaviour type, which is defined according to a set of numerical boundaries. In addition to this, the liquefaction cutoff point is defined as Ic > 2.6, whereby it is assumed that any soils with an Ic value above this will not liquefy due to clay-like tendencies (Robertson and Wride, 1998). The method has been identified in this thesis as being potentially unsuitable for some areas of Christchurch as it was developed for mostly sandy soils. An alternative methodology involving adjustment of the Robertson and Wride (1998) soil behaviour type boundaries is proposed as follows: Ic < 1.31 – Gravelly sand to dense sand 1.31 < Ic < 1.90 – Sands: clean sand to silty sand 1.90 < Ic < 2.50 – Sand mixtures: silty sand to sandy silt 2.50 < Ic < 3.20 – Silt mixtures: clayey silt to silty clay 3.20 < Ic < 3.60 – Clays: silty clay to clay Ic > 3.60 – Organics soils: peats. When the soil behaviour type boundary changes were applied to 15 test sites throughout Christchurch, 67% showed an improved change of soil behaviour type, while the remaining 33% remained unchanged, because they consisted almost entirely of sand. Within these boundary changes, the liquefaction cutoff point was moved from Ic > 2.6 to Ic > 2.5 and altered the liquefaction potential and vertical settlement to more realistic ii values. This confirmed that the overall soil behaviour type boundary changes appear to solve both the soil behaviour type issues and reduce the overestimation of liquefaction potential and vertical settlement. This thesis acts as a starting point towards researching the issues discussed. In particular, future work which would be useful includes investigation of the CLiq assessment parameter adjustments, and those which would be most suitable for use in clay-rich soils such as those in Christchurch. In particular consideration of how the water table can be better assessed when perched layers of water exist, with the limitation that only one elevation can be entered into CLiq. Additionally, a useful investigation would be a comparison of the known liquefaction and settlements from the Canterbury earthquake sequence with the liquefaction and settlement potentials calculated in CLiq for equivalent shaking conditions. This would enable the difference between the two to be accurately defined, and a suitable adjustment applied. Finally, inconsistencies between the Laser-Sizer and Hydrometer should be investigated, as the Laser-Sizer under-estimated the fines content by up to one third of the Hydrometer values.
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.
The NMIT Arts & Media Building is the first in a new generation of multistorey timber structures. It employs an advanced damage avoidance earthquake design that is a world first for a timber building. Aurecon structural engineers are the first to use this revolutionary Pres-Lam technology developed at the University of Canterbury. This technology marks a fundamental change in design philosophy. Conventional seismic design of multi-storey structures typically depends on member ductility and the acceptance of a certain amount of damage to beams, columns and walls. The NMIT seismic system relies on pairs of coupled LVL shear walls that incorporate high strength steel tendons post-tensioned through a central duct. The walls are centrally fixed allowing them to rock during a seismic event. A series of U-shaped steel plates placed between the walls form a coupling mechanism, and act as dissipators to absorb seismic energy. The design allows the primary structure to remain essentially undamaged while readily replaceable connections act as plastic fuses. In this era where sustainability is becoming a key focus, the extensive use of timber and engineered-wood products such as LVL make use of a natural resource all grown and manufactured within a 100km radius of Nelson. This project demonstrates that there are now cost effective, sustainable and innovative solutions for multi-story timber buildings with potential applications for building owners in seismic areas around the world.
It is fast becoming common practice for civil engineering infrastructure and building structures to be designed to achieve a set of performance objectives. To do so, consideration is now being given to systems capable of sustaining minimal damage after an earthquake while still being cost competitive. This has led to the development of high performance seismic resisting systems, followed by advances in design methodologies. The paper presents the experimental response of four pre-cast, post-tensioned rocking walls with high-performing dissipating solutions tested on the shake-table at the University of Canterbury. The wall systems were designed as a retrofit solution for an existing frame building however, can also be used for the design of new, high-performance structures. The use of externally mounted dampers allowed numerous dissipation schemes to be explored including mild-steel dampers (hysteretic dampers), viscous dampers, a combination of both or no dampers. The advantages of both velocity and displacement dependant dissipation was investigated for protection against strong ground motions with differing rupture characteristics i.e. far-field and near-field events. The experimental results are used to verify a proposed design procedure for post-tensioned rocking systems with supplementary hysteretic and viscous dissipation. The predicted response compared well with the measured shake-table response.
