SESOC President Report
Note from the Editor
Letter to the Editor
Abstract
Fellows Awards Dinner 2023
Professional Indemnity Insurance
Abstract
Engineering New Zealand is frequently asked why we recommend retaining a statement of $200,000 Professional indemnity (PI) insurance minimum on our producer statements. This article explains why PI insurance is required, why we recommend not changing the standard amount on the producer statement, and possible alternatives to increasing the minimum.
Specifying concrete with lower up-front carbon
Abstract
What can structural engineers do to lower the up-front carbon of buildings and infrastructure that we are designing?
Items that have a large influence on carbon (such as changing building form or changing material) are often perceived as difficult to implement on projects. However, there are other relatively simple steps that structural engineers can take to reduce the up-front carbon of projects. The maxims to build nothing, build less and build clever should always be the starting point as shown in Figure 1, but next in line is to specify low carbon.
One of the simplest and most impactful ways for a structural engineer to reduce the embodied carbon of a project is by changing how our materials are specified, noting that Building Code structural performance and durability requirements still need to be met. Steel and concrete make up the majority of the up-front carbon of structures and therefore should be the subject of the most scrutiny.
This article provides recommendations on how concrete with lower up-front carbon can be specified.
NBS Rating Liability
Abstract
UPDATE
A New Building Standard (%NBS) rating is information derived from seismic assessments. Purchasers and lessees often rely on these assessments when entering property transactions. However, %NBS ratings are a common area for dispute.
This year in TADD Management Ltd v Weine, the High Court reviewed the liability of a vendor and their engineer regarding a 60%NBS (obtained through an Initial Seismic Assessment (ISA)) which was used in marketing material of the property but was substantially different to later %NBS ratings of 10% and 30% (in two Detailed Seismic Assessments) by other engineers.
The court held the vendor liable to the purchaser for $592,000 due to contractual misrepresentation and common mistake. Because it found the vendor liable, and because the vendor had joined the engineer to the proceedings, it was required to consider whether the
engineer was liable to the vendor in negligence, breach of contract or breach of the Fair Trading Act 1986.
Warehouse review findings report
Abstract
EXECUTIVE SUMMARY
Following the Masterton buildings inquiry, Engineering New Zealand Te Ao Rangahau commissioned a review of 20 warehouses across New Zealand to understand if issues of poor design quality observed in the Masterton cases were seen elsewhere.
The results of the Warehouse Review suggest issues relating to poor design and internal quality control seen in the Masterton buildings are not isolated. Some design engineers are incorrectly designing or leaving out critical details in their design of warehouses; for example, the restraint of large concrete panels is a commonly-identified issue. Inadequate restraint of a panel may present a life safety risk if it were to collapse in an earthquake.
As a result of this review, Engineering New Zealand will partner with collaborating technical societies and other relevant organisations to provide guidance for better engineering practice as it relates to warehouse design. We will work with stakeholders to disseminate the guidance and educate engineers.
This report is intended for engineers and building consent authorities. If you own a warehouse and have questions about its design, please contact a Chartered Professional Engineer for review.
Don't forget the `weld' in welded beams and columns
Abstract
The electric arc welding together of two flange plates and a web plate to form a doubly symmetric H section for buildings used to be reserved for large girders and very large columns that were deeper or heavier than the largest rolled sections available.
However, recent decades have seen doubly symmetric welded beam and column sections produced in New Zealand on a regular basis, or imported from steel mills in Australia and Asia. Improvements in fabrication equipment and fabricator productivity have improved the cost-competitiveness of welded sections.
Unified approach for the seismic design of Moment Resisting Concrete-To-Concrete Connections
Abstract
Post-installed rebar systems provide a versatile way for concrete-to-concrete connections and are used extensively in the building of new concrete structures and also the seismic retrofitting of existing reinforced concrete structures. Post-installed rebars can provide significantly higher bond strength compared to cast-in straight rebars under confined conditions.
Until recently, international guidelines did not allow the utilization of this higher bond strength in design. The European Organization for Technical Assessment (EOTA) recently published Technical Report TR 069 for seismic design of post-installed rebar connections with improved bond-splitting behavior. This document represents the current state-of-the-art in the seismic design of concrete-to-concrete structural connections.
EOTA TR 069 allows the design of moment resisting connections with post-installed rebars under static, quasi-static, and seismic loading conditions without the need for an overlap splice configuration. The injection mortar systems are required to be assessed by European Assessment Document EAD 332402, and as such, their real bond performance is utilized for design, not limiting it to the performance of cast-in rebars.
This paper provides an overview of TR 069 together with a literature review of its development and recommends future actions for its adoption in New Zealand.
Structural options for a 12-storied timber hybrid building
Abstract
Design options for a conceptual building with a concrete podium, timber or concrete core, and timber structural systems for the balance of the building are explored. The building is designed to be used for commercial occupancy. The assumed location is in Vancouver, Canada, which is a region with high seismic risk and considerable wind load. Timber is intended to be the primary material for the structure, although limited use of other materials is considered for the design.
The structural systems include concrete and concrete-timber hybrid cores in combination with frames, shear walls, and braced frames. The design concepts and various structural system combinations found suitable are compared for their relative merits. This design exercise confirms the feasibility of structural systems as well as provides insights into practical design aspects.
CROSS Report
Building code system & standards activity update
Abstract
ENZ Technical groups Feb report
MBIE Updates
News from the Regional Structural Groups
Abstract
SESOC Emerging Structural Engineers Report
Abstract
SESOC Membership Report
SESOC Treasurer's Report
SESOC President Report
Notes from the Editor
Letter to the Editor
Abstract
SESOC Engineering Excellence Awards
Abstract
Sustainable design at SESOC Conference 2023
Abstract
SESOC Conference June 2023
NBS Rating Liability
Abstract
UPDATE
A New Building Standard (%NBS) rating is information derived from seismic assessments. Purchasers and lessees often rely on these assessments when entering property transactions. However, %NBS ratings are a common area for dispute.
This year in TADD Management Ltd v Weine, the High Court reviewed the liability of a vendor and their engineer regarding a 60%NBS (obtained through an Initial Seismic Assessment (ISA)) which was used in marketing material of the property but was substantially different to later %NBS ratings of 10% and 30% (in two Detailed Seismic Assessments) by other engineers.
