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Research papers, University of Canterbury Library

In recent Canterbury earthquakes, structures have performed well in terms of life safety but the estimated total cost of the rebuild was as high as $40 billion. The major contributors to this cost are repair/demolition/rebuild cost, the resulting downtime and business interruption. For this reason, the authors are exploring alternate building systems that can minimize the downtime and business interruption due to building damage in an earthquake; thereby greatly reducing the financial implications of seismic events. In this paper, a sustainable and demountable precast reinforced concrete (RC) frame system in which the precast members are connected via steel tubes/plates or steel angles/plates and high strength friction grip (HSFG) bolts is introduced. In the proposed system, damaged structural elements in seismic frames can be easily replaced with new ones; thereby making it an easily and quickly repairable and a low-loss system. The column to foundation connection in the proposed system can be designed either as fixed or pinned depending on the requirement of strength and stiffness. In a fixed base frame system, ground storey columns will also be damaged along with beams in seismic events, which are to be replaced after seismic events; whereas in a pin base frame only beams (which are easy to replace) will be damaged. Low to medium rise (3-6 storey) precast RC frame buildings with fixed and pin bases are analyzed in this paper; and their lateral capacity, lateral stiffness and natural period are scrutinized to better understand the pros and cons of the demountable precast frame system with fixed and pin base connections.

Research papers, University of Canterbury Library

Based on the recent developments on alternative jointed ductile dry connections for concrete multistorey buildings, the paper aims to extend and propose similar innovative seismic connections for laminated veneer lumber (LVL) timber buildings. The dry connections herein proposed are characterised by a sort of rocking occurring at the section interface of the structural elements when an earthquake occurs; unbonded post-tensioned techniques and dissipative devices respectively provide self-centring and dissipation capacities. The paper illustrates some experimental investigations of an extensive campaign, still undergoing at the University of Canterbury Christchurch, NZ) are herein presented and critically discussed. In particular, results of cyclic quasi-static testing on exterior beam-column subassemblies and wall-to-foundation systems are herein presented; preliminary results of pseudo-dynamic testing on wall-to-foundation specimens are also illustrated. The research investigations confirmed the enhanced seismic performance of these systems/connections; three key aspects , as the no-damageability in the structural elements, typical “flag-shape” cyclic behaviour (with self-centring and dissipation capacity), negligible residual deformations, i.e. limited costs of repair, joined with low mass, flexibility of design and rapidity of construction LVL timber, all create the potential for an increased use in low-rise multistorey buildings.

Research papers, University of Canterbury Library

The objective of this study is to examine the influence of near-fault motions on liquefaction triggering in Christchurch and neighboring towns during the 2010-2011 Canterbury earthquake sequence (CES). The CES began with the 4 September 2010, Mw7.1 Darfield earthquake and included up to ten events that triggered liquefaction. However, most notably, widespread liquefaction was induced by the Darfield earthquake and the Mw6.2, 22 February 2011 Christchurch earthquake. Of particular relevance to this study is the forward directivity effects that were prevalent in the motions recorded during the Darfield earthquake, and to a much lesser extent, during the Christchurch earthquake. A 2D variant of the Richart-Newmark fatigue theory was used to compute the equivalent number of cycles (neq) for the ground motions, where volumetric strain was used as the damage metric. This study is unique because it considers the contribution and phasing of both the fault-normal and fault-parallel components of motion on neq and the magnitude scaling factor (MSF). It was found that when the fault-normal and fault-parallel motions were treated individually, the former yielded a lower neq than the latter. Additionally, when the combined effects of fault-normal and fault-parallel components were considered, it was found that the MSF were higher than those commonly used. This implies that motions containing near-fault effects are less demanding on the soil than motions that do not. This may be one of several factors that resulted in less severe liquefaction occurring during the Darfield earthquake than the Christchurch earthquake.

