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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper presents the concept and seismic performance of "rocking" internal partition walls with the dual-slot track (DST) and aluminium angles tested under quasi-static cyclic drifts. The DST is formed by tek-screwing two tracks of different widths to provide two separate slots for the studs and plasterboards. The horizontal joint, having a vertical gap, between the top DST and the wall allows it to rock up to the desired level of inter-story drift. Three planar wall specimens with plastered (comprising one and three layers of plaster) and sealant joints between the plasterboards remained undamaged until the designed drift level of 0.72%. Moreover, the "y"-shaped wall specimen with sealant joints exhibited a good bi-directional seismic behaviour avoiding significant damage like corner crushing and internal frame damage; hence validating the superior seismic resilience of this system. [ABSTRACT FROM AUTHOR]

This paper presents the concept, design, construction and seismic performance assessment of internal partition walls with novel slotted and bracketed head-track details. In the slotted head-track walls, the anchors connecting the wall to the slab above are intended to slide within the slot to accommodate the desired in-plane drifts. On the other hand, in the bracketed head-track walls, the story-drift demands are accommodated by sliding of the bolt and flexing of the plastic brackets attached to the slots. In this paper, bi-directional behaviour of a novel flexible bracket is experimentally characterised and a number of wall sub-assemblies with the slotted and bracketed connection details are tested under quasi-static cyclic loading to investigate their seismic performance. The walls with slotted details showed the first signs of damage requiring repair at 0.78% drift. In contrast, when brackets were attached to the slots, the wall remained intact up to 4% drift, demonstrating a superior seismic resiliency. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the reliability of testing idealized prisms to simulate failure mechanisms in RC walls. In-plane cyclic tests on three flexural walls with different transverse reinforcement detailing and axial tests on three rectangular RC prisms idealized as wall boundary zones are conducted and the experimental responses are discussed in this paper. The results confirmed that idealized rectangular RC prisms are susceptible to failure due to the development of global out-of-plane (OOP) instability. These investigations revealed that strain distribution along the height is a key parameter influencing the failure mechanism observed in wall boundaries and idealized prism specimens. [ABSTRACT FROM AUTHOR]

This paper reports the seismic performance of two 'rocking' internal plasterboard partition wall specimens comprising dual-slot tracks (DST) with a) sacrificial L-trim (SLT) joints and b) boxed end-studs and standard plastered joints investigated under quasi-static cyclic drift demands. The top gap between the top DST and the wall allows it to rock up to the desired level of inter-story drift. The SLT joints between adjacent plasterboard panels failed after the top gap in the DST was exhausted. The plaster cracks in the joints between the in-plane and out-of-plane plasterboard panels occurred early at 0.20% drift. However, the 'rocking' specimen with boxed end-studs exhibited a comparable seismic resilience to partition walls with horizontal seismic gap widths along the partition wall indicating that these gaps can be significantly reduced when the wall is allowed to rock using the DST details for the same inter-story drift capacities. [ABSTRACT FROM AUTHOR]

This paper presents the bidirectional (in-plane and out-of-plane) cyclic performance of two-storied precast concrete cladding panel assemblies designed to accommodate, through a 'rocking' mechanism, in-plane and out-of-plane inter-story drifts expected in major earthquakes. Two sub-assemblies comprising four rocking precast concrete panels oriented parallel and perpendicular to the loading direction were subjected to quasi-static lateral cyclic inter-story drift demands. The test results show the ability of slotted rocking connections to accommodate the designed 2.00% inter-story drift without any noticeable damage to the panels or their connections. The only damage observed was the partial detachment of the sealant along the bond-line between the panels at 1.40% drift, possibly because of the test being conducted prematurely (only in 9 days) before the sealant had fully cured, and a relatively weak adhesion due to inadequate cleaning of the dusty concrete panel surfaces before the sealant was applied. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the seismic performance of an innovative 'rocking' precast concrete cladding panel system. Quasi-static cyclic loading tests were conducted on a sub-assembly of three 'rocking' panel pairs attached to a 3D steel structure, with and without sealant in the vertical joints between adjacent panels. The sub-assembly included a flat panel pair, an L-shaped panel pair and an oblique corner panel pair. Although the loading was applied in a single direction, the alignments of the panel pairs allowed scrutinizing their in-plane, out-of-plane and bi-directional performances. The test results validated the low-damage attributes of the novel cladding system, which was able to accommodate large cyclic drifts with minor physical damage to the panels and their connections with the structures. Up to a cyclic drift of 4.0%, the only forms of damage observed were tearing of the sealants in between the panel pairs, dislocation of backer rods behind some sealants, dislodgement of a grout piece, and loosening of a nut supporting a corner panel. All these forms of damage are minor and repairable, which can be avoided by making some minor changes to the details of the system. [ABSTRACT FROM AUTHOR]

Fire sprinkler systems damaged during earthquakes can compromise the functionality of a building facility either by loss of fire protection and/or by damage due to flooding. Shake table tests were conducted on a sprinkler piping specimen, with features representative of actual practices in New Zealand, to characterize its dynamic behavior under seismic floor excitation. The aim of the testing was to signify the need for a reliable procedure in the relevant New Zealand Standard (NZS 4541) for the estimation of seismic demands on these systems. The specimen was subjected to a set of motions including recorded floor acceleration response histories of an instrumented building in New Zealand. This paper first describes the test setup and the piping specimen and then discusses the seismic response of the specimen to multiple floor motions for different bracing variations. The testing showed that bracing segments of piping other than the distribution pipe modifies the dynamic characteristics of the system and consequently the seismic demands. The test results further confirm that seismic demands on pipes can be considerably greater if the system is in resonance with the floor excitation. Recommendations are provided for necessary improvements to NZS 4541 (2020) for a reliable estimation of seismic demands. [ABSTRACT FROM AUTHOR]