This research employs a deterministic seismic risk assessment methodology to assess the potential damage and loss at meshblock level in the Christchurch CBD and Mount Pleasant primarily due to building damage caused by earthquake ground shaking. Expected losses in terms of dollar value and casualties are calculated for two earthquake scenarios. Findings are based on: (1) data describing the earthquake ground shaking and microzonation effects; (2) an inventory of buildings by value, floor area, replacement value, occupancy and age; (3) damage ratios defining the performance of buildings as a function of earthquake intensity; (4) daytime and night-time population distribution data and (5) casualty functions defining casualty risk as a function of building damage. A GIS serves as a platform for collecting, storing and analyzing the original and the derived data. It also allows for easy display of input and output data, providing a critical functionality for communication of outcomes. The results of this study suggest that economic losses due to building damage in the Christchurch CBD and Mount Pleasant will possibly be in the order of $5.6 and $35.3 million in a magnitude 8.0 Alpine fault earthquake and a magnitude 7.0 Ashley fault earthquake respectively. Damage to non-residential buildings constitutes the vast majority of the economic loss. Casualty numbers are expected to be between 0 and 10.
This paper presents the probabilistic seismic performance and loss assessment of an actual bridge– foundation–soil system, the Fitzgerald Avenue twin bridges in Christchurch, New Zealand. A two-dimensional finite element model of the longitudinal direction of the system is modelled using advanced soil and structural constitutive models. Ground motions at multiple levels of intensity are selected based on the seismic hazard deaggregation at the site. Based on rigorous examination of several deterministic analyses, engineering demand parameters (EDP’s), which capture the global and local demand, and consequent damage to the bridge and foundation are determined. A probabilistic seismic loss assessment of the structure considering both direct repair and loss of functionality consequences was performed to holistically assess the seismi risk of the system. It was found that the non-horizontal stratification of the soils, liquefaction, and soil–structure interaction had pronounced effects on the seismic demand distribution of the bridge components, of which the north abutment piles and central pier were critical in the systems seismic performance. The consequences due to loss of functionality of the bridge during repair were significantly larger than the direct repair costs, with over a 2% in 50 year probability of the total loss exceeding twice the book-value of the structure.
Following exposure to trauma, stress reactions are initially adaptive. However, some individuals’ psychological response can become maladaptive with long-lasting impairment to functioning. Most people with initial symptoms of stress recover, and thus it is important to distinguish individuals who are at risk of continuing difficulties so that resources are allocated appropriately. Investigations of predictors of PTSD development have largely focused on relational and combat-related trauma, with very limited research looking at natural disasters. This study assessed the nature and severity of psychological difficulties experienced in 101 people seeking treatment following exposure to a significant earthquake that killed 185 people. Peritraumatic dissociation, posttraumatic stress symptoms, symptoms of anxiety, symptoms of depression, and social isolation were assessed. Descriptive analyses revealed the sample to be a highly impaired group, with particularly high levels of posttraumatic stress symptoms. Path analysis was used to determine whether the experience of some psychological difficulties predicted experience of others. As hypothesised, peritraumatic dissociation was found to predict posttraumatic stress symptoms and symptoms of anxiety. Posttraumatic stress symptoms then predicted symptoms of anxiety and symptoms of depression. Depression and anxiety were highly correlated. Contrary to expectations, social isolation was not significantly related to any other psychological variables. These findings justify the provision of psychological support following a natural disaster and suggest the benefit of assessing peritraumatic dissociation and posttraumatic stress symptoms soon after the event to identify people in need of monitoring and intervention.