Research papers, University of Canterbury Library

On 22 February 2011, Canterbury and its largest city Christchurch experienced its second major earthquake within six months. The region is facing major economic and organisational challenges in the aftermath of these events. Approximately 25% of all buildings in the Christchurch CBD have been “red tagged” or deemed unsafe to enter. The New Zealand Treasury estimates that the combined cost of the February earthquake and the September earthquake is approximately NZ$15 billion[2]. This paper examines the national and regional economic climate prior to the event, discusses the immediate economic implications of this event, and the challenges and opportunities faced by organisations affected by this event. In order to facilitate recovery of the Christchurch area, organisations must adjust to a new norm; finding ways not only to continue functioning, but to grow in the months and years following these earthquakes. Some organisations relocated within days to areas that have been less affected by the earthquakes. Others are taking advantage of government subsidised aid packages to help retain their employees until they can make long-term decisions about the future of their organisation. This paper is framed as a “report from the field” in order to provide insight into the early recovery scenario as it applies to organisations affected by the February 2011 earthquake. It is intended both to inform and facilitate discussion about how organisations can and should pursue recovery in Canterbury, and how organisations can become more resilient in the face of the next crisis.

Research papers, University of Canterbury Library

This study uses 44 high quality liquefaction case histories taken from 22 locations affected by the 2010-2011 Canterbury earthquake sequence to evaluate four commonly used CPT-VS correlations (i.e., Robertson, 2009; Hegazy and Mayne, 2006; Andrus et al., 2007; McGann et al., 2015b). Co-located CPT soundings and VS profiles, developed from surface wave testing, were obtained at 22 locations and case histories were developed for the Mw 7.1, 4 September 2010 Darfield and Mw 6.2, 22 February 2011 Christchurch earthquakes. The CPT soundings are used to generate VS profiles using each of four CPT-VS correlations. These correlated VS profiles are used to estimate the factor of safety against liquefaction using the Kayen et al. (2013) VS-based simplified liquefaction evaluation procedure. An error index is used to quantify the predictive capabilities of these correlations in relation to the observations of liquefaction (or the lack thereof). Additionally, the error indices from the CPT-correlated VS profiles are compared to those obtained using: (1) the Kayen et al. (2013) procedure with surface wave-derived VS profiles, and (2) the Idriss and Boulanger (2008) CPT-based liquefaction evaluation procedure. Based on the error indices, the evaluation procedures based on direct measurements of either CPT or VS provided more accurate liquefaction triggering estimates than those obtained from any of the CPT-VS correlations. However, the performance of the CPT-VS correlations varied, with the Robertson (2009) and Hegazy and Mayne (2006) correlations performing relatively poorly for the Christchurch soils and the Andrus et al. (2007) and McGann et al. (2015b) correlations performing better. The McGann et al. (2015b) correlation had the lowest error indices of the CPT-VS correlations tested, however, none of the CPT-VS correlations provided accurate enough VS predictions to be used for the evaluation of liquefaction triggering using the VS-based liquefaction evaluation procedures.

Research papers, University of Canterbury Library

This paper describes part of an extensive experimental programme in progress at the University of Canterbury to develop Laminated Veneer Lumber (LVL) structural systems and connections for multistorey timber buildings in earthquake-prone areas. The higher mechanical properties of LVL, when compared to sawn timber, in addition to its low mass, flexibility of design and rapidity of construction, create the potential for increased use of LVL in multi-storey buildings. The development of these innovative ductile connections in LVL, proposed here for frame systems, have been based on the successful implementation of jointed ductile connections for precast concrete systems, started in the early 1990s with the PRESSS Program at the University of California, San Diego, further developed in Italy and currently under further refinement at the University of Canterbury. This paper investigates the seismic behaviour of the so-called “hybrid” connection, characterised by the combination of unbonded post-tensioned tendons and either external or internal energy dissipaters passing through the critical contact surface between the structural elements. Experimental results on hybrid exterior beam-to-column and column-to-foundation subassemblies under cyclic quasi-static unidirectional loading are presented. The proposed innovative solutions exhibit a very satisfactory seismic performance characterised by an appreciable energy dissipation capacity (provided by the dissipaters) combined with self-centring properties (provided by the unbonded tendons) and negligible damage of the LVL structural elements.

Research papers, University of Canterbury Library

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.

Research papers, University of Canterbury Library

The 2010-2011 Canterbury earthquakes were recorded over a dense strong motion network in the near-source region, yielding significant observational evidence of seismic complexities, and a basis for interpretation of multi-disciplinary datasets and induced damage to the natural and built environment. This paper provides an overview of observed strong motions from these events and retrospective comparisons with both empirical and physics-based ground motion models. Both empirical and physics-based methods provide good predictions of observations at short vibration periods in an average sense. However, observed ground motion amplitudes at specific locations, such as Heathcote Valley, are seen to systematically depart from ‘average’ empirical predictions as a result of near surface stratigraphic and topographic features which are well modelled via sitespecific response analyses. Significant insight into the long period bias in empirical predictions is obtained from the use of hybrid broadband ground motion simulation. The comparison of both empirical and physics-based simulations against a set of 10 events in the sequence clearly illustrates the potential for simulations to improve ground motion and site response prediction, both at present, and further in the future.