In multi-storey structural wall buildings, the structural walls are required to resist additional shear force due to their interactions with the floors and gravity-resisting system, which is not fully catered for in current seismic design provisions and assessment guidelines. This paper scrutinizes the mechanics of the interaction between structural reinforced concrete (RC) structural walls, floors and gravity frames in multi-storey RC structural wall buildings during elastic and nonlinear response phases. It also investigates the implications of this interaction on design of multi-story RC wall buildings. Generic expressions are derived to predict the drift and rotation profiles of multi-storey RC wall buildings. Then, a simple hand calculation method is developed to estimate the system (moment) overstrength of multi-storey RC wall buildings due to system (wall-floor-frames) interaction. The proposed method is applied to a prototype building with different slab dimensions and stiffness, and verified by comparing with the system overstrength factor obtained using finite element analysis. The simplified method estimates, and the nonlinear finite element analyses results agree, that a system overstrength factor of 1.7 can be used to account for the 3D interaction between the structural walls, floors and gravity frames in design and assessment of typical ductile RC wall buildings. [ABSTRACT FROM AUTHOR]

This paper presents the development (concept, design, detailing, and fabrication) and experimental validation of a novel low-damage precast concrete cladding panel system that can accommodate significant inter-story drift demand through the rocking mechanism of the panels facilitated by smartly designed connections between the panels and the structural members. Two adjacent in-plane panels separated by 'one-stage' sealant joint were subjected to in-plane quasi-static cyclic drifts. The cladding system suffered no damage until 1.92% inter-story drift when the sealant tearing occurred. Furthermore, comparison with the seismic performance of traditional panel connections, reported in the literature, also demonstrated the system's significantly improved seismic resilience. [ABSTRACT FROM AUTHOR]

Following observations of out-of-plane instability in slender ductile structural walls in some recent earthquakes, this mode of wall failure has been and is being investigated by several research groups. Analytical, numerical and experimental investigations have been conducted to study this failure mechanism as well as its controlling parameters. Both singly reinforced and doubly reinforced concrete walls have been studied under unidirectional and bidirectional loading. A simplified approach making use of concrete columns representing boundary zones of rectangular walls has also been used to reduce the computational and experimental costs of the research programs. This paper provides a state-of-the-art on the research conducted on this failure mechanism and the corresponding findings, with the main focus on the walls with rectangular cross-sections and under unidirectional loading. The out-of-plane response of walls is classified into five different modes and the likely forms of force-displacement and out-of-plane displacement history plots corresponding to each mode are discussed. [ABSTRACT FROM AUTHOR]

An editorial is presented on the evolution of hybrid post-tensioned rocking frames as structural systems. It expresses the view that prospect of a rigid body rocking mechanism potentially leading to satisfactory earthquake response. An overview of the study investigating the cyclic behavior of a precast concrete beam-column subassembly, with a combination of mild steel bars (for energy dissipation) and posttensioning (PT) tendons is presented.

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. [ABSTRACT FROM AUTHOR]

Bar buckling in RC structures is a commonly-observed failure mode that adversely affects their deformation capacity. To restrict bar buckling in ductile RC walls, design codes only emphasises on restricting the spacing of transverse reinforcement and does not recognise the importance of the effective stiffness of the ties (which is a combination of the tie leg axial stiffness and spacing) to restrict bar buckling. Therefore, in this paper the design requirements for anti-buckling transverse reinforcement are summarised, and improvements to the current design methodology for anti-buckling transverse reinforcement are proposed. To ensure that the transverse reinforcement detailing in plastic hinge regions is adequate to restrict bar buckling to single tie spacing and the compressive stress deterioration in bars due to buckling is controlled, refinements to the current detailing procedures are proposed. The buckling restraining ability of transverse reinforcement depends on the axial stiffness of the tie legs, while the compressive stress reduction in reinforcing bars due to buckling depends on their unsupported length (in bare bar tests) or buckling length that can include multiple tie spacing (inside RC members). Therefore, restrictions on both the axial stiffness of the tie legs and spacing of transverse reinforcement along the longitudinal reinforcing bars are proposed. The effective axial stiffness of tie legs is controlled by ensuring that the length of the tie legs in the direction of potential buckling is well below the critical length evaluated using a mechanics-based approach. Additionally, compressive stress degradation in reinforcing bars is controlled by limiting the ratio of the transverse reinforcement spacing and the longitudinal bar diameter such that any reduction of compressive stress carried by the longitudinal bars due to buckling at the limiting curvature recommended by New Zealand Concrete Standard is within an acceptable range. Furthermore, recommendations to avoid buckling of unrestrained reinforcing bars in the boundary zone and the wall web are proposed. Using the proposed design methodology, buckling of longitudinal reinforcing bars in ductile RC walls can be delayed and the detrimental effects of buckling on the lateral response of walls can be controlled until the design drift or curvature demands are met. [ABSTRACT FROM AUTHOR]

Observations of out-of-plane (OOP) instability in the 2010 Chile earthquake and in the 2011 Christchurch earthquake resulted in concerns about the current design provisions of structural walls. This mode of failure was previously observed in the experimental response of some wall specimens subjected to in-plane loading. Therefore, the postulations proposed for prediction of the limit states corresponding to OOP instability of rectangular walls are generally based on stability analysis under in-plane loading only. These approaches address stability of a cracked wall section when subjected to compression, thereby considering the level of residual strain developed in the reinforcement as the parameter that prevents timely crack closure of the wall section and induces stability failure. The New Zealand code requirements addressing the OOP instability of structural walls are based on the assumptions used in the literature and the analytical methods proposed for mathematical determination of the critical strain values. In this study, a parametric study is conducted using a numerical model capable of simulating OOP instability of rectangular walls to evaluate sensitivity of the OOP response of rectangular walls to variation of different parameters identified to be governing this failure mechanism. The effects of wall slenderness (unsupported height-to-thickness) ratio, longitudinal reinforcement ratio of the boundary regions and length on the OOP response of walls are evaluated. A clear trend was observed regarding the influence of these parameters on the initiation of OOP displacement, based on which simple equations are proposed for prediction of OOP instability in rectangular walls. [ABSTRACT FROM AUTHOR]

