https://www.bulletin.nzsee.org.nz/index.php/bnzsee/issue/feed Bulletin of the New Zealand Society for Earthquake Engineering 2024-03-01T15:27:47+13:00 Rajesh Dhakal rajesh.dhakal@canterbury.ac.nz Open Journal Systems <p>Bulletin of the New Zealand Society for Earthquake Engineering</p> https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1642 New Zealand specific consequence functions for seismic loss assessment 2024-03-01T15:26:50+13:00 Matthew Fox mat.j.fox@gmail.com Trevor Yeow tyeow.work@gmail.com Jared Keen jared.keen@beca.com Tim Sullivan timothy.sullivan@canterbury.ac.nz Alberto Pavese alberto.pavese@unipv.it <p>Quantitative seismic loss assessment has become an increasingly popular tool for evaluating the seismic performance of structures. The growth in popularity is largely in response to a desire to look beyond the traditional life safety performance objective and instead consider also economic losses and downtime due to earthquakes. A key step in the loss assessment calculation process is relating damage in both structural and nonstructural components to appropriate repair strategies and subsequently repair costs and repair times. This is achieved through the use of so-called consequence functions, which in this paper are derived specifically for the New Zealand context. Furthermore, a framework is established for other researchers and professional engineers to continue to build on and improve the initial dataset. It is shown that using New Zealand specific consequence functions can have a noticeable effect on estimates of expected annual loss when compared to a benchmark case using consequence functions from FEMA P-58. The opportunity is also taken to evaluate the impact of recent updates to the New Zealand National Seismic Hazard Model, with the results for a case-study building in Wellington indicating that the change in hazard has a far more significant effect on estimates of loss when compared to the choice of different consequence functions.</p> 2024-02-29T00:00:00+13:00 Copyright (c) 2024 Matthew Fox, Trevor Yeow, Jared Keen, Tim Sullivan, Alberto Pavese https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1627 Strengthening damaged columns on the soft first story of reinforced concrete building using ultra-high-strength fiber-reinforced concrete panels 2024-03-01T15:27:07+13:00 Su A Lim sualim0126@gmail.com Masanori Tani tani@archi.kyoto-u.ac.jp Hidekazu Watanabe wata_h@kenken.go.jp Tomohisa Mukai mukai-t92ta@mlit.go.jp Eiichirou Nishimura eiichirou.nishimura@toda.co.jp Shinsuke Hori hori.sin@jcity.maeda.co.jp Tsubasa Hattori tsubasa.hattori@ku.kumagaigumi.co.jp Daisuke Matsumoto matsumoto.daisuke@ad-hzm.co.jp Minehiro Nishiyama nishiyama.minehiro.8a@kyoto-u.ac.jp <p>In this study, ultra-high-strength fiber-reinforced concrete (UFC) panels were used as a quick and effective measure for seismic strengthening of damaged reinforced concrete (RC) columns. Four 1/3-scale specimens, which replicated RC columns of the soft-first-story of a 10-story condominium building that was heavily damaged in the 2016 Kumamoto Earthquake, were constructed and tested. The specimens were strengthened using UFC panels after being preloaded to the drift ratio, at which the maximum load capacity of the target column was measured, and then subjected to the main loading until the ultimate state was reached. The UFC panels were installed on the two faces of the column in a direction parallel to the assumed loading direction. Two of the specimens had a UFC or RC wing wall attached to one side of the column, which was also aligned with the assumed loading direction. During the preloading and main loading, the specimens were subjected to a cyclic lateral load and varying axial load that simulated an earthquake load. The proposed method improved the maximum strength and ultimate drift ratio, and helped restore the initial stiffness of specimens with UFC panels and a wing wall to that of a column specimen during preloading. The test results of a previous study, wherein the target column, loading method, and strengthening method were the same but the specimens were not damaged before strengthening, were compared to study the impact of the damage on the RC column before strengthening.</p> <p> </p> 2024-02-29T00:00:00+13:00 Copyright (c) 2024 Su A Lim, Masanori Tani, Hidekazu Watanabe, Tomohisa Mukai, Eiichirou Nishimura, Shinsuke Hori, Tsubasa Hattori, Daisuke Matsumoto, Minehiro Nishiyama https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1625 Structures incorporating damping devices: Are we correct in our design thinking? 