Research papers, University of Canterbury Library

The 2015 New Zealand strong-motion database provides a wealth of new strong motion data for engineering applications. An important component of this database is the compilation of new site metadata, describing the soil conditions and site response at GeoNet strong motion stations. We have assessed and compiled four key site parameters for the ~460 GeoNet stations that recorded significant historical ground motions. Parameters include: site classification (NZS1170.5), Vs30, fundamental site period (Tsite) and depth to bedrock (Z1.0, i.e. depth to material with Vs > 1000 m/s). In addition, we have assigned a quality estimate (Quality 1 – 3) to these parameters to provide a qualitative estimate of the uncertainty. New highquality Tsite estimates have largely been obtained from newly available HVSR amplification curves and spectral ratios from inversion of regional strong motion data that has been reconciled with available geological information. Good quality Vs30 estimates, typically in urban centres, have also been incorporated following recent studies. Where site-specific measurements of Vs30 are not available, Vs30 is estimated based on surface geology following national Vs30 maps. New Z1.0 values have been provided from 3D subsurface models for Canterbury and Wellington. This database will be used in efforts to guide development and testing of new and existing ground motion prediction models in New Zealand. In particular, it will allow reexamination of the most important site parameters that control and predict site response in a New Zealand setting. Furthermore, it can be used to provide information about suitable rock reference sites for seismological research, and as a guide to site-specific references in the literature. We discuss compilation of the database, preliminary insights so far, and future directions.

Research papers, University of Canterbury Library

In the period between September 2010 and December 2011, Christchurch (New Zealand) and its surroundings were hit by a series of strong earthquakes including six significant events, all generated by local faults in proximity to the city: 4 September 2010 (Mw=7.1), 22 February 2011 (Mw=6.2), 13 June 2011 (Mw=5.3 and Mw=6.0) and 23 December 2011 (M=5.8 and (M=5.9) earthquakes. As shown in Figure 1, the causative faults of the earthquakes were very close to or within the city boundaries thus generating very strong ground motions and causing tremendous damage throughout the city. Christchurch is shown as a lighter colour area, and its Central Business District (CBD) is marked with a white square area in the figure. Note that the sequence of earthquakes started to the west of the city and then propagated to the south, south-east and east of the city through a set of separate but apparently interacting faults. Because of their strength and proximity to the city, the earthquakes caused tremendous physical damage and impacts on the people, natural and built environments of Christchurch. The 22 February 2011 earthquake was particularly devastating. The ground motions generated by this earthquake were intense and in many parts of Christchurch substantially above the ground motions used to design the buildings in Christchurch. The earthquake caused 182 fatalities, collapse of two multi-storey reinforced concrete buildings, collapse or partial collapse of many unreinforced masonry structures including the historic Christchurch Cathedral. The Central Business District (CBD) of Christchurch, which is the central heart of the city just east of Hagley Park, was practically lost with majority of its 3,000 buildings being damaged beyond repair. Widespread liquefaction in the suburbs of Christchurch, as well as rock falls and slope/cliff instabilities in the Port Hills affected tens of thousands of residential buildings and properties, and shattered the lifelines and infrastructure over approximately one third of the city area. The total economic loss caused by the 2010-2011 Christchurch earthquakes is currently estimated to be in the range between 25 and 30 billion NZ dollars (or 15% to 18% of New Zealand’s GDP). After each major earthquake, comprehensive field investigations and inspections were conducted to document the liquefaction-induced land damage, lateral spreading displacements and their impacts on buildings and infrastructure. In addition, the ground motions produced by the earthquakes were recorded by approximately 15 strong motion stations within (close to) the city boundaries providing and impressive wealth of data, records and observations of the performance of ground and various types of structures during this unusual sequence of strong local earthquakes affecting a city. This paper discusses the liquefaction in residential areas and focuses on its impacts on dwellings (residential houses) and potable water system in the Christchurch suburbs. The ground conditions of Christchurch including the depositional history of soils, their composition, age and groundwater regime are first discussed. Detailed liquefaction maps illustrating the extent and severity of liquefaction across Christchurch triggered by the sequence of earthquakes including multiple episodes of severe re-liquefaction are next presented. Characteristic liquefaction-induced damage to residential houses is then described focussing on the performance of typical house foundations in areas affected by liquefaction. Liquefaction impacts on the potable water system of Christchurch is also briefly summarized including correlation between the damage to the system, liquefaction severity, and the performance of different pipe materials. Finally, the characteristics of Christchurch liquefaction and its impacts on built environment are discussed in relation to the liquefaction-induced damage in Japan during the 11 March 2011 Great East Japan Earthquake.