In this paper, the axial behaviour of boundary elements of rectangular ductile reinforced concrete (RC) walls is investigated. For this purpose, axial tests on rectangular RC prisms representing the boundary zones of ductile RC walls are carried out. Critical design parameters influencing the local compression response of ductile wall boundaries are identified and the effect of these parameters on the axial response of RC prisms is experimentally investigated. Key parameters investigated in this study include loading history, transverse reinforcement detailing (arrangement, spacing and diameter), longitudinal reinforcement detailing (yield strength and area) and cover concrete. The influence of these parameters on the performance of RC wall boundary zones is discussed in light of the experimental observations of the prisms tested in this study. The experimental test results reaffirm the susceptibility of isolated wall boundary elements to the progression of large out-of-plane deformations and subsequent instability. The experiment test results show that loading history and transverse reinforcement detailing are the critical parameters that influence the failure modes of boundary zone prisms. [ABSTRACT FROM AUTHOR]

The research presented here seeks to address the key parameters influential on out-of-plane (OOP) instability of rectangular walls, which was observed in the 2010 Chile and the 2011 New Zealand earthquakes in some well-confined modern walls. For this purpose, a finite element model, previously verified for its capability to reliably simulate different failure modes of this type of structural walls, was adopted. The parametric matrix included a series of specimens designed to be tested by the authors and other specimens already tested by other researchers. The effect of slenderness (unsupported height-to-thickness) ratio, reinforcement ratio, length and axial load on the OOP response of these specimens is scrutinized using the predicted response of the boundary region longitudinal reinforcement at the elevation corresponding to the maximum OOP displacement in each case. For a given slenderness and longitudinal reinforcement ratio, development of a critical average tensile strain over a certain height can lead to formation of OOP instability in walls. Therefore, the effect of these parameters on the strain history, strain gradient along the wall height, as well as the stress–strain response of the longitudinal bars throughout the cyclic loading are evaluated and the variation of the OOP response attributable to the effect of each parameter is discussed. This parametric study indicated that the initiation of OOP displacement in doubly reinforced walls after unloading from a peak displacement and during reloading in the opposite direction is in line with the significant reduction of compressive stiffness (yielding in compression) in the boundary region longitudinal bars along a specific height (at least 60% of the wall height). Based on the findings of this study, an experimental campaign was designed and four of the parametric models were experimentally tested under in-plane cyclic loading. In addition to the parameters noted above, the effects of shear strength, boundary conditions and eccentricity of material properties across the wall thickness on the OOP response of the benchmark parametric model are also briefly discussed. The experimental observations as well as the numerical versus experimental comparisons are presented in a companion paper. [ABSTRACT FROM AUTHOR]

This study investigates the ability of a finite element model based on curved shell element formulation in predicting nonlinear behavior of planar RC structural walls, identifying the strengths and limitations of this modeling approach. For this purpose, a parametric validation is conducted in addition to verification of the model simulation against experimental results of several wall specimens tested in literature. The effects of variations in total length, thickness, shear-span ratio, axial load ratio, confinement, as well as the horizontal and vertical reinforcement ratios are investigated at both global and local levels. For scrutinizing the global response, lateral load versus total, flexural and shear deformation predictions are used. For local response, sensitivity of the stress and strain distributions throughout the length and height of the wall models to the parameters noted above is evaluated. The capabilities and deficiencies of the modelling approach are discussed in detail in light of the numerical versus experimental as well as parametric verifications. The model is found to be able to predict most of the experimentally observed failure mechanisms of rectangular walls including global out-of-plane instability under in-plane loading, concrete crushing at the base, diagonal tension and diagonal compression as well as sliding shear. The model is not able to represent bar buckling, bar fracture and the potential subsequent secondary failure modes such as instability of the compression boundary zone due to progressive asymmetric concrete crushing at the base. The parametric study indicated sensitivity of the model response to the variation of the parameters known to be influential on the nonlinear response of planar RC walls. [ABSTRACT FROM AUTHOR]

• A new path-dependent cyclic constitutive model for reinforcing bars that incorporates the effect of bar buckling and low-cycle fatigue is proposed. • Comprehensive experimental test program is carried out to investigate the effect of buckling on the stress–strain response of reinforcing bars. • The influence of different bar parameters on the hysteretic response of reinforcing bars is investigated. In this paper, a path-dependent cyclic stress–strain model for reinforcing bars that incorporates the effect of bar buckling, low-cycle fatigue damage and loading history is proposed. A comprehensive experimental campaign is conducted to investigate the hysteretic behaviour of buckling-prone bars and the test results are used to develop and calibrate cyclic average stress versus average strain relationship for reinforcing bars. The parameters considered in this study include the slenderness ratio of reinforcing bars, grade of reinforcing bars and the loading history. Through a detailed analysis of test results, the effect of geometrical nonlinearity on the hysteretic response of the bar is evaluated and an analytical model simulating the effect of buckling on hysteretic response of the bar is developed. The cyclic model proposed herein captures the post-buckling stress deterioration, reduction of compressive stresses due to residual tensile strains (i.e. plastic strains), and reduction of unloading and reloading stiffnesses due to buckling and low-cycle fatigue damage in reinforcing bars. Comparison between experimental and analytical results shows that the proposed model can reliably predict the cyclic response of reinforcing bars including the effects of buckling and low-cycle fatigue. [ABSTRACT FROM AUTHOR]

