- Vol. 31 (1)
- Vol. 31 (2)
- Vol. 32 (1)
- Vol. 32 (2)
- Vol. 33 (1)
- Vol. 33 (2)
- Vol. 34 (1)
- Vol. 34 (2)
- Vol. 35 (1)
- Vol. 35 (2)
President's Report
Abstract
4 President's Report SESOC Journal Vol31 No1 APR 2018 Pdf
Note from the editor
Abstract
5 Note From The Editor SESOC Journal Vol31 No1 APR 2018 Pdf
Letters to Editor
Abstract
7 Letters To Editor SESOC Journal Vol31 No1 APR 2018 Pdf
Simplified Capacity Design Procedure
Abstract
This paper proposes a “Simplified Capacity Design” procedure (SCD) that enables designers to utilise modern analysis and design software to perform capacity design and feedback (via the SESOC journal) would be appreciated.
8 Simplified Capacity Design Procedure SESOC Journal Vol31 No1 APR 2018 Pdf
Seismic Assessment and Strengthening of the Majestic Centre, Wellington
Abstract
The Majestic Centre is located in central Wellington, New Zealand. Constructed circa 1991, the building comprises a 25 storey tower above a five storey podium. The tower has a dual lateral load resisting system; a perimeter reinforced concrete moment frame and two central shear cores. Following the Canterbury Earthquakes, the building’s owner, Kiwi Property, commissioned seismic assessments of their property portfolio. An Initial Seismic Assessment (ISA) of the Majestic Centre was followed by Detailed Seismic Assessment (DSA, 2011) of the structure using both modal response spectrum (MRSA) and non-linear time-history (NLTHA) analysis methods. NLTHA and performance based assessment methodology concluded a seismic assessment rating in the range 35-45%NBS which, whilst above an Earthquake Prone threshold, identified a number of critical structural weaknesses (CSW’s). This was considered inconsistent with the building’s ‘Grade A’ office status and posed a risk to the building occupants and the surrounding Wellington CBD. CSW’s identified included; L5 transfer beams, shear core foundations, non-ductile shear core walls, tower diaphragms, precast cladding panel connections, podium roof load paths and seismic displacements and tower floor related issues associated with 1980s precast flooring detailing. These issues are covered in further detail as part of this paper.
Design and construction of strengthening works progressed in parallel from 2012 whilst maintaining a fully tenanted building. The project was completed in late 2016. This extremely ambitious and challenging project, undertaken by Kiwi Property and their consultant and contractor team has served to demonstrate that seismic strengthening of large commercial buildings ‘in- service’ is possible provided owners, designers, contractors, regulators, and tenants are willing to work together. This paper aims only to provide an overview of the assessment, analysis, design and construction processes from a Structural Engineering perspective.
9 Seismic Assessment And Strengening Of The Majestic Centre, Wellington SESOC Journal Vol31 No1 APR 2018 Pdf
Performance of Panel-to-Foundation Connections in low-rise precast concrete buildings
Abstract
Low-rise precast concrete wall buildings represent a significant portion of the New Zealand building stock, but there is limited evidence of the seismic performance of existing connections between panels and other structural elements. An experimental program investigating the seismic response of dowel type panel-to-foundation connections was undertaken. The testing program consisted of over thirty singly reinforced concrete panels incorporating both details currently used in practice as well as alternative connection details that have been proposed to improve connection robustness. Specimens were subjected to out-of-plane, in-plane, and bidirectional actions. It was found that in the out-of-plane direction, current connection details utilising shallow embedded threaded inserts resulted in brittle joint failure and as such do not meet performance criteria in NZS 3101:2006. Improved joint behaviour can be achieved either through adding additional reinforcement to the joint area to force damage to occur in the panel outside the joint region or by providing sufficiently deep embedment of the starter bars into the panel. It was also determined that the use of anchor pull out equations in NZS 3101:2006 are inappropriate for the design of threaded insert connections as the connection is not in direct tension but instead fails through the propagation of a flexural crack behind the insert. The performance of the panel was similar when subjected to either in-plane or bi-axial loading due to the flexible out-of-plane panel behaviour resulting from the single layer of reinforcement
10 Performance Of Panel To Foundation Connections SESOC Journal Vol31 No1 APR 2018 Pdf
Adopt a Ductility for Steel Portal Frame Structures
Abstract
Steel portal frames are a simple and commonly used structural form. It is also common to design portal frames to support heavy precast concrete cladding panels. This paper aims to outline the Steel Structures Standard NZS 3404 requirements for the seismic design of portal frames and show that the premise of ‘adopt a ductility’ can be irrelevant in highly seismic zones.
11 Adopt A Ductility For Steel Portal Frame Structure SESOC Journal Vol31 No1 APR 2018 Pdf
An Overview of the Use of Glass Fiber Reinforced Polymer Bars as Reinforcement in Concrete Structures
Abstract
This paper provides an overview of the use of glass fiber reinforced polymer bars as concrete reinforcement. Comparisons are made against steel reinforcement to highlight the key differences between the two materials, including differences in material composition, mechanical properties, behavior, design philosophies and applications. The results of tensile testing of GFRP bars at the University of Canterbury are also presented and discussed, which showed the typical linear behavior of the bars up to brittle failure.
12 An Overview Of The Use Of Glass Fibre Reforced Polmer Bars SESOC Journal Vol31 No1 APR 2018 Pdf
Improving City Resilience - The Role of Structural Engineering
Abstract
Concerns have been expressed at the scale of disruption, damage and demolition following the Canterbury earthquakes, particularly in the Christchurch CBD. More recently damage to Wellington buildings in the Kaikoura Earthquake, though at a much lesser scale, caused concern in terms of its impact on the city’s function and economy. With the increased emphasis on designing for resilience of cities it is timely to examine options available to structural designers and regulators to improve building resilience through changes in approach to structural
design and/or requirements for structural performance.