Research papers, University of Canterbury Library

Very little research exists on total house seismic performance. This testing programme provides stiffness and response data for five houses of varying ages including contributions of non-structural elements. These light timber framed houses in Christchurch, New Zealand had minor earthquake damage from the 2011 earthquakes and were lateral load tested on site to determine their strength and stiffness, and preliminary damage thresholds. Dynamic characteristics were also investigated. Various loading schemes were utilised including quasi-static loading above the foundation, unidirectional loading through the floor diaphragm, cyclic quasi-static loading and snapback tests. Dynamic analysis on two houses provided the seismic safety levels of post-quake houses with respect to local hazard levels. Compared with New Zealand Building Standards all the tested houses had an excess of strength, damage is a significant consideration in earthquake resilience and was observed in all of the houses. A full size house laboratory test is proposed.

Audio, Radio New Zealand

With Adrian Regnault, the General Manager of Building Systems Performance at the Ministry of Business, Innovation and Employment; Stefano Pampanin, an Associate Professor in Structural Engineering at Canterbury University and the President of the NZ Society for Earthquake Engineering and John Finnegan - structural engineer, Aurecon.

Research papers, University of Canterbury Library

Anyone keeping a global tally of recent disasters is likely to be asking: What role will the hazards and disasters of coastal plains play in the lives and economies of 21st century humanity? In this article, we reflect on this question using examples of how different types of coastal land performed during the Christchurch and other earthquake events to examine the complex of coastal-tectonic hazards that are being constructed in the Tokyo megacity

Research papers, University of Canterbury Library

The city of Christchurch and its surrounds experienced widespread damage due to soil liquefaction induced by seismic shaking during the Canterbury earthquake sequence that began in September 2010 with the Mw7.1 Darfield earthquake. Prior to the start of this sequence, the city had a large network of strong motion stations (SMSs) installed, which were able to record a vast database of strong ground motions. This paper uses this database of strong ground motion recordings, observations of liquefaction manifestation at the ground surface, and data from a recently completed extensive geotechnical site investigation program at each SMS to assess a range of liquefaction evaluation procedures at the four SMSs in the Christchurch Central Business District (CBD). In general, the characteristics of the accelerograms recorded at each SMS correlated well with the liquefaction evaluation procedures, with low liquefaction factors of safety predicted at sites with clear liquefaction identifiers in the ground motions. However, at sites that likely liquefied at depth (as indicated by evaluation procedures and/or inferred from the characteristics of the recorded surface accelerograms), the presence of a non-liquefiable crust layer at many of the SMS locations prevented the manifestation of any surface effects. Because of this, there was not a good correlation between surface manifestation and two surface manifestation indices, the Liquefaction Potential Index (LPI) and the Liquefaction Severity Number (LSN).

Research papers, University of Canterbury Library

This poster aims to present fragility functions for pipelines buried in liquefaction-prone soils. Existing fragility models used to quantify losses can be based on old data or use complex metrics. Addressing these issues, the proposed functions are based on the Christchurch network and soil and utilizes the Canterbury earthquake sequence (CES) data, partially represented in Figure 1. Figure 1 (a) presents the pipe failure dataset, which describes the date, location and pipe on which failures occurred. Figure 1 (b) shows the simulated ground motion intensity median of the 22nd February 2011 earthquake. To develop the model, the network and soil characteristics have also been utilized

Research papers, University of Canterbury Library

In this paper, we perform hybrid broadband (0-10 Hz) ground motion simulations for the ten most significant events (Mw 4.7-7.1) in the 2010-2011 Canterbury earthquake sequence. Taking advantage of having repeated recordings at same stations, we validate our simulations using both recordings and an empirically-developed ground motion prediction equation (GMPE). The simulation clearly captures the sedimentary basin amplification and the rupture directivity effects. Quantitative comparisons of the simulations with both recordings and the GMPE, as well as analyses of the total residuals (indicating model bias) show that simulations perform better than the empirical GMPE, especially for long period. To scrutinize the ground motion variability, we partitioned the total residuals into different components. The total residual appears to be unbiased, and the use of a 3D velocity structure reduces the long period systematic bias particularly for stations located close to the Banks Peninsula volcanic area.