Mr Wayne Tobeck, Director of Southrim Group (SRG), sponsored this 2013 MEM Project titled; A Technical and Economic Feasibility Study for the Integration of GSHP Technology in the Christchurch Rebuild. Following the recent Christchurch earthquakes, a significant amount of land has become too unstable to support traditional building foundations. This creates an opportunity to implement new and unique foundation designs previously unconsidered due to high costs compared to traditional methods. One such design proposes that an Injection Micro-Piling technique could be used. This can also be coupled with HVAC technology to create a Ground Source Heat Pump (GSHP) arrangement in both new buildings and as retrofits for building requiring foundation repair. The purpose of this study was to complete a feasibility study on the merits of SRG pursuing this proposed product. A significant market for such a product was found to exist, while the product was also found to be technically and legally feasible. However, the proposed product was found to not be economically feasible with respect to Air Source Heat Pumps due to the significantly higher capital and installation costs required. Further analysis suggests GSHPs may become more economically attractive in operating temperatures lower than -9oC, though the existence of markets with this climate in NZ has not been studied. It is therefore suggested that SRG do not proceed with plans to develop a GSHP coupled foundation solution for the Christchurch rebuild.
Tertiary students, not just working populations, might be experiencing feelings of burnout following the Christchurch earthquakes of 2010 and 2011. In the aftermath of a major disaster, the gap between the resources available to handle pressures (e.g., support) and the demands inherent in the pursuit of an academic degree (e.g., heavy workload) may lead to feelings of burnout among students. This study hypothesised that burnout dimensions (emotional exhaustion and disengagement) would be related to students’ perceptions of immediate institutional support, extended institutional support, peer support, family support, and work overload. Additionally, it was proposed that institutional and social support would moderate the relationship between work overload and burnout. Two hundred and seventy one third and fourth year students were sampled using an online questionnaire. These particular students were expected to be at greater risk of emotional exhaustion and academic disengagement because they were at the earliest stage of their tertiary education when the major earthquakes first hit. Family support and extended institutional support were found to be associated with decreased levels of emotional exhaustion and disengagement. Meanwhile, work overload was found to be related to increased levels of emotional exhaustion and disengagement. Furthermore, both peer support and immediate institutional support were found to have a moderating effect on the relationship between work overload and disengagement. This study has exposed unique findings which contribute to burnout research especially in a post-disaster context, and raises the importance of providing the right types of support for individuals who are particularly dealing with the consequences of a natural disaster.
This thesis focuses attention on the ongoing effects of the earthquakes on children in Christchurch. It identifies the learning and behavioural difficulties evident in an increasing number of students and cautions the use of the word 'resilient' to describe children who may be just managing. This assumption has a significant impact on the wellbeing of many Christchurch children who, disaster literature warns, are likely to be under-served. This thesis suggests that, because of the scale of need, schools are the best place to introduce practices that will foster wellbeing. Mindfulness practices are identified as a potential tool for ameliorating the vulnerabilities experienced by children, while at the same time working to increase their capabilities. This thesis argues that, through mindful practices, children can learn to be more reflective of their emotions and respond in more considered ways to different situations. They can become more relational, having a greater understanding of others through a deeper understanding of themselves, and they can build resilience by developing the protective factors that promote more adaptive functioning. This thesis identifies the strong links between mindfulness and the holistic wellbeing concept of Te Whare Tapa Whã and a Mãori worldview. Strong links are also identified with the vision, values and key competencies of the New Zealand Curriculum and 21st Century learners. Both short and long term recommendations are made for the introduction of mindfulness practices in schools to enhance the wellbeing of children.
