High demolition rates were observed in New Zealand after the 2010-2011 Canterbury Earthquake Sequence despite the success of modern seismic design standards to achieve required performance objectives such as life safety and collapse prevention. Approximately 60% of the multi-storey reinforced concrete (RC) buildings in the Christchurch Central Business District were demolished after these earthquakes, even when only minor structural damage was present. Several factors influenced the decision of demolition instead of repair, one of them being the uncertainty of the seismic capacity of a damaged structure. To provide more insight into this topic, the investigation conducted in this thesis evaluated the residual capacity of moderately damaged RC walls and the effectiveness of repair techniques to restore the seismic performance of heavily damaged RC walls. The research outcome provided insights for developing guidelines for post-earthquake assessment of earthquake-damaged RC structures. The methodology used to conduct the investigation was through an experimental program divided into two phases. During the first phase, two walls were subjected to different types of pre-cyclic loading to represent the damaged condition from a prior earthquake, and a third wall represented a repair scenario with the damaged wall being repaired using epoxy injection and repair mortar after the pre-cyclic loading. Comparisons of these test walls to a control undamaged wall identified significant reductions in the stiffness of the damaged walls and a partial recovery in the wall stiffness achieved following epoxy injection. Visual damage that included distributed horizontal and diagonal cracks and spalling of the cover concrete did not affect the residual strength or displacement capacity of the walls. However, evidence of buckling of the longitudinal reinforcement during the pre-cyclic loading resulted in a slight reduction in strength recovery and a significant reduction in the displacement capacity of the damaged walls. Additional experimental programs from the literature were used to provide recommendations for modelling the response of moderately damaged RC walls and to identify a threshold that represented a potential reduction in the residual strength and displacement capacity of damaged RC walls in future earthquakes. The second phase of the experimental program conducted in this thesis addressed the replacement of concrete and reinforcing steel as repair techniques for heavily damaged RC walls. Two walls were repaired by replacing the damaged concrete and using welded connections to connect new reinforcing bars with existing bars. Different locations of the welded connections were investigated in the repaired walls to study the impact of these discontinuities at the critical section. No significant changes were observed in the stiffness, strength, and displacement capacity of the repaired walls compared to the benchmark undamaged wall. Differences in the local behaviour at the critical section were observed in one of the walls but did not impact the global response. The results of these two repaired walls were combined with other experimental programs found in the literature to assemble a database of repaired RC walls. Qualitative and quantitative analyses identified trends across various parameters, including wall types, damage before repair, and repair techniques implemented. The primary outcome of the database analysis was recommendations for concrete and reinforcing steel replacement to restore the strength and displacement capacity of heavily damaged RC walls.
The November 2016 MW 7.8 Kaikōura Earthquake initiated beneath the North Culverden basin on The Humps fault and propagated north-eastwards, rupturing at least 17 faults along a cumulative length of ~180 km. The geomorphic expression of The Humps Fault across the Emu Plains, along the NW margin of Culverden basin, comprises a series of near-parallel strands separated by up to 3 km across strike. The various strands strike east to east-northeast and have been projected to mainly dip steeply to the south in seismic data (~80°). In this area, the fault predominantly accommodates right-lateral slip, with uplift and subsidence confined to releasing and restraining bends and step-overs at a range of scales. The Kaikōura event ruptured pre-existing fault scarps along the Emu Plains, which had been partly identified prior to the earthquake. Geomorphology and faulting expression of The Humps Fault on The Emu Plains was mapped, along with faulting related structures which did not rupture in the 2016 earthquake. Fault ruptures strands are combined into sections and the kinematic deformation of sections analysed to provide a moment tensor fault plane solution. This fault plane solution is consistent with the regional principal horizontal shortening direction (PHS) of ~115°, similar to seismic focal mechanism solutions of some of the nearby aftershocks of the Kaikōura earthquake, and similar to the adjacent Hope Fault. To constrain the timing of paleoseismic events, a trench was excavated across the fault where it crossed a late Quaternary alluvial fan. Mapping of stratigraphy exposed in the trench walls, and dating of variably deformed strata, constrains the pre-historic earthquake event history at the trench site. The available data provides evidence for at least three paleo-earthquakes within the last 15.1 ka, with a possible fourth (penultimate) event. These events are estimated to have occurred at 7.7-10.3 ka, 10.3-14.8 ka, and one or more events that are older than ~15.1 ka. Some evidence suggests an additional penultimate event between 1850 C.E and 7.7 ka. Time-integrated slip-rates at three locations on the fault are measured using paleo-channels as piercing points. These sites give horizontal slip rates of 0.57 ± 0.1 mm/year, 0.49 ± 0.1 mm/year and one site constrains a minimum of between 0.1 - 0.4 mm/year. Two vertical slip-rates are calculated to be constrained to a maximum of 0.2 ± 0.02 mm/year at one site and between 0.02 and 0.1 mm/year at another site. Prior to this study, The Humps fault had only been partially documented in reconnaissance level mapping in the district, and no previous paleoseismic or slip rate data had been reported. This project has provided a detailed fault zone tectonic geomorphic map and established new slip-rate and paleoseismic data. The results highlight that The Humps fault plays an important role in regional seismicity and in accommodating plate boundary deformation across the North Canterbury region.