Research papers, University of Canterbury Library

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

Research papers, University of Canterbury Library

In the last century, seismic design has undergone significant advancements. Starting from the initial concept of designing structures to perform elastically during an earthquake, the modern seismic design philosophy allows structures to respond to ground excitations in an inelastic manner, thereby allowing damage in earthquakes that are significantly less intense than the largest possible ground motion at the site of the structure. Current performance-based multi-objective seismic design methods aim to ensure life-safety in large and rare earthquakes, and to limit structural damage in frequent and moderate earthquakes. As a result, not many recently built buildings have collapsed and very few people have been killed in 21st century buildings even in large earthquakes. Nevertheless, the financial losses to the community arising from damage and downtime in these earthquakes have been unacceptably high (for example; reported to be in excess of 40 billion dollars in the recent Canterbury earthquakes). In the aftermath of the huge financial losses incurred in recent earthquakes, public has unabashedly shown their dissatisfaction over the seismic performance of the built infrastructure. As the current capacity design based seismic design approach relies on inelastic response (i.e. ductility) in pre-identified plastic hinges, it encourages structures to damage (and inadvertently to incur loss in the form of repair and downtime). It has now been widely accepted that while designing ductile structural systems according to the modern seismic design concept can largely ensure life-safety during earthquakes, this also causes buildings to undergo substantial damage (and significant financial loss) in moderate earthquakes. In a quest to match the seismic design objectives with public expectations, researchers are exploring how financial loss can be brought into the decision making process of seismic design. This has facilitated conceptual development of loss optimisation seismic design (LOSD), which involves estimating likely financial losses in design level earthquakes and comparing against acceptable levels of loss to make design decisions (Dhakal 2010a). Adoption of loss based approach in seismic design standards will be a big paradigm shift in earthquake engineering, but it is still a long term dream as the quantification of the interrelationships between earthquake intensity, engineering demand parameters, damage measures, and different forms of losses for different types of buildings (and more importantly the simplification of the interrelationship into design friendly forms) will require a long time. Dissecting the cost of modern buildings suggests that the structural components constitute only a minor portion of the total building cost (Taghavi and Miranda 2003). Moreover, recent research on seismic loss assessment has shown that the damage to non-structural elements and building contents contribute dominantly to the total building loss (Bradley et. al. 2009). In an earthquake, buildings can incur losses of three different forms (damage, downtime, and death/injury commonly referred as 3Ds); but all three forms of seismic loss can be expressed in terms of dollars. It is also obvious that the latter two loss forms (i.e. downtime and death/injury) are related to the extent of damage; which, in a building, will not just be constrained to the load bearing (i.e. structural) elements. As observed in recent earthquakes, even the secondary building components (such as ceilings, partitions, facades, windows parapets, chimneys, canopies) and contents can undergo substantial damage, which can lead to all three forms of loss (Dhakal 2010b). Hence, if financial losses are to be minimised during earthquakes, not only the structural systems, but also the non-structural elements (such as partitions, ceilings, glazing, windows etc.) should be designed for earthquake resistance, and valuable contents should be protected against damage during earthquakes. Several innovative building technologies have been (and are being) developed to reduce building damage during earthquakes (Buchanan et. al. 2011). Most of these developments are aimed at reducing damage to the buildings’ structural systems without due attention to their effects on non-structural systems and building contents. For example, the PRESSS system or Damage Avoidance Design concept aims to enable a building’s structural system to meet the required displacement demand by rocking without the structural elements having to deform inelastically; thereby avoiding damage to these elements. However, as this concept does not necessarily reduce the interstory drift or floor acceleration demands, the damage to non-structural elements and contents can still be high. Similarly, the concept of externally bracing/damping building frames reduces the drift demand (and consequently reduces the structural damage and drift sensitive non-structural damage). Nevertheless, the acceleration sensitive non-structural elements and contents will still be very vulnerable to damage as the floor accelerations are not reduced (arguably increased). Therefore, these concepts may not be able to substantially reduce the total financial losses in all types of buildings. Among the emerging building technologies, base isolation looks very promising as it seems to reduce both inter-storey drifts and floor accelerations, thereby reducing the damage to the structural/non-structural components of a building and its contents. Undoubtedly, a base isolated building will incur substantially reduced loss of all three forms (dollars, downtime, death/injury), even during severe earthquakes. However, base isolating a building or applying any other beneficial technology may incur additional initial costs. In order to provide incentives for builders/owners to adopt these loss-minimising technologies, real-estate and insurance industries will have to acknowledge the reduced risk posed by (and enhanced resilience of) such buildings in setting their rental/sale prices and insurance premiums.

