This paper compares the responses of two 3D building models subjected to recorded and simulated ground motions following New Zealand (NZ) code-based ground-motion selection and scaling provisions to examine the applicability of simulated ground motions for use in conventional engineering practice in NZ. The buildings were designed according to NZ building codes and physically constructed in Christchurch prior to the 2010-2011 Canterbury earthquakes. 40 recorded ground motions from the 22 February 2011 Christchurch earthquake, along with previously published simulated ground motions for this event were considered. The seismic responses of the structures are principally quantified via the peak floor acceleration and peak inter-storey drift ratio. The peak floor accelerations of both buildings, and peak drifts of the 13 storey in-plan regular RC wall structure, were statistically consistent; whereas the peak drifts for the seven storey in-plan irregular mixed system are approximately 30% different. Overall, the results indicate a general agreement in seismic demands obtained using the recorded and simulated ground motion ensembles, and hence provide further evidence that state-of-the-art simulated ground motions can be used in code-based structural performance assessments in place of, or in combination with, ensembles of historically recorded ground motions.
In seismic-prone regions, construction projects face elevated vulnerability risks that extend beyond structural design. While technical evaluations are common, few frameworks integrate managerial, human, and logistical dimensions into seismic risk assessment. This study addresses this gap by applying the Analytic Hierarchy Process (AHP) to evaluate seismic vulnerability using a structured multi-criteria decision-making model. Key parameters—including human resources, materials, supply logistics, and organizational practices—are weighted through expert input and analysed in three Algerian case studies across various seismic zones. Findings reveal that human and organizational factors significantly influence overall vulnerability. The study offers a replicable framework and highlights opportunities for enhancing decision-making through AI integration.
This study examines the impact of gusset plate design on the collapse risk of two buckling-restrained braced frame (BRBF) buildings, incorporating superX and diagonal brace configurations. Nonlinear dynamic analysis shows that the gusset plate axial compressive strength is, on average, 30% lower than the design strength estimated by NZS-3404, indicating that the current design approach may be non-conservative. This study explores three alternative design methods: (i) NZS-3404 design with modifications (NZS-3404-revised), (ii) Court-Patience (CP) method, and (iii) Notional load yield line (NLYL) method. On average, the gusset plate axial compressive strength obtained from dynamic analysis aligns closely with the design strengths predicted by the NZS-3404-revised and CP methods. The NLYL method explicitly accounts for the reduced strength of mid-span gusset plates in super-X and chevron-configured BRBFs. The gusset plate strengths from dynamic analysis are approximately 30% greater than those estimated by the NLYL method, demonstrating that this approach is sufficiently conservative and therefore recommended for design. Within the limited range of brace and gusset plate configurations studied, the collapse risk is reduced by a factor of 3.5 when the NLYL method is used instead of the NZS-3404 method.
This short manuscript describes how three different schools of thought, combining observation, pragmatism, physics, and judgment, have arrived at strikingly similar approaches to proportion RC building structures that can sustain intense earthquake demands without incurring excessive structural and non-structural damage. The examined traditions, which can be traced back to Japan, the University of Illinois at Urbana-Champaign, and Chile, were shaped by independent calibration processes. Yet they all share a common idea: structural robustness is crucial to reduce building earthquake damage. The success of this simple idea has been demonstrated repeatedly in the field. For that reason, New Zealand engineering students, at the very least, should be made aware of these practices, especially considering that the local tradition is radically different.
This paper explores the influence of ground improvement on building seismic demands through parametric site response analyses of low-to-mid-rise buildings supported on mat foundations. A set of soil profiles, containing liquefiable strata, and two building archetypes are analysed using two-dimensional finite element models, both with and without improved zones underneath the buildings. The densification/stiffness of the improved zone and the depth of the improvement is varied as part of the parametric study. The seismic demand on the buildings and foundations for the unimproved and improved sites is assessed. The results show that ground improvement effectively reduces foundation displacements but often increases base shear and inter-storey drift demands. Under total stress conditions, amplified structural seismic demands show a good correlation with increases in shear-wave velocity of the improved ground. However, when liquefiable soil behaviour is modelled, the ratio of the depth of improvement to the depth of the liquefiable stratum (Zi/Zsoft,liq) is a more reliable predictor of seismic demands. When Zi/Zsoft,liq = 0.50, foundation subsidence relative to the adjacent unimproved ground is limited to less than 50 mm in most cases, and rocking drift remains below 0.5%, provided that bearing pressures do not exceed 80 kPa. This improved depth ratio is identified as a good threshold for limiting the potential for damage. However, beyond this threshold, the ability of the building to sustain repairable damage after an ULS earthquake relies on its capacity to accommodate increased flexural drift caused by soil–foundation–structure interaction effects. The trends identified in this study offer valuable insights into how ground improvement influences seismic demand on buildings.