Capacity design and hierarchy of strength philosophies at the base of modern seismic codes allow inelastic response in case of severe earthquakes and thus, in most traditional systems, damage develops at well-defined locations of reinforced concrete (RC) structures, known as plastic hinges. The 2010 and 2011 Christchurch earthquakes have demonstrated that this philosophy worked as expected. Plastic hinges formed in beams, in coupling beams and at the base of columns and walls. Structures were damaged permanently, but did not collapse. The 2010 and 2011 Christchurch earthquakes also highlighted a critical issue: the reparability of damaged buildings. No methodologies or techniques were available to estimate the level of subsequent earthquakes that RC buildings could still sustain before collapse. No repair techniques capable of restoring the initial condition of buildings were known. Finally, the cost-effectiveness of an eventual repair intervention, when compared with a new building, was unknown. These aspects, added to nuances of New Zealand building owners’ insurance coverage, encouraged the demolition of many buildings. Moreover, there was a perceived strong demand from government and industry to develop techniques for assessing damage to steel reinforcement bars embedded in cracked structural concrete elements. The most common questions were: “Have the steel bars been damaged in correspondence to the concrete cracks?”, “How much plastic deformation have the steel bars undergone?”, and “What is the residual strain capacity of the damaged bars?” Minimally invasive techniques capable of quantifying the level and extent of plastic deformation and residual strain capacity are not yet available. Although some studies had been recently conducted, a validated method is yet to be widely accepted. In this thesis, a least-invasive method for the damage-assessment of steel reinforcement is developed. Based on the information obtained from hardness testing and a single tensile test, it is possible to estimate the mechanical properties of earthquake-damaged rebars. The reduction in the low-cycle fatigue life due to strain ageing is also quantified. The proposed damage assessment methodology is based on empirical relationships between hardness and strain and residual strain capacity. If damage is suspected from in situ measurements, visual inspection or computer analysis, a bar may be removed and more accurate hardness measurements can be obtained using the lab-based Vickers hardness methodology. The Vickers hardness profile of damaged bars is then compared with calibration curves (Vickers hardness versus strain and residual strain capacity) previously developed for similar steel reinforcement bars extracted from undamaged locations. Experimental tests demonstrated that the time- and temperature-dependent strain-ageing phenomenon causes changes in the mechanical properties of plastically deformed steels. In particular, yield strength and hardness increases, whereas ductility decreases. The changes in mechanical properties are quantified and their implications on the hardness method are highlighted. Low-cycle fatigue (LCF) failures of steel reinforcing bars have been observed in laboratory testing and post-earthquake damage inspections. Often, failure might not occur during a first seismic event. However, damage is accumulated and the remaining fatigue life is reduced. Failure might therefore occur in a subsequent seismic event. Although numerous studies exist on the LCF behaviour of steel rebars, no studies had been conducted on the strain-ageing effects on the remaining fatigue life. In this thesis, the reduction in fatigue life due to this phenomenon is determined through a number of experimental tests.
The 2010 Darfield earthquake is the largest earthquake on record to have occurred within 40 km of a major city and not cause any fatalities. In this paper the authors have reflected on their experiences in Christchurch following the earthquake with a view to what worked, what didn’t, and what lessons can be learned from this for the benefit of Australian earthquake preparedness. Owing to the fact that most of the observed building damage occurred in Unreinforced Masonry (URM) construction, this paper focuses in particular on the authors’ experience conducting rapid building damage assessment during the first 72 hours following the earthquake and more detailed examination of the performance of unreinforced masonry buildings with and without seismic retrofit interventions.
This paper develops representative ground motion ensembles for several major earthquake scenarios in New Zealand. Cases considered include representative ground motions for the occurrence of Alpine, Hope, and Porters Pass earthquakes in Christchurch, and the occurrence of Wellington, Wairarapa, and Ohariu, fault ruptures in Wellington. Challenges in the development of ground motion ensembles for subduction zone earthquakes are also highlighted. The ground motions are selected based on the generalized conditional intensity measure (GCIM) approach, ensuring that the ground motion ensembles represent both the mean, and distribution of ground motion intensity which such scenarios could impose. These scenario-based ground motion sets can be used to complement ground motions which are often selected in conjunction with probabilistic seismic hazard analysis, in order to understand the performance of structures for the question “what if this fault ruptures?”
The paper discusses modelling of cyclic stress-strain behaviour of soil, in particular a simple model that can produce a desired stiffness and hysteretic damping for a given strain level as observed in laboratory testing is formulated. The unloading-reloading relationship is developed for total stress seismic site response analysis with appropriate damping at large strain. The constitutive model employs a hyperbolic equation as the backbone curve, and uses a modification of the extended Masing unloading-reloading relationship leading to correct measured modulus reduction and damping curves simultaneously. A quasi-static cyclic loading of increasing amplitude is used to demonstrate the model’s performance and its capability to allow improved modelling of the magnitude of energy dissipation based on an experimental program on native sandy soils from Christchurch, New Zealand.
© 2017 The Royal Society of New Zealand. This paper discusses simulated ground motion intensity, and its underlying modelling assumptions, for great earthquakes on the Alpine Fault. The simulations utilise the latest understanding of wave propagation physics, kinematic earthquake rupture descriptions and the three-dimensional nature of the Earth's crust in the South Island of New Zealand. The effect of hypocentre location is explicitly examined, which is found to lead to significant differences in ground motion intensities (quantified in the form of peak ground velocity, PGV) over the northern half and southwest of the South Island. Comparison with previously adopted empirical ground motion models also illustrates that the simulations, which explicitly model rupture directivity and basin-generated surface waves, lead to notably larger PGV amplitudes than the empirical predictions in the northern half of the South Island and Canterbury. The simulations performed in this paper have been adopted, as one possible ground motion prediction, in the ‘Project AF8’ Civil Defence Emergency Management exercise scenario. The similarity of the modelled ground motion features with those observed in recent worldwide earthquakes as well as similar simulations in other regions, and the notably higher simulated amplitudes than those from empirical predictions, may warrant a re-examination of regional impact assessments for major Alpine Fault earthquakes.
A Line of Best Fit explores weakness and disconnection in the city. Weakness: There are over 600 earthquake prone buildings in Wellington. The urgency to strengthen buildings risks compromising the aesthetic integrity of the city through abrasive strengthening techniques, or losing a large portion of our built environment to demolition. The need for extensive earthquake strengthening in Wellington, Christchurch and other New Zealand cities provides an exciting opportunity for architecture. Disconnection: In Wellington pedestrian activity is focused around three main routes: Cuba Street, Lambton Quay and Courtney Place. The adjacent areas are often disconnected and lack vibrancy due to large building footprints, no-exit laneways and lack of public spaces. The Design proposes a strategy for earthquake strengthening, preserving and upgrading the built environment, and expanding and connecting the pedestrian realm. The site is two earthquake prone buildings on the block between Marion Street and Taranaki Street in central Wellington. A cut through the centre of the Aspro and Cathie Buildings ties the buildings together to strengthen and create a new arcade as public space. The cut aligns with existing pedestrian routes connecting the block with the city. The Design is divided into three components: Void, Curve, and Pattern and Structure. Void investigates the implications of cutting a portion out the existing buildings and the opportunities this provides for connection, urban interaction, and light. Curve discusses the unusual form of The Design in terms of scale, the human response and the surrounding spaces. Pattern and Structure considers the structural requirements of the project and how a void enveloped in perforated screens can strengthen the earthquake prone buildings. The importance of connection, providing strength in the city, a dialogue between old and new, and engagement with the unexpected are evaluated. Opportunities for further development and research are discussed, with particular reference to how the principles of The Design could be implemented on a larger scale throughout our cities. A Line of Best Fit is an architectural proposal that creates strength and connection.