Despite their good performance in terms of their design objectives, many modern code-prescriptive buildings built in Christchurch, New Zealand had to be razed after the 2010-2011 Canterbury earthquakes because repairs were deemed too costly due to widespread sacrificial damage. Clearly a more effective design paradigm is needed to create more resilient structures. Rocking, post-tensioned connections with supplemental energy dissipation can contribute to a damage avoidance designs (DAD). However, few have achieved all three key design objectives of damage-resistant rocking, inherent recentering ability, and repeatable, damage-free energy dissipation for all cycles, which together offer a response which is independent of loading history. Results of experimental tests are presented for a near full-scale rocking beam-column sub-assemblage. A matrix of test results is presented for the system under varying levels of posttensioning, with and without supplemental dampers. Importantly, this parametric study delineates each contribution to response. Practical limitations on posttensioning are identified: a minimum to ensure static structural re-centering, and a maximum to ensure deformability without threadbar yielding. Good agreement between a mechanistic model and experimental results over all parameters and inputs indicates the model is robust and accurate for design. The overall results indicate that it is possible to create a DAD connection where the non-linear force-deformation response is loading history independent and repeatable over numerous loading cycles, without damage, creating the opportunity for the design and implementation of highly resilient structures.
Base isolation is arguably the most reliable method for providing enhanced protection of buildings against earthquake-induced actions, by virtue of a physical separation between the structure and the ground through elements/devices with controlled force capacity, significant lateral deformation capacity and (often) enhanced energy dissipation. Such a design solution has shown its effectiveness in protecting both structural and non-structural components, hence preserving their functionality even in the aftermath of a major seismic event. Despite lead rubber bearings being invented in New Zealand almost forty years ago, the Christchurch Women's hospital was the only isolated building in Christchurch when the Canterbury earthquake sequence struck in 2010/11. Furthermore, a reference code for designing base-isolated buildings in New Zealand is still missing. The absence of a design standard or at least of a consensus on design guidelines is a potential source for a lack of uniformity in terms of performance criteria and compliance design approaches. It may also limit more widespread use of the technology in New Zealand. The present paper provides an overview of the major international codes (American, Japanese and European) for the design of base-isolated buildings. The design performance requirements, the analysis procedures, the design review process and approval/quality control of devices outlined in each code are discussed and their respective pros and cons are compared through a design application on a benchmark building in New Zealand. The results gathered from this comparison are intended to set the basis for the development of guidelines specific for the New Zealand environment.
Peri-urban environments are critical to the connections between urban and rural ecosystems and their respective communities. Lowland floodplains are important examples that are attractive for urbanisation and often associated with the loss of rural lands and resources. In Christchurch, New Zealand, damage from major earthquakes led to the large-scale abandonment of urban residential properties in former floodplain areas creating a rare opportunity to re-imagine the future of these lands. This has posed a unique governance challenge involving the reassessment of land-use options and a renewed focus on disaster risk and climate change adaptation. Urban-rural tensions have emerged through decisions on relocating residential development, alternative proposals for land uses, and an unprecedented opportunity for redress of degraded traditional values for indigenous (Māori) people. Immediately following the earthquakes, existing statutory arrangements applied to many recovery needs and identified institutional responsibilities. Bespoke legislation was also created to address the scale of impacts. Characteristics of the approach have included attention to information acquisition, iterative assessment of land - use options, and a wide variety of opportunities for community participation. Challenges have included a protracted decision-making process with accompanying transaction costs, and a high requirement for coordination. The case typifies the challenges of achieving ecosystem governance where both urban and rural stakeholders have strong desires and an opportunity to exert influence. It presents a unique context for applying the latest thinking on ecosystem management, adaptation, and resilience, and offers transferable learning for the governance of peri-urban floodplains worldwide.