This technical note presents comparisons between the emergency response and recovery efforts following two significant seismic events: the 2010-11 Canterbury Earthquake Sequence in New Zealand and the 2024 Noto Peninsula Earthquake in Japan. Drawing on the author's firsthand observations from both events, the paper highlights key differences in infrastructure resilience, emergency coordination, and community recovery. The aim is to inform future disaster response strategies in New Zealand by learning from Japan's approach, particularly in terms of speed, adaptability, and community integration.
Functional recovery is a new design strategy in earthquake engineering that prioritises rapid recovery and building re-use after severe natural disasters. It suggests holistic building performance goals focused on structural robustness, enhanced safety, and a rapid return to operations post-event. To paint a realistic picture of post-earthquake building recovery trajectories, there remains a significant gap in knowledge for calibrating existing building seismic performance assessment frameworks using empirical data from earthquakes. The 2024 Hualien Earthquake in Taiwan provides a unique opportunity to calibrate this approach and improve our understanding of building seismic performance and how the functional recovery of buildings affects community resilience. A reconnaissance trip was undertaken in Hualien, and damage data from 16 buildings were collected to generate functional recovery lessons and benchmark the FEMA-P58 framework using SP3 software. The research suggests that the closure or limited use of some residential buildings was largely due to extensive damage to non-structural elements, including egress and elevators, ceilings, partitions, facades, and glazing. Business disruptions were mainly caused by restricted access or cordons put in place for the safe demolition of adjacent buildings. The adaptive resilience and preparedness of building owners, residents, and businesses appeared to play a significant role in the re-use of buildings. The functional recovery data and lessons learned from Hualien, particularly the positive outcomes of its building retrofit programmes, would support the ongoing development of low-damage design guidelines and seismic design practice in New Zealand that can enhance the seismic performance and recovery of buildings.
To provide evidence on the performance of retrofitting systems for informing retrofit practice in New Zealand, 18 buildings with retrofits including reinforced concrete (RC) column jacketing, RC wing walls, RC shear walls, and steel frames with braces were surveyed after the 2024 Hualien Earthquake in Taiwan. The primary goal of this study was to quantity amounts of retrofitting installed in vulnerable existing buildings prior to the earthquake observed to be sufficient to prevent severe structural damage and disruption to building functionality. The idea would be to use these quantified amounts as a rough threshold for comparing between competing retrofitting systems in preliminary design. In general, the retrofits observed in Taiwan were low-cost and designed to target mitigation of soft and weak first stories, a well-known structural vulnerability within the Taiwanese building stock. Nevertheless, the scope of retrofits ranged from being installed in first story only to along the full height of the building. Simple indices estimated as ratios of cross-sectional areas of columns and walls to total floor area used as a proxy for base shear strength showed that on average, retrofitting nearly doubled the base shear capacity compared with the original state. To observe the effect of retrofitting on observed earthquake damage, case studies consisting of sets of building pairs, one building without retrofitting that experienced severe or moderate damage and one building with low-cost retrofitting that had minor or no damage, were investigated. Building pairs were selected to have similar size, structural layout, and seismic demand. Based on three case studies, if the amount of retrofitting increased column and wall indices to a certain threshold, no severe damage was observed. A cost assessment of typical retrofitting systems was performed based on estimated cost schedules provided by Taiwanese structural consulting firms. For a 5-story mixed-use building consisting of both commercial and residential units, and assuming the cost to build a new structure is approximately USD $1000 per square meter, the cost of installing a retrofitting system comprising RC column jacketing and additional shear walls to double base shear strength was estimated to be between 15-20% of the rebuilding cost of the original building (USD $165/m2) based on current construction practice in Taiwan. The average cost of retrofitting installed in 23 private residential buildings was less expensive at approximately USD $130/m2 indicating that increasing seismic capacity of vulnerable buildings can be achieved at a reasonable cost.