This thesis investigates life-safety risk in earthquakes. The first component of the thesis utilises a dataset of earthquake injuries and deaths from recent earthquakes in New Zealand to identify cause, context, and risk factors of injury and death in the 2011 MW6.3 Christchurch earthquake and 2016 MW7.8 Kaikōura earthquake. Results show that nearly all deaths occurred from being hit by structural elements from buildings, while most injuries were caused by falls, strains and being hit by contents or non-structural elements. Statistical analysis of injured cases compared to an uninjured control group found that age, gender, building damage, shaking intensity, and behaviour during shaking were the most significant risk factors for injury during these earthquakes. The second part of the thesis uses the empirical findings from the first section to develop two tools for managing life-safety risk in earthquakes. The first tool is a casualty estimation model for health system and emergency response planning. An existing casualty model used in New Zealand was validated against observed data from the 2011 Christchurch earthquake and found to underestimate moderate and severe injuries by an order of magnitude. The model was then updated to include human behaviour such as protective actions, falls and strain type injuries that are dependent on shaking intensity, as well as injuries and deaths outside buildings. These improvements resulted in a closer fit to observed casualties for the 2011 Christchurch earthquake. The second tool that was developed is a framework to set seismic loading standards for design based on fatality risk targets. The proposed framework extends the risk-targeted hazard method, by moving beyond collapse risk targets, to fatality risk targets for individuals in buildings and societal risk in cities. The framework also includes treatment of epistemic uncertainty in seismic hazard to allow this uncertainty to be used in risk-based decision making. The framework is demonstrated by showing how the current New Zealand loading standards could be revised to achieve uniform life-safety risk across the country and how the introduction of a new loading factor can reduce risk aggregation in cities. Not on Alma, moved and emailed. 1/02/2023 ce
Damage distribution maps from strong earthquakes and recorded data from field experiments have repeatedly shown that the ground surface topography and subsurface stratigraphy play a decisive role in shaping the ground motion characteristics at a site. Published theoretical studies qualitatively agree with observations from past seismic events and experiments; quantitatively, however, they systematically underestimate the absolute level of topographic amplification up to an order of magnitude or more in some cases. We have hypothesized in previous work that this discrepancy stems from idealizations of the geometry, material properties, and incident motion characteristics that most theoretical studies make. In this study, we perform numerical simulations of seismic wave propagation in heterogeneous media with arbitrary ground surface geometry, and compare results with high quality field recordings from a site with strong surface topography. Our goal is to explore whether high-fidelity simulations and realistic numerical models can – contrary to theoretical models – capture quantitatively the frequency and amplitude characteristics of topographic effects. For validation, we use field data from a linear array of nine portable seismometers that we deployed on Mount Pleasant and Heathcote Valley, Christchurch, New Zealand, and we compute empirical standard spectral ratios (SSR) and single-station horizontal-to-vertical spectral ratios (HVSR). The instruments recorded ambient vibrations and remote earthquakes for a period of two months (March-April 2017). We next perform two-dimensional wave propagation simulations using the explicit finite difference code FLAC. We construct our numerical model using a high-resolution (8m) Digital Elevation Map (DEM) available for the site, an estimated subsurface stratigraphy consistent with the geomorphology of the site, and soil properties estimated from in-situ and non-destructive tests. We subject the model to in-plane and out-of-plane incident motions that span a broadband frequency range (0.1-20Hz). Numerical and empirical spectral ratios from our blind prediction are found in very good quantitative agreement for stations on the slope of Mount Pleasant and on the surface of Heathcote Valley, across a wide range of frequencies that reveal the role of topography, soil amplification and basin edge focusing on the distribution of ground surface motion.
In major seismic events, a number of plan-asymmetric buildings which experienced element failure or structural collapse had twisted significantly about their vertical axis during the earthquake shaking. This twist, known as “building torsion”, results in greater demands on one side of a structure than on the other side. The Canterbury Earthquakes Royal Commission’s reports describe the response of a number of buildings in the February 2011 Christchurch earthquakes. As a result of the catastrophic collapse of one multi-storey building with significant torsional irregularity, and significant torsional effects also in other buildings, the Royal Commission recommended that further studies be undertaken to develop improved simple and effective guides to consider torsional effects in buildings which respond inelastically during earthquake shaking. Separately from this, as building owners, the government, and other stakeholders, are planning for possible earthquake scenarios, they need good estimates of the likely performance of both new and existing buildings. These estimates, often made using performance based earthquake engineering considerations and loss estimation techniques, inform decision making. Since all buildings may experience torsion to some extent, and torsional effects can influence demands on building structural and non-structural elements, it is crucial that demand estimates consider torsion. Building seismic response considering torsion can be evaluated with nonlinear time history analysis. However, such analysis involves significant computational effort, expertise and cost. Therefore, from an engineers’ point of view, simpler analysis methods, with reasonable accuracy, are beneficial. The consideration of torsion in simple analysis methods has been investigated by many researchers. However, many studies are theoretical without direct relevance to structural design/assessment. Some existing methods also have limited applicability, or they are difficult to use in routine design office practice. In addition, there has been no consensus about which method is best. As a result, there is a notable lack of recommendations in current building design codes for torsion of buildings that respond inelastically. There is a need for building torsion to be considered in yielding structures, and for simple guidance to be developed and adopted into building design standards. This study aims to undertaken to address this need for plan-asymmetric structures which are regular over their height. Time history analyses are first conducted to quantify the effects of building plan irregularity, that lead to torsional response, on the seismic response of building structures. Effects of some key structural and ground motion characteristics (e.g. hysteretic model, ground motion duration, etc.) are considered. Mass eccentricity is found to result in rather smaller torsional response compared to stiffness/strength eccentricity. Mass rotational inertia generally decreases the torsional response; however, the trend is not clearly defined for torsionally restrained systems (i.e. large λty). Systems with EPP and bilinear models have close displacements and systems with Takeda, SINA, and flag-shaped models yield almost the same displacements. Damping has no specific effect on the torsional response for the single-storey systems with the unidirectional eccentricity and excitation. Displacements of the single-storey systems subject to long duration ground motion records are smaller than those for short duration records. A method to consider torsional response of ductile building structures under earthquake shaking is then developed based on structural dynamics for a wide range of structural systems and configurations, including those with low and high torsional restraint. The method is then simplified for use in engineering practice. A novel method is also proposed to simply account for the effects of strength eccentricity on response of highly inelastic systems. A comparison of the accuracy of some existing methods (including code-base equivalent static method and model response spectrum analysis method), and the proposed method, is conducted for single-storey structures. It is shown that the proposed method generally provides better accuracy over a wide range of parameters. In general, the equivalent static method is not adequate in capturing the torsional effects and the elastic modal response spectrum analysis method is generally adequate for some common parameters. Record-to-record variation in maximum displacement demand on the structures with different degrees of torsional response is considered in a simple way. Bidirectional torsional response is then considered. Bidirectional eccentricity and excitation has varying effects on the torsional response; however, it generally increases the weak and strong edges displacements. The proposed method is then generalized to consider the bidirectional torsion due to bidirectional stiffness/strength eccentricity and bidirectional seismic excitation. The method is shown to predict displacements conservatively; however, the conservatism decreases slightly for cases with bidirectional excitation compared to those subject to unidirectional excitation. In is shown that the roof displacement of multi-storey structures with torsional response can be predicted by considering the first mode of vibration. The method is then further generalized to estimate torsional effects on multi-storey structure displacement demands. The proposed procedure is tested multi-storey structures and shown to predict the displacements with a good accuracy and conservatively. For buildings which twist in plan during earthquake shaking, the effect of P-Δλ action is evaluated and recommendations for design are made. P-Δλ has more significant effects on systems with small post- yield stiffness. Therefore, system stability coefficient is shown not to be the best indicator of the importance of P-Δλ and it is recommended to use post-yield stiffness of system computed with allowance for P-Δλ effects. For systems with torsional response, the global system stability coefficient and post- yield stiffness ration do not reflect the significance of P-Δλ effects properly. Therefore, for torsional systems individual seismic force resisting systems should be considered. Accuracy of MRSA is investigated and it is found that the MRSA is not always conservative for estimating the centre of mass and strong edge displacements as well as displacements of ductile systems with strength eccentricity larger than stiffness eccentricity. Some modifications are proposed to get the MRSA yields a conservative estimation of displacement demands for all cases.