The court held the vendor liable to the purchaser for $592,000 due to contractual misrepresentation and common mistake. Because it found the vendor liable, and because the vendor had joined the engineer to the proceedings, it was required to consider whether the
engineer was liable to the vendor in negligence, breach of contract or breach of the Fair Trading Act 1986.
Design advice for FRP ties on diaphragms
Abstract
Concrete floor diaphragms of existing buildings are often inadequate to resist tension forces developed as the diaphragm spans between the lateral load resisting elements. A common
strengthening method to provide additional tension capacity is through fibre reinforced polymer (FRP) ties. However existing research is not applicable because it was conducted on thin and short
FRP ties which are dissimilar to those typically required for diaphragm strengthening applications. This paper summarises the progress to date on an extensive research programme, including
experimental testing on thick and long FRP ties, and a summary of the upcoming work. More importantly, specific FRP detailing advice is provided which is intended to prevent inadequate designs that may result in undesirable
premature failure modes occurring during an earthquake. This advice is to: a) use an FRP design strain significantly lower than the fracture strain of the FRP and compatible with the deformation tolerance of the
floor system, b) provide robustness and redundancy in the FRP detailing to protect the building against unpredictable performance through FRP anchor detailing, and c) consider the expected global
ductility and deformation of the structure, specifically any damage that may be induced in the slab due to deformation incompatibilities and the corresponding impact on any FRP ties.
This project is still underway, so this paper is not to be taken as specific design guideline. More content will be published in the coming months.
Case study: CRL Te Waihorotiu Station - Sustainability in design and construction
Abstract
The City Rail Link (CRL) engaged Link Alliance to design and build all station structures on Auckland’s $5.5 Billion underground railway project. The structures include two new underground
rail stations – Te Waihorotiu located beneath Albert Street, extending between Wellesley and Victoria Streets, and Karanga-a-Hape, between Beresford Square and Mercury Lane. The existing
Maungawhau surface station is to be redeveloped, and twin bored tunnels will connect the stations extending from Albert Street to Maungawhau where they bifurcate through a grade-separated
interchange. The CRL is the largest transport infrastructure project ever to be undertaken in New Zealand. It is estimated that it will allow the current rail network to at least double in capacity to cope with 54,000 passengers an hour at peak travel times, and is the catalyst for reshaping a vibrant and sustainable city for people to live in. This paper focuses on the sustainability objectives of the CRL project and aligning these with cultural, industry, and global initiatives to positively contribute to the environment and society. The paper will discuss the initiatives adopted during the design and construction of the Te Waihorotiu Station to achieve the sustainability targets; how efforts toward these targets were measured during the station’s progression; and a review of the lessons learnt and the future/legacy of sustainable design in major projects.
Capacity design of nominally ductile shear wall systems in New Zealand
Abstract
The current provisions of NZS 3101:2006 (and its interaction with NZS 1170.5:2004) provide ambiguous instruction on the requirements for the capacity design of nominally ductile shear wall systems. The recent release of the National Seismic Hazard Model update, along with Earthquake Design for Uncertainty document, has been a timely reminder of the criticality of capacity design, even for nominally ductile structures. This paper highlights the perceived confusing aspects of the current requirements of NZS 3101:2006 and proposes a design pathway for a variety of wall-based structural systems that addresses compliance and best-practice requirements.
Design and construction of the Christ Church Cathedral foundation retrofit
Abstract
The Christ Church Cathedral is a major landmark at the heart of Christchurch and has long been considered an iconic symbol of the city. In the 2010/2011 Canterbury earthquake sequence the
Cathedral sustained severe damage, leading to the building’s closure. In 2017 the Synod endorsed a solution to retain and reinstate as much of the Cathedral’s historic and cultural significance as possible. The primary feature of the reinstatement and strengthening of the Cathedral is introducing seismic isolation at the base. This paper focuses on design of the raft foundation below the isolation system, which was a complex and staged design requiring an innovative and collaborative design response. The two key evolving drivers as the design progressed were geotechnical considerations and construction sequencing. As understanding of the site and liquefaction design developed, and construction sequences evolved with the contractor, the number of load cases required to be analysed increased significantly. Dynamic tools such as grasshopper provided an effective way to respond to increasing complexity in foundation analysis and process the large quantity of data to provide an efficient and robust design. The complexity of design cases considered in the Cathedral foundation also highlighted a number of gaps in industry guidance and understanding. Ultimately more development is required at an industry level around liquefaction design, soft spot analysis, and combining static and dynamic soil conditions, to determine appropriate approaches to the increasing complexity of foundation design. This will be critical in providing a consistent benchmark for foundation design in the future.
New horizons in the fire resistance of post-installed rebar connections
Abstract
Post-installed rebars (PIR) provide versatile solutions for the rehabilitation and strengthening of existing concrete structures or for new concrete construction by offering a feasible and economical method for adding concrete sections to existing members. This paper provides a summary of the fire design of post-installed rebar connections according to Eurocode 2, where the system holds an ETA (give long-form of ETA at first instance) assessed as per European Assessment Document (EAD) 330087 and provides recommendations for the fire design of stress development and splicing of post-installed rebar connections in New Zealand, using the logic of Clause 4.10 of NZS 3101 that delegates the fire design to Eurocode 2 or other recognised method of calculation. It is demonstrated that a straightforward and transparent approach can be recommended for the adoption of EAD 330087 for the fire design of stress development and splicing of post-installed rebar connections based on NZS 3101 for scenarios of uniform temperature distribution along the development length or the splice length during a fire event.
Recent New Zealand PhD thesis abstracts from University of Auckland and University of Canterbury
Abstract
CROSS Report
Building code system & standards activity update
Abstract
MBIE updates
SESOC Emerging Structural Engineers Report
Abstract
SESOC Bridge Reports
IStructE & Bridge Report
News from the Regional Structural Groups
Abstract
SESOC Membership Report
SESOC Treasurer's Report
SESOC President’s Report
Note from the Editor
Letter to the Editor
Abstract
Upfront & whole-of-life embodied carbon: what structural engineers need to know
Abstract
The term ‘embodied carbon’ is now commonplace in structural engineering. Working knowledge or at least familiarity with the concept of the emissions associated with building structures is fast becoming something expected from the engineers who design and specify them. Reducing the embodied carbon of their designs has been shown to be an extremely effective action structural engineers can take to address the climate emergency1.
You can’t manage what you don’t measure, so calculation or assessment of embodied carbon is the first step to reducing these emissions.