Taiwan’s emergency management practices have rapidly evolved over recent decades, driven by frequent large-scale natural disasters, a desire to enhance inter-agency collaboration, and advancements in geospatial technology. This paper introduces Taiwan’s integrated geospatial information systems and initiatives—including the National Geographic Information System (NGIS) initiative, the Civil IoT Taiwan programme, the Platform for Risk Information and Safety Management (PRISM), and the Hualien County Geographic Information Integration Application Platform—and their crucial roles in supporting decision-making at both national and local levels. We present the development history, system architecture, and practical applications of these systems, highlighting their integration of big data, IoT (Internet of Things), 3D spatial modelling, AI analytics, and real-time information exchange capabilities. Case studies such as the 2024 Hualien Earthquake and Hualien County’s comprehensive digital governance initiatives are used to illustrate how these systems facilitate effective disaster preparedness, emergency response, and post-event recovery. The Taiwan experience demonstrates how continuous technological innovation, robust cross-agency collaboration, and standardised spatial data management can significantly enhance national and local resilience and operational efficiency in emergency management and other business-as-usual operations.
A Mw 7.4 earthquake struck off the east coast of Taiwan on 3 April 2024. Strong ground shaking was felt across Taiwan, with the highest intensities recorded in Hualien County, resulting in 18 fatalities, three people missing, over 1,100 injuries, the collapse of several buildings, and significant disruptions to infrastructure. Compared with other major recent earthquakes in Taiwan, such as 1999 Chi-Chi Earthquake (Mw 7.6), and 2016 Meinong Earthquake (Mw 6.4), the overall damage and casualty levels were relatively low, demonstrating the benefits of important advancements in seismic resilience in Taiwan since the Chi-Chi Earthquake. To gain a detailed understanding of the impacts of the earthquake and of Taiwan’s seismic resilience developments over the past two decades, a New Zealand Society for Earthquake Engineering (NZSEE) Learning from Earthquakes (LFE) team was deployed to Taiwan between May and June 2024. This journal article reports the observations and key insights from field inspections, meetings with government officials, and discussions with researchers and professors at local universities. The lessons learned from Taiwan’s experience provide valuable insights for New Zealand, highlighting the importance of pragmatic, cost-effective retrofit schemes, proactive emergency management, and rapid functional recovery strategies.
Nepal lies within the Himalayan seismic belt, making it one of the most earthquake-prone regions globally. Non-engineered masonry structures, though widely used, are highly vulnerable to seismic disasters. Replacing these structures is impractical and culturally insensitive due to their deep traditional and cultural significance. Retrofitting is a practical and culturally appropriate approach to enhance a building's strength and safety against earthquakes. This study evaluates retrofitting and reinforcement techniques for unreinforced masonry (URM) structures in Nepal's mid-Himalayan region through numerical modelling, nonlinear static analysis, and fragility assessment. Pushover analysis revealed that reconstruction models significantly improve base shear capacity compared to the URM model. Although gabion wire retrofitting has a limited effect at the initial stage, it significantly improves strength at larger displacements. Vertical reinforcements and horizontal bands in the reconstruction model consistently enhance performance. The URM model exhibits concentrated cracking near openings and corners, while the retrofitted model improves stress distribution and reduces crack widths. Additionally, the reconstruction model confines cracks within bands, preventing vertical propagation and ensuring superior structural integrity. Fragility curves reveal that reinforcement significantly enhances seismic performance, as the retrofitted model improves resistance across damage states, with exceptional collapse resistance due to its ductility, allowing energy absorption and delayed failure. The reconstruction model offers consistent protection with lower probabilities of damage across all states, underscoring its reliability during seismic events. Although the reconstruction model incurs higher costs than the retrofitted model due to its extensive reinforcement features, both models provide substantial seismic benefits compared to the base URM model.
To aid with seismic design and assessment, the force-displacement capacity of a structural wall is commonly determined by evaluating a total rotation capacity comprising elastic and plastic deformation components, utilising a moment-curvature section analysis approach. The plastic rotation capacity is dependent on the adopted equivalent plastic hinge length. Although numerous equations for determining the plastic hinge length of slender walls are documented in the literature, their precision remains uncertain. This research collected a database of slender reinforced concrete wall specimens that demonstrated flexural failure modes, in order to evaluate the accuracy of the moment curvature method. For this purpose, the observed drift capacity is compared with the drift capacity estimated using commonly referred to equations for the plastic hinge length of reinforced concrete walls and subsequently, a new plastic hinge length expression is proposed to improve accuracy and reduce variability in predictions. Moreover, the displacement capacities of slender walls calculated using the moment-curvature method are contrasted with results from a direct rotation approach. (based on EN1998-03, ASCE 41-17, and ACI 369-22). The moment-curvature method aligns more closely with the experimental data compared to the direct rotation method and offers additional insights into the seismic performance of slender walls.