The paper examines three basic approaches: a) Retaining conventional design techniques but lifting the threshold of current regulatory requirements (for example requiring design to 2500-year shaking rather than to 500-year shaking); b) Adopting low-damage design techniques and c) incorporating seismic isolation. The effectiveness of each of these measures is discussed in terms of likely improvements in the Operational, Immediate Occupancy, Life Safety and Collapse Prevention states. Relative costs and benefits of each approach are indicated.
Indications are that seismic isolation holds the greatest promise in reducing both structural and non- structural damage – and thus reducing downtimes and cost. Low-damage design (of the structure) allows early reinstatement of the structure but non-structural damage remains potentially costly and disruptive. Lifting current regulatory thresholds reduces overall impact but does not remove the spectre of costly and time-consuming repairs, especially to the structure, or total replacement.
These broad comparisons highlight the need for a more comprehensive examination of the extent to which structural design approaches can improve the resilience of buildings and cities.
While the benefits of these approaches are clear in concept, achieving increased resilience in practice requires owners and their structural designers, to adopt them for the design of new buildings and the retrofit of existing buildings. This will require active promotion of the benefits of structural resilience amongst owners, tenants, users and the public. Development of awareness of the value of earthquake engineering in the property market is central to this and recent efforts in the US and New Zealand to establish earthquake rating schemes for buildings is encouraging in this regard. These should help develop and sustain this awareness with resulting improvement of building resilience over time. This will benefit owners, tenants, users and the community.
13 Improving City Resilience The Role Of Structure Engineering SESOC Journal Vol31 No1 APR 2018 Pdf
BRBF and CBF Gusset Plates: Out-of-Plane Stability Design using a implfied Notional Load Yield Line (NLYL) Method
Abstract
Gusset plates are a key component of braced frame systems, connecting the braces to the framing system. With traditional concentrically braced frames (CBFs), the braces are designed for controlled inelastic action, which involves brace buckling when the brace is in compression. Buckling restrained braces (BRBs) were developed in Japan in the late 1980s in order to avoid the undesirable effects of brace buckling. BRBs allow a brace to yield in compression without global buckling, thus making the brace of similar stiffness and strength when it is in tension and compression. Testing on individual braces has demonstrated that BRBs can perform very well, however such braces can also fail prematurely if their connections are not appropriately designed and buckle before the brace core yields in compression. Despite the importance of gusset plates, their behaviour has not been well researched, with engineers still using a design method originally proposed by Thornton (1984). This method uses a column analogy to describe plate behaviour and a number of recent studies have shown that while this method is too conservative in CBF connections, it could not be reliable in buckling restrained brace frame (BRBF) connections. This paper proposes a simplified notional load yield line (NLYL) model for both CBF and BRBF systems, which can adequately take into account the actual collapse mechanisms of brace-to-frame connections, ensuring gusset plate stability is maintained as required in each system. A comparison of existing experimental test results and those of the proposed method is made, which shows that the NLYL model is suitably conservative for application in both CBFs and BRBFs.
14 BRBF And CBF Gusset Plates Out Of Plane Stability Design SESOC Journal Vol31 No1 APR 2018 Pdf
Book Review - Tall Wood Buildings - Design, Construction and Performance by Michael Green, Jim Taggart
Abstract
15 BOOK REVIEW TALL WOOD BUILDINGS Design, Construction And Performance SESOC Journal Vol31 No1 APR 2018 Pdf
SCOSS Report
Abstract
16 SCOSS Report SESOC Journal Vol31 No1 APR 2018 Pdf
MBIE and Standards New Zealand Update
Abstract
17 MBIE And Standards New Zealand Update SESOC Journal Vol31 No1 APR 2018 Pdf
News from the Regional Structural Groups
Abstract
18 News From The Regional Structural Groups SESOC Journal Vol31 No1 APR 2018 Pdf
The Institute of Structural Engineers Report
Abstract
19 The Institute Of Structure Engineers Report SESOC Journal Vol31 No1 APR 2018 Pdf
SESOC President's Report
Abstract
4 SESOC President's Report SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Note from the Editor
Abstract
5 Note From The Editor SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Obituaries - Esli J Forrest
Abstract
6 Obituaries Esli J Forrest SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Obituaries - Carl Robert O'Grady
Abstract
7 Obituaries Carl Robert O'Grady SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Letters to the Editor
Abstract
8 Letters To The Editor SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Sourcing reliable large structure steel hollow sections
Abstract
9 Sourcing Reliable Large Structure Steel Hollow Sections SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SESOC Reflections - Barry Brown, lan Billings, Trevor Robertson
Abstract
To understand the catalyst for the formation of the New Zealand Structural Engineering Society, SESOC, it is useful to reflect on the professional, construction industry and regulatory environment in the first half of the 1980s decade. The years prior to SESOC’s launch in 1988 were a time of significant change. The building industry was in a state of flux. The financial crash of 1987 and the practices in the building industry stretched by the boom preceding this were fresh in everyone’s minds. Developers had become a market force, demanding lower fees and
shorter design and construction times. The government had sold the Ministry of Works, an historic setter of standards for engineering and construction in New Zealand. The government had ruled that scale fees were
not permitted. Local Authorities granted Building Permits, but had no empowerment to enforce construction standards, because there was in reality no recognised ‘completion certificate’.
10 SESOC Reflctions Barry Brown, Lan Billings, Trevor Robertson SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SESOC Reflections - Barry Davidson
Abstract
Today, Building Consents are being approved for designs that don’t comply with the Standards.Consequently, buildings are being constructed that are not fit for purpose.
11 SESOC Reflectinos Barry Davidson SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SESOC Reflections - Ashley Smith
Abstract
To give some background to my involvement as SESOC president, I was first co-opted onto the management committee for a period in the early 90’s, and so got a glimpse of the activities of the society in its early years, around the time the Building Act 1992 was introduced.
12 SESOC Reflections Ashley Smith SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SESOC Reflections - Mark Batchelar
Abstract
It has been my privilege to be involved in SESOC management and to serve as President for a term. Since its establishment SESOC has focused on assisting to maintain the quality and standing of the profession of structural engineering. The increasing membership of the society bears testimony to the value and the support it provides to the profession. The members who I served with on the SESOC management committee were without exception all people of integrity with a strong sense of responsibility.