The progressive damage and subsequent demolition of unreinforced masonry (URM) buildings arising from the Canterbury earthquake sequence is reported. A dataset was compiled of all URM buildings located within the Christchurch CBD, including information on location, building characteristics, and damage levels after each major earthquake in this sequence. A general description of the overall damage and the hazard to both building occupants and to nearby pedestrians due to debris falling from URM buildings is presented with several case study buildings used to describe the accumulation of damage over the earthquake sequence. The benefit of seismic improvement techniques that had been installed to URM buildings is shown by the reduced damage ratios reported for increased levels of retrofit. Demolition statistics for URM buildings in the Christchurch CBD are also reported and discussed. VoR - Version of Record
Extended Direct Analysis (EDA), developed at the University of Canterbury, is an advance on the AISC Direct Analysis method for the analysis of frames subjected to static forces. EDA provides a faster, simple and more rational way to properly consider the second-order effects, initial residual stresses (IRS) and the initial imperfections or steel structures under one directional loading than conventional analysis methods. This research applied the EDA method to quantify the effect of member overstrength on frame behaviour for a single storey frame. Also, the effects of IRS, which were included in the EDA static analysis, but which are not considered explicitly in non-linear seismic analysis, were evaluated in two ways. Firstly, they were considered for simple structures subject to increasing cyclic displacement in different directions. Secondly, incremental dynamic analysis with realistic ground motion was used to quantify the likely effect of IRS in earthquakes. It was found that, contrary to traditional wisdom and practice, greater member strengths can result in lower frame strengths for frames under monotonic lateral loading. The structural lateral capacity of the overstrength case was reduced by 6% compared to the case using the dependable member strengths. Also, it resulted significantly different in member demands. Therefore, it is recommended that when either plastic analysis or EDA is used, that both upper and lower bounds on the likely member strength should be considered to determine the total frame strength and the member demands. Results of push-pull analysis under displacement control showed that for IRS ratio, gamma < 0.5 and axial compressive force ratio, N*/Ns, up to 0.5, IRS did affect the structural behaviour in the first half cycle. However, the behavior in the later cycles was not significantly affected. It also showed that the effect of initial residual stresses in the frame was less significant than for the column alone when the column was subjected to similar axial compressive force. The incremental dynamic analysis results from both cantilever column and the three-storey steel frame showed that by increasing gamma = 0 to 0.5, the effect of IRS on seismic responses, based on the 50% confidence level, was less than 3% for N*/Ns, up to 0.5.
Floor systems with precast concrete hollow-core units have been largely used in concrete buildings built in New Zealand during the 1980’s. Recent earthquakes, such as the Canterbury sequence in 2010-2011 and the Kaikoura earthquake in 2016, highlighted that this floor system can be highly vulnerable and potentially lead to the floor collapse. A series of research activities are in progress to better understand the seismic performance of floor diaphragms, and this research focuses on examining the performance of hollow core units running parallel to the walls of wall-resisting concrete structures. This study first focused on the development of fragility functions, which can be quickly used to assess likelihood of the hollow-core being able to survive given the buildings design drift, and secondly to determine the expected performance of hollow-core units that run parallel to walls, focusing on the alpha unit running by the wall. Fragility functions are created for a range of different parameters for both vertical dislocation and crack width that can be used as the basis of a quick analysis or loss estimation for the likely impact of hollow-core floors on building vulnerability and risk. This was done using past experimental tests, and the recorded damage. Using these results and the method developed by Baker fragility curves were able to be created for varying crack widths and vertical dislocations. Current guidelines for analysis of hollow-core unit incompatible displacements are based on experimental vertical displacement results from concrete moment resisting frame systems to determine the capacity of hollow-core elements. To investigate the demands on hollow-core units in a wall-based structure, a fibre-element model in the software Seismostruct is created and subject to quasi-static cyclic loading, using elements which are verified from previous experimental tests. It is shown that for hollow-core units running by walls that the 10 mm displacement capacity used for hollow-core units running by a beam is insufficient for members running by walls and that shear analysis should be used. The fibre-element model is used to simulate the seismic demand induced on the floor system and has shown that the shear demand is a function of drift, wall length, hollow-core span, linking slab length and, to a minor extent, wall elongation.
Five years after the devastating series of earthquakes in Christchurch, New Zealand, the structural engineering community is now focussing on low damage design by either proactively reducing the possibility of significant damage to primary steel members (i.e. developing seismic resisting systems that will deliver a high damage threshold in severe earthquakes) or by improved detailing of the primary steel members for rapid replacement. This paper presents a development of Eccentrically Braced Frames (EBFs) with replaceable active links. It uses the bolted flange- and web splicing concept to connect the active link to the collector beam or column. Finite element analyses have been performed to investigate the behaviour and reliability of EBFs with this new type replaceable active link. The results show a stable hysteretic behaviour and more significantly easier replacement of the damaged active link in comparison with conventional EBFs.