The greater Wellington region, New Zealand, is highly vulnerable to large earthquakes. While attention has been paid to the consequences of earthquake damage to road, electricity and water supply networks, the consequences of wastewater network damage for public health, environmental health and habitability of homes remain largely unknown for Wellington City. The Canterbury and Kaikōura earthquakes have highlighted the vulnerability of sewerage systems to disruption during a disaster. Management of human waste is one of the critical components of disaster planning to reduce faecal-oral transmission of disease and exposure to disease-bearing vectors. In Canterbury and Kaikōura, emergency sanitation involved a combination of Port-a-loos, chemical toilets and backyard long-drops. While many lessons may be learned from experiences in Canterbury earthquakes, it is important to note that isolation is likely to be a much greater factor for Wellington households, compared to Christchurch, due to the potential for widespread landslides in hill suburbs affecting road access. This in turn implies that human waste may have to be managed onsite, as options such as chemical toilets and Port-a-loos rely completely on road access for delivering chemicals and collecting waste. While some progress has been made on options such as emergency composting toilets, significant knowledge gaps remain on how to safely manage waste onsite. In order to bridge these gaps, laboratory tests will be conducted through the second half of 2019 to assess the pathogen die-off rates in the composting toilet system with variables being the type of carbon bulking material and the addition of a Bokashi composting activator.
Research indicates that aside from the disaster itself, the next major source of adverse outcomes during such events, is from errors by either the response leader or organisation. Yet, despite their frequency, challenge, complexity, and the risks involved; situations of extreme context remain one of the least researched areas in the leadership field. This is perhaps surprising. In the 2010 and 2011 (Christchurch) earthquakes alone, 185 people died and rebuild costs are estimated to have been $40b. Add to this the damage and losses annually around the globe arising from natural disasters, major business catastrophes, and military conflict; there is certainly a lot at stake (lives, way of life, and our well-being). While over the years, much has been written on leadership, there is a much smaller subset of articles on leadership in extreme contexts, with the majority of these focusing on the event rather than leadership itself. Where leadership has been the focus, the spotlight has shone on the actions and capabilities of one person - the leader. Leadership, however, is not simply one person, it is a chain or network of people, delivering outcomes with the support of others, guided by a governance structure, contextualised by the environment, and operating on a continuum across time (before, during, and after an event). This particular research is intended to examine the following: • What are the leadership capabilities and systems necessary to deliver more successful outcomes during situations of extreme context; • How does leadership in these circumstances differ from leadership during business as usual conditions; • Lastly, through effective leadership, can we leverage these unfortunate events to thrive, rather than merely survive?
The 2010-2011 Christchurch earthquakes generated damage in several Reinforced Concrete (RC) buildings, which had RC walls as the principal resistant element against earthquake demand. Despite the agreement between structural engineers and researchers in an overall successfully performance there was a lack of knowledge about the behaviour of the damaged structures, and even deeper about a repaired structure, which triggers arguments between different parties that remains up to these days. Then, it is necessary to understand the capacity of the buildings after the earthquake and see how simple repairs techniques improve the building performance. This study will assess the residual capacity of ductile slender RC walls according to current standards in New Zealand, NZS 3101.1 2006 A3. First, a Repaired RC walls Database is created trying to gather previous studies and to evaluate them with existing international guidelines. Then, an archetype building is designed, and the wall is extracted and scaled. Four half-scale walls were designed and will be constructed and tested at the Structures Testing Laboratory at The University of Auckland. The overall dimensions are 3 [m] height, 2 [m] length and 0.175 [m] thick. All four walls will be identical, with differences in the loading protocol and the presence or absence of a repair technique. Results are going to be useful to assess the residual capacity of a damaged wall compare to the original behaviour and also the repaired capacity of walls with simpler repair techniques. The expected behaviour is focussed on big changes in stiffness, more evident than in previously tested RC beams found in the literature.