SESOC Reflections - John Hare and Paul Campbell
Abstract
John Hare and Paul Campbell were both heavily engaged with the Christchurch earthquake recovery, through involvement with CERA. Both spent time assisting and appearing before the Canterbury Earthquakes Royal Commission. John Hare was President of SESOC from
November 2011 to February 2014, Paul Campbell from February 2014 to February 2017.
14 SESOC Reflections John Hare And Paul Campbell SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SESOC Reflections - Jason Ingham
Abstract
As my term as SESOC president draws towards an end, I have found myself reflecting on the past, the present, and the future of the structural engineering profession in New Zealand. Gazing into the past is clearly the easiest of these activities. For me this reflection primarily occurred in conjunction with the 2017 SESOC conference in Wellington, where as part of my SESOC President’s Address I wished to discuss the first 30 years of SESOC’s history, and what has been achieved since the original conception of SESOC.
15 SESOC Reflections Jason Ingham SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SESOC - A visual history
Abstract
The first SESOC journal was produced in 1988 and edited by Charles Clifton. Since small beginnings we moved to 2 –colour covers and then full colour covers with black and white text/pictures in 2010. Since April 2013 the journal has been produced in full colour. The SESOC logo has experienced several changes and the latest logo has come about in this September 2018 issue of the journal. The adaptation to a new logo was brought about by its presence for the web and our new website came into being this year.
16 SESOC A Visual History SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Fresh concrete performance guideline in New Zealand
Abstract
Fresh concrete properties are often poorly defined in construction projects and this can be problematic when these specification requirements affect productivity and hardened properties of concrete. This paper discusses four fresh concrete properties that have a strong influence on the workability and hardened concrete performance; slump, air content, bleeding, and setting time. Each property is discussed in terms of its overall role in influencing fresh concrete properties, and also how these affect hardened properties such as strength, dimensional stability and durability. Examples from case studies are also used to illustrate the role these fresh properties have on the performance of concrete supplied to projects around New Zealand. Slump and air content are thought to be well understood but are sometimes specified in an impractical manner both in terms of limits and tolerances. Bleed rate, segregation and setting of concrete are generally assumed to be normal until there is an issue on site and resolution then becomes difficult without clear methods and benchmarks to assess these properties. The issue is further complicated by adopting performance limits from other countries without any acknowledgement that local materials might differ significantly, which affects the perceived in situ performance. Outcomes from this paper are presented graphically to illustrate that these fresh properties are strongly linked and cannot be viewed or specified in isolation. Recommendations are made that will allow a better framework to be developed by concrete suppliers in order that fresh properties may be more accurately predicted and measured.
17 Fresh Concrete Performance Guideline In New Zealand SESs Pdf
An Example procedure for preliminary sizing of Resilient Slip Friction Joints (RSFJs) in seismic resistant structures
Abstract
The innovative Resilient Slip Friction Joint (RSFJ) technology has recently been developed and introduced to the New Zealand construction industry. This self-czentring low damage avoidance technology not only aims to provide life safety, but also to minimise the earthquake-induced damage so that the building can be reoccupied quickly with minimal business disruption. The RSFJ technology provides the required seismic performance regardless of the material used for the main structural components, and can be used in various arrangements and applications to provide self-centring damage avoidance lateral load resisting systems. These applications include (but are not limited to) shear walls, tension-compression braces, tension-only braces and moment resisting frames. The performance of the RSFJ technology has previously been verified by joint component testing and full-scale experimental tests.
This paper aims to provide a simple analysis and design procedure for use by structural engineers when using RSFJs in a structure. A step-by-step forced-based design procedure is provided which generally requires the use of the Equivalent Static Method (ESM) based on the New Zealand standard for structural design actions together with nonlinear static push-over and non-linear dynamic time-history simulations. A case-study prototype structure that uses RSFJ braces as the lateral load resisting members is considered to demonstrate the proposed design procedure. Furthermore, the seismic forces for the same structure are calculated using the Displacement Based Design (DBD) approach and the results are compared with those from the Forced-Based Design (FBD) approach. Overall, the findings of this paper confirms that the proposed approaches can be efficiently used when a seismic resilient design with the RSFJ technology is targeted.
18 An Example Procedure For Preliminary Sizing Of Resilient Slip Friction Joints(RSFJs) SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Steel Compliance
Abstract
Much has been written in recent times about imported steel used in construction and the problems of ensuring conformance of the steel. Obviously there have been serious issues with pile sections and reinforcing mesh, and questions remain about other imported steel, both fabricated and as raw materials used by local fabricators.
The current situation is that materials used in NZ are generally AS/NZS standard certified. In order for the product to be certified steel mills must meet the requirements of the standard for quality management and factory production controls, type testing and production testing, and have an accredited laboratory producing ILAC endorsed material certificates. Third party certification (eg by ACRS, BSI or another similar body) can be a useful method employed by mills to demonstrate conformance. Some overseas mills are now certified to produce AS/NZS plate, sheet/coil, reinforcing bar or mesh, and rolled or hollow sections.
Whether sourcing from overseas or from Australasian steel mills there are some questions that need to be asked that were not previously required:
1. Does the mill have third party certification specifically for the AS/NZS product being supplied?
2. Does the mill have recent history of producing conforming product? If not then initial type testing is a requirement.
3. Does the laboratory have ILAC accreditation to perform the mechanical and chemical tests to the relevant Australian standards, and will the certificates be ILAC endorsed?