2024-03-01T15:27:27+13:00 Athol J. Carr athol.carr@canterbury.ac.nz Arun M. Puthanpurayil Arun.Puthanpurayil@beca.com Richard Sharpe Richard.Sharpe@beca.com Rob Jury Rob.Jury@beca.com <p>The use of discrete damping devices in New Zealand buildings is increasing as designers seek to limit damage to both architectural and structural building elements in moderate earthquakes. The overall damping of the structure becomes a combination of inherent material damping, hysteretic damping from yielding of building elements at specific locations and damping from discrete devices. For over 60 years, engineers have used simplified analysis procedures (e.g., modal response spectrum analysis) to predict building response under seismic actions. The design of structures incorporating viscous dampers requires a paradigm shift in approach as the force each damper resists is a function of the relative velocity between its ends. Popular pseudo-static design methodologies promote the use of a <em>viscous strut</em> in the analysis model to represent them. However, it is incorrect to use elastic, mode-based analysis for a structure incorporating damping devices and relying on significant inelastic behaviour. This paper elucidates the complex mechanics of damper-structure interaction by reviewing some of the established classical, modal‑based, simplified analysis techniques used in seismic design. A series of numerical investigations demonstrate how these techniques are usually invalid for structures that incorporate viscous dampers because they violate the laws of physics. The reason why mode-based techniques are invalid is explored with reference to the imaginary components of the natural modes of vibration and the effect on them of significant inelasticity within the structure. The dynamic characteristics of viscous dampers challenge conventional design approaches such as displacement-based design. This paper establishes that nonlinear time-history analysis is the only meaningful way of predicting the dynamic response of a structure incorporating viscous dampers when significant inelastic behaviour of the structure is expected.</p> 2024-02-29T00:00:00+13:00 Copyright (c) 2024 Athol J. Carr, Arun M. Puthanpurayil, Richard Sharpe, Rob Jury https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1619 Sectional response of non-rectangular concrete walls with minimum vertical reinforcement 2024-03-01T15:27:47+13:00 Tianhua Deng tianhua.deng@auckland.ac.nz Richard S Henry rs.henry@auckland.ac.nz <p>Past research that investigated the behaviour of rectangular lightly reinforced concrete walls resulted in revisions to minimum vertical reinforcement provisions in concrete design standards in both New Zealand (NZS 3101:2006) and the United States (ACI 318-19). However, the minimum vertical reinforcement provisions developed for rectangular wall sections may not be suitable for non-rectangular walls due to the influence of flanges on the nominal flexural and cracking section capacities. A parametric study confirmed that non-rectangular wall sections with minimum vertical reinforcement in accordance with current NZS 3101 design provisions exhibit a lower margin between cracking and nominal flexural strength than comparable rectangular wall sections. The ratio of the sectional nominal flexural strength to cracking strength (Mn/Mcr ) was less than 1.0 for non-rectangular sections with long flange lengths and low axial loads. The model results indicated that current vertical reinforcement requirements are insufficient to prevent a sudden and potentially unstable strength drop when cracking occurs in non-rectangular walls. A theoretical equation to calculate the required minimum vertical reinforcement was proposed for the typical I-shaped wall sections, including the impact of concrete strength and flange to web ratio. The proposed equation highlighted the need for an increase in the minimum vertical reinforcement limits for non-rectangular wall sections compared to the existing minimum vertical reinforcement requirement applicable to rectangular wall sections.</p> 2024-02-29T00:00:00+13:00 Copyright (c) 2024 Tianhua Deng, Richard S Henry https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1680 Seismic design of buildings: Where to next? 2024-03-01T15:26:36+13:00 Rajesh Dhakal rajesh.dhakal@canterbury.ac.nz <p>This paper critically reviews the current building seismic design approach based on the observed performance of modern building stock in recent earthquakes, highlights the inability of the current design approach in controlling seismic damage and losses, and proposes a conceptual framework for next generation seismic design codes that is likely to meet public expectations. In addition to ensuring life-safety in rare earthquakes, the proposed loss-optimization seismic design approach also aims to ensure quick functional recovery and minimum loss (i.e. repair, downtime, and injury/fatality) in moderate-strong earthquakes by limiting damage to building’s structural and non-structural components. Based on comparison of performances of building stock in some recent major earthquakes in different countries, the paper presents some simple strategies to render buildings more resilient and suffer significantly less seismic damage (and consequentially incur less loss). Finally, the paper scrutinizes the efficacy of some commonly used low-damage technologies in minimizing building seismic losses.</p> 2024-02-29T00:00:00+13:00 Copyright (c) 2024 Rajesh Dhakal