Bulletin of the New Zealand Society for Earthquake Engineering https://bulletin.nzsee.org.nz/index.php/bnzsee <p>Bulletin of the New Zealand Society for Earthquake Engineering</p> en-US <ol> <li>You warrant that you have the authority to act as the agent of all the authors of this article for the purpose of entering into this agreement.</li> <li>You hereby grant a <a href="https://creativecommons.org/licenses/by/4.0" target="_blank" rel="noopener">Creative Commons Attribution (CC-BY) license</a> in the article to the general public.</li> <li>You agree to require that a citation to the original publication of the article in the Bulletin of the New Zealand Society for Earthquake Engineering be included in any attribution statement satisfying the attribution requirement of the Creative Commons license of paragraph 2.</li> <li>You retain ownership of all rights under copyright in all versions of the article, and all rights not expressly granted in this agreement.</li> <li>To the extent that any edits made by the publisher to make the article suitable for publication in the journal amount to copyrightable works of authorship, the publisher hereby assigns all right, title, and interest in such edits to you. 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You agree to indemnify the publisher against any claim or action alleging facts which, if true, constitute a breach of any of the foregoing warranties or other provisions of this agreement, as well as against any related damages, losses, liabilities, and expenses incurred by the publisher.</li> </ol> </li> <li>This is the entire agreement between you and the publisher, and it may be modified only in writing. It will be governed by the laws of New Zealand. It will bind and benefit our respective assigns and successors in interest, including your heirs.</li> </ol> rajesh.dhakal@canterbury.ac.nz (Rajesh Dhakal) reagan.c@canterbury.ac.nz (Reagan Chandramohan) Sun, 02 Jun 2024 14:55:13 +1200 OJS 3.3.0.8 http://blogs.law.harvard.edu/tech/rss 60 Method to identify if torsional mode of a building is its first mode https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1645 <p><em>Torsionally flexible</em> buildings (that have <em>torsional mode</em> as fundamental mode) twist during earthquake shaking, and may <em>collapse</em> <em>partially</em> or <em>completely</em> depending upon the direction and level of shaking. The problem is aggravated when the building is <em>torsionally</em> <em>unsymmetrical</em>. Some design codes (<em>like Eurocode, Indian Code</em>) explicitly prohibit the design of such buildings. This paper presents a simple approximate method to identify torsionally flexible <em>RC Moment Frame </em>and <em>RC Structural Wall</em> buildings at the <em>initial</em> <em>proportioning</em> stage itself without carrying out a detailed structural analysis. It is possible to identify whether or not the first mode is torsional mode of a building (<em>i.e.,</em> torsionally flexible building) if <em>Natural Period Ratio τ&gt;</em>1 by modelling the building with rigid diaphragm and distribution of mass &amp; stiffness along the height of building, and estimating: (1) radius of gyration of rotational mass <em>r<sub>m</sub></em> of each floor plan geometry by lumping the masses of slabs, beams and all vertical elements at each nodes, (2) radius of gyration of twisting stiffness <em>r<sub>Kθ</sub></em> of all vertical elements using their translational and torsional stiffnesses (considering flexibility of adjoining beams and vertical elements accounting for both flexural and shear deformations), and (iv) <em>τ</em> <em>(=r<sub>m</sub>/r<sub>Kθ</sub>)</em>. The method is validated with <em>3D Modal Analysis</em> (using <em>τ =T<sub>θ</sub>/T, where T<sub>θ</sub> is Uncoupled Torsional Natural Period and T Uncoupled Translational Natural Period</em>) of hypothetical buildings using a commercial structural analysis software. Also, parameters are identified that lead to <em>τ&gt;</em>1, and solutions suggested to avoid torsional flexibility in buildings. Further, the method helps identify <em>vertical stiffness irregularity</em> in buildings. Draft provisions are suggested for inclusion in seismic codes. Also, poor performance of multi-storey building (with <em>τ&gt;</em>1) is demonstrated using nonlinear static and nonlinear time history analyses.</p> TAMIZHARASI G, C.V.R.Mury Copyright (c) 2024 TAMIZHARASI G, C.V.R.Mury https://creativecommons.org/licenses/by/4.0 https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1645 Sun, 02 Jun 2024 00:00:00 +1200 A comparative investigation on experimental lateral behaviour of bare RC frame, non-strengthened and ferrocement strengthened masonry infilled RC frame https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1656 <p>Although concrete framed structures are widely used with masonry infills, the contribution of masonry infills in structural design is limited to their dead loads only. Therefore, the full-fledged stiffness characteristics of masonry infill are not often considered. However, recent earthquakes showed the impact of masonry infill on the lateral behavior of surrounding RC frames. Moreover, sometimes existing masonry infills are strengthened using Ferrocement (FC), Textile Reinforced Mortar (TRM), Carbon Fiber Reinforced Polymer (CFRP), etc., which might also have a similar impact on surrounding RC frames. The impact includes enhanced shear demand, damage, etc. However, the effect of the enhanced shear demand on RC columns is a relatively less investigated issue. In this context, an experimental program was designed to compare the effect of non-strengthened and FC strengthened masonry infill on the behavior of the surrounding RC frame in terms of lateral strength, hinge formation, shear demand enhancement, and damage to columns. The test specimens, including a bare RC frame, a