Highlights • Low-cycle fatigue life of Grade 300E and 500E reinforcing bars. • Effect of buckling on low-cycle fatigue behaviour of reinforcing bars. • Low-cycle fatigue model incorporating the effect of buckling. • Effect of mean strain ratio on fatigue response of bars. Abstract Low-cycle fatigue life of Grade 300E and 500E reinforcing bars including the effect of buckling is evaluated. Low-cycle fatigue tests are carried out on un-machined specimens subjected to constant axial strain loading with strain amplitude ranging from 1% to 5%. The experimental test observations suggest that buckling of reinforcing bars has detrimental effect on its fatigue life and increase in slenderness ratio of the reinforcing bars results in substantial reduction of their low-cycle fatigue life. Equations relating the fatigue life (i.e. number of reversals to failure) with total strain amplitude and total energy dissipated as a function of buckling parameter is proposed. Also, experimental tests are carried out to investigate the influence of mean strain ratio on low-cycle fatigue behaviour of reinforcing bars. Comparative evaluation of the fatigue life models with the results of experimental investigation shows that the proposed model can predict the fatigue life of buckled and unbuckled reinforcing bars with reasonable accuracy. [ABSTRACT FROM AUTHOR]

An editorial is presented on the NZSEE Bulletin presents four papers covering diverse topics spanning into seismic performance of nonstructural elements (SPONSE) and learning from earthquakes (LFE). It mentions that this method enables improved prediction of floor acceleration demands for acceleration sensitive non-structural components and contents provided the building period is known.

Instability failure (also referred to as out-of-plane instability) has been observed in several experimental studies conducted on seismic performance of rectangular structural walls under in-plane loading. Observation of this failure pattern in some well-confined modern walls during the 2010 Chile and the 2011 Christchurch earthquakes has raised concerns about the reliability of current design code provisions. In this study, a numerical model composed of nonlinear shell-type finite elements was proposed and validated for seismic performance prediction and simulation of out-of-plane instability failure in rectangular walls. The plane sections are not enforced to remain plane in the planar direction in this type of model, and the in-plane axial-flexure-shear interaction can be simulated without requiring any empirical adjustment. The element used in the model (curved shell element) had integration points along the thickness unlike flat shell elements in which integration is performed in one plane only. This element was consequently able to capture the variation of strain along the thickness and simulate the deformation in the out-of-plane direction. Experimental results of cantilever wall specimens which failed in out-of-plane mode were used for verification of the adopted modeling and analysis approach. The numerical model was found to be able to predict the trend of initiation, increase, and recovery of out-of-plane deformation as well as the formation of out-of-plane instability that was observed during the tests. Development of this failure mechanism in the numerical model has been scrutinized using detailed response of the reinforcement and concrete elements positioned along the thickness of one of the specimens and at different stages of the failure mode. Also, the dependency of initiation and amount of the out-of-plane deformation on the maximum tensile strain developed in the longitudinal reinforcement during a specific loading cycle, and consequently all the parameters that influence its value (e.g., axial load, wall length, and cyclic loading protocol), as well as wall thickness has been confirmed by a set of parametric studies conducted on the models developed for one of the wall specimens. [ABSTRACT FROM AUTHOR]

In this paper, finite element analysis software "DIANA" is implemented to simulate quasi-static cyclic loading test results of three full-scale beam-column joints cast with high-strength self-compacting concrete (HSSCC). The specimens were designed according to the New Zealand concrete standard (NZS3101 2006). Material models for concrete and steel were calibrated based on the physical characteristics of the materials derived either from laboratory tests or using expressions available in literature. Two-dimensional curved-shell elements were used in modelling the specimens. As the specimens were designed following the code requirements for seismic actions, bond between the reinforcement and concrete was assumed as perfect. In order to obtain a more representative prediction, both the longitudinal and transverse reinforcement were modelled in their actual locations. Pushover analyses were first conducted to check the mesh sensitivity; after which the modelled specimens were subjected to reversed cyclic loading histories applied in the experimental tests. Seismically important response parameters such as damping, stiffness, concrete and steel contributions in the joint shear resistance, joint shear deformation, strain development in the joint stirrups, elongation of the plastic hinge zone, development of compressive stress, and cracking pattern were extracted from the analytical predictions and compared to the experimental results. It was found that the adopted modelling and analysis approach was capable of predicting cyclic performance of HSSCC beam-column subassemblies with reasonable accuracy. [ABSTRACT FROM AUTHOR]

This paper describes the blind prediction carried out to simulate the response of a thin reinforced concrete wall tested under uni-directional (in-plane) quasi-static reverse cyclic loading. The specimen was a singly reinforced T-shaped wall panel with a shear-span ratio of 3.7. The response of the test specimen was simulated prior to the release of test results using a finite element model which had already been verified for its capabilities in capturing different failure patterns of rectangular walls, particularly out-of-plane instability. The numerical model predicted a flexural dominated response for the specimen accompanied by considerable out-of-plane deformations. The blind prediction report, submitted in advance to the principal investigator of the experimental campaign, included lateral load-top displacement response of the specimen, maximum out-of-plane deformation corresponding to each drift level, evolution of out-of-plane displacements throughout in-plane loading, response of the longitudinal reinforcement at the section exhibiting the maximum out-of-plane deformation, and von Mises as well as reinforcement stress distribution at some key points of the wall response. Furthermore, a parametric study was carried out addressing the effects of shear-span ratio, reinforcement eccentricity and axial load ratio on the wall response. Results of the numerical simulation that had been included in the blind prediction report have been compared with the experimental measurements indicating that the evolution of the out-of-plane deformation was well captured by the model. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study conducted to investigate the seismic performance and out-ofplane response of three rectangular doubly reinforced ductile wall specimens subjected to an in-plane cyclic quasi-static loading. The specimens were half-scale, representing the first story of four story prototype walls designed according to NZS3101:2006. The experimental program including details of the specimens, material properties, test setup, loading protocol and instrumentation is described. Also, the test observations, with focus on the significant stages of wall response as well as the failure patterns of the specimens, are reported considering the correlation between seismic damage and lateral drift. Two of the specimens failed at 2% drift, and their failure modes comprised of bar fracture, bar buckling, concrete crushing and out-of-plane instability. The failure pattern of the third specimen was pure out-of-plane instability which proved to have the potential to cause sudden collapse of slender ductile walls that are designed to resist other failure modes. In light of the test results, the efficacy of wall design provisions in the New Zealand concrete design standard (NZS3101) associated with the observed failure modes is scrutinised. [ABSTRACT FROM AUTHOR]