19 Steel Compliance Rob Penny SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Structure Engineering CPEng Level Body of knowledge and skills (BOKs)
Abstract
The following is a reprint of the BOKs as approved by SESOC management committee and is available on the website. It is important to be aware that this is a “live” document and may be subject to change from time to time. The BOKs will likely be used as a basis for CPEng assessment or registration when it comes in – Editor
20 Structure Engineering CPEng Level Body Of Knowledge And Skills (BOKs) Editor SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SCOSS ALERT July 2018 Building a Safer Future - Independent Review of Building Regulations and Fire Safety: Final Report
Abstract
This Alert is a summary of selected parts of the Independent Review of Building Regulations and Fire
Safety: Final Report that is relevant to structural and civil engineers. The final report should be read in full to appreciate all of the facts and the implications, and to absorb the wealth of information and the
recommendations made by Dame Judith Hackitt. The report proposes a fundamental shift in the approach
to regulation, that being one from prescription (and rote compliance) to one of the professions looking at
buildings as a whole and demonstrating them to be safe. Although there has been much public focus on the
Grenfell Tower fire and the role of cladding in that incident, the Hackitt report takes a much broader view tackling the basic challenge of making HRRBs safe overall. The government will have to enact legislation, but there is no doubt that, if adopted, the Hackitt recommendations will have wide ranging implications for the construction industry. Significant effort will be required by government and industry to assess and comment on the many implications.
21 SCOSS ALERT July 2018 Building A Safer Future SESOC Journal Vol 31 No 2 Sep 2018 Pdf
MBlE and Standards New Zealand Update
Abstract
22 MBlE And Standards New Zealand Update SESOC Journal Vol 31 No 2 Sep 2018 Pdf
Seismic Designs for Suspended Ceilings
Abstract
Suspended ceilings fared poorly in recent earthquakes. In response, the relevant standard was revised, and there are stringent design and installation requirements to prevent collapse in a 1-in-500-year event.
23 Seismic Designs For Suspended Ceilings By Hedda Maria Oosterhoff SESOC Journal Vol 31 No 2 Sep 2018 Pdf
News from the Regional Structural Groups
Abstract
SESOC Membership Report
Abstract
25 SESOC Membership Report SESOC Journal Vol 31 No 2 Sep 2018 Pdf
SESOC Treasurer's Report
SESOC President's Report
Abstract
4. SESOC President's Report - SESOC Journal Vol 32 No 1 April 2019.pdf
Notes from the Editor
Abstract
5. Note from the Editor - SESOC Journal Vol 32 No 1 April 2019.pdf
Learning from Complaints
Abstract
6. Learning from Complaints-Helen Davidson - SESOC Journal Vol 32 No 1 April 2019.pdf
Letters to the Editor
Abstract
7. Letters to the Editor - SESOC Journal Vol 32 No 1 April 2019.pdf
Design and Remediation of Low-rise Industrial/Commercial Buildings
Abstract
The following information has been provided by a SESOC/MBIE joint working group for practicing engineers and highlights critical weaknesses in design of industrial.commerical buildings.
8. Design and Remediation of Low-Rise Industrial&Commercial Buildings - SESOC Journal Vol 32 No 1 April 2019.pdf
Restoration of Port Craig Viaducts-Heritage in Southland's Wild West
Abstract
Port Craig, in Western Southland, is New Zealand’s most complete historic sawmilling site. It includes an old schoolhouse, a bush tramway and four impressive wooden viaducts. The viaducts are more than 90 years old, and late last year the largest of the four, the Percy Burn, was reopened after restoration work. The viaducts are a special feature of the Hump Ridge and South Coast tracks and are visited by approximately 4,000 people each year.
This article celebrates both the original technical skill, the expertise employed in the restoration work and the story of Port Craig itself: a unique place with a special heritage.
I spoke with Stephen Canny, General Manager Business and Strategic Projects, Venture Southland and founding Trustee of Southland’s Port Craig Viaducts Charitable Trust; Derek Chinn, Senior Structural Engineer, Stantec; and Phil Fahey, Project Manager for the Percy Burn restoration, Fulton Hogan, who shared their experiences working on the restoration project.
9. Restoration of Port Craig Viaducts... - SESOC Journal Vol 32 No 1 April 2019.pdf
Estimation of the static vertical subgrade reaction modulus ks from CPT
Abstract
A methodology for the estimation of the static vertical subgrade reaction modulus (ks) for cohesionless soils from the Cone Penetration Test (CPT) has been introduced in 2013 (Barounis et al). And 2015 (Barounis and McMahon and has recently been integrated (Barounis and Philpot, 2017). In this paper, the conclusion from the early two papers are utilized for developing an integrated methodology based on the correlation between qc and N (Robertson, 2012). The fundamental concepts and the theory of the proposed methodology are presented with a step-by-step procedure in this paper. The methodology returns one value termed KF, which is the equivalent spring stiffness for any foundation depth and shape under consideration. The methodology produces values that are as conservative as the traditional SPT approach proposed by Scott (Scott, 1981). The methodology is applied on numerous sandy sites in New Zealand for different foundation typologies.
10. Estimation of the Static Vertical Subgrade Reaction Modulus... - SESOC Journal Vol 32 No 1 April 2019.pdf
Precast Double Tee Support Systems - 10 Years on
Abstract
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 engineers not utilise the detail. Recently, consequential to the failure of double tee units during the Kaikoura earthquake (MBIE 2017, 2018a), MBIE issued a formal warning confirming that the pigtail detail is unlikely to comply with the Building Code (MBIE 2018b). This paper revisits the findings of the SESOC working group in light of developments in the intervening period and reiterates why the pigtail detail is not compliant with the Building Code. Significant issues that have arisen since the original publication that are addressed include: 1. Revelation of a new failure mechanism for flange hung double tees related to support rotation that was identified during post-earthquake evaluations, primarily on Statistics House.
2. Consideration of tolerances, noting that there are three major factors, and that the timing of these manifesting is not necessarily favourable:
a. The distance between the supports
b. The length of the precast unit, itself bifurcated between the length of the ribs and the outstand of the nibs c. The location of the loop bars within the tee.
3. Safety in design – noting that there is a requirement to consider this all the way through to safe demolition and that there have been several premature failures which are arguably either due to inappropriate (but ‘industry standard’) demolition techniques (nibbling onto the floor below before sweeping off) or a failure of the floor/tees to consistently provide support.