masonry infilled RC frame, and a FC strengthened masonry infilled RC frame, were subjected to a quasi-static cyclic lateral loads. The experimental result showed that the masonry infill and FC strengthened masonry infill increased lateral strength, on average, by 81% and 244%, respectively, when compared to that of the bare RC frame. Meanwhile, FC strengthening of masonry infill improved the lateral strength, on average, by 90% when compared with the masonry infilled RC frame’s lateral strength. In this study, low-strength masonry infill caused the formation of a short column on the tension column of the RC frame. The application of ferrocement to low-strength masonry altered the position of the plastic hinge formed on the tension column of the RC frame when compared to that of the masonry infilled RC frame. Therefore, ferrocement strengthening of masonry eliminated the short column phenomenon in this particular study. Nevertheless, the shear demand (in terms of strain on the column tie) enhancement of the tension column was not substantial due to the ferrocement strengthening of the masonry infill when compared to that of the masonry infilled RC frame. Moreover, the damage concentration on RC columns (i.e., residual crack width) after insertion of masonry infill and ferrocement strengthened masonry infill changed to a smaller extent when compared to the bare RC frame damages, where the residual crack widths were within 1.0 ~ 2.0 mm.</p> Dr. Debasish Sen, Dr. Fatema Tuz Zahura, Mr. Anik Das, Dr. Hamood Alwashali, Dr. Md. Shafiul Islam, Dr. Masaki Maeda, Dr. Matsutaro Seki, Dr. Muhammad Abdur Rahman Bhuiyan Copyright (c) 2024 Dr. Debasish Sen, Dr. Fatema Tuz Zahura, Mr. Anik Das, Dr. Hamood Alwashali, Dr. Md. Shafiul Islam, Dr. Masaki Maeda, Dr. Matsutaro Seki, Dr. Muhammad Abdur Rahman Bhuiyan https://creativecommons.org/licenses/by/4.0 https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1656 Sun, 02 Jun 2024 00:00:00 +1200 Liquefaction hazard of Wellington reclamations based on conventional analysis https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1675 <p class="Summary">Severe liquefaction-induced damage occurred in reclamation fills at the port of Wellington (CentrePort) in the 2016 Kaikōura earthquake, but little or no damage was reported in areas of older and shallower reclamations in central Wellington. Recent studies have therefore primarily focused on understanding the liquefaction hazard of the port, while little is still understood with regards to the fill characteristics and liquefaction potential of the Wellington reclamations outside CentrePort. This study utilizes data from comprehensive field investigations, including 58 new cone penetration tests (CPTs) performed both within and outside the port in the Wellington waterfront area, supplemented with over 100 CPTs from our previous studies at CentrePort, to characterize the liquefaction resistance of the reclaimed fills in Wellington. The geotechnical data is first used to define simplified schematic soil profiles and to determine characteristic CPT parameter values (25<sup>th</sup>–50<sup>th</sup>–75<sup>th</sup> percentiles) for fills encountered in different reclamation areas. These analyses highlight differences in the soil profiles, and the relative similarity in the estimate of liquefaction resistance based on conventional CPT-based assessment, of fills encountered in different reclamation areas despite differences in the age, techniques, and materials employed in the construction of these reclamations. Conventional liquefaction assessments of reclamation fills based on CPT data are then performed over the wider waterfront area for a range of earthquake scenarios and ground motion intensities relevant for Wellington. For recent, past earthquakes, correspondence between predicted and observed severity of the manifestations of liquefaction vary depending on the earthquake event and area of observations. Likelihood of liquefaction occurrence and severity of the effects of liquefaction are then discussed for characteristic return periods, in the context of the seismic hazard of Wellington.</p> Claudio Cappellaro, Riwaj Dhakal, Misko Cubrinovski Copyright (c) 2024 Claudio Cappellaro, Riwaj Dhakal, Misko Cubrinovski https://creativecommons.org/licenses/by/4.0 https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1675 Sun, 02 Jun 2024 00:00:00 +1200 Monotonic testing of brace assemblies for piping systems and considerations for capacity design https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1678 <p>Distributed nonstructural elements (NSEs), such as piping systems, are restrained against seismic actions using proprietary or, at times, custom-designed braces. The strengths of these elements are provided in the component brochures published by the manufacturers, with no information on their deformation capacities. Previous research on the seismic performance of NSEs provide several formulations to calculate possible reductions in design force by relying on ductility capacity of their seismic restraints. However, designers require a realistic estimate of the ductility capacity of the seismic restraints to use these formulations. This paper discusses the results of a test program on the behavior of brace assemblies under monotonic tensile and compression loading. The results are used to identify the potential failure modes of the tested brace assemblies and to quantify their ductility capacity. Further, design examples are presented to highlight the need for the use of capacity design principles in the design of brace assemblies and their anchors.</p> Muhammad Rashid, Rajesh Dhakal, Timothy Sullivan Copyright (c) 2024 Muhammad Rashid, Rajesh Dhakal, Timothy Sullivan https://creativecommons.org/licenses/by/4.0 https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1678 Sun, 02 Jun 2024 00:00:00 +1200