A finite-element modeling approach has been used in this study to predict the nonlinear behavior and failure patterns of rectangular reinforced concrete structural walls. Efficiency of the model has been evaluated using experimental results of walls with different shear-span ratios, which failed in different modes. The walls are modeled in a finite-element analysis program. Reinforced concrete sections of the walls are represented by curved shell elements along with embedded bar elements. The plane sections are not enforced to remain plane in this type of model, and the in-plane axial-flexure-shear interaction can be simulated without requiring any empirical adjustment. The model is found to be able to reasonably capture the lateral load versus top displacement response of the specimens and predict most of the experimentally observed failure mechanisms of rectangular walls except bar buckling. The simulated failure patterns include shear, flexure, flexure-shear, and flexure-out-of-plane modes, and the failure to predict bar buckling was expected because of inherent deficiencies of embedded bar elements and limitations of material models available in the program. Moreover, the strain profile and crack pattern captured by the model are found to be in good agreement with experimental observations, indicating that in addition to the overall global response predictions, local behavior of the wall models can also be predicted reasonably well. [ABSTRACT FROM AUTHOR]

Nepal is one of the most earthquake-prone countries in the world, and at the same time is one of the most economically deprived. On 25 April 2015 mid-western Nepal was hit by the devastating Gorkha earthquake measuring Mw 7.8 with the epicentre located 76 km north-west of Kathmandu. The earthquake was followed by a series of aftershocks, with the most significant occurring on 12 May 2015 with Mw 7.3 and an epicentre located north-east of Kathmandu. The earthquake and the associated aftershocks resulted in the destruction of halt a million buildings, leaving millions of people homeless and causing a loss of more than $3.5 billion (USD) to the housing sector alone. Approximately 9,000 people were killed and over 23,000 people were injured - mostly due to damaged or collapsed buildings. A number of documents have been published pertaining to general observations following the 2015 Gorkha earthquake and aftershocks. Here the common building typologies and related failure modes observed during inspection surveys by the authors who were part of the various reconnaissance teams following the earthquakes are summarised. A brief background on the 2015 Gorkha earthquake is provided with an outline of the tectonic environment and seismological background of Nepal and a brief summary of previous earthquake activities in the region is presented. Common construction practices identified during the reconnaissance are illustrated and briefly explained to provide context to the observed earthquake damage, with an emphasis placed on unreinforced masonry (URM) building typologies and construction practices. Comparisons between URM building damage and published macro-element failure modes are provided using various photographic and schematic examples. Commonly observed failure modes and potential causes of failure are also highlighted for buildings constructed of reinforced concrete (RC) frames with masonry infill. A brief review of adopted temporary shoring techniques is also included. [ABSTRACT FROM AUTHOR]

The most important structural parameter in the estimation of the seismic demand on a building is the natural period of the building's fundamental/first mode of vibration. There are several existing empirical, analytical, and experimental methods which can be used to estimate the fundamental period of a building. The empirical equations prescribed in the building codes are simple, but they do not consider actual building properties, and are very approximate. On the other hand, analytical methods like Eigenvalue analysis and Rayleigh method are able to consider most of the structural parameters that are known to affect the period of a building. Nevertheless, the analytical methods require considerable effort and expertise; often requiring structural analysis software's to estimate the fundamental period of a building. In this paper, a generic method is developed to estimate the fundamental period of regular frame buildings and a simple yet reliable equation is proposed. The equation is derived using the basic concept of MacLeod's method for estimation of roof/top deflection of a frame building, which is modified to more accurately predict the lateral stiffness of moment resisting frames under triangular lateral force distribution typically used in seismic design and analysis of frame buildings. To verify the reliability and versatility of the developed equation, the fundamental periods predicted are compared with the periods obtained from Eigenvalue analysis for a large number of low to medium rise RC frame buildings. The fundamental period predicted using the proposed equation is also verified using the period obtained using the Rayleigh method and measured in experimental tests. Since the proposed equation was found to closely predict the fundamental period, the results are used to study the limitations of the empirical equations prescribed in building codes. The applicability of the proposed equation to predict the fundamental period of low to medium rise frame buildings with minor irregularity is also investigated, and it was found that the proposed equation can be used for slightly irregular frame buildings without inducing any additional error. The proposed equation is simple enough to be implemented into building design codes and can be readily used by practicing engineers in design of new buildings as well as assessment of existing buildings. [ABSTRACT FROM AUTHOR]

