Bulletin of the New Zealand Society for Earthquake Engineering

Prediction of direct economic losses from earthquakes in Mainland China

2026-03-13T18:04:27+13:00

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 (MAPE) 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.

Future developments in performance-based seismic design and related qualification of post-installed anchors in New Zealand

2026-03-13T17:50:31+13:00

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.

Seismic enhancement of community housings in Nepal’s mid-Himalayas: Retrofitting and reconstruction scenarios

2026-03-13T17:50:23+13:00

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, non-linear 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.

Estimating the dynamic properties of wall-frame structures

2026-03-13T17:50:10+13:00

This study outlines a robust method to approximate the dynamic properties of wall-frame structures with a reasonable degree of reliability based on simple mechanics. The seismic response and drift demand of a structure are largely influenced by its first translational period and mode-shape. This study develops a method to estimate the storey stiffness of a wall, which can be combined with the storey stiffness of a frame to estimate the fundamental period and mode-shape for wall-frame structures. The fundamental period and mode-shape are calculated using this effective storey stiffness and Rayleigh’s principle. A total of 301 wall-frame structures were sized to evaluate the reliability of the proposed method. Structures ranged from 2 to 25 storeys tall. The fundamental period and mode-shape estimated using the proposed method were compared with results from eigenvalue analysis of a detailed linear structural model. The proposed method leads to approximately 4% error on average for estimating the fundamental period of regular structures. The proposed method leads to 5% error on average for irregular structures with partial height walls, as well as variations in storey height, and lateral stiffness. For regular wall-frame structures, the proposed method led to average errors of 4% when estimating the roof mode-shape factor and 2% when estimating the maximum difference in mode-shape factor from one floor to the next, a proxy for storey drift. These errors were 5% and 15% for irregular structures with partial height walls. Results were also compared with estimates obtained from existing empirical equations to approximate the period of wall-frame structures, highlighting that empirical equations lead to greater error, between 15 and 70% depending on the equation. The method outlined in this paper enables users to estimate or corroborate the fundamental period, mode-shape, and lateral displacement for a dual wall-frame structure with a reasonable degree of reliability, suitable for preliminary design and linear analysis. Tools have been developed in MathCAD and python to automate the procedure for estimating the dynamic properties of wall-frame structures and are available here.

Evaluating the displacement capacity of slender rectangular reinforced concrete walls using moment-curvature analysis

2026-03-13T17:50:26+13:00

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.

Seismic performance of precast hollow-core floors: Experimental findings and updates to C5

2026-03-13T17:50:08+13:00

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 Kaikōura 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 (~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.