Bulletin of the New Zealand Society for Earthquake Engineering 2021-12-01T16:36:22+13:00 Rajesh Dhakal Open Journal Systems <p>Bulletin of the New Zealand Society for Earthquake Engineering</p> Seismic design of acceleration-sensitive non-structural elements in New Zealand: State-of-practice and recommended changes 2021-12-01T16:36:18+13:00 Muhammad Rashid Rajesh Dhakal Timothy Sullivan <p>Acceleration-sensitive non-structural elements not only constitute a significant portion of a building’s component inventory, but also comprise components and systems that are indispensable to the operational continuity of essential facilities. In New Zealand, Section 08 of the seismic loadings standard, NZS 1170.5: Earthquake Actions, and a dedicated standard, NZS 4219: Seismic Performance of Engineering Systems in Buildings, address the seismic design of non-structural elements. This paper scrutinizes the design provisions for acceleration-sensitive non-structural elements in NZS 1170.5 and NZS 4219, and provides an international perspective by comparing with the design provisions for non-structural elements specified in ASCE 7-16, the latest ATC approach and Eurocode 8. This is followed by a detailed discussion on the improvements required for component demand estimation, the need for design criteria that are consistent with performance objectives, definition of realistic ductility factors, and recommendations for the future way forward in the form of an improved design procedure and its application through a new seismic rating framework.</p> 2021-12-01T00:00:00+13:00 Copyright (c) 2021 Muhammad Rashid, Rajesh Dhakal, Timothy Sullivan Theoretical and experimental evaluation of timber-framed partitions under lateral drift 2021-12-01T16:36:22+13:00 Jitendra Bhatta Joshua Mulligan Rajesh P. Dhakal Timothy J. Sullivan Hans Gerlich Frank Kang <p>This paper identifies the inherent strengths/weaknesses of rigid timber-framed partitions and quantifies the onset drifts for different damage thresholds under bi-directional seismic actions. It reports construction and quasi-static lateral cyclic testing of a multi-winged timber-framed partition wall specimen with details typical of New Zealand construction practice. Furthermore, the cyclic performance of the tested rigid timber-framed partition wall is also compared with that of similar partition walls incorporating ‘partly-sliding’ connection<br>details, and ‘seismic gaps’, previously tested under the same test setup.</p> <p>Based on the experimentally recorded cyclic performance measures, theoretical equations proposed/derived in the literature to predict the ultimate strength, initial stiffness, and drift capacity of different damage states are scrutinized, and some equations are updated in order to alleviate identified possible shortcomings. These theoretical estimates are then validated with the experimental results. It is found that the equations can reasonably predict the initial stiffness and ultimate shear strength of the partitions, as well as the onset-drifts<br>corresponding to the screw damage and diagonal buckling failure mode of the plasterboard. The predicted bi-linear curve is also found to approximate the backbone curve of the tested partition wall sensibly.</p> 2021-12-01T00:00:00+13:00 Copyright (c) 2021 Jitendra Bhatta, Joshua Mulligan, Rajesh P. Dhakal, Timothy J. Sullivan, Hans Gerlich, Frank Kang Recycling of damaged RC frames: Replacing crumbled concrete and installing steel haunches below/above the beam at connections 2021-12-01T16:36:07+13:00 Naveed Ahmad Arifullah Babar Ilyas Sida Hussain <p>Experimental and numerical studies are presented evaluating the efficacy of a recycling technique applied to a 1:3 reduced scale damaged RC frame. The crumbled concrete at the beam-column connections was replaced with new high-strength concrete. Epoxy mortar was applied at the interface to secure bonding between the old and new concrete. Additionally, the connections were provisioned with steel haunches, applied below and above the beams. The retrofitted frame was tested under quasi-static cyclic loads. The lateral resistance-displacement hysteretic response of the tested frame was obtained to quantify hysteretic damping, derive the lateral resistance-displacement capacity curve, and develop performance levels. The technique improved the response of the frame; exhibiting an increase in the lateral stiffness, resistance and post-yield stiffness of the frame in comparison to the undamaged original frame. This good behaviour is attributed to the steel haunches installed at connections. A representative numerical model was calibrated in the finite element program SeismoStruct. A set of spectrum compatible ground motions were input to the numerical model for response history analysis. The story drift demands were computed for both the design basis and maximum considered earthquakes. Moreover, the technique was extended to a five-story frame, which was evaluated through nonlinear static pushover and response history analyses. Overstrength factor W<sub>R</sub> = 4.0 is proposed to facilitate analysis and preliminary design of steel haunches and anchors for retrofitting the low-/mid-rise RC frames.