The 2010-2011 Canterbury earthquake sequence, and the resulting extensive data sets on damaged buildings that have been collected, provide a unique opportunity to exercise and evaluate previously published seismic performance assessment procedures. This poster provides an overview of the authors’ methodology to perform evaluations with two such assessment procedures, namely the P-58 guidelines and the REDi Rating System. P-58, produced by the Federal Emergency Management Agency (FEMA) in the United States, aims to facilitate risk assessment and decision-making by quantifying earthquake ground shaking, structural demands, component damage and resulting consequences in a logical framework. The REDi framework, developed by the engineering firm ARUP, aids stakeholders in implementing resilience-based earthquake design. Preliminary results from the evaluations are presented. These have the potential to provide insights on the ability of the assessment procedures to predict impacts using “real-world” data. However, further work remains to critically analyse these results and to broaden the scope of buildings studied and of impacts predicted.
A major lesson from the 2011 Christchurch earthquake was the apparent lack of ductility of some lightly reinforced concrete (RC) wall structures. In particular, the structural behaviour of the critical wall in the Gallery Apartments building demonstrated that the inelastic deformation capacity of a structure, as well as potentially brittle failure of the reinforcement, is dependent on the level of bond deterioration between reinforcement and surrounding concrete that occurs under seismic loading. This paper presents the findings of an experimental study on bond behaviour between deformed reinforcing bars and the surrounding concrete. Bond strength and relative bond slip was evaluated using 75 pull-out tests under monotonic and cyclic loading. Variations of the experiments include the loading rate, loading history, concrete strength (25 to 70 MPa), concrete age, cover thickness, bar diameter (16 and 20 mm), embedded length, and the position of the embedded bond region within the specimen (deep within or close to free surface). Select test results are presented with inferred implications for RC structures.
There is a growing awareness of the need for the earthquake engineering practice to incorporate in addition to empirical approaches in evaluation of liquefaction hazards advanced methods which can more realistically represent soil behaviour during earthquakes. Currently, this implementation is hindered by a number of challenges mainly associated with the amount of data and user-experience required for such advanced methods. In this study, we present key steps of an advanced seismic effective-stress analysis procedure, which on the one hand can be fully automated and, on the other hand, requires no additional input (at least for preliminary applications) compared to simplified cone penetration test (CPT)-based liquefaction procedures. In this way, effective-stress analysis can be routinely applied for quick, yet more robust estimations of liquefaction hazards, in a similar fashion to the simplified procedures. Important insights regarding the dynamic interactions in liquefying soils and the actual system response of a deposit can be gained from such analyses, as illustrated with the application to two sites from Christchurch, New Zealand.
The overarching goal of this dissertation is to improve predictive capabilities of geotechnical seismic site response analyses by incorporating additional salient physical phenomena that influence site effects. Specifically, multidimensional wave-propagation effects that are neglected in conventional 1D site response analyses are incorporated by: (1) combining results of 3D regional-scale simulations with 1D nonlinear wave-propagation site response analysis, and (2) modelling soil heterogeneity in 2D site response analyses using spatially-correlated random fields to perturb soil properties. A method to combine results from 3D hybrid physics-based ground motion simulations with site-specific nonlinear site response analyses was developed. The 3D simulations capture 3D ground motion phenomena on a regional scale, while the 1D nonlinear site response, which is informed by detailed site-specific soil characterization data, can capture site effects more rigorously. Simulations of 11 moderate-to-large earthquakes from the 2010-2011 Canterbury Earthquake Sequence (CES) at 20 strong motion stations (SMS) were used to validate simulations with observed ground motions. The predictions were compared to those from an empirically-based ground motion model (GMM), and from 3D simulations with simplified VS30- based site effects modelling. By comparing all predictions to observations at seismic recording stations, it was found that the 3D physics-based simulations can predict ground motions with comparable bias and uncertainty as the GMM, albeit, with significantly lower bias at long periods. Additionally, the explicit modelling of nonlinear site-response improves predictions significantly compared to the simplified VS30-based approach for soft-soil or atypical sites that exhibit exceptionally strong site effects. A method to account for the spatial variability of soils and wave scattering in 2D site response analyses was developed and validated against a database of vertical array sites in California. The inputs required to run the 2D analyses are nominally the same as those required for 1D analyses (except for spatial correlation parameters), enabling easier adoption in practice. The first step was to create the platform and workflow, and to perform a sensitivity study involving 5,400 2D model realizations to investigate the influence of random field input parameters on wave scattering and site response. Boundary conditions were carefully assessed to understand their effect on the modelled response and select appropriate assumptions for use on a 2D model with lateral heterogeneities. Multiple ground-motion intensity measures (IMs) were analyzed to quantify the influence from random field input parameters and boundary conditions. It was found that this method is capable of scattering seismic waves and creating spatially-varying ground motions at the ground surface. The redistribution of ground-motion energy across wider frequency bands, and the scattering attenuation of high-frequency waves in 2D analyses, resemble features observed in empirical transfer functions (ETFs) computed in other studies. The developed 2D method was subsequently extended to more complicated multi-layer soil profiles and applied to a database of 21 vertical array sites in California to test its appropriate- ness for future predictions. Again, different boundary condition and input motion assumptions were explored to extend the method to the in-situ conditions of a vertical array (with a sensor embedded in the soil). ETFs were compared to theoretical transfer functions (TTFs) from conventional 1D analyses and 2D analyses with heterogeneity. Residuals of transfer-function- based IMs, and IMs of surface ground motions, were also used as validation metrics. The spatial variability of transfer-function-based IMs was estimated from 2D models and compared to the event-to-event variability from ETFs. This method was found capable of significantly improving predictions of median ETF amplification factors, especially for sites that display higher event-to-event variability. For sites that are well represented by 1D methods, the 2D approach can underpredict amplification factors at higher modes, suggesting that the level of heterogeneity may be over-represented by the 2D random field models used in this study.