The idea of assessing ‘whole-of-life’ embodied carbon of a building, which requires estimating emissions associated with processes and activities that will occur many years in the future, can be both daunting and confusing. In line with SESOC’s Position Statement on Sustainable Design2, this paper is intended to support structural engineers to understand the difference between upfront and whole-of-life emissions, and the relative impact of actions to reduce these emissions.
Understanding carbon emissions of structural timber products: the full story
Abstract
Structural engineers are increasingly being expected to engage with and talk about the relative benefits of different structural solutions and materials with respect to their embodied carbon outcomes. Engineering New Zealand has just released Draft Practice Note 32: Climate Action – the role of the engineer1. SESOC also has a position statement on Sustainable Design2. In this context, it becomes increasingly important that structural engineers understand the carbon profile of different structural materials.
The carbon profile of structural timber products is complex. Before talking about the sources of carbon emissions and removals over the lifetime of a timber product, it is helpful to understand the underlying concepts. Therefore the first part of the article discusses the carbon cycle as it relates to trees, and explains sequestration and biogenic carbon. The second section discusses carbon emissions in the timber industry, and what to consider when designing and specifying timber on a project for lower-carbon outcomes.
Building a hybrid future together - Seminar
Abstract
On 2 November 2023, Timber Unlimited hosted a Hybrid Buildings Seminar in Auckland in collaboration with the Timber Design Society (TDS), aimed at discussing current practice in the industry especially as it relates to engineered timber.
Timber Unlimited is a collaboration between the New Zealand Timber Design Society, Wood Processors and Manufacturers Association, BRANZ and SCION. Timber Unlimited is hosted at SCION Research and is financially supported for establishment through the Ministry for Primary Industries.
Updating New Zealand’s guidance for seismic assessment of existing concrete buildings
Abstract
It is five years since the technical guide used as the basis for seismic assessments of existing concrete buildings in New Zealand was last updated. Since that update, use of the guide and ongoing research has led to identification of aspects of the guidance document that warrant further improvement. To address this need, Compusoft Engineering were commissioned to produce change proposals for Section C5 and other related parts of the guidance.
Key change proposals include:
• Better defining the intent of assessments in Section C1,
• Changes to Section C5 to improve assessment of splices and mechanical connections, to include guidance for corroding structures, to resolve contradictions related to stiffness modifiers, and improving the clarity of provisions aimed at preventing loss of gravity load carrying capacity,
• Improvements to diaphragm assessment provisions in Sections C2 and C5, particularly as they relate to collector elements and the impact of wide cracks on diaphragm load paths, and
• Adjusting procedures for assessment of precast concrete floors so that the outcomes align better with experimental results.
While not yet evaluated quantitatively, it is expected that the proposed changes would generally improve
assessment outcomes and lead to higher earthquake ratings for buildings.
Paradigm change in the seismic design of post-installed fasteners in New Zealand
Abstract
The current requirements for post-installed mechanical anchors and post-installed adhesive anchors in New Zealand is given in Section 17.5.5 of NZS 3101:2006 that compare the topic to European documents both for fastener assessment and design. NZS 3101 is largely based on ACI 318 in the majority of its content. In 2023, the ACI 355 Committee updated the old simulated seismic testing protocols of fasteners in both ACI CODE-355.2 and ACI CODE-355.4 which is expected to be acknowledged in the next edition of ACI CODE-318 in 2025. This paper gives an overview of the current challenges in the seismic assessment and design of fasteners in New Zealand, supplemented with a detailed introduction and critical analysis of the current international state-of-the-art, and provides recommendations for immediate, short-term and long-term actions in these topics in New Zealand.
CROSS Report
Building code system & standards activity update
MBIE Updates
SESOC Emerging Structural Engineers Report
Abstract
SESOC Bridge Reports
News from the Regional Structural Groups
Abstract
IStructE update
SESOC Membership Report
SESOC Treasurer’s Report
SESOC President’s Report
Note from the Editor
Letter to the Editor
Demystifying Green Star and Homestar for structural engineers
Abstract
Structural engineers often find themselves working on projects which are targeting a green building rating. These rating tools get updated every couple of years, and what may have been done on one project is not necessarily going to be the same on the next.
This article aims to demystify the two main rating tools operated by the New Zealand Green Building Council (NZGBC) which impact structural engineers on projects1. The first section of the article provides a quick overview of relevant aspects of the certification which structural engineers need to either understand, take account of, or action. The second section of the article provides an overview of the important things structural engineers need to consider at each stage of a project, from bidding and pricing, through design, to specification.
Reducing steel's carbon impact: Industrial decarbonisation and specification considerations for structural engineers
Abstract
Structural engineers are increasingly being expected to engage with and talk about the relative benefits of different structural solutions and materials with respect to their embodied carbon outcomes. Engineering New Zealand has just released Draft Practice Note 32: Climate Action – the role of the engineer1. SESOC also has a position statement on Sustainable Design2. In this context, it becomes increasingly important that structural engineers understand the sustainability and carbon profile of different structural materials.
University PhD research papers
Code of practice for the seismic performance of non-structural elements
Abstract
Despite having design provisions for non-structural elements (NSEs) in Aotearoa New Zealand for over 40 years, research indicates that most NSEs in New Zealand buildings are not adequately seismically restrained. Shockingly, sometimes up to 90% of elements lack proper
restraints. The 2010-2011 Canterbury earthquakes, the 2013 Seddon earthquake, and the 2016 Kaikoura earthquake all revealed that the costs associated with damage to NSEs often exceed those of structural damage. This damage can also result in significant disruptions to businesses, as highlighted in the Building Innovation Partnership (BIP) White Paper 20201. Recent studies in New Zealand pinpoint a significant knowledge gap regarding the seismic behaviour of NSEs, particularly the relationship between their seismic behaviour and their
ability to function post-earthquake².
The seismic restraint of NSEs predominantly involves achieving life-safety performance objectives, but the seismic performance of NSEs is dependent on the overall building design philosophy. This necessitates deliberate design considerations and actions from multiple disciplines, including structural engineers, architects, fire protection engineers, and building services engineers. The seismic performance of NSEs includes more than just their restraint. While seismic restraint is crucial, other factors – such as the ability to accommodate movements, the robustness of components against shaking, and their flexibility – also play significant roles in overall performance.