Post-disaster reconnaissance reports frequently list non-structural components (NSCs) as a major source of financial loss in earthquakes. Moreover, minimizing their damage is also of vital significance to the uninterrupted functionality of a building. For efficient decision making, it is important to be able to estimate the cost and downtime associated with the repair of the damage likely to be caused at different hazard levels used in seismic design. Generalized loss functions for two important NSCs commonly used in New Zealand, namely suspended ceilings and drywall partitions are developed in this study. The methodology to develop the loss functions, in the form of engineering demand parameter vs. expected loss due to the considered components, is based on the existing framework for the storey level loss estimation. Nevertheless, exhaustive construction/field data are employed to make these loss ftmctions more generic. In order to estimate financial losses resulting from the failure of suspended ceilings, generalized ceiling fragility functions are developed and combined with the cost functions, which give the loss associated with typical ceilings at various peak acceleration demands. Similarly, probabilities of different damage states in drywall partitions are combined with their associated repair/replacement costs to find the cumulative distribution of the expected loss due to partitions at various drift levels, which is then normalized in terms of the total building cost. Efficiencies of the developed loss functions are investigated through detailed loss assessment of case study reinforced concrete (RC) buildings. It is observed that the difference between the expected losses for ceilings, predicted by the developed generic loss function, and the losses obtained from the detailed loss estimation method is within 5%. Similarly, the developed generic loss function for partitions is able to estimate the partition losses within 2% of that from the detailed loss assessment. The results confirm the accuracy of the proposed generic seismic loss functions. [ABSTRACT FROM AUTHOR]

Current standards and guidelines for the design and installation of perimeter-fixed suspended ceilings are briefly reviewed and a summary of common damage in recent earthquakes is provided. Component failure fragility curves have been derived following experiments on typical NZ suspended ceilings, considering loading in tension, compression and shear. A simple method to analyse perimeter-fixed ceilings using peak floor acceleration (PFA) is described, allowing for ceiling system fragility to be obtained from component fragilities. This is illustrated in an example of a 5 storey building. It was found that single rivet end-fixings and cross-tee connections were the most critical elements of the ceilings governing the system capacity. In the design examples it was shown that ceilings at different elevations of the structure showed different probabilities of failure and larger ceiling areas with heavier tiles were most susceptible to damage. [ABSTRACT FROM AUTHOR]

Application of a fibre-element nonlinear modelling technique for seismic collapse capacity assessment of RC frame buildings in comparison with conventional lumped plasticity models is investigated in this paper. Constitutive material models of concrete and steel for fibre elements are adopted to enable simulation of the loss in vertical load carrying capacity of structural columns. Inclusion of the nonlinear second order P -- δ effects accelerated by degrading behaviour of steel and concrete materials in the fibre model allows prediction of the sidesway mode of collapse. The model is compared with nonlinear lumped plasticity models in which stiffness and strength degradation is replicated through degrading parameters in structural components. Static cyclic analyses of an example cantilever column and a portal frame indicate that the variation of axial loads in columns may result in accelerated degradation and failure of structural components which is not taken into account by lumped plasticity models. Moreover, incremental dynamic analysis of a ten-storey RC frame shows that the lumped plasticity model may overestimate building collapse capacity when vertical failure of structural components occurs prior to sidesway instability. [ABSTRACT FROM AUTHOR]

Structural walls (also known as shear walls) are one of the common lateral load resisting elements in reinforced concrete (RC) buildings in seismic regions. The performance of RC structural walls in recent earthquakes has exposed some problems with the existing design of RC structural walls. The main issues lie around the buckling of bars, out-of plane defonnation of the wall (especially the zone deteriorated in compression), reinforcement getting snapped beneath a solitary thin crack etc. This study compares performance of a typical wall designed by different standards. For this purpose, a case study RC shear wall is taken from the Hotel Grand Chancellor in Christchurch which was designed according to the 1982 version of the New Zealand concrete structures standard (NZS3101:1982). The wall is redesigned in this study to comply with the detailing requirements of three standards; ACI-318-11, NZS3101:2006 and Eurocode 8 in such a way that they provide the same flexural and shear capacity. Based on section analysis and pushover analysis, nonlinear responses of the walls are compared in terms of their lateral load capacity and curvature as well as displacement ductilities, and the effect of the code limitations on nonlinear responses of the different walls are evaluated. A parametric study is also carried out to further investigate the effect of confinement length and axial load ratio on the lateral response of shear walls. [ABSTRACT FROM AUTHOR]

Highlights: [•] A high-strength self-compacting concrete mix (approximately 90MPa) was developed. [•] A comparable conventionally vibrated high-strength concrete mix was also developed. [•] Post-yield bond between deformed bars and both concretes was investigated using pullout tests. [•] Significant difference was observed between the bond strength of 300 and 500MPa grade bars in post yield range. [•] Reduction of bar diameter in post-yield range was found to be the main culprit for bond discrepancy. [Copyright &y& Elsevier]

This paper describes the development and validation of an analytical multispring plastic hinge element that can predict elongation of ductile RC plastic hinges together with its flexural and shear responses. The element consists of layers of longitudinal and diagonal springs that represent the behavior of concrete, reinforcing bars, and diagonal compression struts. Beam tests reported in the literature, for which elongation of plastic hinges was measured at different stages of the lateral cyclic loading, were used to validate the effectiveness of the newly developed plastic hinge element. Comparisons of the analytical predictions with experimental results show that the proposed element predicts elongation of plastic hinges satisfactorily. The ability of the model to predict elongation of a plastic hinge together with its flexural and shear deformations offers a significant advancement in seismic performance assessment of RC structures. [ABSTRACT FROM AUTHOR]

Abstract: Incremental dynamic analysis (IDA) is applied in a performance-based earthquake engineering context to investigate expected structural response, damage outcomes, and financial loss from highway bridges. This quantitative risk analysis procedure consists of: adopting a suitable suite of ground motions and performing IDA on a nonlinear model of the prototype structure; summarizing and parameterizing the IDA results into various percentile performance bounds; and integrating the results with respect to hazard intensity–recurrence relations into a probabilistic risk format. An illustrative example of the procedure is given for reinforced concrete highway bridge piers, designed to New Zealand, Japan and Caltrans specifications. It is shown that bridges designed to a “Design Basis Earthquake” that has a 10% probability in 50 years with , and detailed according to the specification of each country, should perform well without extensive damage. However, if a larger earthquake occurs, such as a maximum considered event which has a probability of 2% in 50 years, then extensive damage with the possibility of collapse may be expected. The financial implications of this vulnerability are also given, revealing a fourfold variation between the three countries. [Copyright &y& Elsevier]