4. Whether it is appropriate to use double tees on steel composite beams, and what form of support is required during construction and in service.
11. Precast Double Tee Support Systems-10 Years On - SESOC Journal Vol 32 No 1 April 2019.pdf
The University of Auckland clock tower east wing: A new lease of life
Abstract
The Clock Tower is arguably the most iconic building at the University of Auckland. It was originally constructed in 1923-1926 and is listed by Heritage New Zealand as a Historic Place Category 1. A seismic upgrade project was undertaken in 2015-2018 which focused on the East Wing building that is adjacent to the tower.
The design and construction processes employed were developed through close collaboration between the project and heritage architects, structural engineer and contractors. A key driver for the project was to ensure that the heritage character of the building was not adversely affected by the seismic upgrade works.
12. The University of Auckland Clock Tower East Wing - SESOC Journal Vol 32 No 1 2019.pdf
ReCast Floors - Seismic Assessment and improvement of existing precast concrete floors
Abstract
13. Recast Floors-Seismic Assessment and Improvement... - SESOC Journal Vol 32 No 1 April 2019.pdf
Earthquake performance of shopfront canopies connected to URM buildings
Abstract
14. Earthquake Performance of Shopfront Canopies Connected to URM Buildings - SESOC Journal Vol 32 No 1 April 2019.pdf
Damage assessment and remedial strengthening of the Thorndon Hotel following the Kaikoura earthquake
Abstract
During the Kaikoura earthquake many multi-storey ductile frame buildings in the Wellington CBD, experienced significant damage to their structural frames and precast floor systems. The Thorndon Hotel was an example of this. Yielding in the building’s beam hinges concetrated in a single crack and resulted in significant resideual elongation at the corner columns. This case study describes the assessment of observed damage and remedial strengthening implemented to achieve a seismic rating to 80%NBS for the building. Full scale testing of a specimen beam was carried out to investigate the residual capacity of the yielded beam hinges and also their low cycle fatigue resilience.
15. Damage Assessment and Remedial Strengthening of Thorndon Hotel…Kaikoura Earthquake - SESOC Journal Vol 32 No 1 April 2019.pdf
SCOSS Report
Abstract
16. SCOSS Fabrication different from design drawings (2015) - SESOC Journal Vol 32 No 1 April 2019.pdf
MBIE and Standards New Zealand Update
Abstract
17. MBIE and Standards NZ Update - SESOC Journal Vol 32 No 1 April 2019.pdf
News from the Regional Structures Groups
Abstract
18. News from the Regional Structural Groups - SESOC Journal Vol 32 No 1 April 2019.pdf
SESOC Membership Report
Abstract
19. SESOC Membership Report - SESOC Journal Vol 32 No 1 April 2019.pdf
SESOC Treasurer's Report
Abstract
20. Treasurer's Report - SESOC Journal Vol 32 No 1 April 2019.pdf
SESOC President's Report
Abstract
Notes from the Editor
Abstract
5. Note from the Editor - SESOC Journal Vol 32 No 2 September 2019.pdf
Letters to the Editor
Abstract
6. Letters to the Editor - SESOC Journal Vol 32 No 2 September 2019.pdf
Submission to Ministry of Business, Innovation and Employment
Abstract
SESOC is generally supportive of the MBIE consultation document and endorse the broad objective to improve quality outcomes in the Building Sector. SESOC believes that improved quality standards will only be achieved by having a regulatory framework that supports a holistic view of quality – supported by evidence-based data.
With reference to the specifics of our proposal;
• SESOC supports the regulation of Structural Engineers through licensing. SESOC has put forward a proposal of how we think Licencing could work and is keen to work collaboratively with MBIE, Engineering New Zealand and other Technical Societies to further develop the detail of such a licensing system.
• SESOC does not support Government regulation of general competence through a voluntary certification scheme.
• SESOC does not support using factors such as building size, building use and ground conditions as outlined in section 3.2 figure 1 of the discussion paper, for defining a threshold for Restricted Engineering Design Work for Structural Engineering. SESOC has proposed an alternate threshold that is consistent with current industry (unregulated) practice.
• SESOC does not support lowering of the Building Levy. SESOC would like to be actively involved in helping MBIE shape the detail of the proposals and believe we have an important role to play in any subsequent implementation phases.
8. Submission to Ministry of Business, Innovation and Employment - SESOC Journal Vol 32 No 2 September 2019.pdf
EG Best Practice - B2 Durability
Abstract
Engineering New Zealand has been hearing from engineers and councils that demonstrating durability under B2 remains a problem, so we’ve been looking for solutions.
9. FG Best Practice - B2 Durability - SESOC Journal Vol 32 No 2 September 2019.pdf
Two Inspiring Deans
Abstract
Extract from Two Inspiring Deans with kind permission of the authors. Please note that this extract commences from Part 2. Part 1 is a history of the careers of the two deans TDJ Leech and GCJ Dalton and the actions they took to transform the engineering school. Parts 2.5 et seq (not included) cover the biographies of many of the successful students and staff who attended engineering school. This book is an interesting read and was first published in March 2019 (Opuzen Press). It is available from Wheelers Books online.
10. Two Inspiring Deans - SESOC Journal Vol 32 No 2 September 2019.pdf
Improvements to the New Zealand component of the Wind loading Standard AS/NZS 1170.2
Abstract
A broad range of research in a programme undertaken over the past 4 years, and in earlier closely related research programmes, has led to the development of recommendations for the New Zealand component of the joint Australia/ New Zealand Wind Loadings Standard AS/NZS 1170.2. These recommendations mainly concern the analysis of the design wind speeds used for structural design in New Zealand. The proposed changes to the standard represent an evolution of the knowledge on which the standard is based, and the methodology used in the standard, to achieve more accurate and more reliable design of buildings and structures.
The research has included: reanalysis of historical wind speed data; analysis of recent weather data; analysis of the influence of various different types of weather monitoring instruments, and their monitoring locations; interpretation of damage from wind storm events; comparisons between on-site measurements, wind tunnel simulations, computer modelling, and wind speeds currently calculated using AS/NZS 1170.2; sophisticated numerical weather prediction models; and the expected effects of climate change.
