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Bulletin of the New Zealand Society for Earthquake Engineering

Publisher:
—
ISSN:
1174-9857
Category:
ENGINEERING, GEOLOGICAL
Impact factor:
0.8

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2 parsed articles

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Latest articles

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

2026-03-03

Arsalan Niroomandi, Mahshid Firoozbakhtian, Mohammad Amir Najafgholipour, Timothy Sullivan, Craig Stevenson

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.

Estimating the dynamic properties of wall-frame structures

2026-03-03

Liam Pledger, Santiago Pujol, Reagan Chandramohan

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.