The presence of seismic restraints provides a basic indication that seismic considerations have been made, but it does not offer a complete picture.
Traditionally, New Zealand has approached the design of seismic restraints for NSEs with a ‘just in time’ attitude, following the completion of detailed designs for primary structures and building services. This often entails separate designers handling seismic restraint designs for
different trades or disciplines, leading to poorly coordinated solutions and clashes during construction. Additionally, there has been minimal enforcement of design or installation standards, allowing unresolved issues to persist due to a lack of oversight.
A 2009 survey by the Earthquake Engineering Research Institute (EERI) in the United States highlighted similar challenges. Key issues included a lack of assigned responsibility. Structural engineers or knowledgeable enforcement agents were seldom present on job sites during the installation of NSEs. This diffused responsibility matrix led to unclear accountability, minimal regulatory enforcement, and normative behaviour based on perceived industry practices.
Similar issues clearly exist in New Zealand, and the New Zealand construction industry is beginning to respond to these challenges. The Structural Engineering Society of New Zealand (SESOC) identified six key recommendations related to these issues that are further discussed later in this article (SESOC, 2022).
Towards proposing and piloting a framework for low carbon design: An introduction
Abstract
Through the New Zealand Climate Change Response (Zero Carbon) Amendment Bill1, Aotearoa New Zealand has committed to the Paris Agreement’s goal2 of limiting the mean global temperature rise to less than 1.5°C before 2050. MBIE’s Building for Climate Change programme reflects these goals for the built environment and proposes a programme of work that would require consideration and reduction of whole-of-life carbon impacts of buildings.
To assist the sector to reduce carbon in the built environment, a HERA-led project involving Aurecon and WSP input aims to develop:
1. a materials- and typology-agnostic design guidance framework (“the framework”). The vision is that this will form the basis for the development over time of a series of design manuals which cover different building typologies.
2. specific guidance and case studies, using the framework, relating to low-rise commercial buildings using steel and steel-hybrid design. This paper effectively acts as a pilot of the framework and feeds into its development. Case studies are included in this specific design guidance to demonstrate potential carbon reductions that can be achieved when the guidance is applied; and
3. a report identifying impediments and key knowledge and research gaps that are important for the sector to address over time, in order to inform future design guidance based on the framework. The framework considers whole-of-life (cradle-to–cradle) carbon emissions, which are given as stages (or modules) A to D in EN 158043. It identifies opportunities for their reduction at the concept design stage and ascertains their interaction with the New Zealand Building Code (NZBC)4, especially Clause B (Stability), which includes both B1 (Structure) and B2(Durability), E (Moisture), and H (Energy Efficiency). A key part of the project is also using and refining this framework for the specific case of low-rise commercial buildings based on steel. Given the project’s limited scope, it was considered important to identify knowledge and research gaps for further attention and future focus.
This paper introduces the project and work done to date, building upon an earlier 2023 SESOC conference paper entitled Designing Sustainable Low-Rise Buildings – Development of a Design Guidance Manual5.
Providing robust Vs30 estimates for seismic site classification in Aotearoa New Zealand
Abstract
The recent update to the National Seismic Hazard Model has changed the approach to seismic site classification in Aotearoa New Zealand, with the time-averaged shear wave velocity over the top 30 m of the subsurface profile (VS30) at a site now being a key site classification metric. To provide robust estimates of VS30, the profession needs to have a good understanding of the advantages and limitations of the different geophysical site investigation methods that are used to define the shear wave velocity (VS) profiles needed to calculate VS30. The general characteristics and the constraints inherent to the methods themselves are discussed in this paper. The influence of the size of a site, topography across a site and the presence of existing infrastructure is summarised. The impact of the different geologic conditions on the choice of methods are highlighted. A relative comparison of costs associated with different methods is presented.
Approaches to data interpretation for each method are discussed, including the translation of these into site classification metrics.
Developing seismic design and assessment guidance for post-installed fasteners in Aotearoa New Zealand
Abstract
It can be demonstrated that the current methods for post-installed fastener seismic assessment and design in Aotearoa New Zealand (based on Section 17.5.5 of NZS 3101:2006) are very loosely connected. Fastener seismic design can be either overly conservative or unsafe due to this detachment. The European documents cited in NZS 3101 for fastener assessment and design do not represent the state-of-the-art. Current changes in overseas codes and related regulations imply that the involvement of the engineering community in the development process of fastener seismic assessment methods is not effective enough. Related to the upcoming revision of NZS 3101, this paper gives a
New Zealand specific outlook for possible directions in developing fastener seismic assessment methods, which are driven by and provide direct input for the seismic design of steel-to-concrete connections.
CROSS Report
Building code system & standards activity update
Abstract
MBIE Updates
SESOC Emerging Structural Engineers (ESE) Groups
Abstract
SESOC Bridge Reports
News from the Regional Structural Groups
Abstract
IStructE update
SESOC Sustainable Design Task Force updates
Abstract
SESOC Membership Report
SESOC Treasurer’s Report
SESOC President Report
Note from the Editor
Reaffirming the SESOC Position on Sustainable Design
Abstract
With the change of government, we have seen a change in pace in the national response to climate change. MBIE’s climate change work programme (previously The Building for Climate Change Programme) is currently being refreshed, and the previously advised timeframes for mandatory reporting of embodied carbon have been removed, as the focus of government action is shifted from regulatory change to incentivising industry-led action instead. SESOC Management Committee alongside the Sustainable Design Task Force have refreshed the SESOC Position Statement on Sustainable Design (see below). This update is to reaffirm our position on the important role structural engineers have in minimising environmental impact of our professional work and driving embodied carbon emissions towards zero. The carbon savings that we can make in our professional roles far exceed any reductions possible in our personal lives, no matter how many flights you avoid, or takeaway cups you don’t use (but don’t stop, it all helps).
Demystifying EPDs PCRs and other TLAs for structural embodied carbon conversations
Abstract
As carbon literacy grows in the construction sector, Environmental Product Declarations (EPDs) are becoming more familiar to professionals, including structural engineers, and are recognised as robust and credible sources of primary data for embodied carbon coefficients (or ‘carbon intensities’) of construction materials and products.
Multiplying the carbon intensity of a construction material (such as structural steel, 30 MPa concrete or kiln-dried framing timber) by the quantity of those materials used, is the fundamental basis for calculating embodied carbon (see Top Tip #1 in the SESOC Top Tips for Low Carbon Design1).