Research papers, University of Canterbury Library

Seismic behaviour of typical unreinforced masonry (URM) brick houses, that were common in early last century in New Zealand and still common in many developing countries, is experimentally investigated at University of Canterbury, New Zealand in this research. A one halfscale model URM house is constructed and tested under earthquake ground motions on a shaking table. The model structure with aspect ratio of 1.5:1 in plan was initially tested in the longitudinal direction for several earthquakes with peak ground acceleration (PGA) up to 0.5g. Toppling of end gables (above the eaves line) and minor to moderate cracking around window and door piers was observed in this phase. The structure was then rotated 90º and tested in the transverse (short) direction for ground motions with PGA up to 0.8g. Partial out-of-plane failure of the face loaded walls in the second storey and global rocking of the model was observed in this phase. A finite element analysis and a mechanism analysis are conducted to assess the dynamic properties and lateral strength of the model house. Seismic fragility function of URM houses is developed based on the experimental results. Damping at different phases of the response is estimated using an amplitude dependent equivalent viscous damping model. Financial risk of similar URM houses is then estimated in term of expected annual loss (EAL) following a probabilistic financial risk assessment framework. Risks posed by different levels of damage and by earthquakes of different frequencies are then examined.

Research papers, University of Canterbury Library

Over 6.3 million waste tyres are produced annually in New Zealand (Tyrewise, 2021), leading to socioeconomic and environmental concerns. The 2010-11 Canterbury Earthquake Sequence inflicted extensive damage to ~6,000 residential buildings, highlighting the need to improve the seismic resilience of the residential housing sector. A cost-effective and sustainable eco-rubber geotechnical seismic isolation (ERGSI) foundation system for new low-rise buildings was developed by the authors. The ERGSI system integrates a horizontal geotechnical seismic isolation (GSI) layer i.e., a deformable seismic energy dissipative filter made of granulated tyre rubber (GTR) and gravel (G) – and a flexible rubberised concrete raft footing. Geotechnical experimental and numerical investigations demonstrated the effectiveness of the ERGSI system in reducing the seismic demand at the foundation level (i.e., reduced peak ground acceleration) (Hernandez et al., 2019; Tasalloti et al., 2021). However, it is essential to ensure that the ERGSI system has minimal leaching attributes and does not result in long-term negative impacts on the environment.

Research papers, University of Canterbury Library

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.

Research papers, University of Canterbury Library

This paper presents insights from recent advanced laboratory testing of undisturbed and reconstituted specimens of Christchurch silty-sands. The purpose of the testing was to establish the cyclic strength of silty-sands from sites in the Central Business District (CBD), where liquefaction was observed in 4 September 2010, 22 February 2011, and 13 June 2011. Similar overall strengths were obtained from undisturbed and reconstituted tests prepared at similar densities, albeit with higher variability for the reconstituted specimens. Reconstituted specimens exhibited distinctly different response in terms of lower compressibility during initial loading cycles, and exhibited a more brittle response when large strains were mobilised, particularly for samples with high fines content. Given the lower variability in natural sample response and the possibility of age-related strength to be significant for sites not subjected to earthquakes, high quality undisturbed samples are recommended over the use of reconstituted specimens to establish the cyclic strength of natural sands.

