https://www.bulletin.nzsee.org.nz/index.php/bnzsee/issue/feed Bulletin of the New Zealand Society for Earthquake Engineering 2022-06-01T04:33:55+12:00 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/1510 Incremental dynamic analysis of rigid blocks subjected to ground and floor motions and shake table protocol inputs 2022-06-01T04:33:55+12:00 Danilo D'Angela danilo.dangela@unina.it Gennaro Magliulo gmagliul@unina.it Edoardo Cosenza cosenza@unina.it <p>This paper reports the results of an extensive campaign of incremental dynamic analyses (IDA) of rigid rocking blocks under various loading histories, including real ground/floor motions and shake table testing protocol loading histories. Several block geometries are investigated considering various size and slenderness combinations representative of building contents, monumental elements, art objects, components of critical facilities, and other unanchored elements. The spectral response of the block to different loading histories is firstly assessed by highlighting the characteristics of the different seismic input sets. Dimensionless acceleration- and velocity-based parameters are considered as intensity measures, and the block rotation normalized considering the critical angle (i.e., dimensionless rocking amplitude) is assumed as an engineering demand parameter. The IDA curves are evaluated, and the dynamic response of the blocks is characterized in terms of: (a) type of loading history, (b) intensity measure, and (c) block geometry.</p> <p>New information and technical insights are presented regarding the assessment of seismic response of structural and nonstructural rocking systems. The dynamic response of the blocks subjected to the investigated protocols is found to be not always compatible with the capacities related to real ground/floor motions, often producing non-conservative estimations. The discrepancy identified between the block responses associated with the protocol inputs and real motions is found to be significantly affected by both block geometry and intensity measure.</p> 2022-05-31T00:00:00+12:00 Copyright (c) 2022 Danilo D'Angela, Gennaro Magliulo, Edoardo Cosenza https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1519 Highlighting the need for multiple loading protocols in bi-directional testing 2022-06-01T04:33:14+12:00 Giovanni De Francesco giovanni.defrancesco@canterbury.ac.nz Timothy Sullivan timothy.sullivan@canterbury.ac.nz Cecilia Nievas cecilia.nievas@gfz-potsdam.de <p>Major earthquakes, such as the Canterbury and Kaikoura events recorded in New Zealand in 2010-2011 and 2016 respectively, highlighted that floor systems can be heavily damaged. Quasi-static cyclic experimental tests of structural sub-assemblies can help to establish the seismic performance of structural systems. However, the experimental performance obtained with such tests is likely to be dependent on the loading protocol adopted. This paper provides an overview of the loading protocols which have been assumed in previous experimental activities, with emphasis on those adopted for testing floor systems. The paper also describes the procedure used to define the loading protocol applied in the testing of a large precast concrete floor diaphragm as part of the ReCast floor project jointly conducted by the University of Canterbury, the University of Auckland and BRANZ. Subsequently the limitations of current loading protocols for bi-directional testing are discussed. The relevance of local seismicity on bidirectional demand is demonstrated by examining a large dataset of records from the RESORCE database. It is concluded that bi-directional experimental testing be undertaken using at least two loading protocols that impose different ratios of demand in orthogonal directions.</p> 2022-05-31T00:00:00+12:00 Copyright (c) 2022 Giovanni De Francesco, Timothy Sullivan, Cecilia Nievas https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1532 Experimental and numerical analysis of the lateral response of full-scale bridge piers 2022-06-01T04:32:34+12:00 Pavan Chigullapally pchi893@aucklanduni.ac.nz Lucas Hogan lucas.hogan@auckland.ac.nz Liam Wotherspoon l.wotherspoon@auckland.ac.nz Max Stephens max.stephens@auckland.ac.nz Michael Pender m.pender@auckland.ac.nz <p>This paper presents the results of in-situ testing of two integrated pile-columns of a partially demolished bridge located in Auckland, New Zealand. A series of tests involving lateral monotonic pushover and subsequent dynamic free vibration snapback tests were used to quantify the variation in the stiffness and damping behaviour of the pile-column specimens over a range of lateral load levels. Each testing sequence consisted of incrementally increasing peak monotonic loads followed by the