Kenneth J. Elwood

University of Auckland

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 additio...

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...

Estimation of the torsional capacity of precast hollow-core floor units is required as a step for assessing the expected seismic performance of these floors according to the seismic assessment procedure followed in New Zealand. Due to limited research on the torsional behaviour of hollow-core units, there are multiple uncertainties regarding the ac...

This paper is focused on the design and implementation of a functional tool to evaluate and communicate the seismic risk to increase resilience and reduce human and economic loss. Wellington has been selected as the case study for this research due to the existence of a robust database of buildings within the central business district. In the first...

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 du...

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, socio-cultural characteristics, economy, institutional and governance structures affect decisions and operational procedures, including aspects related to spatial and temp...

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 crucia...

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 t...

Based on observed behaviour in previous earthquakes and subsequent extensive research, it is now well understood that hollow-core floors can be highly vulnerable to earthquake damage. This is particularly the case for older floors with poorly configured support details. Between the ‘Purple Book’ and the Appendix C5E of the ‘Yellow Chapter’ the indu...

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...

The 2010/2011 Canterbury Earthquake Sequence resulted in severe loss and disruption in Christchurch, New Zealand due to liquefaction and damage from strong shaking. Following the earthquake, over 60% of concrete buildings with 3 + stories in the Christchurch CBD were demolished, resulting in a widespread displacement of people and business, an exce...

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....

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 arti...

Precast floors are the dominant flooring system in New Zealand's multi-storey buildings stock, where hollow-core floors are the most ubiquitous flooring system. Following the 2016 Kaikoura Earthquake, significant damage was observed in multiple buildings that incorporated hollow-core floors. Hollow-core flooring systems vulnerability in regions of...

This paper makes a case for the propagation of relevant uncertainties in prediction of the seismic response of reinforced concrete components. Conventional probabilistic seismic assessment studies only consider parameter uncertainty and model error as the dominant forms of uncertainty in a component’s capacity. In this paper, firstly, experimental...

Ductile slender reinforced masonry shear walls (DSRMSWs) designed and detailed according to modern seismic design provisions, such as those prescribed by the Canadian masonry design code CSA S304-14, are expected to demonstrate ductile performance when subjected to earthquake effects. These walls have shown good energy dissipation characteristics s...

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) Dis...

Seismic provisions in building codes arguably constitute the most important and effective means for improving the performance of the built environment during earthquakes. Because they serve as the minimum and mandatory requirements for new construction that accumulates over time, building codes can and have reduced disaster risk in cities around th...

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...

As a consequence of recent earthquakes in New Zealand, many concrete buildings have been demolished due to structural damage. Observations of damage to concrete walls led to substantial research and revisions to design standards to ensure that a satisfactory ductile response was achieved. However, even when the current performance objectives of the...

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...

The 2010–2011 Canterbury Earthquakes in New Zealand highlighted the vulnerability of gravity load resisting reinforced concrete frames in older buildings that do not comply with modern building design standards. Three full-scale reinforced concrete beam-column-joint frame subassemblies, representative of 1980s construction in New Zealand, were cons...

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 h...

Modern reinforced concrete buildings are often designed to dissipate energy during strong earthquakes by permitting the controlled formation of plastic hinges. Plastic hinges require assessment of residual capacity in post-earthquake situations. However, few past studies have investigated this topic, and results from experiments focused on undamage...

Many pre-1970s reinforced concrete (RC) buildings were constructed with smooth longitudinal reinforcement, particularly in southern Europe and New Zealand. It is conventionally accepted that the cyclic behaviour of components with smooth longitudinal reinforcement differ from those with deformed bars. An important factor that influences the cyclic...

*Experimental investigation of reinforced masonry shear wall slenderness limits. *Full-scale tests on out-of-plane stability of reinforced masonry shear walls. * Tests show importance of flanged boundary elements and loading symmetry. *Results indicate revisions to current slenderness limits may be warranted.

The use of deformation capacity limits is becoming increasingly common in seismic design and assessment of reinforced concrete (RC) walls. Deformation capacity limits for RC walls in existing design and assessment documents are reviewed using a comprehensive database. It is found that the existing models are inconsistent and do not account for vari...

The current knowledge of seismic performance of reinforced concrete (RC) components under bidirectional loading is limited in comparison to that of components under unidirectional lateral loading. Several questions on the effect of bidirectional displacement history on seismic response of RC components still remain unanswered. This paper appraised...

Precast concrete floors comprise precast floor units with in-situ (often lightly) reinforced concrete topping to form a composite floor system that generally also functions as a diaphragm. Such floors are a common feature of New Zealand buildings, being almost ubiquitous during the 1980s and early 1990s. Precast concrete floors are commonly specifi...

This study compares seismic losses considering initial construction costs and direct-repair costs for New Zealand steel moment-resisting frame buildings with friction connections and those with extended bolted-end-plate connections. A total of 12 buildings have been designed and analysed considering both connection types, two building heights (4-st...

Poor seismic performance of older reinforced concrete buildings in past seismic events has frequently been attributed to failure of non-ductile columns not detailed for seismic demands. The Seismic Assessment of Existing Buildings Guidelines developed in New Zealand (NZ Guideline) provides a performance-based engineering framework for assessment of...