Post-earthquake cordons have been used after seismic events around the world. However, there is limited understanding of cordons and how contextual information of place such as geography, socio-cultural characteristics, economy, institutional and governance structure etc. affect decisions, operational procedures as well as spatial and temporal attributes of cordon establishment. This research aims to fill that gap through a qualitative comparative case study of two cities: Christchurch, New Zealand (Mw 6.2 earthquake, February 2011) and L’Aquila, Italy (Mw 6.3 earthquake, 2009). Both cities suffered comprehensive damage to its city centre and had cordons established for extended period. Data collection was done through purposive and snowball sampling methods whereby 23 key informants were interviewed in total. The interviewee varied in their roles and responsibilities i.e. council members, emergency managers, politicians, business/insurance representatives etc. We found that cordons were established to ensure safety of people and to maintain security of place in both the sites. In both cities, the extended cordon was met with resistance and protests. The extent and duration of establishment of cordon was affected by recovery approach taken in the two cities i.e. in Christchurch demolition was widely done to support recovery allowing for faster removal of cordons where as in L’Aquila, due to its historical importance, the approach to recovery was based on saving all the buildings which extended the duration of cordon. Thus, cordons are affected by site specific needs. It should be removed as soon as practicable which could be made easier with preplanning of cordons.
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.
With origins in the South Bronx area of New York in the early 1970s, hip-hop culture is now produced and consumed globally. While hip-hop activities can be varied, hip-hop is generally considered to have four forms or “elements”: DJing, MCing, b-boying/b-girling, and graffiti. Although all four elements of hip-hop have become a part of many youth work initiatives across the globe, public debate and controversy continue to surround hip-hop activities. Very little research and literature has explored the complexities involved in the assembling of hip-hop activities in youth work sites of practice using these hip-hop elements. This study attends to the gap in hip-hop and human service literature by tracing how hip-hop activities were assembled in several sites of youth work activity in Christchurch, New Zealand. Actor-network theory (ANT) is the methodological framework used to map the assemblage of hip-hop-youth work activities in this study. ANT follows how action is distributed across both human and non-human actors. By recognising the potential agency of “things”, this research traces the roles played by human actors, such as young people and youth workers, together with those of non-human actors such as funding documents, social media, clothing, and youth venue equipment. This ethnographic study provides rich descriptions or “snapshots” of some of the key socio-material practices that shaped the enactment of hip-hop-youth work activities. These are derived from fieldwork undertaken between October 2009 and December 2011, where participant observation took place across a range of sites of hip-hop-youth work activity. In addition to this fieldwork, formal interviews were undertaken with 22 participants, the majority being youth workers, young people, and youth trust administrators. The ANT framework reveals the complexity of the task of assembling hip-hop in youth work worlds. The thesis traces the work undertaken by both human and non-human actors in generating youth engagement in hip-hop-youth work activities. Young people’s hip-hop interests are shown to be varied, multiple, and continually evolving. It is also shown how generating youth interest in hip-hop-youth work activities involved overcoming young people’s indifference or lack of awareness of the hip-hop resources a youth trust had on offer. Furthermore, the study highlights where hip-hop activities were edited or “tinkered” with to avoid hip-hop “bads”. The thesis also unpacks how needed resources were enlisted, and how funders’ interests were translated into supporting hip-hop groups and activities. By tracing the range of actors mobilised to enact hip-hop-youth work activities, this research reveals how some youth trusts could avoid having to rely on obtaining government funds for their hip-hop activities. The thesis also includes an examination of one youth trust’s efforts to reconfigure its hip-hop activities after the earthquakes that struck Christchurch city in 2010 and 2011. Working both in and on the world, the text that is this thesis is also understood as an intervention. This study constitutes a deliberate attempt to strengthen understandings of hip-hop as a complex, multiple, and fluid entity. It therefore challenges traditional media and literature representations that simplify and thus either stigmatise or celebrate hip-hop. As such, this study opens up possibilities to consider the opportunities, as well as the complexities of assembling hip-hop in youth work sites of practice.