Unexpected failure modes were observed in RC walls in the 2010 Chile and 2011 New Zealand earthquakes. A peculiar failure mode, not previously reported in the structural engineering literature, was the brittle collapse of one of the structural walls of the 28-story Grand Chancellor Hotel in Christchurch, New Zealand. As one of the first steps toward the understanding of this failure mode, three rectangular RC walls were tested under bidirectional quasi-static cyclic loading. The only parameter varied among the three specimens was the structural detailing associated to various level of ductility design of the wall cross section. It was found that whereas the wall with nominal ductility section detailing (μ=1.25) experienced an out-of-plane shear-axial failure, those with higher ductility section detailing (1.25<μ<3 and μ>3) performed reasonably well. However, a relatively abrupt axial crushing failure was observed in the ductile walls at higher drift levels that needs further investigation. The bidirectional loading, rarely adopted in experimental tests or in numerical simulation due to its inherent complexity, was found to be one of the key factors in the development of out-of-plane shear-axial failure. Moreover, it was observed that walls with 0.3Agfc′ axial load, which is the maximum limit of the current New Zealand standard for concrete structures, and designed according to nominal ductile detailing might be prone to out-of-plane shear-axial failure. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue on topics including seismic performance of partition walls, ceiling diaphragms made of plasterboard, and fundamentals of seismic design of structures such as method for spectral analysis.

• Quasi-static reversed cyclic testing of slender RC walls. • Effect of concrete compressive strength on deformation capacity of ductile RC walls. • Effect of transverse reinforcement spacing on deformation capacity of RC walls. • Bar buckling in high-strength and normal-strength ductile RC walls. • Nonlinear finite-element analysis of high-strength concrete walls. In this paper, the results of an experimental campaign carried out to investigate the effect of concrete compressive strength on the deformation capacity of RC walls are presented. Information about the test programme, along with the details of the initiation and propagation of different damage states observed during the experiments are reported. The specimens were designed according to the New Zealand Concrete Standard (NZS3101:2006) and varied in terms of concrete compressive strength and boundary zone detailing. All the tested wall specimens exhibited flexural response and underwent failure due to bar buckling followed by bar fracture, concrete crushing and development of out-of-plane instability. Comparison of the observed response of the tested specimens shows that increasing the concrete compressive strength results in improved wall deformation capacity. A delay in the local compression controlled failure modes (such as bar buckling and concrete crushing) was also observed. Furthermore, a validated finite element model capable of simulating the nonlinear response of RC walls is adopted to simulate the cyclic response of the specimens. The numerical model is found to be capable of simulating the global response of RC walls with normal-strength as well as high-strength concrete with reasonable accuracy. The global out-of-plane deformation observed in high-strength RC wall specimens is also well predicted by the numerical model. [ABSTRACT FROM AUTHOR]

• Quasi-static reversed cyclic testing of slender RC walls. • Effect of bar buckling on the deformation capacity of RC walls. • Effect of boundary zone detailing on buckling tendency of longitudinal reinforcing bars. • Design of transverse reinforcement to restrict bar buckling in slender RC walls. The performance of reinforced concrete (RC) structural walls during the past earthquakes in New Zealand (2010–11) and Chile (2010) have highlighted the susceptibility of these critical structural components to several undesirable modes of failure. One such failure mode is premature buckling of the longitudinal reinforcing bars, which has also been observed in experimental tests of flexurally-dominant structural walls. This paper presents the results of an experimental program investigating the effects of transverse reinforcement detailing on buckling resistance of longitudinal reinforcement located in the boundary regions of RC structural walls. Three large-scale rectangular walls with different boundary zone transverse reinforcement detailing were tested under in-plane cyclic loading. The effects of these three types of detailing are reported in terms of drift capacity, buckling length of the longitudinal bars and cumulative energy dissipation capacity of the specimens. The test results confirm that bar buckling modes depend on transverse reinforcement detailing, which consequently also influences the ultimate flexural deformation capacity of ductile walls. By comparing the responses of the tested wall specimens, the inadequacy of code-compliant transverse reinforcement to restrain bar buckling is discussed and the effect of improved transverse reinforcement detailing (designed using a mechanics-based approach) on deformation capacity of slender walls is scrutinised. [ABSTRACT FROM AUTHOR]

This paper identifies the inherent strengths/weaknesses of rigid timber-framed partitions and quantifies the onset drifts for different damage thresholds under a unidirectional quasi-static cyclic loading. It reports construction and testing of a multi-winged timber-framed partition wall specimen, with details typical of New Zealand construction practice. As the tested subassembly included four partition wall wings oriented along four different directions, bi-directional performance of the tested wall system could be assessed despite the loading being unidirectional. Furthermore, the tested rigid timber-framed partition wall's cyclic performance is also compared with that of similar partition walls incorporating "partly-sliding" connection details and "seismic gaps", previously tested under the same test setup. Theoretical equations proposed/derived in the literature to predict the ultimate strength, initial stiffness, and onset drifts of different damage states are scrutinized based on the experimentally recorded cyclic performance measures. 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 corresponding to the screw damage and diagonal buckling failure mode of the plasterboard. [ABSTRACT FROM AUTHOR]

