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Summarized in this article are the major findings from a detailed damage investigation of an instrumented ductile reinforced concrete moment frame building subjected to a design-level earthquake. The building sustained widespread damage during the 2016 M-7.8 Kaikoura earthquake and was subsequently demolished. Prior to demolition, the structural system was extensively surveyed to document the severity and distribution of the damage sustained in the reinforced concrete frames and the flooring system. Furthermore, the building response during the earthquake was reconstructed from the acceleration records obtained from instruments installed throughout the building. The site seismic demands were also obtained from a local free-field instrument. The data collected from this damage investigation provide a high-quality dataset that is valuable to researchers investigating different parameters related to the seismic performance of reinforced concrete moment frame buildings. The dataset is published and publicly available on DesignSafe-CI (project PRJ-3444); https://www.designsafe-ci.org/data/browser/public/designsafe.storage.published/PRJ-3444v2. The data collection methodology is described, and a roadmap for navigating the dataset is presented to support future use of the archived dataset. [ABSTRACT FROM AUTHOR]

Recent earthquakes have demonstrated that code-conforming modern (i.e. post-1970s) reinforced concrete (RC) buildings can satisfy life safety performance objectives. However, the accumulated earthquake damage in these modern buildings raised concerns about their performance in future events, contributing to widespread demolition and long-term closure of damaged buildings. The economic and environmental impacts associated with the demolition and long-term closure of modern buildings led to societal demands for improved design procedures to limit damage and shorten recovery time after earthquakes. To address societal demands, this study proposes a damage-control-oriented seismic design approach that targets functional recovery by ensuring structural component demands do not exceed the damage-control limit state (DLS) under design-level events. Herein, DLS is defined as the post-earthquake state beyond which the strength and deformation capacity of a structural component is compromised, and its performance in a future event cannot be relied upon without safety-critical repair. This study proposes a methodology to determine component deformation limits for the design of structures for damage control. Using the developed methodology, we propose component rotation limits for RC beams, columns, and walls. The seismic performance and capability of buildings designed using the proposed design approach to satisfy recovery-based performance objectives is demonstrated through nonlinear response history and recovery analyses (using the ATC-138 methodology) of four archetype frame buildings, designed per New Zealand standards to different beam deformation limits. The analyses show that building codes can achieve functional recovery using the proposed component deformation limits without the need for sophisticated recovery analyses. [ABSTRACT FROM AUTHOR]

Hollow-core flooring systems were damaged in Wellington buildings during the 2016 Kaikoura earthquake (7.8 Mw) and have been shown to be susceptible to undesirable failure mechanisms (loss of seating, negative moment, and positive moment failure modes) at low drift demands. These undesirable damage mechanisms have also been observed in sub-assembly and super-assembly laboratory testing of hollow-core flooring systems and the test data obtained has enhanced the state-of-the-art knowledge of the probable seismic behaviour of hollow-core floor units. In this study, using currently available sub-assembly test data, fragility functions are defined for hollow-core flooring systems. Furthermore, the proposed fragility functions are combined with fragility information derived from nonlinear dynamic analyses for two eight-storey bare-frame reinforced concrete (RC) buildings designed based on New Zealand standards. This study shows that, in comparison with RC buildings with flooring systems that are not susceptible to gravity load failures, RC buildings with vulnerable hollow-core floors have a significantly higher likelihood of exceeding the collapse prevention limit state, as defined in this study. [ABSTRACT FROM AUTHOR]

The risk‐targeted seismic design framework is used to set design intensities, based on achieving a target risk level (e.g., collapse or fatality risk) with respect to an assumed building collapse response. This paper assesses the distribution of fatality risk associated with the risk‐targeted design intensity, considering uncertainty in both the hazard and the variety of buildings that can satisfy the minimum design requirement. The randomness among buildings and their response is due to other design decisions (aleatory variability with respect to the design intensity) and can be represented by a distribution of fragility curves that quantify the collapse probabilities of as‐built, code‐conforming buildings. First, a single design intensity is calculated based on a "design fragility," the mean hazard curve, and a risk target. The design fragility is taken as a conservative estimate from the distribution of collapse fragilities and the selected risk target approximates the risk associated with New Zealand's previous (non‐risk‐targeted) criteria for design intensities. Then the risk distribution is assessed, considering the aleatory variability in as‐built fragilities and the epistemic uncertainty in the new National Seismic Hazard Model. Accounting for variability in design decisions and uncertainty in the hazard model produces a risk distribution that more fully represents the potential risk associated with a given design intensity. This distribution can be compared to guidance on tolerable risk ranges, which suggest that risk can be variable among buildings but should fall within acceptable bounds. Sensitivity studies consider epistemic uncertainty in the assumed model for the distribution of as‐built fragilities. This inclusion of uncertainty to assess the risk distribution offers a powerful extension to the risk‐targeted framework. While this extension would not affect engineering practice (as the output is still a single design intensity), it allows building code developers to better understand and consider the risk implications associated with the selected design intensity. [ABSTRACT FROM AUTHOR]