Sewerage systems convey sewage, or wastewater, from residential or commercial buildings through complex reticulation networks to treatment plants. During seismic events both transient ground motion and permanent ground deformation can induce physical damage to sewerage system components, limiting or impeding the operability of the whole system. The malfunction of municipal sewerage systems can result in the pollution of nearby waterways through discharge of untreated sewage, pose a public health threat by preventing the use of appropriate sanitation facilities, and cause serious inconvenience for rescuers and residents. Christchurch, the second largest city in New Zealand, was seriously affected by the Canterbury Earthquake Sequence (CES) in 2010-2011. The CES imposed widespread damage to the Christchurch sewerage system (CSS), causing a significant loss of functionality and serviceability to the system. The Christchurch City Council (CCC) relied heavily on temporary sewerage services for several months following the CES. The temporary services were supported by use of chemical and portable toilets to supplement the damaged wastewater system. The rebuild delivery agency -Stronger Christchurch Infrastructure Rebuild Team (SCIRT) was created to be responsible for repair of 85 % of the damaged horizontal infrastructure (i.e., water, wastewater, stormwater systems, and roads) in Christchurch. Numerous initiatives to create platforms/tools aiming to, on the one hand, support the understanding, management and mitigation of seismic risk for infrastructure prior to disasters, and on the other hand, to support the decision-making for post-disaster reconstruction and recovery, have been promoted worldwide. Despite this, the CES in New Zealand highlighted that none of the existing platforms/tools are either accessible and/or readable or usable by emergency managers and decision makers for restoring the CSS. Furthermore, the majority of existing tools have a sole focus on the engineering perspective, while the holistic process of formulating recovery decisions is based on system-wide approach, where a variety of factors in addition to technical considerations are involved. Lastly, there is a paucity of studies focused on the tools and frameworks for supporting decision-making specifically on sewerage system restoration after earthquakes. This thesis develops a decision support framework for sewerage pipe and system restoration after earthquakes, building on the experience and learning of the organisations involved in recovering the CSS following the CES in 2010-2011. The proposed decision support framework includes three modules: 1) Physical Damage Module (PDM); 2) Functional Impact Module (FIM); 3) Pipeline Restoration Module (PRM). The PDM provides seismic fragility matrices and functions for sewer gravity and pressure pipelines for predicting earthquake-induced physical damage, categorised by pipe materials and liquefaction zones. The FIM demonstrates a set of performance indicators that are categorised in five domains: structural, hydraulic, environmental, social and economic domains. These performance indicators are used to assess loss of wastewater system service and the induced functional impacts in three different phases: emergency response, short-term recovery and long-term restoration. Based on the knowledge of the physical and functional status-quo of the sewerage systems post-earthquake captured through the PDM and FIM, the PRM estimates restoration time of sewer networks by use of restoration models developed using a Random Forest technique and graphically represented in terms of restoration curves. The development of a decision support framework for sewer recovery after earthquakes enables decision makers to assess physical damage, evaluate functional impacts relating to hydraulic, environmental, structural, economic and social contexts, and to predict restoration time of sewerage systems. Furthermore, the decision support framework can be potentially employed to underpin system maintenance and upgrade by guiding system rehabilitation and to monitor system behaviours during business-as-usual time. In conjunction with expert judgement and best practices, this framework can be moreover applied to assist asset managers in targeting the inclusion of system resilience as part of asset maintenance programmes.
The Canterbury earthquakes of 2010 and 2011 have shone the spotlight on a number of tax issues. These issues, and in particular lessons learned from them, will be relevant for revenue authorities, policymakers and taxpayers alike in the broader context of natural disasters. Issues considered by this paper include the tax treatment of insurance monies. For example, building owners will receive pay-outs for destroyed assets and buildings which have been depreciated. Where the insurance payment is more than the adjusted tax value, there will be a taxable "gain on sale" (or depreciation recovery income). If the building owner uses those insurance proceeds to purchase a replacement asset, legislative amendments specifically enacted following the earthquakes provide that rollover relief of the depreciation recovery income is available. The tax treatment of expenditure to seismically strengthen a building is another significant issue faced by building owners. Case law has determined that this expenditure will usually be capital expenditure. In the past such costs could be capitalised to the building and depreciated accordingly. However, since the 2011-2012 income year owners have been prohibited from claiming depreciation on buildings and therefore currently no deduction is available for such strengthening expenditure (whether immediate or deferred). This has significant potential implications for landlords throughout New Zealand facing significant seismic retrofit costs. Incentives, or some form of financial support, whether delivered through the tax system or some other mechanism may be required. International Financial Reporting Standards (IFRS) require insurance proceeds, including reimbursement for expenditure of a capital nature, be reported as income while expenditure itself is not recorded as a current period expense. This has the effect of overstating current income and creating a larger variation between reported income for accounting and taxation purposes. Businesses have obligations to maintain certain business records for tax purposes. Reconstructing records destroyed by a natural disaster depends on how the information was originally stored. The earthquakes have demonstrated the benefits of ‘off-site’ (outside Canterbury) storage, in particular electronic storage. This paper considers these issues and the Inland Revenue Department (Inland Revenue) Standard Practice Statement which deals with inter alia retention of business records in electronic format and offshore record storage. Employer provided accommodation is treated as income to the benefitting employee. A recent amendment to the Income Tax Act 2007 retrospectively provides that certain employer provided accommodation is exempt from tax. The time aspect of these rules is extended where the employee is involved in the Canterbury rebuild and comes from outside the region.
To reduce seismic vulnerability and the economic impact of seismic structural damage, it is important to protect structures using supplemental energy dissipation devices. Several types of supplemental damping systems can limit loads transferred to structures and absorb significant response energy without sacrificial structural damage. Lead extrusion dampers are one type of supplemental energy dissipation devices. A smaller volumetric size with high force capacities, called high force to volume (HF2V) devices, have been employed in a large series of scaled and full-scaled experiments, as well as in three new structures in Christchurch and San Francisco. HF2V devices have previously been designed using very simple models with limited precision. They are then manufactured, and tested to ensure force capacities match design goals, potentially necessitating reassembly or redesign if there is large error. In particular, devices with a force capacity well above or below a design range can require more testing and redesign, leading to increased economic and time cost. Thus, there is a major need for a modelling methodology to accurately estimate the range of possible device force capacity values in the design phase – upper and lower bounds. Upper and lower bound force capacity estimates are developed from equations in the metal extrusion literature. These equations consider both friction and extrusion forces between the lead and the bulged shaft in HF2V devices. The equations for the lower and upper bounds are strictly functions of device design parameters ensuring easy use in the design phase. Two different sets of estimates are created, leading to estimates for the lower and upper bounds denoted FLB,1, FUB,1, FUB,2, respectively. The models are validated by comparing the bounds with experimental force capacity data from 15 experimental HF2V device tests. All lower bound estimates are below or almost equal to the experimental device forces, and all upper bound estimates are above. Per the derivation, the (FLB,1, FUB,1) pair provide narrower bounds. The (FLB,1, FUB,1) pair also had a mean lower bound gap of -34%, meaning the lower bound was 74% of device force on average, while the mean upper bound gap for FUB,1 was +23%. These are relatively tight bounds, within ~±2 SE of device manufacture, and can be used as a guide to ensure device forces are in range for the actual design use when manufactured. Therefore, they provide a useful design tool.