11. Improvements to the New Zealand component of the wind loadings Standard AS,NZS 1170.2 - SESOC Journal Vol 32 No 2 September 2019.pdf
Epoxy Resin Injection as a repair strategy for concrete
Abstract
In the wake of the Canterbury Earthquake Sequence, BMC has been engaged in the assessment of damaged structures and determining strategies to effectively repair damaged concrete structural elements, as have many of our contemporaries. To that end we considered if and when epoxy resin could be used as part of a remedial strategy and we wanted to be sure we had made informed decisions to provide appropriate advice to our clients.
This literature review was commissioned and funded entirely by BMC as an internal project to gain the best understanding we could regarding the efficacy of epoxy resin as a repair technique for damaged concrete elements.
The conclusions from this literature review are our summary of the outcomes of the latest research we could find on the topic. We encourage the reader to consider the continually developing advances in epoxy technology with a view to providing background relevant information to help make informed decisions when prescribing appropriate remedial strategies for damaged concrete elements. We intentionally make no assertions or comment on earlier guidance on the efficacy of epoxy as a remedial strategy and merely present our summary of the latest research current at the time of our review.
12. Epoxy Resin Injection as a repair strategy for concrete - SESOC Journal Vol 32 No 2 September 2019.pdf
Evolution of tubular structures for tall buildings
Abstract
Some examples of tubular structures are reviewed where the structural system predominantly determined the form of the tall building. Instances of such buildings exist from the evolution of tall buildings in the urban environments, but the custom flourished during the 1960s and the 1970s. The rich tradition of this practice is illustrated, leading up to a view towards the future. Some building forms planned for the future promise to continue the trend.
13. Evolution of tubular strcture for tall buildings - SESOC Journal Vol 32 No 2 September 2019.pdf
Structural Design – Challenges, obligations and responsibilities
Abstract
The structural engineering profession is under some pressure. The performance of some modern buildings in recent earthquakes has been widely observed and questioned across the community. Various newspapers have in recent times, published articles expressing concern about the structural integrity of various modern buildings. These comments naturally attract the attention of the public who wonder what is going on.
This paper explores the possible issues and challenges. It presents the perspective of the authors as to what are our obligations and responsibilities as structural engineers. It then concludes with some suggestions as to possible ways we, as a profession, can address the expressed concerns and improve the public’s confidence in structural engineering in New Zealand.
14. Structural Design - Challenges, obligations and responsibilities - SESOC Journal Vol 32 No 2 September 2019.pdf
Design and construction of the Wellington Airport Hotel Building
Abstract
This paper covers the design and construction of the new Rydges Wellington Airport hotel. This six storey, 24 metre tall building has a combination of steel moment-resisting frames and eccentrically braced frames, with ComFlor composite floor slabs. The building is supported entirely on steel screw piles, which is considered a first for a building of this size in Wellington. In this paper we cover lessons learnt during the project, both what worked well and what could have been done differently, in the hope that these will inform future building designs in New Zealand.
15. Design and constrction of the Wellington Airport Hotel Building - SESOC Journal Vol 32 No 2 September 2019.pdf
SESOC software overview
Abstract
SESOC has, over a period of time, developed and acquired a number of Structural Software Design Programs.
This paper will overview the SESOC software, covering the broad capabilities and uses of the various programs, including the recently launched MemDes+ software.
It will preview two new developments, namely (i) “GenWall”, and (ii) the SESOC Simplified Structural Design Guide for Cantilever Timber Pole Retaining Walls.
“BridgeBeam”, a sectional composite bridge beam program will also be presented, seeking feedback regarding whether there is sufficient support for upgrading this program for wider deployment.
16. SESCO software overview - SESOC Journal Vol 32 No 2 September 2019.pdf
SCOSS Report
Abstract
17. SESCO Report - SESOC Journal Vol 32 No 2 September 2019.pdf
MBIE and Standards New Zealand Update
Abstract
18. MBIE and Standard - SESOC Journal Vol 32 No 2 September 2019.pdf
News from the Regional Structures Groups
Abstract
19. News from the Regional Structural Groups - SESOC Journal Vol 32 No 2 September 2019.pdf
IStructE & Bridge Report
Abstract
20. IStructE and Bridge Report - SESOC Journal Vol 32 No 2 September 2019.pdf
SESOC Membership Report
Abstract
21. SESCO Membership Report - SESOC Journal Vol 32 No 2 September 2019.pdf
SESOC Treasurer's Report
Abstract
22. SESCO Treasurer's Report - SESOC Journal Vol 32 No 2 September 2019.pdf
SESOC President's Report
Abstract
4. SESOC President's report - SESOC Journal Vol 33 No.1 April 2020.pdf
Notes from the Editor
Abstract
6. Note from the Editor - SESOC Journal Vol 33 No.1 April 2020.pdf
Errata
Abstract
7. Errata - SESOC Journal Vol 33 No.1 April 2020.pdf
Letter to Editor - Nearly two decades wasted so far
Abstract
An opinion piece by John Scarry
8. Letters to the Editor - SESOC Journal Vol 33 No.1 April 2020.pdf
Book Review - Rottenomics - The story of NZ's Leaky building disaster
Abstract
9. Book Review ROTTENOMICS The Story of New Zealand’s Leaky Building Disaster - SESOC Journal Vol 33 No.1 April 2020.pdf
What structural engineers should know about glass
Abstract
The glass used in many structural applications in buildings has become more familiar with its unique mechanical, optical and aesthetic properties. Currently, there is a lack of design aids and comprehensive standards to guide designers and engineers towards appropriate structural design for glass and glazing. There have been many cases of structural glass failure due to poor design or construction that could be avoided with some basic glass design knowledge.