As demand and interest in embodied carbon assessment has grown, so too has the scrutiny on these calculations, especially on the quality of the carbon intensity data being used. When design or procurement decisions are being made based on the embodied carbon of different options, how can we be sure we are comparing ‘apples with apples’, i.e. does the data capture the carbon impact of different materials and products in a fair and comparable way?
This short article explains some key aspects of EPDs to equip structural engineers in conversations about the validity of data used in embodied carbon assessments, especially when comparing different materials. It introduces the concept of Product Category Rules (PCR),
a set of rules that must be followed when producing an EPD so that the environmental impacts of products can be compared in a fair and equitable way. It also translates some of the more common TLAs (Three Letter Acronyms) that litter this space. This article is intended to give
structural engineers more confidence in the data used in embodied carbon assessments, which they are increasingly expected to help undertake or interpret as part of the structural design process.
Low damage seismic design performance framework
Abstract
Low Damage Seismic Design (LDSD) is a building design philosophy that achieves better than New Zealand Building Code minimum requirements. A key goal of LDSD is to deliver buildings that are less likely to be damaged and thereby limit disruption and losses in future earthquakes. The Ministry of Business, Innovation, and Employment, in partnership with The Natural Hazards Commission Toka Tu Ake and Structural Engineering Society NZ, are collectively developing a performance framework for LDSD which defines hierarchy and inter-relationships between the overall outcome objectives and corresponding performance goals and physical states. This performance framework establishes the context for technical design criteria which are being developed as part of a parallel project. This paper provides an overview of the LDSD performance framework and supporting benchmarking studies.
Carbon in a seismic context - a discussion piece
Abstract
As engineers we are at home with critically evaluating design options, making trade-offs, weighing each design decision against a spectrum of needs. But are we correctly accounting for the weight of each of those needs? Are we giving enough weight to the very real and pressing need to drive construction emissions towards zero and minimise the impact of climate change, or is it time for carbon to step out from the shadows and take its place alongside resilience as one of our primary responsibilities? Improved seismic resilience, a drive for above-code
performance, has been the mindset for sector-leading structural engineers for the past decade. Through the lens of sustainability, the question of how we are achieving this resilience is asked, and if we are applying the goal of ‘better than code minimum’ to the right features. Structural failures as a result of the Otautahi Christchurch and Kaikoura earthquakes were largely contained to historic construction forms (URM), isolated instances of poor practice, and specific detailing issues in modern buildings, rather than systemic underperformance. The huge volume of postevent demolitions were predominantly driven by ground conditions and our insurance landscape – not by structural failure. The images showing the patchwork city centre left behind following the Waitaha Canterbury earthquakes spurred the call for resilient construction, but in driving to improve resilience have we reached for the hammer (increasing design loads, base isolation, adding material) instead of applying the key techniques that we know give better certainty in performance – including regularity, capacity design, ductile detailing and direct load paths?
SImplifying the effect of lap splices on the inelastic rotation capacity of reinforced concrete shear walls
Abstract
Two reduction factors (ß1 and ß2) are introduced as part of a method to estimate the mean inelastic rotation capacity of shear
walls with lap splices near sections where reinforcement yields.
Recent experiments (Pollalis et al. 2024, Pujol et al. 2024) have shown that RC walls with staggered lap splices near sections where reinforcement yields behave in much the same way as RC walls with non-staggered lap splices. It was also shown that staggered lap splices can be even more detrimental to the deformation capacity of RC walls than non-staggered lap splices. These findings contradict current design and assessment practices in New Zealand, which most often treat staggered lap splices as equivalent to continuous reinforcement. To that end, this article (a) reviews how lap splices near sections where reinforcement yields reduce the deformability of RC walls and (b) provides a method to quantify the reduction in wall deformation capacity associated with any layout of lap splices (staggered or non-staggered).
Case-hardened steel fasteners & mass timber construction
McDonnell, D., Scheibmair, F1, Stankowitz,B.
Abstract
Case-Hardened Steel Fasteners & Mass Timber Construction
The use of large (8 mm diameter and larger) fully threaded and partially threaded screws are critical to facilitate the design and construction of Mass Timber (MT) structures. This includes basic applications such as fixing Cross-Laminated Timber (CLT) panels to supporting gluedlaminated beams, but also at critical gravity (i.e. beam-tocolumn) and seismic (timber lateral systems and/or steel collector plates to timber) connections.
In general, case-hardened steel timber screws (i.e. fasteners) have been used on thousands of projects globally, with relatively few reported failures. That said, there are reports of screw failures in large numbers on isolated projects in Europe, the USA and Canada, where project
conditions (e.g. prolonged exposure to excessive moisture) have led to Environmental Hydrogen Embrittlement (EHE) in the fasteners. These have often occurred where thick steel plates are being fixed to timber. In Aotearoa New Zealand, some projects have observed similar failures as well. While the projects affected are small in number, the consequence to individual projects can be significant, and thus this issue deserves additional scrutiny for the betterment of the industry.
The following technical note will explain the conditions required for hydrogen embrittlement to occur, how to identify connections with a higher risk profile, along with recommendations on how to mitigate the risk.
Towards the performance-based seismic design of post-installed anchor connections
Abstract
Performance-based seismic design of connections with post-installed anchors is not possible in Aotearoa New Zealand based on NZS 3101 that references the current international state-of-the-art in seismic design and qualification of postinstalled anchors. A performance-based framework was proposed recently for the seismic behaviour of post-installed anchors, in which seismic damage of the concrete-anchor system is the focus. The proposed framework offers a transparent, design-driven platform for future developments. This article provides further insights for the practical application of the proposed framework in Aotearoa NZ.
Plywood panels for the in-plane retrofit of URM walls - full-scale experimental validation
Abstract
The susceptibility of unreinforced masonry (URM) walls to collapse under seismic loading has been repeatedly observed and documented across a multitude of earthquakes worldwide. Various seismic retrofit techniques exist. However, there continues to be a developing need for experimentally validated, simple, and cost-effective solutions that also consider the impact on building tenants, aesthetics, and the heritage fabric of a structure. Because of this, timberbased retrofit strategies have been gaining popularity both in academia and industry as a method of achieving the developing performance, sustainability, and cost requirements of URM retrofit projects.
The retrofit technique studied herein is the use of plywood panels for in-plane strengthening of URM walls. With the use of mechanical fixings, this retrofit becomes a fully reversible, cost effective, and low impact solution.