Results of a study performed on the out-of-plane instability of reinforced masonry shear walls (RMSW) under seismic loading are presented. The study was conducted to gain understanding of the out-of-plane instability mechanism and the key factors influencing its development through the testing of five reinforced masonry uniaxial specimens under reversed cyclic tension and compression. The specimens represented the end zone of a RMSW. The design parameters considered in the study included longitudinal reinforcement ratio and height-to-thickness ratio for the test specimens. It was found that onset of out-of-plane instability is strongly influenced by the level of tensile strains developed in the specimens, the reinforcement ratio, and the bar size. In this case, out-of-plane instability occurred when out-of-plane displacements exceeded the critical value equal to half the wall thickness. A study on full-scale RMSW specimens subjected to reversed cyclic loading, also undertaken under this research program, is expected to verify the findings of this study and contribute towards development of design criteria for out-of-plane stability of RMSW. Key words: reinforced masonry, shear wall, seismic resistance, out-of-plane instability, in-plane reversed cyclic loading. Les resultats d'une etude de l'instabilite hors-plan de murs de contreventement en maconnerie armee (<< MCMA >>) soumis a des charges sismiques sont presentes. L'etude a ete menee afin de mieux comprendre le mecanisme d'instabilite hors plan et les facteurs cles influant sur son developpement, et ce, au moyen d'essais sur cinq specimens uniaxiaux de maconnerie armee sous traction et compression cycliques inversees. Les specimens representaient la zone de l'extremite d'un MCMA. Les parametres de conception consideres dans l'etude comprenaient le rapport d'armature longitudinal et le rapport de hauteur-aepaisseur pour les specimens d'essai. On a trouve que le degre des allongements en traction developpes dans les specimens ainsi que le rapport d'armature et la taille des barres influent fortement sur le debut de l'instabilite hors plan. Dans ce cas, l'instabilite hors plan est arrivee quand les glissements hors plan ont excede la valeur critique equivalant a la moitie de l'epaisseur du mur. Une etude sur des specimens de MCMA en grandeur nature soumis a des charges cycliques inversees, aussi entrepris conformement a ce programme de recherche, est censee verifier les conclusions de cette etude et contribuer a l'elaboration de criteres de conception en matiere de stabilite hors plan des MCMA. [Traduit par la Redaction] Mots-cles : maconnerie armee, mur de contreventement, resistance sismique, instabilite hors plan, charge cyclique inversee en plan., Introduction Reinforced masonry shear walls (RMSW) constructed using hollow concrete blocks reinforced with vertical and horizontal steel bars are commonly used as a seismic force resisting system (SFRS) in Canada [...]

One of the key damage observations in modern reinforced concrete (RC) frame buildings, damaged following the 2010/2011 Canterbury and 2016 Kaikoura earthquakes, was localised cracking at the beam‐column interface of capacity‐designed beams. The localised cracking in the beams was due to curtailed longitudinal bars at the beam‐column interface. Following these observations, without experimental data to justify desirable seismic performance, modern beams controlled by localised cracking were assumed to be potentially earthquake‐vulnerable. To address this, an experimental program was carried out on six RC beam specimens susceptible to single‐crack plastic hinge behaviour due to curtailed longitudinal bars. The experimental data show that RC beams with single‐crack plastic hinge behaviour can undergo significant inelastic drift demands without loss of lateral resistance. However, contrary to conventional beams with distributed cracking, the response of RC beams with single‐crack plastic hinge behaviour due to curtailed longitudinal bars is mainly dominated by hinge rotation (via bond‐slip) and shear sliding at the column face. The current paper studies the interdependence of axial elongation, bond‐slip and shear sliding deformation of RC beams with single‐crack plastic hinge behaviour under cyclic demands. A procedure for seismic assessment of RC beams with single‐crack plastic hinge behaviour due to curtailed longitudinal bars is proposed. The proposed formulations can be adopted to develop adequate numerical models for simulating the response of RC frames with beams susceptible to single‐crack plastic hinge behaviour due to curtailed longitudinal bars. [ABSTRACT FROM AUTHOR]

Post-earthquake assessment procedures require component deformation limits to identify locations for visual inspection and locations needing structural repair. This study proposes a framework for defining component deformation limits for detailed visual inspection and repair for earthquake-damaged concrete buildings. First, observations from cyclic tests of ductile concrete components (beams, columns, and walls) suggested that the residual capacity (in terms of strength and deformation capacity) of such components is likely uncompromised if the deformation at the initiation of lateral strength loss (LSL) is not exceeded in prior loading histories. The results also revealed that the deformation at the initiation of LSL typically corresponds to the onset of longitudinal bar buckling in ductile components. Furthermore, using experimental data, multipliers are developed as fractions of ASCE/SEI 41 modeling parameters at lateral failure (i.e. a or d) to predict deformation at initiation of LSL. Subsequently, a probabilistic approach is proposed for defining the component deformation limits, considering uncertainty in both capacity and demand. Component deformation limits for detailed visual inspection are defined such that there is a low probability (adopted as <10%) of exceeding the deformation at the initiation of LSL. The component deformation limit for repair is defined as the median deformation at the initiation of LSL (i.e. 50% probability of exceedance). [ABSTRACT FROM AUTHOR]

Following the 2010/2011 Canterbury and 2016 Kaikoura earthquakes, a number of reinforced concrete (RC) beams in high-rise structures developed a single primary crack at the beam-column interface without the formation of distributed secondary cracks along the beam length. Detailed assessments showed that these beams have conforming longitudinal steel ratios and the single-crack mechanism may be due to design and/or construction practices for beam-column joints in the 1980s. In order to investigate the seismic behavior of reinforced concrete beams with detailing that inhibited the spread of flexural yielding, an experimental program was carried out on RC beam specimens, having similar reinforcement detailing to that of beams that developed a single crack at their ends during the Kaikoura earthquake to understand their seismic behavior, postearthquake repairability, and residual low-cycle fatigue life. Experimental results showed that the beams were able to undergo significant inelastic drift demands without loss of lateral resistance and have sufficient residual drift capacity following moderate and large earthquake demands. The response of the beam specimens was dominated by hinge rotation via the bond-slip mechanism. Comparisons showed that the measured drift capacities of the beams exceeded the predicted drift capacities computed using state-of-the-practice procedures. [ABSTRACT FROM AUTHOR]