It is now widely recognized that the performance of non-structural elements is crucial to the performance of building systems during earthquakes. Field surveys and experimental studies have shown that light steel or timber framed plasterboard partition walls are particularly vulnerable. The objective of this study is to investigate the seismic performance of a novel seismic gap partition system with angled return walls under quasi-static cyclic loading applied obliquely and to investigate the benefits of using acrylic gap-filler in the seismic gaps. Two specimens were tested: a steel stud specimen and a timber stud specimen. Observed drift capacities were significantly greater than traditional plasterboard partition systems. Equations were used to predict the drift at which damage state 1 (DS1) and damage state 2 (DS2) would initiate. The equation used to estimate the drift at the onset of DS1 accurately predicted the onset of plaster cracking but overestimated the drift at which the gap filling material was damaged. The equation used to predict the onset of DS2 provided a lower bound for both specimens and also when used to predict results of previous experimental tests on seismic gap systems. The gap-filling material reduced the drift at the onset of DS1, however, it had a beneficial effect on the re-centring behaviour of the linings. Out-of-plane displacements and return wall configuration did not appear to significantly impact the onset of plaster cracking in the specimens. [ABSTRACT FROM AUTHOR]

Good seismic performance of glazing systems is essential to maintaining building functionality and limiting repair costs in a post-earthquake scenario. This paper reports on experimental research into the seismic performance of a standard commercial glazing system used in New Zealand. The focus of the research is to provide information not only on the life-safety performance of glazing but also on the serviceability of glazing systems, considering post-earthquake weather-tightness. This paper first describes the experimental testing set-up developed at the University of Canterbury to achieve this, then details the damage observed and finally, fragility functions for different damage states are reported. Leakage of the glazing is seen to initiate at a median storey drift demand of only 0.35%, whereas glass breakage did not occur until a median drift storey demand of 5.0%. The results obtained from this research demonstrate that the life-safety risk posed by modern commercial glazing in earthquakes will typically be low but the serviceability performance, and in particular weather-tightness post-earthquake, should be improved. [ABSTRACT FROM AUTHOR]

The effects of different parameters on the evolution of Out-Of-Plane (OOP) instability in rectangular walls were studied using a validated FEM model. Based on this parametric analysis, a test matrix was designed to experimentally investigate the progression of this mode of failure in rectangular walls. Results of the parametric study were presented within a companion paper, while the experimental observations as well as the numerical versus experimental comparisons are presented in this paper. The wall specimens were tested under in-plane cyclic loading and they exhibited different OOP responses. The development of OOP mechanisms was observed in all tested specimens, albeit with different values of maximum OOP displacement and followed by different types of instability. Progression of OOP deformation was suppressed by other failure modes in all specimens except one which failed due to large OOP displacement and global instability. In this study, the progression of OOP deformation and its relationship with the inelastic strain gradients of the longitudinal reinforcement along the length and height of the specimens are scrutinized and the numerical predictions are compared with the test measurements. The experimental findings regarding the evolution of this mode of failure and the influential parameters are in good agreement with the numerical predictions. However, the onset of OOP deformation typically had a delay in the numerical model when compared to the test results. One of the factors inducing this difference could be the effect of inherent and mostly unmeasurable eccentricities, including material, geometry as well as loading imperfections, which were not included in the model. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including geotechnical and building damages, and the 2016 Meinong, Taiwan earthquake.

An introduction to the journal is presented in which the editor discusses articles in the issue on topics including safeguard adjacent buildings from potential pounding, seismic design spectra along with other upcoming issues.

This paper presents modifications to the adoption of a Performance-Based Earthquake Engineering (PBEE) framework in Probabilistic Structural Fire Engineering. Potential Fire Severity Measures, which capture significant characteristics of fire scenarios, are investigated. A suitable Fire Severity Measure (FSM), which best relates fire hazard intensity with structural response, is identified by satisfying efficiency and sufficiency criteria as described by the PBEE framework. The study also implements a new analysis method called Fire Stripe Analysis (FSA) to obtain the relationship between FSM and the structural response. In order to obtain the annual rate of exceedance of damage and repair cost/time for an office building, an occurrence model and an attenuation model for office structure fires are generated for both Christchurch city and New Zealand. The process is demonstrated with the help of a case study performed for a steel–concrete composite beam. Structural response is recorded for the beam exposed to several fire profiles which are generated by varying fuel loads from 200 MJ/m2 to 1000 MJ/m2 and ventilation factors from 0.02 m1/2 to 0.08 m1/2. FSA and dispersion curves of structural response are plotted for every fire severity measure. Cumulative incident radiation is found to be the most efficient and sufficient FSM. The mean annual rate of exceedance of given levels of fire severity and structural response are evaluated for both New Zealand and Christchurch city. It is found that Christchurch city has a 15% less probability of exceedance of the given fire severity level in comparison to the whole of New Zealand. The extension of this work would facilitate designers/insurers to evaluate the probability of damage or failure of a structure due to a probable fire hazard. [ABSTRACT FROM AUTHOR]

In order to have a more generic representation of the damping phenomenon in seismic analysis of structures, in this paper, the already existing nonlocal elasticity continuum damping models have been adapted and extended to the inelastic domain. Adaptations of two nonlocal elasticity based damping models, Russell’s spatial hysteresis model and the extended Sorrentino model, into the nonlinear dynamic analysis is presented. Galerkin based finite element schemes are developed and the numerical implementation of the models are outlined. The performances of the nonlocal elasticity-based damping models are illustrated by studying the nonlinear dynamic responses of a four-story Reinforced Concrete frame designed to the Eurocodes. The incremental dynamic analysis study presented illustrates the fact that the proposed models are devoid of the large spurious damping actions commonly exhibited by the popular classical Rayleigh damping model. It has also been shown that in a nonlinear dynamic analysis, the proposed adaptation of the nonlocal elasticity continuum damping models might be a more realistic alternative to the popular classical Rayleigh damping model. The proposed models may be easily implemented in an existing software framework capable of solving both ordinary and integro-differential equations without adding markedly to the computational effort. [ABSTRACT FROM AUTHOR]

The article presents a message from the editor about his completion of the first two years as editor of the Bulletin, the retirement of his predecessor Les Megget, and aspects on which the Bulletin has not made the intended progress under his editorship.

The author presents information on the changes in the journal and acknowledges the contributors.