</p> 2021-12-01T00:00:00+13:00 Copyright (c) 2021 The oscillation resistance ratio (ORR) for understanding inelastic response 2021-12-01T16:36:11+13:00 Hossein Soleimankhani Greg MacRae Tim Sullivan <p>Single-storey systems with different hysteretic characteristic are subjected to impulse-type short duration and long duration earthquake records to investigate the effects of hysteretic behaviour and ground motion characteristics on the seismic response. EPP, bilinear, Takeda, SINA, and flag-shaped hysteretic models loops are considered and an energy approach is taken to explain the inelastic behaviour. The first part of the work is based on analyses of the single-storey systems without any torsion, however; torsional irregularity is considered in the later analyses.</p> <p>It is shown that structures with the same backbone curve, but different hysteretic characteristics, tend to experience the same maximum response under short duration earthquake records, where there is one major displacement excursion. The likelihood of further displacement in the reverse (i.e. negative) direction is characterized using energy methods and free vibration analyses along with a new proposed “oscillation resistance ratio (ORR)” are employed to improve the understanding of the seismic response. Hysteretic models with low <em>ORR</em>, such as SINA and flag-shaped, are shown to have a greater likelihood of higher absolute displacement response in the negative direction compared with those with fatter hysteretic loops. The understanding of the response in terms of energy reconciles some differences in the ability of initial stiffness versus secant stiffness based methods to predict peak displacement demands with account for different ground motion characteristics.</p> <p>The same peak displacements in the primary direction was also observed for structures with stiffness/strength eccentricities under an impulse-type earthquake record. However, during unloading, the elastic energy stored in the out-of-plane elements is released causing greater displacement on the weak side in the reverse direction.</p> 2021-12-01T00:00:00+13:00 Copyright (c) 2021 Hossein Soleimankhani, Greg MacRae, Tim Sullivan Hybrid posttensioned rocking (HPR) frame buildings: Low-damage vs low-loss paradox 2021-12-01T16:36:03+13:00 Rajesh Dhakal <p>The 2010-11 Canterbury Earthquake Sequence inflicted seismic losses worth more than $40B, which is about 25% of the GDP of New Zealand (as per 2011 data). More than 80% of these losses were insured, which comprised of more than $10B covered by the <em>Earthquake Commission</em> (a New Zealand crown entity providing insurance to residential property owners) and more than $22B (comprising of roughly equal split between domestic and commercial claims) by private insurers [1]. The scale of financial impact has been perceived to be disproportionately large given the building regulatory regime in New Zealand is relatively stringent and the earthquakes and aftershocks were of moderate magnitude. As it is well known that some of the major faults spread in the Wellington region and the subduction boundary passing through the centre of New Zealand can generate much bigger earthquakes (upwards of magnitude 8), people are left pondering whether New Zealand is able to cope with the financial impact of larger earthquakes. This fearful realisation gradually led to people being dissatisfied with merely life-safe buildings and demanding more resilient buildings that meet the objectives of performance based design; i.e. suffer less damage, incur less loss, and can remain functional after earthquakes.</p> <p>In light of the extensive building damage resulting in high financial loss in recent earthquakes, practicing engineers and researchers in New Zealand have been advocating for revising the current design approach to improve performance of new structures and infrastructure in future earthquakes [2-5]. As a result, large proportion of buildings constructed in the last decade (including those built to replace earthquake-damaged buildings) have shied away from the traditional damage-friendly ductile structural systems and instead adopted one of the new and emerging structural systems claimed to be “low-damage”. In many cases, the adopted structural systems are not covered by existing design standards and are approved as alternate solutions through expert peer review. The “low-damage” attribute of most structural systems has been validated by component (or sub-assembly) level experimental tests, but their interactions with other building components and implications of their use in buildings have not been rigorously scrutinised. Hence, the rushed adoption of some of these systems in buildings can surprise the engineering community in future earthquakes with mismatch between the expected and real performances of the buildings; akin to what New Zealand engineering fraternity is currently going through due to realisation of poor seismic performance of precast hollow-core flooring system that has been widely used in New Zealand buildings without rigorous scrutiny.</p> <p>One such “low-damage” structural system is precast post-tensioned rocking frames with supplemental energy dissipaters. This paper summarises the development of this structural system, critically reviews the literature reporting the seismic performance of this system, and qualitatively evaluates system-level implications of its use in buildings. This paper is intended to better inform engineers of the likely seismic performance of buildings with this structural system so that they can optimise its benefits by giving due consideration to its effect on other building components.</p> 2021-12-01T00:00:00+13:00 Copyright (c) 2021