Architectural features and other irregularities in the gravity system which apply gravity-induced lateral demands to the seismic force resisting system are being incorporated in new buildings. These gravity-induced demands have raised concerns due to the perceived potential for a ratcheting effect to occur during seismic loading. This paper summarizes the results of a study to identify if there are behavioral trends not recognized within the scope of current building codes. To this end, a nonlinear, parametric study was conducted in OpenSees to investigate the inelastic response of concrete shear wall buildings with a range of design characteristics, including gravity-induced lateral demands. The results demonstrated that a seismic ratcheting effect can develop and amplify inelastic displacement demands. The effect is significantly more prevalent in coupled shear walls compared with cantilevered shear walls. An irregularity class to address buildings with gravity-induced lateral demands on the seismic force resisting system is proposed for the 2015 National Building Code of Canada. Key words: irregularities, nonlinear dynamic analysis, shear walls, hysteresis, seismic design, coupled shear walls, inclined columns, national building code. Des caracteristiques architecturales et d'autres irregularites dans le systeme gravitaire, qui appliquent des demandes laterales induites par la gravite au systeme de resistance aux forces sismiques, sont incorporees dans les nouveaux batiments. Ces demandes induites par la gravite ont souleve des inquietudes en raison du potentiel per^u d'un effet d'amplification qui pourrait survenir durant un chargement sismique. Cet article resume les resultats d'une etude pour determiner s'il y a des tendances comportementales non reconnues dans la portee des codes de batiments actuels. A cette fin, une etude parametrique non lineaire a ete realisee avec le logiciel OpenSees afin d'examiner la reponse inelastique de batiments munis de murs de contreventement en beton; le logiciel offre une plage de caracteristiques de conception, dont les demandes laterales induites par la gravite. Les resultats ont demontre que l'effet d'amplification sismique peut se developper et ainsi amplifier les demandes de deplacement inelastique. L'effet est beaucoup plus important dans les murs de contreventement jumeles par rapport a des murs de contreventement en porte-a-faux. Une classe d'irregularites pour aborder les batiments ayant des demandes laterales induites par la gravite sur le systeme de resistance aux forces sismiques est proposee pour le Code national du batiment du Canada 2015. [Traduit par la Redaction] Mots-cles: irregularites, analyse dynamique non lineaire, murs de contreventement, hysterese, conception sismique, murs de contreventement jumeles, colonnes inclinees, Code national du batiment., Introduction Building structural systems are commonly idealized as being composed of a seismic force resisting system, designed to resist all lateral demands during strong ground shaking, and a gravity system. [...]

Post-earthquake cordons have been used after seismic events around the world. However, there is limited understanding of cordons and how contextual information such as geography, sociocultural characteristics, economy, and institutional and governance structures affects decisions and operational procedures, including aspects related to spatial and temporal attributes of cordon establishment. This research aims to fill the gap in cordon knowledge through a qualitative comparative case study of two cities: Christchurch, New Zealand (Mw 6.2 earthquake, February 2011) and L'Aquila, Italy (Mw 6.3 earthquake, 2009). Both cities suffered comprehensive damage to their city centers and had cordons established for extended periods of time. Data collection was done through purposive and snowball sampling whereby 23 key informants were interviewed in total. Research participants held expert knowledge in their roles and responsibilities, that is, council members, emergency managers, politicians, business/insurance representatives, academics, and police. Results illustrate that cordons were primarily established to ensure safety of people and to maintain security. The extent and duration of the cordons were affected by the recovery approaches taken in respective cities, that is, in Christchurch demolition was widely undertaken which supported recovery and allowed for faster removal of cordons. In contrast, authorities in L'Aquila placed high value on heritage buildings which led to recovery strategy based on preserving and restoring most of the buildings which extended the duration of cordon. Extended cordons have many similarities but evolve overtime. This evolution of cordons is affected by site-specific needs; thus, cordons should be understood and planned based on contextual realities. [ABSTRACT FROM AUTHOR]

Due to the extrusion manufacturing process, hollow‐core units in New Zealand do not have transverse shear reinforcement. The prestressing strands will not be fully developed near the ends of the hollow‐core units, which significantly affects the shear capacity and makes them prone to transverse and web cracking under deformation demands. In addition, initial end slip of the strands caused during cutting of the units in the production process may exacerbate this effect. This vulnerability of hollow‐core slabs was remarked during the 2016 Kaikōura earthquake, where an estimated 22% of the damaged buildings presented transverse cracking to hollow‐core units, sometimes accompanied by evident web cracking. The observed damaged, produced by earthquake‐imposed deformations, highlighted the urgency to advance the understanding of the behavior of hollow‐core floors. Subsequently, an experimental testing program was initiated to investigate the properties of extruded concrete and the shear strength of hollow‐core units under different shear span‐to‐depth or aspect ratios. The 200 mm deep specimens were loaded well beyond the peak shear force to study the postpeak behavior of the hollow‐core units. Additionally, the present study evaluates the effect of initial end slip of the prestressing strands on the pre and postpeak capacity of the units. The results obtained are compared against the formulations provided by commonly used design standards such as the New Zealand concrete standard NZS3101:2006, the ACI 318‐19, as well as the fib Model Code 2010 and the BS EN 1168:2005. [ABSTRACT FROM AUTHOR]

At 12:51 pm local time on 22 February 2011, a M 6.2 aftershock of the 4 September 2010, Darfield earthquake shook the city of Christchurch, New Zealand. The aftershock occurred on an unmapped fault less than 10 km from the city centre resulting in significant damage, particularly in the Central Business District (CBD). The earthquake resulted in the collapse of two reinforced concrete office buildings, one parking garage, and numerous unreinforced masonry buildings, including many heritage structures, leading to 185 deaths. Liquefaction was wide spread in the CBD and the eastern suburbs, resulting in foundation movement for housing and office buildings alike. Many buildings in the CBD experienced severe damage, some requiring demolition, necessitating careful controlled access to the CBD in the months following the earthquake. This paper summarizes the recorded earthquake shaking and observed damage to concrete buildings in CBD, with a specific focus on identifying future research and possible changes for seismic design practice and codes in Canada to address the Christchurch observations. Key words: earthquakes, collapse, concrete buildings, shear walls, irregularities, precast stairs, deformation compatibility, NBCC. A 12 h 51 heure locale le 22 fevrier 2011, la Ville de Christchurch, Nouvelle-Zelande, a subi une replique sismique d'une magnitude de 6,2 du seisme du 4 septembre 2010 de Darfield. La replique sismique est survenue dans une faille non repertoriee a moins de 10 km du centre-ville, engendrant de graves dommages, particulierement au district des affaires (CBD). Le seisme a cause l'effondrement de deux immeubles a bureaux en beton arme, d'un garage de stationnement et de nombreux immeubles en maconnerie non armee, dont plusieurs batiments patrimoniaux, causant 185 deces. La liquefaction etait etendue dans le CBD et dans les banlieues a l'est, entrainant des mouvements des fondations des maisons et des immeubles a bureaux. Plusieurs immeubles dans le CBD ont subi de graves dommages, certains devant etre demolis, demandant un acces tres controle au CBD pendant les mois suivant le seisme. Le present article resume la secousse sismique enregistree et les dommages observes aux immeubles en beton dans le CBD; il porte une attention speciale a l'identification des recherches futures et aux changements possibles aux pratiques de conception et aux codes sismiques canadiens afin de traiter les observations de Christchurch. Mots-cles : seismes, effondrement, immeubles en beton, murs de refend, irregularites, escaliers prefabrique, compatibilite des deformations, CNBC. [Traduit par la Redaction], Introduction New Zealand lies at the boundary of the Australian and Pacific tectonic plates, experiencing more than 25 earthquakes over magnitude 6 in the past 10 years (GeoNet 2011). Most [...]