Following the 2010/2011 Canterbury earthquakes the seismic design of buildings with precast concrete panels has received significant attention. Although this form of construction generally performed adequately in Christchurch, there were a considerable number of precast concrete panel connection failures. This observation prompted a review of more than 4700 panel details from 108 buildings to establish representative details used in both existing and new multi-storey and low rise industrial precast concrete buildings in three major New Zealand cities of Auckland, Wellington and Christchurch. Details were collected from precast manufacturers and city councils and were categorised according to type. The detailing and quantity of each reviewed connection type in the sampled data is reported, and advantages and potential deficiencies of each connection type are discussed. The results of this survey provide a better understanding of the relative prevalence of common detailing used in precast concrete panels and guidance for the design of future experimental studies. http://www.nzsee.org.nz/publications/nzsee-quarterly-bulletin/
Shaking table testing of a full-scale three storey resilient and reparable complete composite steel framed building system is being conducted. The building incorporates a number of interchangeable seismic resisting systems of New Zealand and Chinese origin. The building has a steel frame and cold formed steel-concrete composite deck. Energy is dissipated by means of friction connections. These connections are arranged in a number of structural configurations. Typical building nonskeletal elements (NSEs) are also included. Testing is performed on the Jiading Campus shaking table at Tongji University, Shanghai, China. This RObust BUilding SysTem (ROBUST) project is a collaborative China-New Zealand project sponsored by the International Joint Research Laboratory of Earthquake Engineering (ILEE), Tongji University, and a number of agencies and universities within New Zealand including BRANZ, Comflor, Earthquake Commission, HERA, QuakeCoRE, QuakeCentre, University of Auckland, and the University of Canterbury. This paper provides a general overview of the project describing a number of issues encountered in the planning of this programme including issues related to international collaboration, the test plan, and technical issues.
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.
This presentation summarizes the development of high-resolution surficial soil velocity models in the Canterbury, New Zealand basin. Shallow (<30m) shear wave velocities were primarily computed based on a combination of a large database of over 15,000 cone penetration test (CPT) logs in and around Christchurch, and a recently-developed Christchurch-specific empirical correlation between soil shear wave velocity and CPT. Large active-source testing at 22 locations and ambient-wavefield surface wave and H/V testing at over 80 locations were utilized in combination with 1700 water well logs to constrain the inter-bedded stratigraphy and velocity of Quaternary sediments up to depths of several hundred meters. Finally, seismic reflection profiles and the ambient-wavefield surface wave data provide constraint on velocities from several hundred meters to several kilometres. At all depths, the high resolution data illustrates the complexity of the soil conditions in the region, and the developed 3D models are presently being used in broadband ground motion simulations to further interpret the observed strong ground motions in the 2010-2011 Canterbury earthquake sequence.
Reinforced concrete buildings that satisfied modern seismic design criteria generally behaved as expected during the recent Canterbury and Kaikoura earthquakes in New Zealand, forming plastic hinges in intended locations. While this meant that life-safety performance objectives were met, widespread demolition and heavy economic losses took place in the aftermath of the earthquakes.The Christchurch central business district was particularly hard hit, with over 60% of the multistorey reinforced concrete buildings being demolished. A lack of knowledge on the post-earthquake residual capacity of reinforced concrete buildings was a contributing factor to the mass demolition.Many aspects related to the assessment of earthquake-damaged reinforced concrete buildings require further research. This thesis focusses on improving the state of knowledge on the post earthquakeresidual capacity and reparability of moderately damaged plastic hinges, with an emphasis on plastic hinges typical of modern moment frame structures. The repair method focussed on is epoxy injection of cracks and patching of spalled concrete. A targeted test program on seventeen nominally identical large-scale ductile reinforced concrete beams, three of which were repaired by epoxy injection following initial damaging loadings, was conducted to support these objectives. Test variables included the loading protocol, the loading rate, and the level of restraint to axial elongation.The information that can be gleaned from post-earthquake damage surveys is investigated. It is shown that residual crack widths are dependent on residual deformations, and are not necessarily indicative of the maximum rotation demands or the plastic hinge residual capacity. The implications of various other types of damage typical of beam and column plastic hinges are also discussed.Experimental data are used to demonstrate that the strength and deformation capacity of plastic hinges with modern seismic detailing are often unreduced as a result of moderate earthquake induced damage, albeit with certain exceptions. Special attention is given to the effects of prior yielding of the longitudinal reinforcement, accounting for the low-cycle fatigue and strain ageing phenomena. A material-level testing program on the low-cycle fatigue behaviour of grade 300E reinforcing steel was conducted to supplement the data available in the literature.A reduction in stiffness, relative to the initial secant stiffness to yield, occurs due to moderate plastic hinging damage. This reduction in stiffness is shown to be correlated with the ductility demand,and a proposed model gives a conservative lower-bound estimate of the residual stiffness following an arbitrary earthquake-type loading. Repair by epoxy injection is shown to be effective in restoring the majority of stiffness to plastic hinges in beams. Epoxy injection is also shown to have implications for the residual strength and elongation characteristics of repaired plastic hinges.