After an earthquake, the rapid assessment of economic losses enables government agencies to accurately evaluate the severity of the disaster, thereby initiating the appropriate level of emergency response in a timely manner. By analysing the scope of the affected area and the scale of property losses, rescue resources can be rationally allocated to the most severely impacted regions, thereby effectively mitigating the losses caused by the disaster, while securing valuable time for emergency rescue and disaster relief efforts. To address the challenges in predicting earthquake economic losses, including numerous influencing factors, high computational demands, and complex model training, this study develops a Support Vector Machine (SVM) model optimized by Principal Component Analysis (PCA) and Genetic Algorithm (GA). PCA reduces the dimensionality of economic loss-related factors by eliminating redundancy, selecting principal components with high contribution rates as SVM inputs, with economic loss as the output. GA optimizes SVM performance parameters to establish the PCA-GA-SVM model. Testing on sample data shows it outperforms GA-SVM, GA-BP (Genetic Algorithm-optimized Back-Propagation neural network), and PCA-GA-BP models, achieving an average prediction accuracy of 95.94%, with a mean absolute percentage error (MADE) of 4.0522%, normalized root mean square error (NRMSE) of 2.361%, and coefficient of determination (R2) of 0.9994. These results underscore the model's accuracy and generalization ability, making it an effective tool for rapid, reliable earthquake loss prediction.
Performance-based seismic design of post-installed anchors needs the development of a new framework that can provide tools for designers to anticipate a realistic concrete-anchor system damage in seismic design scenarios relevant for New Zealand. Seismic capacity of anchors is not available for performance-based seismic design from anchor qualification methods considered currently as state-of-the-art. An outlook is provided in this article for the potential first steps in future developments based on a comprehensive assessment of the current state-of-the-art design and qualification approaches, incorporating a novel holistic framework proposed for post-installed anchor seismic performance.
Precast, prestressed hollow-core floors are susceptible to earthquake-induced damage and collapse. While significant progress has been made in New Zealand in understanding and assessing their seismic behaviour, the 2016 Kaikoura earthquake and recent testing demonstrated several unexpected damage patterns. This paper presents experimental evidence and proposes modifications to assessment procedures to account for the detrimental effect of web cracking and the heightened damageability of hollow-core floor units that are seated at or on intermediate columns (so-called 'beta units'). The experimental investigation involved two full-scale super-assembly experiments on a two-bay by one-bay reinforced concrete moment frame structure with hollow-core floors. Results showed that web cracking can initiate at low inter-storey drifts (similar to 0.5%) and become widespread as drifts increase. Beta units exhibited distinct damage patterns and higher vertical dislocations at lower drifts compared to other units. A comparison between the tested response and predictions from the 2018 version of the New Zealand Assessment Guidelines C5 demonstrated low accuracy in the positive moment failure assessment, particularly for beta units. A revised positive moment failure assessment is proposed to simplify the assessment and account for the damageability of beta units. Additionally, the experimental data showed that beam elongation predictions according to C5 (2018) are overly conservative within the elastic range, and a mechanics-based modification is proposed to enhance the accuracy of the assessment. The proposed assessment changes aim to improve the predictive accuracy and better indicate when seismic retrofitting is necessary.
Self-centering friction dampers like the Resilient Slip-Friction Joint (RSFJ) are increasingly relevant for their ability to (1) damp earthquake-induced vibrations without degradation, and (2) prevent residual deformations after earthquakes, thus reducing both damage and downtime. One of their main advantages is a highly customizable load-deformation behaviour, which makes them versatile across various structural applications. Taking advantage of this, however, requires a degree of intuition and iteration to obtain suitable designs. This paper derives an objective and systematic procedure to generate all possible combinations of damper parameters that can produce a custom flag-shaped hysteresis. Equations are obtained to calculate the parameters explicitly and the procedure is validated with existing experimental data. A modelling example is included to demonstrate how the dampers in a three-storey structure can be tuned automatically to provide the global response required. Nonlinear time-history analyses show that the procedure is effective at tuning the dampers simultaneously to achieve the displacement targets and linear deformation profile specified from a displacement-based design.
This paper revisits the sentiments expressed in a 2015 paper published by the author regarding site-specific seismic hazard analysis in New Zealand (NZ) [1]. While many of the general principles expressed remain the same, the completion of the 2022 NZ National Seismic Hazard Model (NSHM), and accompanying Draft Technical Specification TS1170.5:2024 have significantly altered how such analyses are performed in NZ, and the incremental value that they can provide beyond a code-based approach. This paper identifies instances where site-specific analyses remain valuable (and where they do not), where they will likely depart from the 'baseline' 2022 NZ NSHM (and TS1170.5:2024) results to a practically significant degree, and past practices for seismic source and ground-motion modelling choices which are now considered unviable. Lastly, challenges for practitioners and researchers are briefly addressed in order to further advance the practice of site-specific seismic hazard analysis over the next decade.