In this study, a performance-based model is proposed, capable of simulating seismic behavior of typical confined masonry (CM) walls whose response is governed by shear deformations. This model is developed on the basis of both monotonic and reversed-cyclic experiments assembled in an extensive database, and derived through an iterative linear regression analysis. Owing to the limited data available and inconsistencies in observed behavior in some tests, only specimens with two tie columns, one on either edge of the wall; multiple longitudinal rebar per confining element; no bed joint reinforcement; no openings within the confined panel; and a height-to-length ratio that varies from 0.7 to 1.2, are considered for the purpose of model development. The effect of openings on strength characteristics, the capability of existing models to predict seismic behavior of CM walls, and the limitations of the proposed equations are discussed in detail. The accuracy of the model is also verified for CM walls with different characteristics. The proposed model simulates reasonably well the seismic behavior of CM walls whose properties conform to the assumptions of the model and that correspond to typical CM walls. DOI: 10.1061/(ASCE)ST.1943-541X.0000012 CE Database subject headings: Masonry; Seismic design; Walls; Deformation.

Analytical and experimental studies were undertaken to assess and improve modeling techniques for capturing the nonlinear behavior of flat-plate systems using results from shake table tests of two, approximately one-third scale, two-story reinforced concrete and posttensioned concrete slab--column frames. The modeling approach selected accounts for slab flexural yielding, slab flexural yielding due to unbalanced moment transfer, and loss of slab-to-column moment transfer capacity due to punching shear failure. For punching shear failure, a limit state model based on gravity shear ratio and lateral interstory drift was implemented into a computational platform (OpenSees). Comparisons of measured and predicted responses indicate that the proposed model was capable of reproducing the experimental results well for an isolated connection test, as well as the two shake table test specimens. DOI: 10.1061/(ASCE)0733-9445(2009)135:2(147) CE Database subject headings: Shake table tests; Concrete slabs; Connections; Punching; Limit states; Post tensioning; Plates.

A large number of reinforced concrete buildings constructed prior to the mid-1970s in western North America rely on lightly reinforced, perforated, perimeter shear walls to resist earthquake-induced lateral forces. Although a substantial number of piers may exist, deformation demands can significantly exceed acceptable levels for plastic deformations published in common acceptance criteria such as FEMA 356. A shear-friction model is used to establish the ability of wall piers to support vertical loads after substantial loss of pier lateral-load capacity. The model results indicate that typical wall piers are capable of sustaining relatively large lateral drift ratios prior to loss of vertical load-carrying capacity, which is consistent with postearthquake observations. However, preliminary test results indicate that the drift capacity may be substantially less for poorly detailed walls, where axial failure occurred at a lateral drift ratio of approximately one percent. DOI: 10.1061/(ASCE)0733-9445(2008)134:9(1548) CE Database subject headings: Axial loads; Piers; Walls; Reinforcement; Concrete structures; Drift.

Reinforced concrete columns with light transverse reinforcement may be susceptible to shear and subsequent axial-load failures during strong earthquake ground shaking. An experimental program examined the behavior of two half-scale, one-story frames with axial loads representative of those expected for the lower story of a multistory building. The frames were subjected to unidirectional simulated earthquake motion applied at the base. Shear failures of an interior column led to axial-load failure and redistribution of internal forces to adjacent framing components. Recorded data illustrated the details of the shear and axial failures and the redistribution to adjacent components. This paper discusses the global response of the frames and the shear and axial-load response of the shear-critical interior column. CE Database subject headings: Collapse; Concrete columns; Seismic effects; Shake table tests; Shear failure; Axial loads.

Uncertainty about when post‐earthquake repairs are needed delays decision making, and can lead either to unnecessary demolition or repair, or to inadequate repair actions. This study proposes a framework for assessing the effect of earthquake damage on the future seismic performance of a building. In this framework, we first assess drift demands during a maximum considered earthquake (MCER) level ground motion in an undamaged building, and then compare the drift demands in the same building during the same motion when it has been damaged by a prior shaking. We assess each building for a range of prior shaking events and 15 MCER‐level motions. From these analyses, we determine the relationship between damage in the first motion—quantified as peak story drift demand—and the MCER‐level motion drift demands—quantified as the ratio of peak drift demands in the damaged building to those in the undamaged building. This trend is used to indicate the level of damage at which performance is impaired, and repair is needed due to structural safety concerns. We apply this framework to a set of single‐degree‐of‐freedom structures and reinforced concrete moment frame buildings representative of construction in the United States. The results show that code‐conforming structures do not see significant drift amplifications in the damaged building when story drifts in the damaging motion do not exceed 2%, indicating they would not require major repairs for structural safety. Structures with less deformation capacity saw larger amplifications, and were affected when story drift demands in the damaging motion were lower. We also found that stiffer structures tend to see larger amplifications of drift demands. [ABSTRACT FROM AUTHOR]

The shake table tests presented in this article aims to explore seismic displacement demands for existing reinforced concrete buildings resulting from inelastic torsion associated with different sources of irregularities. Two half-scale seven-story reinforced concrete structures were subjected to unidirectional earthquake excitations on the shake table at the National Center for Research on Earthquake Engineering (NCREE) Tainan laboratory. The specimens reflected structural weaknesses of buildings which collapsed during the Meinong earthquake in Taiwan. This data paper presents an overview of the project as well as the organization of obtained test datasets. The data are available for public use under the Designsafe-CI project "Shake table tests of seven-story reinforced concrete structures with torsional irregularities." [ABSTRACT FROM AUTHOR]