The collapse of Redcliffs’ cliff in the 22 February 2011 and 13 June 2011 earthquakes were the first times ever a major failure incident occurred at Redcliffs in approximately 6000 years. This master’s thesis is a multidisciplinary engineering geological investigation sought to study these particular failure incidents, focusing on collecting the data necessary to explain the cause and effect of the cliff collapsing in the event of two major earthquakes. This study provides quantitative and qualitative data about the geotechnical attributes and engineering geological nature of the sea-cut cliff located at Redcliffs. Results from surveying the geology of Redcliffs show that the exposed lithology of the cliff face is a variably jointed rock body of welded and (relatively intact) unwelded ignimbrite, a predominantly massive unit of brecciated tuff, and a covering of wind-blown loess and soil deposit (commonly found throughout Canterbury) on top of the cliff. Moreover, detailing the external component of the slope profile shows that Redcliffs’ cliff is a 40 – 80 m cliff with two intersecting (NE and SE facing) slope aspects. The (remotely) measured geometry of the cliff face comprises of multiple outstanding gradients, averaging a slope angle of ~67 degrees (post-13 June 2011), where the steepest components are ~80 degrees, whereas the gentle sloping sections are ~44 degrees. The physical structure of Redcliffs’ cliff drastically changed after each collapse, whereby seismically induced alterations to the slope geometry resulted in material deposited on the talus at the base of the cliff. Prior to the first collapse, the variance of the gradient down the slope was minimal, with the SE Face being the most variable with up to three major gradients on one cross section. However, after each major collapse, the variability increased with more parts of the cliff face having more than one major gradient that is steeper or gentler than the remainder of the slope. The estimated volume of material lost as a result of the gradient changes was 28,267 m³ in February and 11,360 m³ in June 2011. In addition, surveys of the cliff top after the failure incidents revealed the development of fissures along the cliff edge. Monitoring 10 fissures over three months indicated that fissured by the cliff edge respond to intense seismicity (generally ≥ Mw 4) by widening. Redcliffs’ cliff collapsed on two separate occasions as a result of an accumulated amount of damage of the rock masses in the cliff (caused by weathering and erosion over time), and two Mw 6.2 trigger earthquakes which shook the Redcliffs and the surrounding area at a Peak Ground Acceleration (PGA) estimated to be around 2 g. The results of the theoretical study suggests that PGA levels felt on-site during both instances of failure are the result of three major factors: source of the quake and the site affected; topographic amplification of the ground movement; the short distance between the source and the cliff for both fault ruptures; the focus of seismic energy in the direction of thrust faulting along a path that intercepts Redcliffs (and the Port Hills). Ultimately, failure on the NE and SE Faces of Redcliffs’ cliff was concluded to be global as every part of the exposed cliff face deposited a significant volume of material on the talus at the base of the cliff, with the exception of one section on the NE Face. The cliff collapses was a concurrent process that is a single (non-monotonic) event that operated as a complex series of (primarily) toppling rock falls, some sliding of blocks, and slumping of the soil mantle on top of the cliff. The first collapse had a mixture of equivalent continua slope movement of the heavily weathered / damaged surface of the cliff face, and discontinuous slope movement of the jointed inner slope (behind the heavily weathered surface); whereas the second collapse resulted in only discontinuous slope movement on account of the freshly exposed cliff face that had damage to the rock masses, in the form of old and (relatively) new discontinuous fractures, induced by earthquakes and aftershocks leading up to the point of failure.
In most design codes, infill walls are considered as non-structural elements and thus are typically neglected in the design process. The observations made after major earthquakes (Duzce 1999, L’Aquila 2009, Christchurch 2011) have shown that even though infill walls are considered to be non-structural elements, they interact with the structural system during seismic actions. In the case of heavy infill walls (i.e. clay brick infill walls), the whole behaviour of the structure may be affected by this interaction (i.e. local or global structural failures such as soft storey mechanism). In the case of light infill walls (i.e. non-structural drywalls), this may cause significant economical losses. To consider the interaction of the structural system with the ‘non-structural ’infill walls at design stage may not be a practical approach due to the complexity of the infill wall behaviour. Therefore, the purpose of the reported research is to develop innovative technological solutions and design recommendations for low damage non-structural wall systems for seismic actions by making use of alternative approaches. Light (steel/timber framed drywalls) and heavy (unreinforced clay brick) non-structural infill wall systems were studied by following an experimental/numerical research programme. Quasi-static reverse cyclic tests were carried out by utilizing a specially designed full scale reinforced concrete frame, which can be used as a re-usable bare frame. In this frame, two RC beams and two RC columns were connected by two un-bonded post tensioning bars, emulating a jointed ductile frame system (PRESSS technology). Due to the rocking behaviour at the beam-column joint interfaces, this frame was typically a low damage structural solution, with the post-tensioning guaranteeing a linear elastic behaviour. Therefore, this frame could be repeatedly used in all of the tests carried out by changing only the infill walls within this frame. Due to the linear elastic behaviour of this structural bare frame, it was possible to extract the exact behaviour of the infill walls from the global results. In other words, the only parameter that affected the global results was given by the infill walls. For the test specimens, the existing practice of construction (as built) for both light and heavy non-structural walls was implemented. In the light of the observations taken during these tests, modified low damage construction practices were proposed and tested. In total, seven tests were carried out: 1) Bare frame , in order to confirm its linear elastic behaviour. 2) As built steel framed drywall specimen FIF1-STFD (Light) 3) As built timber framed drywall specimen FIF2-TBFD (Light) 4) As built unreinforced clay brick infill wall specimen FIF3-UCBI (Heavy) 5) Low damage steel framed drywall specimen MIF1-STFD (Light) 6) Low damage timber framed drywall specimen MIF2-TBFD (Light) 7) Low damage unreinforced clay brick infill wall specimen MIF5-UCBI (Heavy) The tests of the as built practices showed that both drywalls and unreinforced clay brick infill walls have a low serviceability inter-storey drift limit (0.2-0.3%). Based on the observations, simple modifications and details were proposed for the low damage specimens. The details proved to be working effectively in lowering the damage and increasing the serviceability drift limits. For drywalls, the proposed low damage solutions do not introduce additional cost, material or labour and they are easily applicable in real buildings. For unreinforced clay brick infill walls, a light steel sub-frame system was suggested that divides the infill panel zone into smaller individual panels, which requires additional labour and some cost. However, both systems can be engineered for seismic actions and their behaviour can be controlled by implementing the proposed details. The performance of the developed details were also confirmed by the numerical case study analyses carried out using Ruaumoko 2D on a reinforced concrete building model designed according to the NZ codes/standards. The results have confirmed that the implementation of the proposed low damage solutions is expected to significantly reduce the non-structural infill wall damage throughout a building.
This section considers forms of collaboration in situated and community projects embedded in important spatial transformation processes in New Zealand cities. It aims to shed light on specific combinations of material and semantic aspects characterising the relation between people and their environment. Contributions focus on participative urban transformations. The essays that follow concentrate on the dynamics of territorial production of associations between multiple actors belonging both to civil society and constituted authority. Their authors were directly engaged in the processes that are reported and conceptualised, thereby offering evidence gained through direct hands-on experience. Some of the investigations use case studies that are conspicuous examples of the recent post-traumatic urban development stemming from the Canterbury earthquakes of 2010-2011. More precisely, these cases belong to the early phases of the programmes of the Christchurch recovery or the Wellington seismic prevention. The relevance of these experiences for the scope of this study lies in the unprecedented height of public engagement at local, national and international levels, a commitment reached also due to the high impact, both emotional and concrete, that affected the entire society.