10. What structural engineers should know about glass - SESOC Journal Vol 33 No.1 April 2020.pdf
Vibration performance of timber-concrete composite floors: A case study
Abstract
Modern architectural design has shifted towards buildings with large open areas, which require floors to span longer distances. This shift has had a negative impact on the vibration performance of floors, particularly when caused by human actions such as walking. Modern Timber Concrete Composite (TCC) floors have been developed as a design
solution for spanning long distances, whilst still maintaining a low self-weight due to efficient use of materials. Despite success commercially, there is limited research on TCC floors in-situ vibration performance. This paper presents a case study on an in-situ modern TCC floor and by the means of heel drops and walking tests. Results show that, although the floor might be considered sensitive to footfall vibration due to its fundamental frequency, it performs reasonably well with respect to human annoyance.
11. Vibration performance of timber-concrete composite floors_A case study - SESOC Journal Vol 33 No.1 April 2020.pdf
Numerical and wind-tunnel investigation of wind flow over urban areas
Abstract
The study investigates one of the major causes of damage in severe wind events in urban areas: windborne debris, using a case study of a location in the Auckland city centre, New Zealand. The probability and risk of paving stone ballast becoming windborne from the podium of a tall building was evaluated through wind-tunnel experiments and
numerical simulations. These results were used to determine: the local wind speeds at the location of the stones; overall wind behaviour in the urban area; the threshold wind speed at which the stones start rolling or becoming windborne debris. These results were combined with long-term Auckland Meteorological data to predict the expected
probability of the “rolling” and “take-off” wind speeds being exceeded in the vicinity of the case study building. It was found that there was a very low risk of stone ballast being blown off the podium.
12. Numerical and wind-tunnel investigation of wind flow over urban areas - SESOC Journal Vol 33 No.1 April 2020.pdf
Braced frame system for tall timber building
Abstract
Options for a tall building with timber structural systems are investigated as part of a desktop exercise. The proposed commercial building has a concrete podium at ground level. There is a central core and structure along the perimeter providing for a column-free internal space. The structural system includes a concrete-timber hybrid core in combination with braced frames. The building is located in a region of high seismic risk and considerable wind load. The results confirm the feasibility of the structural system in tall buildings. The design is governed by drift under wind or seismic load. Code requirements can be met with the appropriate combinations of structural systems and materials.
13. Braced frame system for tall timber building - SESOC Journal Vol 33 No.1 April 2020.pdf
Seismic strengthening of Wellington East Girls' college main block - Cat1 heritage building
Abstract
This project is a major redevelopment of a multi-storey Category 1 Heritage URM building in the heart of one of Wellington’s largest schools with a very constrained site with the requirement for the College to continue school activities during all construction phases made this a particularly complex project. The Client brief was to provide a safe, high quality, modern learning environment that brings the school’s usable area up to the Ministries acceptable standard and respects the heritage of the Main Block while ensuring the overall solution delivers a building that is designed for >100%NBS of IL3.
Key design features for the superstructure are:
• Robust, safe structure that can support the important heritage features,
• Large spans and open spaces, to provide a flexible modern learning environment.
• Efficient and sustainable construction.
• Minimise structural weight.
The Ministry of Education Structural and Geotechnical Guidelines V 2.0 (SGG) require a significant level of resilience above the New Zealand Building Code and require the building to have repairable damage at greater than a moderate earthquake in this case the 1/250 year event. The result is that the building has needed to be designed for an additional SLS2 Serviceability Limit State requirement of 1/250years (equating to repairable damage at 85% of current code at IL2) and is approximately 3.5 times the
normal SLS1 requirement. The building also had to be designed for an Ultimate Limit State requirement of 100% of IL3 (1/1000 year return period).
Significant temporary work to protect the Heritage façade and vestibule as well as foundation underpinning was required to protect areas of most significant heritage value while the rear of the building was removed to allow for the increased footprint and upgraded structure. The result has been an efficient structural solution that is still sympathetic to the original building envelope, crucial for a heritage listed structure. This paper discusses the technical design process and project challenges in strengthening a significant Category 1 Heritage building.
14. Seismic strengthening of Wellington East Girls’ College main block - SESOC Journal Vol 33 No.1 April 2020.pdf
The low-damage design of hybrid concrete rocking walls for Turanga library, Christchurch, NZ
Abstract
In the aftermath of the Canterbury (New Zealand) Earthquake Sequence in 2010-2011, the mismatch between societal expectations and the reality of seismic performance of modern buildings was dramatically highlighted. The increased awareness of the various stakeholders of the severe socio-economic impacts of strong earthquakes in
terms of damage/dollars/downtime, stimulated the wider acceptance of cost-efficient damage-control technologies. This paper presents and describes the analysis, design and actual implementation of a low-damage 5-storey building system for the New Central Library – Tūranga for the Christchurch City Council in New Zealand. Following a Design-
Build competition, Lewis Bradford Consulting Engineers carried out the structural engineering design of Tūranga as part of the winning team led by Southbase Construction. Prof. Stefano Pampanin was the specialist peer reviewer for the seismic design of the low-damage hybrid (rocking-dissipative) unbonded post-tensioned concrete walls.
Tūranga was designed and constructed to very stringent performance criteria, targeting a damage-control limit state for a large intensity earthquake (1/1000 years return period), to sustain repairable structural damage during a rare event. Low-damage technology, consisting of integrated self-centering & dissipative mechanisms, that allows the building to sway and then return to its original position, was thus implemented.
Part of the innovative system is the displacement-based design and implementation of a primary lateral resisting system consisting of a series of large scale precast concrete core walls, with pivot columns in the edges/corners to decouple the bi-directional response and to activate U-shape Flexural Plates (UFP) devices during the relative rocking motions. The walls are designed to open a gap at the base (e.g. rock, instead of forming a typical plastic hinge) and displace to a targeted interstorey drift level, while shifting the fundamental period of the building (through an internal isolation mechanism) in order to protect the building from the peak earthquake spectral accelerations during a significant seismic event. A second layer of seismic resistance and redundancy is provided by perimeter steel moment resisting frames with dog-bone flanges in the beams and rocking connections at the base. The unbonded post-tensioned rocking & dissipative walls are arranged into three main cores.