The in-plane behavior of as-built, retrofitted, and repaired masonry walls was investigated by conducting full scale insitu semi-static in-plane shear tests on as-built, damaged, repaired, and retrofitted masonry walls. The outcomes of this testing regime include quantification of improvement in seismic capacity, force vs displacement behaviour of test specimens, and observation of critical failure modes.
Design of a diagrid tall wood building
Abstract
Analysis and design of a virtual 10-storied wood building with diagrid structure is presented here. The building is designed as per provisions of Canadian National Building Code (NBCC) and British Columbia Building Code (BCBC).
Standard wood design practices and local material specifications are used for a realistic solution. Analysis results show the wooden diagrid structure and central core can resist gravity and lateral loads acting on the building. The diagrid structure is found to be an efficient and practical system for tall wood buildings.
CROSS Report
SESOC Sustainable Design Task Force Updates
Abstract
MBIE Updates
Standards Activity Update
SESOC Emerging Structural Engineers (ESE) Groups
Abstract
SESOC Bridge Reports
News from the Regional Structural Groups
Abstract
IStructE update
SESOC Membership Report
SESOC Treasurer’s Report
SESOC President Report
Note from the Editor
Reaffirming the SESOC Position on Sustainable Design
Abstract
With the change of government, we have seen a change in pace in the national response to climate change. MBIE’s climate change work programme (previously The Building for Climate Change Programme) is currently being refreshed, and the previously advised timeframes for mandatory reporting of embodied carbon have been removed, as the focus of government action is shifted from regulatory change to incentivising industry-led action instead. SESOC Management Committee alongside the Sustainable Design Task Force have refreshed the SESOC Position Statement on Sustainable Design (see below). This update is to reaffirm our position on the important role structural engineers have in minimising environmental impact of our professional work and driving embodied carbon emissions towards zero. The carbon savings that we can make in our professional roles far exceed any reductions possible in our personal lives, no matter how many flights you avoid, or takeaway cups you don’t use (but don’t stop, it all helps).
Demystifying EPDs PCRs and other TLAs for structural embodied carbon conversations
Abstract
As carbon literacy grows in the construction sector, Environmental Product Declarations (EPDs) are becoming more familiar to professionals, including structural engineers, and are recognised as robust and credible sources of primary data for embodied carbon coefficients (or ‘carbon intensities’) of construction materials and products.
Multiplying the carbon intensity of a construction material (such as structural steel, 30 MPa concrete or kiln-dried framing timber) by the quantity of those materials used, is the fundamental basis for calculating embodied carbon (see Top Tip #1 in the SESOC Top Tips for Low Carbon Design1).
As demand and interest in embodied carbon assessment has grown, so too has the scrutiny on these calculations, especially on the quality of the carbon intensity data being used. When design or procurement decisions are being made based on the embodied carbon of different options, how can we be sure we are comparing ‘apples with apples’, i.e. does the data capture the carbon impact of different materials and products in a fair and comparable way?
This short article explains some key aspects of EPDs to equip structural engineers in conversations about the validity of data used in embodied carbon assessments, especially when comparing different materials. It introduces the concept of Product Category Rules (PCR),
a set of rules that must be followed when producing an EPD so that the environmental impacts of products can be compared in a fair and equitable way. It also translates some of the more common TLAs (Three Letter Acronyms) that litter this space. This article is intended to give
structural engineers more confidence in the data used in embodied carbon assessments, which they are increasingly expected to help undertake or interpret as part of the structural design process.
Low damage seismic design performance framework
Abstract
Low Damage Seismic Design (LDSD) is a building design philosophy that achieves better than New Zealand Building Code minimum requirements. A key goal of LDSD is to deliver buildings that are less likely to be damaged and thereby limit disruption and losses in future earthquakes. The Ministry of Business, Innovation, and Employment, in partnership with The Natural Hazards Commission Toka Tu Ake and Structural Engineering Society NZ, are collectively developing a performance framework for LDSD which defines hierarchy and inter-relationships between the overall outcome objectives and corresponding performance goals and physical states. This performance framework establishes the context for technical design criteria which are being developed as part of a parallel project. This paper provides an overview of the LDSD performance framework and supporting benchmarking studies.
Carbon in a seismic context - a discussion piece
Abstract
As engineers we are at home with critically evaluating design options, making trade-offs, weighing each design decision against a spectrum of needs. But are we correctly accounting for the weight of each of those needs? Are we giving enough weight to the very real and pressing need to drive construction emissions towards zero and minimise the impact of climate change, or is it time for carbon to step out from the shadows and take its place alongside resilience as one of our primary responsibilities? Improved seismic resilience, a drive for above-code
performance, has been the mindset for sector-leading structural engineers for the past decade. Through the lens of sustainability, the question of how we are achieving this resilience is asked, and if we are applying the goal of ‘better than code minimum’ to the right features. Structural failures as a result of the Otautahi Christchurch and Kaikoura earthquakes were largely contained to historic construction forms (URM), isolated instances of poor practice, and specific detailing issues in modern buildings, rather than systemic underperformance. The huge volume of postevent demolitions were predominantly driven by ground conditions and our insurance landscape – not by structural failure. The images showing the patchwork city centre left behind following the Waitaha Canterbury earthquakes spurred the call for resilient construction, but in driving to improve resilience have we reached for the hammer (increasing design loads, base isolation, adding material) instead of applying the key techniques that we know give better certainty in performance – including regularity, capacity design, ductile detailing and direct load paths?
SImplifying the effect of lap splices on the inelastic rotation capacity of reinforced concrete shear walls
Abstract
Two reduction factors (ß1 and ß2) are introduced as part of a method to estimate the mean inelastic rotation capacity of shear
walls with lap splices near sections where reinforcement yields.
Recent experiments (Pollalis et al. 2024, Pujol et al. 2024) have shown that RC walls with staggered lap splices near sections where reinforcement yields behave in much the same way as RC walls with non-staggered lap splices. It was also shown that staggered lap splices can be even more detrimental to the deformation capacity of RC walls than non-staggered lap splices. These findings contradict current design and assessment practices in New Zealand, which most often treat staggered lap splices as equivalent to continuous reinforcement. To that end, this article (a) reviews how lap splices near sections where reinforcement yields reduce the deformability of RC walls and (b) provides a method to quantify the reduction in wall deformation capacity associated with any layout of lap splices (staggered or non-staggered).