The paper presents experimental results and findings from several large-scale prototype moment-resisting timber frames. The overarching objective of this research was to provide standardised moment-resisting timber frame connections to support the increased application of timber in multistorey structures in NZ, akin to the 'Steel Connect' guide by SCNZ. The project was led by Red Stag Timberlab with support and funding by Callaghan Innovation. Enovate provided structural engineering design/detailing services for several prototype internal beam-column joint subassemblies, consulted on the experimental test set-up, apparatus, loading protocol and preliminary findings. Experimental testing on the sub-assemblies was performed by BRANZ. The prototype sub-assemblies incorporated either Glue-laminated (Glulam) or Laminated Veneer Lumber (LVL) beams/column elements, and capacity-designed connections consisting of ductile steel plastic hinges/fuses designed to suppress brittle failure in the timber elements and provide energy dissipation/damping. This paper presents findings from the experimental testing to-date, highlights some critical design/detailing issues (identified through experimental testing), compares predicted versus observed frame flexibly, and makes recommendations for future design and research.
Following a damaging earthquake, emergency managers and decision-makers require reliable shaking information to be able to make decisions and prioritise interventions. Until now, in New Zealand, these decisions needed to be made with incomplete geographical information, relying solely on observed data points from either strong-motion stations or felt reports. The New Zealand Shaking Layers project has been designed to fill that gap. Using the ShakeMap software, configured to satisfy New Zealand's characteristics, a tool is now available to end-users that provides shaking intensity maps for Peak Ground Acceleration, Peak Ground Velocity, Modified Mercalli Intensity and spectral acceleration at different periods. The Shaking Layers tool covers the entire country, helping decision-makers make better-informed decisions. The maps are generated for magnitude 3.5 or above earthquakes in New Zealand and use strong-motion data from the GeoNet network, as well as intensity derived from felt report data, and fault rupture information when available. To ensure scientific robustness, the tool has been developed with the support of a Science Advisory Panel and has been designed with similar configuration as the updated 2022 National Seismic Hazard Model. Moreover, to ensure the tool is fit-for-purpose, it has been co-designed with an End-User Advisory Panel comprising emergency managers, response engineers, city councils, risk analysts, duty officers and Civil Defence, amongst others. This paper provides the project overview, as well as the tool's main components and functionalities.
We develop large scenario earthquakes on active faults in the vicinity of Dunedin and use them to develop ground motion simulations for a site in Dunedin (St Kilda – St Clair area, referred to as “St Beach”) and Mosgiel (centre of Mosgiel, referred to as “Taieri Basin”). The scenarios are developed to represent large Akatore Fault (within 15 km of Dunedin and Mosgiel) and Hyde Fault (within 40-50 km) earthquakes. The simulations utilise the Southern California Earthquake Centre Broadband Simulation Platform and the Graves–Pitarka simulation method. Site response analysis is conducted with two-dimensional basin models, and the nonlinear finite element software OpenSees. The dynamic response characteristics of the soft sedimentary layers are modelled with a pressure-independent multi-yield plasticity model. Some confidence in the simulation method is gained by undertaking historical validations, using the only instrumentally recorded earthquake of significance in the region (the Mw 4.7 2015 Lees Valley earthquake). The simulations provide close matches to the amplitudes and durations of the recorded time histories. The Akatore and Hyde fault earthquake simulations show peak ground accelerations of up to 0.8 g and 0.3g respectively, with durations of strong shaking of around 10 to 20 seconds. Uncertainty in the simulated ground motions due to source is quantified by comparing the spectra for repeated simulations, in which the range of source parameters are sampled. The resulting range of simulations shows a spread of as much as 0.5g. The Akatore – St Beach spectra are also compared to NZS1170.5 and New Zealand national seismic hazard model 2022 (NZ NSHM 2022) spectra, for site classes relevant to those of the St Beach site. In general, the simulated spectra exceed the NZS1170.5 spectra at the 0.1-0.3 second periods, but are similar to the mean NZ NSHM 2022 spectra at these periods. Future updates to NZS1170.5 based on NZ NSHM 2022 will therefore be expected to produce design spectra that are more consistent with the results of our study. The study represents the first ground motion simulations developed for southern New Zealand, and the simulation methods could be used to further advance understanding of seismic hazard in the region.