The increasing need to reduce damage and downtime in modern buildings has led to the development of a low‐damage design philosophy, where the earthquake loads can be resisted with damage confined to easily replaceable components. Post‐tensioned (PT) concrete walls have emerged as a popular low‐damage structural system that have been implemented in a range of buildings. In order to provide essential evidence to support the development of low‐damage concrete structures, a system‐level shake‐table test was conducted on a two‐storey low‐damage concrete wall building implementing state‐of‐art design concepts. The test building included PT rocking walls that provide the primary lateral‐load resistance in both directions, a frame that utilized slotted beam connections, and a range of alternative energy dissipation devices that were installed at wall base or/and beam‐column joints. The building was subjected to 39 tests with a range of intensity ground motions, incorporating both unidirectional and bidirectional ground motions on the structure with different combinations of wall strength and energy dissipating devices. The building performed exceptionally well during the intense series of tests, confirming the suitability of both the design methods and the connection detailing implemented. The building achieved an immediate occupancy performance objective even when subjected to maximum considered earthquake hazard shaking. The building exhibited only minor damage at the conclusion of testing, with distributed cracking in the floors and cosmetic spalling in the wall toes that did not compromise structural capacity or integrity and could be easily repaired with minimal disruption. The test has provided a rich dataset that is available for further analysis of the building response and validation of design methods and numerical models. [ABSTRACT FROM AUTHOR]

Several studies have looked at the development of hinge models to simulate the hysteretic response of flexure‐ and shear‐critical reinforced concrete (RC) beam‐column components from damage initiation to onset of gravity collapse. However, few studies have been conducted to develop similar models for older type bond‐critical beam‐column components. First, using existing experimental data, this paper describes the calibration of simple and efficient hinge models to simulate the inelastic hysteretic response of as‐built and retrofitted splice‐deficient columns. Subsequently, to demonstrate the applicability of the hinge models, the seismic performance of as‐built and fibre‐reinforced polymer (FRP) ‐retrofitted two‐ and four‐story nonductile RC frame buildings with splice‐deficient columns are assessed using nonlinear dynamic analysis procedures. The results show that buildings with bond‐critical columns may have a lower collapse potential than buildings with shear‐critical columns, implying that in certain cases a longer splice length may actually worsen performance. According to the analyses, local retrofitting of the columns can significantly improve the seismic performance of the buildings. Contrary to results presented in this study, a significant U.S. evaluation methodology for RC frame buildings, FEMA P‐2018, indicates that buildings with bond‐critical columns have similar collapse potential as buildings with shear‐critical columns. Modifications are proposed to improve the FEMA P‐2018 provisions. The modelling approach presented in this paper are recommended for incorporation into ASCE/SEI 41, engineering practice and future research. [ABSTRACT FROM AUTHOR]

Past research has indicated that precast concrete hollow-core floors in buildings are susceptible to non-ductile failure modes when subjected to earthquake deformations. While this research has led to the development of more robust connection details suitable for hollow-core floors in new buildings, the existing building stock with hollow-core floors in New Zealand is still at risk and needs to be assessed. Damage to buildings containing hollow-core floors in Wellington, New Zealand, during the 2016 Kaikoura Earthquake prompted the need to better understand the behavior of hollow-core floors and enable those with limited drift capacity to be retrofitted or replaced. Based on tests described in a companion paper, models are developed for three potential failure modes: loss of seating (LoS), positive moment failure (PMF), and negative moment failure (NMF). Implementation of these models in the New Zealand Seismic Assessment Guidelines is discussed. Applying the Guidelines to a database of 112 existing buildings with hollow-core floor units in Wellington indicates that the most likely mode of failure is loss of seating. [ABSTRACT FROM AUTHOR]

The use of precast concrete hollow-core floors rose to prominence in New Zealand in the 1980s because of an economic boom at that time and the ease of construction. Their widespread use in New Zealand, a region with high seismicity, and observations made after the 1994 Northridge Earthquake prompted a comprehensive research program to better understand the behavior of hollowcore floors in earthquakes. A number of system-level and component- level tests were conducted and results from this research program helped understand vulnerabilities of hollow-core floor systems and led to improvements in design provisions in the New Zealand Concrete Standard. The research program also provided the basis for the development of a seismic assessment procedure for existing hollow-core floors described in a companion paper. A summary of this research program and key design provisions is presented in this paper. [ABSTRACT FROM AUTHOR]

Apartment dwelling is on the increase in many cities in Aotearoa New Zealand, including those in earthquake-prone regions. Hence it is important that people working in disaster management and housing improve their understanding on how the living situations of apartment dwellers influence their disaster management practices. This knowledge is crucial for efforts to promote safety and preparedness. This paper explores what enables and constrains apartment dwellers in their ability to prepare for an earthquake. Eighteen people were interviewed who resided in Te Whanganui-a-Tara (Wellington) two years after the 2016 7.8 magnitude (Mw) Kaikōura earthquake. Of central concern was people's ability to prepare for disasters and access knowledge about building and structural safety and how this knowledge mattered to what apartment dwellers were able to prepare for. We found that the agency to prepare was dependent on whether people owned or rented their dwellings. We report on participant accounts of dealing with body corporations, landlords, emergency kits, other emergency items, and evacuation plans. [ABSTRACT FROM AUTHOR]

Existing reinforced concrete (RC) columns with short splices in older-type frame structures are prone to either a shear or bond mechanism. Experimental results have shown that the force–displacement response of columns exhibiting these failure modes are different from flexure-critical columns and typically have lower deformation capacity. This article presents a failure mode-based approach for seismic assessment of RC columns with short splices. In this approach, first, the probable failure mode of the component is evaluated. Subsequently, based on the failure mode, the force–displacement response of the component can be predicted. In this article, recommendations are proposed for evaluating the probable failure mode, elastic rotation, drift at lateral failure, and drift at axial failure for columns with short splices experiencing shear, flexure, or bond failures. [ABSTRACT FROM AUTHOR]