This thesis studies the behaviour of diaphragms in multi-storey timber buildings by providing methods for the estimation of the diaphragm force demand, developing an Equivalent Truss Method for the analysis of timber diaphragms, and experimentally investigating the effects of displacement incompatibilities between the diaphragm and the lateral load resisting system and developing methods for their mitigation. The need to better understand the behaviour of diaphragms in timber buildings was highlighted by the recent 2010-2011 Canterbury Earthquake series, where a number of diaphragms in traditional concrete buildings performed poorly, compromising the lateral load resistance of the structure. Although shortcomings in the estimation of force demand, and in the analysis and design of concrete floor diaphragms have already been partially addressed by other researchers, the behaviour of diaphragms in modern multi-storey timber buildings in general, and in low damage Pres-Lam buildings (consisting of post-tensioned timber members) in particular is still unknown. The recent demand of mid-rise commercial timber buildings of ten storeys and beyond has further highlighted the lack of appropriate methods to analyse timber diaphragms with irregular floor geometries and large spans made of both light timber framing and massive timber panels. Due to the lower stiffness of timber lateral load resisting systems, compared with traditional construction materials, and the addition of in-plane flexible diaphragms, the effect of higher modes on the global dynamic behaviour of a structure becomes more critical. The results from a parametric non-linear time-history analysis on a series of timber frame and wall structures showed increased storey shear and moment demands even for four storey structures when compared to simplistic equivalent static analysis. This effect could successfully be predicted with methods available in literature. The presence of diaphragm flexibility increased diaphragm inter-storey drifts and the peak diaphragm demand in stiff wall structures, but had less influence on the storey shears and moments. Diaphragm force demands proved to be significantly higher than the forces derived from equivalent static analysis, leading to potentially unsafe designs. It is suggested to design all diaphragms for the same peak demand; a simplified approach to estimate these diaphragm forces is proposed for both frame and wall structures. Modern architecture often requires complex floor geometries with long spans leading to stress concentrations, high force demands and potentially large deformations in the diaphragms. There is a lack of guidance and regulation regarding the analysis and design of timber diaphragms and a practical alternative to the simplistic equivalent deep beam analysis or costly finite element modelling is required. An Equivalent Truss Method for the analysis of both light timber framed and massive timber diaphragms is proposed, based on analytical formulations and verified against finite element models. With this method the panel unit shear forces (shear flow) and therefore the fastener demand, chord forces and reaction forces can be evaluated. Because the panel stiffness and fastener stiffness are accounted for, diaphragm deflection, torsional effects and transfer forces can also be assessed. The proposed analysis method is intuitive and can be used with basic analysis software. If required, it can easily be adapted for the use with diaphragms working in the non-linear range. Damage to floor diaphragms resulting from displacement incompatibilities due to frame elongation or out-of plane deformation of walls can compromise the transfer of inertial forces to the lateral load resisting system as well as the stability of other structural elements. Two post-tensioned timber frame structures under quasi-static cyclic and dynamic load, respectively, were tested with different diaphragm panel layouts and connections investigating their ability to accommodate frame elongations. Additionally, a post-tensioned timber wall was loaded under horizontal cyclic loads through two pairs of collector beams. Several different connection details between the wall and the beams were tested, and no damage to the collector beams or connections was observed in any of the tests. To evaluate the increased strength and stiffness due to the wall-beam interaction an analytical procedure is presented. Finally, a timber staircase core was tested under bi-directional loading. Different connection details were used to study the effect of displacement incompatibilities between the orthogonal collector beams. These experiments showed that floor damage due to displacement incompatibilities can be prevented, even with high levels of lateral drift, by the flexibility of well-designed connections and the flexibility of the timber elements. It can be concluded that the flexibility of timber members and the flexibility of their connections play a major role in the behaviour of timber buildings in general and of diaphragms specifically under seismic loads. The increased flexibility enhances higher mode effects and alters the diaphragm force demand. Simple methods are provided to account for this effect on the storey shear, moment and drift demands as well as the diaphragm force demands. The analysis of light timber framing and massive timber diaphragms can be successfully analysed with an Equivalent Truss Method, which is calibrated by accounting for the panel shear and fastener stiffnesses. Finally, displacement incompatibilities in frame and wall structures can be accommodated by the flexibilities of the diaphragm panels and relative connections. A design recommendations chapter summarizes all findings and allows a designer to estimate diaphragm forces, to analyse the force path in timber diaphragms and to detail the connections to allow for displacement incompatibilities in multi-storey timber buildings.