Case-hardened steel fasteners & mass timber construction
McDonnell, D., Scheibmair, F1, Stankowitz,B.
Abstract
Case-Hardened Steel Fasteners & Mass Timber Construction
The use of large (8 mm diameter and larger) fully threaded and partially threaded screws are critical to facilitate the design and construction of Mass Timber (MT) structures. This includes basic applications such as fixing Cross-Laminated Timber (CLT) panels to supporting gluedlaminated beams, but also at critical gravity (i.e. beam-tocolumn) and seismic (timber lateral systems and/or steel collector plates to timber) connections.
In general, case-hardened steel timber screws (i.e. fasteners) have been used on thousands of projects globally, with relatively few reported failures. That said, there are reports of screw failures in large numbers on isolated projects in Europe, the USA and Canada, where project
conditions (e.g. prolonged exposure to excessive moisture) have led to Environmental Hydrogen Embrittlement (EHE) in the fasteners. These have often occurred where thick steel plates are being fixed to timber. In Aotearoa New Zealand, some projects have observed similar failures as well. While the projects affected are small in number, the consequence to individual projects can be significant, and thus this issue deserves additional scrutiny for the betterment of the industry.
The following technical note will explain the conditions required for hydrogen embrittlement to occur, how to identify connections with a higher risk profile, along with recommendations on how to mitigate the risk.
Towards the performance-based seismic design of post-installed anchor connections
Abstract
Performance-based seismic design of connections with post-installed anchors is not possible in Aotearoa New Zealand based on NZS 3101 that references the current international state-of-the-art in seismic design and qualification of postinstalled anchors. A performance-based framework was proposed recently for the seismic behaviour of post-installed anchors, in which seismic damage of the concrete-anchor system is the focus. The proposed framework offers a transparent, design-driven platform for future developments. This article provides further insights for the practical application of the proposed framework in Aotearoa NZ.
Plywood panels for the in-plane retrofit of URM walls - full-scale experimental validation
Abstract
The susceptibility of unreinforced masonry (URM) walls to collapse under seismic loading has been repeatedly observed and documented across a multitude of earthquakes worldwide. Various seismic retrofit techniques exist. However, there continues to be a developing need for experimentally validated, simple, and cost-effective solutions that also consider the impact on building tenants, aesthetics, and the heritage fabric of a structure. Because of this, timberbased retrofit strategies have been gaining popularity both in academia and industry as a method of achieving the developing performance, sustainability, and cost requirements of URM retrofit projects.
The retrofit technique studied herein is the use of plywood panels for in-plane strengthening of URM walls. With the use of mechanical fixings, this retrofit becomes a fully reversible, cost effective, and low impact solution.
The in-plane behavior of as-built, retrofitted, and repaired masonry walls was investigated by conducting full scale insitu semi-static in-plane shear tests on as-built, damaged, repaired, and retrofitted masonry walls. The outcomes of this testing regime include quantification of improvement in seismic capacity, force vs displacement behaviour of test specimens, and observation of critical failure modes.
Design of a diagrid tall wood building
Abstract
Analysis and design of a virtual 10-storied wood building with diagrid structure is presented here. The building is designed as per provisions of Canadian National Building Code (NBCC) and British Columbia Building Code (BCBC).
Standard wood design practices and local material specifications are used for a realistic solution. Analysis results show the wooden diagrid structure and central core can resist gravity and lateral loads acting on the building. The diagrid structure is found to be an efficient and practical system for tall wood buildings.
CROSS Report
SESOC Sustainable Design Task Force Updates
Abstract
MBIE Updates
Standards Activity Update
SESOC Emerging Structural Engineers (ESE) Groups
Abstract
SESOC Bridge Reports
News from the Regional Structural Groups
Abstract
IStructE update
SESOC Membership Report
SESOC Treasurer’s Report
View whole issue as flipbook
SESOC President’s Report
Note from the Editor
SESOC Conference 2025
A discussion on structural acrylic design
Abstract
After gaining experience in Aotearoa New Zealand, South Africa and London (mostly on industrial, residential and highway design), Mike Murphy’s structural engineering career then led to coolstore and sandwich panel design prior to floating marina design (Westhaven in Tamaki Makaurau Auckland – 700 berth) and finally to aquarium and underwater acrylic tunnel and window design. This final phase of Murphy’s career culminated in the design of two underwater restaurants and a revolutionary underwater villa in the Maldives.
Ten of Murphy’s projects are believed to be world-firsts in the field of acrylic design. In 2018, after completion of his most ambitious project, the world’s first underwater villa (Muraka) in the Maldives, Mike decided to retire. However, a few years later he was persuaded to come out of retirement to consult on another acrylic project for the new Australian giant icebreaker ship, the RSV Nuyina.
Mike Murphy graduated from University of Auckland in 1971 with BE (Civil). He gained registered status in 1980 and formed his own consulting practice, M.J. Murphy Ltd (Murphy), in 1980.
Rigid-inclusion ground improvement design practice in Aotearoa New Zealand
Abstract
The authors have recently been engaged to provide a “high level review” (not a peer review) of the structural design of a rigid-inclusion (RI) ground-improvement system for a new storage tank. Our experience from this review has left us concerned about:
• The design philosophy apparently adopted for rigid-inclusion ground improvement systems by some engineers (with our main concerns being an apparent lack of understanding of horizontal seismic load paths and ductility)
• How some designers claim to demonstrate compliance with NZBC cl. B1 in respect of weak, unreinforced concrete RI systems
• The categorisation by some consultants (both geotechnical and structural) and contractors that rigid inclusions are “ground improvements” and not a foundation system, and therefore do not need to meet the requirements of B1 of the NZBC
• The use of multi-national design teams to produce standardised solutions with little or no regard for Aotearoa New Zealand’s seismic environment, nor the specific requirements of the NZBC
• The lack of obligation on designers to address questions arising from “high level” reviews (as opposed to peer reviews)
Low carbon design: Is French flair at play and where are opportunities for Aotearoa New Zealand to up the game?
Abstract
As awareness on the climate change crisis rises internationally and as the reduction of carbon emissions is identified as a necessary path to a sustainable future, the construction sector, being a significant contributor to carbon emissions, is expected to play a pivotal role in leading change.