Recent analytical studies have highlighted the existence of a failure-mode transition zone within which nominally identical test specimens may experience variability in failure mode between a flexure-dominated and a shear-dominated mechanism. This paper presents a study on the seismic response of four nominally identical nonductile RC circular columns susceptible to failure-mode uncertainty designed to represent typical New Zealand pre-1995 poorly detailed gravity columns. In this study, the influence of inherent material uncertainty and displacement history on the collapse response of the nominally identical columns was investigated. Experimental results showed that the failure mode of lightly confined RC columns can be influenced by displacement history and inherent material uncertainty. As observed in this study, the nominally identical columns experienced different failure modes, even under the same loading protocol, leading to a significant variation in drift capacity at axial failure (ranging from 1.5% to 2.6%) and residual axial capacity of RC columns (ranging from 200 to 650 kN). [ABSTRACT FROM AUTHOR]

The use of post-earthquake cordons as a tool to support emergency managers after an event has been documented around the world. However, there is limited research that attempts to understand the inherent complexities of cordoning once applied, particularly the longer-term impacts and consequences. This research aims to fill the gap by providing a detailed understanding of cordons, their management, and the implications of cordoning in a post-earthquake environment. We use a qualitative method to understand cordons through case studies of two cities where cordons were used at different temporal and spatial scales: Christchurch (M6.3, February 2011) and Wellington (M7.8 in Kaikōura, November 2016), New Zealand. Data was collected through 21 key informant interviews obtained through purposive and snowball sampling of participants who were directly or indirectly involved in a decision-making role and/or had influence in relation to the cordoning process. The participants were from varying backgrounds and roles i.e. emergency managers, council members, business representatives, insurance representatives, police, and communication managers. We find that cordons are used primarily as a tool to control access for the purpose of life safety and security, but cordons can also be adapted to support recovery. Broadly, our analysis suggests two key aspects, 'decision-making' and 'operations and management', which overlap and interact as part of a complex system. The underlying complexity arises in large part due to the multitude of sectors affected by cordons: economics, law, politics, governance, evacuation, civil liberties, available resources etc. The complexity further increases as the duration of cordoning is extended. [ABSTRACT FROM AUTHOR]

Despite the awareness of the adverse effects of biaxial seismic loading on the response of reinforced concrete (RC) components, the current knowledge of seismic performance of RC columns under biaxial loading is limited in comparison to that of columns under uniaxial lateral loading. Several questions on the effect of biaxial lateral displacement history still remain unanswered. Without proper progress on this topic, the codification of seismic assessment of RC columns under the influence of biaxial lateral loading will remain elusive. This study appraised test results from various experimental programs and identified the characteristics and effects of biaxial lateral displacement paths on seismic response of RC columns. Using the available dataset, recommendations are provided on how the influence of biaxial lateral load on lateral strength, deformation capacity, and stiffness degradation can be accounted. [ABSTRACT FROM AUTHOR]

This report presents the observations and findings following the 2017 Puebla earthquake that occurred in Mexico on September 19th, 2017. The reconnaissance mission was a collaboration between the New Zealand Society of Earthquake Engineering (NZSEE), the Universidad Autónoma Metropolitana (UAM) Azcapotzalco, the American Concrete Institute (ACI) Disaster Reconnaissance team, and the Colegio de Ingenieros Civiles de Mexico (CICM). During the earthquake, 77 buildings suffered partial or total collapse and more than 8,000 buildings experienced damage ranging from slight damage to significant structural damage necessitating demolition. As observed in previous earthquakes, the unique soil conditions of Mexico City resulted in extensive damage to the city's infrastructure, primarily due to local site effects. The earthquake caused relatively more damage to buildings built on transition and soft soil zones (i.e. between hard and deep soft soils) than those on hard soils. The NZSEE and UAM team focussed on areas with widespread and extensive damage. They also assessed the performance of repaired and retrofitted buildings after the 1985 Michoacán earthquake. It was found that the lessons learnt from the 1985 Michoacán earthquake led to some risk mitigation measures which benefited several buildings in the 2017 earthquake. Retrofitted buildings were found to have performed very well with little or no damage when compared to other buildings. [ABSTRACT FROM AUTHOR]

Recent research studies have shown that provisions of current seismic assessment and design standards overestimate the effective stiffness of reinforced concrete (RC) components. The influence of slip and shear deformations on the elastic response of RC components is not adequately addressed by these provisions. This paper presents a methodology for estimating the yield rotation and effective stiffness of RC components. Based on first principles, a simple analytical approach accounting for the effect of bar slip and shear deformations is presented. Using a dataset of past experiments on RC columns, the adequacy of the simplified model is demonstrated. The approach is extended to RC components with high-strength steel. Furthermore, recommendations on effective stiffness of RC coupling beams are provided. [ABSTRACT FROM AUTHOR]

A wide range of reinforced concrete (RC) wall performance was observed following the 2010/2011 Canterbury earthquakes, with most walls performing as expected, but some exhibiting undesirable and unexpected damage and failure characteristics. A comprehensive research programme, funded by the Building Performance Branch of the New Zealand Ministry of Business, Innovation and Employment, and involving both numerical and experimental studies, was developed to investigate the unexpected damage observed in the earthquakes and provide recommendations for the design and assessment procedures for RC walls. In particular, the studies focused on the performance of lightly reinforced walls; precast walls and connections; ductile walls; walls subjected to bi-directional loading; and walls prone to out-of-plane instability. This paper summarises each research programme and provides practical recommendations for the design and assessment of RC walls based on key findings, including recommended changes to NZS 3101 and the NZ Seismic Assessment Guidelines. [ABSTRACT FROM AUTHOR]

Modern reinforced concrete structures are typically designed to form plastic hinges during strong earthquakes. In post-earthquake situations, repair of moderate plastic hinging damage can be undertaken by filling the crack system with epoxy resin and reconstituting spalled cover concrete. This study uses available experimental test data, including three large-scale ductile beams tested by the authors, to investigate the effects of epoxy repair on the structural behaviour of plastic hinges, with a focus on beam elements. Factors that have been neglected in past studies, including the effects of residual deformations at the time of repair, are given special attention. It is found that epoxy-repaired plastic hinges can exhibit different behaviour from identical undamaged components in terms of stiffness, strength, deformation capacity, and axial elongation. Potential explanations for the observed differences in behaviour are given, and recommendations are made for how these differences can be quantified in order to relate the expected response of an epoxy-repaired plastic hinge to the response that would be calculated for an identical undamaged component. [ABSTRACT FROM AUTHOR]