Research papers, University of Canterbury Library

On 22 February 2011，a magnitude Mw 6.3 earthquake occurred with an epicenter located near Lyttelton at about 10km from Christchurch in Canterbury region on the South Island of New Zealand (Figure 1). Since this earthquake occurred in the midst of the aftershock activity which had continued since the 4 September 2010 Darfield Earthquake occurrence, it was considered to be an aftershock of the initial earthquake. Because of the short distance to the city and the shallower depth of the epicenter, this earthquake caused more significant damage to pipelines, traffic facilities, residential houses/properties and multi-story buildings in the central business district than the September 2010 Darfield Earthquake in spite of its smaller earthquake magnitude. Unfortunately, this earthquake resulted in significant number of casualties due to the collapse of multi-story buildings and unreinforced masonry structures in the city center of Christchurch. As of 4 April, 172 casualties were reported and the final death toll is expected to be 181. While it is extremely regrettable that Christchurch suffered a terrible number of victims, civil and geotechnical engineers have this hard-to-find opportunity to learn the response of real ground from two gigantic earthquakes which occurred in less than six months from each other. From geotechnical engineering point of view, it is interesting to discuss the widespread liquefaction in natural sediments, repeated liquefaction within short period and further damage to earth structures which have been damaged in the previous earthquake. Following the earthquake, an intensive geotechnical reconnaissance was conducted to capture evidence and perishable data from this event. The team included the following members: Misko Cubrinovski (University of Canterbury, NZ, Team Leader), Susumu Yasuda (Tokyo Denki University, Japan, JGS Team Leader), Rolando Orense (University of Auckland, NZ), Kohji Tokimatsu (Tokyo Institute of Technology, Japan), Ryosuke Uzuoka (Tokushima University, Japan), Takashi Kiyota (University of Tokyo, Japan), Yasuyo Hosono (Toyohashi University of Technology, Japan) and Suguru Yamada (University of Tokyo, Japan).

Research papers, University of Canterbury Library

Since September 2010 Christchurch, New Zealand, has experienced a number of significant earthquakes. In addition to loss of life, this has resulted in significant destruction to infrastructure, including road corridors; and buildings, especially in the central city, where it has been estimated that 60% of buildings will need to be rebuilt. The rebuild and renewal of Christchurch has initially focused on the central city under the direction of the Christchurch City Council. This has seen the development of a draft Central City Plan that includes a number of initiatives that should encourage the use of the bicycle as a mode of transport. The rebuild and renewal of the remainder of the city is under the jurisdiction of a specially set up authority, the Christchurch Earthquake Recovery Authority (CERA). CERA reports to an appointed Minister for Canterbury Earthquake Recovery, who is responsible for coordinating the planning, spending, and actual rebuilding work needed for the recovery. Their plans for the renewal and rebuild of the remainder of the city are not yet known. This presentation will examine the potential role of the bicycle as a mode of transport in a rebuilt Christchurch. The presentation will start by describing the nature of damage to Christchurch as a result of the 2010 and 2011 earthquakes. It will then review the Central City Plan (the plan for the rebuild and renewal for central Christchurch) focusing particularly on those aspects that affect the role of the bicycle. The potential for the success of this plan will be assessed. It will specifically reflect on this in light of some recent research in Christchurch that examined the importance of getting infrastructure right if an aim of transport planning is to attract new people to cycle for utilitarian reasons.

Research papers, University of Canterbury Library

The 4 September 2010 Darfield and 22 February 2011 Christchurch earthquakes caused significant damage to Christchurch and surrounding suburbs as a result of the widespread liquefaction and lateral spreading that occurred. Ground surveying-based field investigations were conducted following these two events in order to measure permanent ground displacements in areas significantly affected by lateral spreading. Data was analysed with respect to the distribution of lateral spreading vs. distance from the waterway, and the failure patterns observed. Two types of failure distribution patterns were observed, a typical distributed pattern and an atypical block failure. Differences in lateral spreading measurements along adjacent banks of the Avon River in the area of Dallington were also examined. The spreading patterns between the adjacent banks varied with the respective river geometry and/or geotechnical conditions at the banks.

Research papers, University of Canterbury Library

This paper provides a summary of the ground motions observed in the recent Canterbury, New Zealand earthquake sequence. The sequence occurred in a region of relatively moderate seismicity, 130km to the east of the Alpine Fault, the major plate-boundary in the region. From an engineering perspective, the sequence has been primarily comprised of the initial 04/09/2010 Darfield earthquake (Mw7.1) followed by the 22/02/2011 Christchurch earthquake (Mw6.3), and two aftershocks on 13/06/ 2011 (Mw5.3 and 6.0, respectively). The dense spacing of strong motions in the region, and their close proximity to the respective causative faults, has resulted in strong ground motions far exceeding the previous catalogue of strong motion observed in New Zealand. The observed ground motions have exhibited clear evidence of: (i) near-source directivity; (ii) sedimentary basin focusing, amplification and basin effect refraction; (iii) non-linear site response; (iv) cyclic mobility postliquefaction; and (v) extreme vertical ground motions exceeding 2g, among others.