In January 2022, the Environmental Regulation RE2020 came into force in France, making it one of the first countries to adopt legislation with regulatory thresholds on whole-of-life embodied carbon for buildings. Following an overview of the French journey to RE2020 and an outline of the regulation’s framework, thoughts are shared on opportunities for Aotearoa New Zealand structural engineers to accelerate change on low carbon design considering the country’s cultural and organisational specificities.
Calculating embodied carbon
Abstract
The need for structural engineers to be able to calculate the embodied carbon of their designs is increasing. This is driven by an awareness of wider climate considerations, client and design team requests, and individuals’ interest in the impact of their own work.
Tools for generating whole-of-life carbon assessments are now readily available. These tools often involve large quantities of both input and output data that can be difficult to interpret and, used without appropriate experience, could detract from the broader goal of making informed decisions to achieve lower carbon outcomes for projects.
Embodied carbon is becoming a more prominent structural design consideration alongside (and heavily linked to) cost, structural efficiency, build-ability and resilience. It is at the early stages of a project that the structural engineer has the greatest ability to influence
the project outcomes, and help achieve lower carbon outcomes.
The purpose of this worked example is to demonstrate the relative ease with which structural engineers can rapidly estimate the life-cycle stage A1-A3 (product stage) embodied carbon of their designs, and then use this to help inform design decisions regarding material selection, primary structural layout and geometry.
This example focuses on one structural system only, for the purpose of demonstrating how calculations can be performed. The intention is to follow this with further worked examples covering whole structure upfront embodied carbon (stages A1-A5), and also full life-cycle
assessment (LCA) considerations.
A teaching tool for steel design from development to implementation
Abstract
Lateral Torsional Buckling (LTB) and Local Buckling (LB) are important modes of failure that can limit the design capacity in steel members. Statistics indicate that many practicing civil engineers and students find it difficult to link the physical behaviour of LTB and LB with the theoretical mathematics. To improve current teaching methods, a novel demonstration teaching tool has been developed to enable this link. This was made possible by employing polyurethane in place of steel. Polyurethane is a polymer that only experiences elastic deformation and has a low Young’s modulus making it a suitable substitute to repeatedly display the behaviours in a classroom. The outcome resulted in a main teaching tool that demonstrates the significant factors influencing LTB of beams, namely the position of the applied load, the position of the applied load relative to the centre of rotation and the influence of support conditions for twist and flange fixity. It also allows the effectiveness of load bearing stiffeners as points of twist restraint to be determined and the deformed shape associated with LB of the flange and web. Altogether, it uses the theoretical expressions for LTB and LB given in Aotearoa New Zealand structural steel standard
NZS 3404:1997 to link the magnitude of applied load on the model to the mathematics while also providing a link to the visualisation of these buckling modes. The teaching tool has since been implemented in the engineering curriculum at the University of Auckland Waipapa Taumata Rau. This paper covers an overview on the development of the teaching tool from concept to implementation.
Can timber construction experience limits to growth?
Abstract
The title of this paper refers to a report of similar title by the Club of Rome1, published over 50 years ago. Since then, the number of people on Earth has doubled. As a result, global CO2 consumption continues to rise despite all efforts to counter this development. An increase in prosperity and an increase in CO2 consumption are, to date, directly linked. Whether it will be possible to decouple further growth from environmental damage remains to be proven in the coming years. The European Union is focusing on green growth. In the Green Deal, timber construction is seen as a source of hope: timber construction is set to grow.
This is a great opportunity for the timber construction community. But can we meet the associated requirements? Or are there factors that could limit the growth of timber construction? And if so, how can we meet these challenges? In this paper, the author – from a European perspective – will attempt to formulate a few thoughts and possible solutions.
Seismic design and qualification of post-installed fasteners: A way forward
Abstract
This paper addresses the open question of performance-based seismic design and qualification of post-installed fasteners. Related to a performance-based framework for the seismic behaviour of post-installed fasteners (pifs) currently proposed in the literature, this paper briefly analyses the complete sequence of performance-based seismic design of connections. Specific future directions and approaches are proposed, and major knowledge gaps are identified. It is highlighted that the relevant performance parameters of pifs for performance-based seismic design should be identified and their embedment into the design processes should be demonstrated.
Development of an unambiguous seismic design and qualification framework is urged, which could acknowledge the current international state-of-the-art and could address the current gaps.
University PhD Theses
Rosa Eva Gonzalez Espinel (University of Auckland)
Supervised by Dr Charlotte Toma and Dr Max Stephens
SYSTEM RESPONSES OF REINFORCED CONCRETE
COUPLED WALLS SYSTEMS
Ren-Jie Tsai (University of Auckland)
Supervised by Associate Professor Rick Henry and Professor Ken Elwood
WALL-TO-FLOOR INTERACTIONS IN LOW-DAMAGE CONCRETE BUILDINGS
Qun Yang (University of Auckland)
Supervised by Associate Professor Rick Henry
SUSTAINABLE MATERIALS FOR 3D CONCRETE PRINTED STRUCTURAL
ELEMENTS IN A QUAKE-PRONE CONTEXT, AOTEAROA NEW ZEALAND
Luis M. de la Flor (University of Canterbury)
Supervised by G. Lopocaro, A. Scott, D. Clucas
RISK-ORIENTED DESIGN OF BASE-ISOLATED BUILDINGS
IN AOTEAROA NEW ZEALAND
Claire Dong (University of Canterbury)
Supervised by T.J. Sullivan, D. Pettinga
DIVERTING SEISMIC WAVES USING INERTER-BASED
SEISMIC METAMATERIALS
Ha-Linh Nguyen (University of Canterbury)
Supervised by C.L. Lee, C.W. Lim
Damping Identification for Seismic Responses: Challenges and
Practical Insights
Yuanqi Zheng (University of Canterbury)
Supervised by C.L. Lee, J. Guo, R. Shen
Abstract
An important message about the use of PS4 producer statements
Abstract
Following concerns raised by Building Consent Authorities (BCAs) regarding altered Producer Statements
– Construction Review (PS4) documents submitted for Code Compliance Certificate application, Engineering
New Zealand, ACE New Zealand, and CEAS provide this advisory to clarify expectations and professional
standards.
CROSS Report
SESOC Sustainable Design Task Force Updates
Abstract
MBIE Updates
Building code and standards activity update
SESOC Emerging Structural Engineers (ESE) Groups
Abstract
News from the Regional Structural Groups
Abstract