Recent earthquakes in New Zealand not only highlighted the vulnerabilities of the existing building stock but also the need for: (i) a better understanding of the building inventory, and (ii) easy access to information for quicker response after an event. In the case of Wellington, efforts over the years by the City Council and other stakeholders have produced a number of useful datasets about the building inventory. These available datasets when put together are critical in understanding the composition and characteristics of the building inventory in Wellington. This paper describes the available information, and the process to combine the different strands of data possessed by multiple stakeholders into an effective and usable multi-disciplinary building inventory database for Wellington's CBD. The uses and future directions for this collated database are also discussed. [ABSTRACT FROM AUTHOR]

Summary: Understanding the impact of prior earthquake damage on residual capacity is important for postearthquake damage assessment of buildings; however, interpretation of such impact is challenging when based on tests using traditional reversed‐cyclic loading protocols. A new loading protocol, consisting of a dynamic earthquake displacement history followed by quasi‐static reversed‐cyclic loading to failure, is presented as an alternative to traditional simulated seismic loading protocols. Data are analyzed from a set of 12 nominally identical ductile reinforced concrete beams that were tested by using variations of this protocol and traditional reversed‐cyclic and monotonic protocols. Differences in the cycle content of the earthquake displacement histories applied to the test specimens allowed for the effects of load history variation below 2.2% drift to be isolated. It is found that such variation had no effect on the beam deformation capacities. The effects of dynamic loading rates are also analyzed and compared against control quasi‐static specimens. Relative strength increases due to dynamic loading are found to be more significant at yield than at ultimate. Dynamic loading rates led to modest reductions in the beam deformation capacities, but the presence of causality between these variables remains uncertain. [ABSTRACT FROM AUTHOR]

One barrier to adopting seismic loss estimation frameworks in New Zealand engineering practice is the lack of relevant fragility functions which provide probabilities of exceeding certain levels of damage (e.g. cracking of gypsum wallboards) for a given demand (e.g. interstorey drifts). This study seeks to address this need for four different building components; interior full-height steel-framed plasterboard partition walls, unbraced suspended ceilings, precast concrete cladding, and steel beam-column joints with extended bolted end-plate connections. Fragility functions were sourced from literature, and their potential for use in New Zealand is evaluated considering similarities in component detailing with local practices. Modifications to a number of fragility functions, including generalizations for easier adoption in practice, are proposed. A loss estimation case study of a 4-storey steel moment-resisting frame is performed to investigate the significance of fragility function selection. It is shown that the definition of damage states can have a noticeable influence on the assessment of incurred repair cost of individual building components. This indicates that fragility functions should be carefully selected, particularly if the performance evaluation of each individual component is of utmost importance. However, the observed difference in expected annual repair cost of the entire building was small, indicating that in cases where fragility functions are not readily applicable for use in New Zealand, other fragility functions may be used as placeholders without drastically altering the outcome of loss analysis for the entire building. [ABSTRACT FROM AUTHOR]

Recent earthquakes have highlighted discrepancies between the intended and observed performance of RC walls and significant research is in progress to improve the seismic performance of RC wall buildings. An international group of researchers and practitioners developed a research framework in order to conduct a project mapping and prioritisation exercise for RC wall research. The process by which this research framework and mapping exercise were conducted is described. The framework was used to identify research priorities that would provide a basis for the direction of future research. High priority topics included, shear demands and capacities, effect of load-rate and loading history, seismic assessment of older walls, residual capacity and repairability, non-rectangular and core walls, and whole of building response. [ABSTRACT FROM AUTHOR]

As a result of the 2010-2011 Canterbury earthquakes, over 60% of the concrete buildings in the Christchurch Central Business District have been demolished. This experience has highlighted the need to provide guidance on the residual capacity and repairability of earthquake-damaged concrete buildings. As limited testing has been performed on repaired components, this study focuses on the performance of severely-damaged lightly-reinforced concrete walls repaired through replacement of reinforcement and concrete in the damaged region. The damage prior to repair included buckling and fracture of longitudinal reinforcement, crushing and spalling of concrete, and, for one of the two specimens, out-of-plane instability of the gross section. Prior to repairing the wall specimens, tensile testing of reinforcement with welded connections was conducted to verify acceptable performance of welds suitable for reinstating the damaged reinforcement. Repairs to the specimens consisted of removal of damaged concrete through either hydrodemolition or jack hammering, followed by cutting and removal of damaged reinforcement and reinstatement of new reinforcement and repair mortar. The two repaired wall specimens were tested using a standard protocol that was identical to that used for one of the two original wall specimens. Aside from a difference in the elastic stiffness, the load-deformation responses of the repaired specimens were similar to that of the originally-tested specimen through to the first loading cycle at 2.0% drift, beyond which strength degradation was more pronounced for the repaired specimens. The overall performance of the repaired walls relative to the original wall indicates that it is feasible to achieve acceptable performance of severelydamaged concrete walls repaired through replacement of reinforcement and concrete in the damaged region. [ABSTRACT FROM AUTHOR]