Ten years ago, the findings of a SESOC working group investigating the performance of double tee support systems were published (Hare et al. 2009). Significantly, the working group identified the non-compliance of the ‘pigtail’ detail with the performance requirements of the New Zealand Building Code, and strongly recommended that structural engine...

Recent earthquakes have focussed the attention of the public on the vulnerabilities of some precast concrete floors that have long been known to engineers, while also revealing some previously unknown behaviour types. As a consequence of this attention, demonstration of the efficacy of retrofit solutions for vulnerable floors has become critically...

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 build...

Experimental testing was conducted on four large-scale, flexure-yielding walls with rectangular cross sections to investigate the impact of imposed axial load ratio (10, 14, and 20% of axial compression capacity) and transverse reinforcement detailing on the seismic performance, including damage and deformability. Variations in detailing included...

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 follow...

A set of tests on 17 large-scale, nominally identical, beam specimens with variations in loading protocol, loading rate, and restraint to axial elongation are described. Three specimens were also repaired by epoxy injection following an initial damaging earthquake loading. This paper provides a detailed description of the test program, and the corr...

The magnitude 7.1 Puebla, Mexico earthquake of September 19th, 2017, centred 55 km south of the city of Puebla, led to significant and extensive damage in central Mexico, especially in Mexico City. One month after the event, a team of four researchers from New Zealand travelled to the affected area with the aim of enabling access to observational d...

It is now mandatory for engineers providing a Territorial Authority with an assessment of an existing building’s capacity in relation to earthquake-prone building legislation to use the Technical Guidelines for Engineering Assessment. The prevalence of concrete construction amongst New Zealand’s existing building stock makes Part C5 of the guidelin...

Reports from the 2010/2011 Canterbury and 2016 Kaikoura earthquakes noted that some reinforced concrete beams in high-rise structures developed a single primary crack at the beam-column interface without formation of distributed secondary cracks along the beam length. Initial assertion supported the possibility of these beams having low reinforceme...

This paper presents the results of a multiphase research program aimed at investigating the out-of-plane stability of slender reinforced masonry shear walls (RMSWs) under in-plane reversed-cyclic loading. The objective of this study was to evaluate the adequacy of the out-of-plane stability provisions specified in the Canadian masonry design standa...

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 repaire...

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 e...

This report outlines the observations of an NZSEE team of practitioners and researchers who travelled to the Kumamoto Prefecture of Japan on a reconnaissance visit following the April 2016 earthquakes. The observations presented in this report are focussed on the performance of reinforced concrete (RC) buildings throughout Kumamoto Prefecture. It w...

Benefit-cost analyses for the seismic retrofit of unreinforced masonry (URM) buildings in downtown Victoria, British Columbia, Canada, were undertaken, considering the seismic hazard, building value, occupant/pedestrian exposure, a variety of strengthening measures, and local construction costs. The analyses are underpinned by building motion-damag...

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 cr...

The 14 November 2016 Kaikoura 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...

This paper represents the second part of a series of four publications on response history analysis for new buildings. It specifically focuses on modeling assumptions, consideration of important effects in the analysis, and interpretation of analysis results via global and local acceptance criteria. A statistical basis for development of both force...

Following the 2010/2011 Canterbury Earthquakes in New Zealand, unexpected failure modes were observed in reinforced concrete (RC) structural walls, despite being designed to ductile provisions of the New Zealand Concrete Structures Standard (NZS3101:2006). These observations have raised concern on the reliability of the current design provisions in...

Results of a study performed on the out-of-plane instability of reinforced masonry shear walls (RMSWs) 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 testing of five reinforced masonry uniaxial specimens under revers...

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...

A detailed inventory of about 350 concrete shear wall buildings in western Canada with 7 or more stories and built prior to 1980 was created. About one hour was spent collecting information from drawings for each building so wall capacities could be estimated and simplified linear dynamic analysis could be used to estimate seismic demands on the bu...

The high demolition rate (~60%) of reinforced concrete (RC) buildings that generally performed well in Christchurch, New Zealand, has been one of the most important lessons from the Canterbury Earthquakes. In an effort to understand such an outcome, various factors influencing the post-earthquake decisions on buildings (demolition or repair) are ex...

Observations following the 2010/2011 Canterbury Earthquakes revealed unexpected damage to reinforced concrete walls, characterized by undesirable failure modes such as crushing of concrete and buckling of longitudinal reinforcement in the web and end regions. In an effort to address these failures, a number of changes have been made to the New Zeal...

The 2016 Mw 7.8 Kaikōura earthquake continued a notable decade of damaging earthquake impacts in New Zealand. The effects were wide ranging across the upper South Island, and included two fatalities, tsunami, tens of thousands of landslides, the collapse of one residential building, and damage to numerous structures and infrastructure. We present a...

Past experimental studies have shown that reinforced masonry shear walls (RMSWs) have good ductility and energy dissipation capability that can be utilized for seismic applications. It is however believed that slender RMSWs, characterized as having high height-to-thickness (h/t) ratios, may be susceptible to out-of-plane instability. Out-of-plane i...

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...

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...

During the 2010/2011 Canterbury Earthquakes several reinforced concrete (RC) walls in modern buildings with ductile detailing performed poorly and exhibited unexpected failure modes (e.g., local buckling of longitudinal reinforcement and global buckling of the wall section out-of-plane). These observations led to a number of revisions to NZS3101:20...