dynamic snapback, with a series of varying peak loads at the end of the testing sequence to evaluate the influence of loading history on the monotonic and dynamic response. The secant stiffness between the monotonic pushover tests performed to the same loading levels before and after the maximum load was applied, reduced by up to 40% in both the pile-columns, primarily due to soil gapping effects, highlighting the significant potential softening of the system prior to pile or column yielding. Progressive reduction in the damping of the system during each snapback test was evident, due to the varying contributions of different energy dissipation mechanisms, and the level of damping varied depending on the peak load applied. These results highlighted the significant influence of soil gapping and nonlinearity on the dynamic response of the system. Numerical models were developed in the open source structural analysis software OpenSeesPy using a Nonlinear Beam on Winkler Foundation approach to further investigate the response of the pile-columns. Models of both the pile-columns using existing p-y curves for clay soils showed good agreement with the experimental data in load-displacement, period and snapback acceleration time histories. Sensitivity analysis showed that the surface soft clay layer had a significant effect on the lateral response and dynamic characteristics of the model, reinforcing the need for good characterisation of the near surface soil profile to capture the behaviour of the system.</p> 2022-05-31T00:00:00+12:00 Copyright (c) 2022 Pavan Chigullapally, Lucas Hogan, Liam Wotherspoon, Max Stephens, Michael Pender https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1520 A method for seismic design of RC frame buildings using fundamental mode and plastic rotation capacity 2022-06-01T04:32:54+12:00 Vijayanarayanan A.R. arvn.iitm@gmail.com Rupen Goswami rg@iitm.ac.in Murty C. V. R. cvrm@iitm.ac.in <p>A seismic design method is proposed for RC frame buildings, with focus on two of the seven virtues of earthquake resistant buildings, namely deformation capacity and desirable collapse mechanism. Fundamental lateral translation mode of the building and plastic rotation capacity of beams are included as input to estimate lateral force demand. Guidelines are provided to proportion beam and column cross-sections through: (a) closed-form expressions of flexural rigidities to maximize participation of the fundamental mode, and (b) relative achievable plastic rotation capacity using current design and detailing practice. This method is seen to surpass two prominent displacement-based design methods reported in literature. Results of nonlinear static pushover and nonlinear time history analyses of buildings of three different heights designed by this and the said two methods are used to make a case for the proposed method; the proposed method is able to control plastic rotation demand in beams and provide at least 20% more lateral deformation capacity than the said methods.</p> 2022-05-31T00:00:00+12:00 Copyright (c) 2022 A. R. Vijayanarayanan, Rupen Goswami, C. V. R. Murty https://www.bulletin.nzsee.org.nz/index.php/bnzsee/article/view/1517 Comparison of nonlinear response of gravity cantilever retaining walls and mechanically stabilised earth (MSE) wall structures 2022-06-01T04:33:35+12:00 Arman Kamalzadeh akam553@aucklanduni.ac.nz Michael Pender m.pender@auckland.ac.nz <p>During the past few decades, gravity cantilever retaining walls (GRW) have shown a relatively reliable performance. However, mechanically stabilised earth (MSE) retention systems have grown in popularity as they are cost-effective and have demonstrated resilience through recent seismic events. In this study, utilising 2D finite element (FE) modelling with OpenSees and the Manzari and Dafalias constitutive models, we have compared the seismic behaviour of GRW and MSE systems, both designed for the same conditions, under three earthquake records. These earthquake excitations were recorded on engineering bedrock (V<sub>s</sub> &gt; 700 m/s) to avoid complexities of deconvolution. Our investigations indicate that the retained MSE reinforced soil block behaves similarly to a rigid block, while this is not the case for the soil over the foundation heel in the GRW system. In addition, the lateral displacement over the height of the wall for MSE is at about half that of a GRW. In the final section of this paper, we discuss the effect of backfill compaction. It is shown that regardless of the retention system, the backfill density increasing from medium (D<sub>r</sub> = 70%) to dense (D<sub>r</sub> = 100%) reduces the lateral displacements by at least 50%.</p> 2022-05-31T00:00:00+12:00 Copyright (c) 2022 Arman Kamalzadeh, Michael Pender