Recent studies have addressed the computation of fragility curves for mainshock (MS)-damaged buildings. However, aftershock (AS) fragilities are generally conditioned on a range of potential post-MS damage states that are simulated via static or dynamic analyses performed on an intact building. Moreover, there are very few cases where the behavior of non-ductile reinforced concrete buildings is analyzed. This paper presents an evaluation of AS collapse fragility conditioned on various return periods of MSs, allowing for the rapid assessment of post-earthquake safety variations based solely on the intensity of the damaging earthquake event. A refined multi-degree-of-freedom model of a seven-storey non-ductile building, which includes brittle failure simulations and the evaluation of a system level collapse, is adopted. Aftershock fragilities are obtained by performing an incremental dynamic analysis for a number of MS-AS ground motion sequences and a variety of MS intensities. The AS fragilities show that the probability of collapse significantly increases for higher return periods for the MS. However, this result is mainly ascribable to collapses occurred during MSs. When collapse cases that occur during a MS are not considered in the assessment of AS collapse probability, a smaller shift in the fragility curves is observed as the MS intensity increases. This result is justified considering the type of model and collapse modes introduced, which strongly depend on the brittle behavior of columns failing in shear or due to axial loads. The analysis of damage that is due to MSs when varying the return period confirms this observation. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The 14 November 2016 Kaikōura earthquake resulted in long duration shaking in excess of the code demand for many buildings with fundamental periods between 1 and 2 seconds in Wellington, particularly in those parts of the city where shaking has been amplified due to basin effects and deeper deposits, notably in the port area or Thorndon basin. This paper outlines the initial response of engineers and the engineering assessment processes undertaken in Wellington in the weeks following the Kaikōura Earthquake, along with the technical support provided to Wellington City Council through the establishment of the Critical Buildings Team and the Wellington Engineering Leadership Group. An overview is provided of the Targeted Assessment Programme subsequently undertaken by Wellington City Council to look more closely at the buildings most likely to be affected. Background is provided to the key elements of the Targeted Damage Evaluation Guidelines that were developed in support of this programme, including the relationship with the Detailed Engineering (Damage) Evaluation process used following the Canterbury Earthquake Sequence. [ABSTRACT FROM AUTHOR]

The 2016 Kaikoura earthquake resulted in shaking in excess of design level demands for buildings with periods of 1-2s at some locations in Wellington. This period range correlated to concrete moment frame buildings of 5-15 storeys, many of which had been built in Wellington since the early 1980s, and often with precast concrete floor units. The critical damage states used to assess buildings during the Wellington City Council Targeted Assessment Programme are described and examples of observed damage correlating to these damage states are presented. Varying degrees of beam hinging were observed, most of which are not expected to reduce the frame capacity significantly. Buildings exhibiting varying degrees of residual beam elongation were observed. Cases of significant beam elongation and associated support beam rotation resulted in damage to precast floor unit supports; in one case leading to loss of support for double-tee units. The deformation demands also resulted in damage to floor diaphragms, especially those with hollowcore floor units. Cracking in floor diaphragms was commonly concentrated in the corners of the building, but hollowcore damage was observed both at the corners and in other locations throughout several buildings. Transverse cracking of hollowcore floor units was identified as a particular concern. In some cases, transverse cracks occurred close to the support, as is consistent with previous research on hollowcore floor unit failure modes. However, transverse cracks were also observed further away from the support, which is more difficult to assess in terms of severity and residual capacity. Following the identification of typical damage, attention has shifted to assessment, repair, and retrofit strategies. Additional research may be required to determine the reduced capacity of cracked hollowcore floor units and verify commonly adopted repair and retrofit strategies. [ABSTRACT FROM AUTHOR]

A number of strong earthquakes occurred within the last three years with significant civil engineering implications. Among them are the 12 January 2010 Leogane Earthquake in Haiti; the 27 February [...]

A numerical rigid body model for the out-of-plane response of unreinforced masonry (URM) walls connected to flexible diaphragms is validated against the shake table test results presented in a companion paper. It is demonstrated that the model is able to reproduce the observed rocking behavior with reasonable accuracy, particularly the intensity of shaking resulting in collapse of the walls. The validated model is used to undertake a parametric study investigating the effects of numerous parameters on out-of-plane wall stability. Ground motion variability is accounted for by using a large suite of motions. Based on the results of the modeling, an updated out-of-plane assessment procedure is proposed. The procedure, which could be incorporated into ASCE 41, provides reference curves of h / t versus S a (1.0), along with correction factors for axial load, wall thickness, ground-level walls, and exposure. [ABSTRACT FROM AUTHOR]

Given sufficient anchorage to the diaphragms, an unreinforced masonry (URM) wall subjected to out-of-plane inertial forces will likely develop a horizontal crack at an intermediate height about which the wall will rock as semirigid bodies. The effect of wall slenderness on out-of-plane stability has been demonstrated in past studies, but treatment of the effects of diaphragm flexibility and ground motion variability has been limited. This paper presents an experimental study examining the out-of-plane stability under seismic loading of URM walls connected to flexible diaphragms. Five full-scale unreinforced solid clay brick wall specimens spanning one story were subjected to earthquake ground motions using a shake table. The top and bottom of the walls were independently connected to the shake table through coil springs, simulating the flexibility of diaphragms. Variables examined experimentally included diaphragm stiffness and wall height. Both the amount of rocking observed as well as the ground motion scale causing collapse varied significantly with changes in the diaphragm properties. The test results provided data used for validation of a rigid-body rocking model, enabling an extensive parametric study on wall stability and the development of new assessment guidelines in a companion paper. [ABSTRACT FROM AUTHOR]

Following the devastating 1931 Hawke's Bay earthquake, buildings in Napier and surrounding areas in the Hawke's Bay region were rebuilt in a comparatively homogenous structural and architectural style comprising the region's famous Art Deco stock. These interwar buildings are most often composed of reinforced concrete two-way space frames, and although they have comparatively ductile detailing for their date of construction, are often expected to be brittle, earthquake-prone buildings in preliminary seismic assessments. Furthermore, the likelihood of global collapse of an RC building during a design-level earthquake became an issue warranting particular attention following the collapse of multiple RC buildings in the February 22, 2011 Christchurch earthquake. Those who value the architectural heritage and future use of these iconic Art Deco buildings--including building owners, tenants, and city officials, among others--must consider how they can be best preserved and utilized functionally given the especially pressing implications of relevant safety, regulatory, and economic factors. This study was intended to provide information on the seismic hazard, geometric weaknesses, collapse hazards, material properties, structural detailing, empirically based vulnerability, and recommended analysis approaches particular to Art Deco buildings in Hawke's Bay as a resource for professional structural engineers tasked with seismic assessments and retrofit designs for these buildings. The observed satisfactory performance of similar low-rise, ostensibly brittle RC buildings in other earthquakes and the examination of the structural redundancy and expected column drift capacities in these buildings, led to the conclusion that the seismic capacity of these buildings is generally underrated in simple, force-based assessments. [ABSTRACT FROM AUTHOR]