15. The low-damage design of hybrid concrete rocking walls for Turanga Library, Christchurch, NZ - SESOC Journal Vol 33 No.1 April 2020.pdf
SCOSS Alert
Abstract
16. SCOSS alert - SESOC Journal Vol 33 No.1 April 2020.pdf
MBIE and Standards New Zealand update
Abstract
17. MBIE and Standards - SESOC Journal Vol 33 No.1 April 2020.pdf
SESOC Emerging Structural Engineers update
Abstract
18. SESOC Emerging Structural Engineers - SESOC Journal Vol 33 No.1 April 2020.pdf
News from the Regional Structures Groups
Abstract
19. News from the Regional Structural Groups - SESOC Journal Vol 33 No.1 April 2020.pdf
SESOC Membership Report
Abstract
20. SESOC Membership Report - SESOC Journal Vol 33 No.1 April 2020.pdf
SESOC Treasurer's Report
Abstract
21. SESOC Treasurer's Report - SESOC Journal Vol 33 No.1 April 2020.pdf
SESOC President's Report
Abstract
4. SESOC President's Report - SESOC Journal Vol 33 No 2 September 2020.pdf
Notes from the Editor
Abstract
6. Note from the Editor - SESOC Journal Vol 33 No 2 September 2020.pdf
Letters to the Editor - Response to letter John Scarry Vol. 33 No1. April 2020
Abstract
8. Letters to the Editor - SESOC Journal Vol 33 No 2 September 2020.pdf
The SESOC Awards for Structural Engineering Excellence - 2019
Abstract
9. The SESOC Awards for Structural Engineering Excellence 2019 - SESOC Journal Vol 33 No 2 September 2020.pdf
To the rescue of the Category 1 Heritage Ashleigh Court building
Abstract
The iconic Ashleigh Court is a 1907 three-storey unreinforced clay-brick masonry Category 1 Heritage building located in Wellington. The distinctive neoclassical style and triangular shape make it the most recognisable building in Newtown, with popular shops and cafes and beautiful apartments. Due to the high cost of early estimates for structural strengthening the building was at risk of demolition.
Past building refurbishments included localised seismic retrofit in 1997. Following the Kaikōura earthquakes, the seismic risk was exacerbated, particularly with parapets and facades on a busy thoroughfares 300 m away from the hospital, presenting significant risks to life-safety. With a very tight budget for the seismic securing and structural strengthening of the Ashleigh Courts building, and limited timeframe due to government pressure for action, our team embarked on a major challenge to devise costeffective and heritage friendly solutions engaging state-of-the-art masonry modelling and retrofit design as well as using innovative retrofit techniques. Our work included extensive on-site investigation and material characterisation to best assess the as-built state, and tailor the retrofit intervention. The building earthquake response was investigated using a Finite-Element-Model and subjected to non-linear-static analysis (pushover) and non-linear-dynamic analysis (time-history). The in-plane response was assessed using force- and displacement-based approaches, while the out-of-plane was evaluated using the inelastic displacement-based approach.
The retrofit implementation is being completed in two stages: (1) address the immediate government requirements to secure parapets and façades, (2) retrofit the building to achieve 67% NBS. The cost of upgrading the building was $1.5 million less than previously estimated, thanks to smart use of existing building-fabric, application of ‘simple’ proof-tested engineering solutions, and close consultation with heritage experts and contractors from the early stages of the project.
10. To the Rescue of the Cat 1 Heritage Ashleigh Court Building - SESOC Journal Vol 33 No 2 September 2020.pdf
Retrofitted URM cavity walls experimentally validated and a simplified out-of-plane assessment
Abstract
How should the post-retrofit capacity of URM cavity walls be assessed? An extensive testing programme was executed to determine the out-of-plane capacity of cavity walls when retrofitted with shear-transferring cavity ties. Walls were tested under semi-cyclic and dynamic shake-table loading. A tie pattern was devised that enabled a cavity wall response corresponding to the model for solid wall behaviour as contained in Part C8 of the MBIE/NZSEE Guidelines. Two different cavity wall typologies were tested (1) two single clay brick leaves separated by an air cavity and (2) two-leaf solid clay brick walls with an external single leaf brick layer separated by an air cavity. Retrofitted walls were able to sustain large mid-height displacements when subjected to out-of-plane loading and had a substantial increase in load-carrying capacity when compared to the walls without shear-transferring ties. Experimentally attained results showed good agreement with theoretical displacement and load-carrying predictions. It was concluded that for practical seismic out-of-plane assessment purposes, walls tied using shear-transferring cavity ties at sufficiently close spacing can be assessed as solid walls of the same gross thickness.
11. Retrofitted URM Cavity Walls Experimentally Validated - SESOC Journal Vol 33 No 2 September 2020.pdf
Assessment of existing precast concrete floors: Hollow-core assessment worked example
Abstract
The ‘yellow’ version of section C5 of the Engineering Assessment Guidelines that was released in November 2018 introduced expanded and simplified procedures for assessing precast concrete floors. Shortly after publication of this technical proposal, seminars explaining and demonstrating the new provisions were organised by Concrete New Zealand Learned Society. Part of these seminars focussed on an assessment example for a typical hollowcore floor unit that was developed by Chris Poland of Clendon Burns & Park.
Further use of the new guidance led to the conclusion that expansion of the hollowcore assessment example would be of benefit to structural engineers, and, by extension, society.
12. Assessment Existing Precast Concrete Flloors_Hollowcore Assess Worked Example - SESOC Journal Vol 33 No 2 September 2020.pdf
Commercial Bay Tower wind loading assessment: an integrated approach to design
Abstract
The Commercial Bay tower in Auckland is currently the tallest office building in New Zealand. This article presents the methodology followed by the structural designer to assess the wind loads. It summarises the key wind principles and the wind tunnel tests methodology used in the assessment. It is shown that the methodology of the New Zealand Standard for Wind Loading was successful in predicting the wind loads and the dynamic response of the building, highlighting early in the design process potential risks of excessive accelerations, although the method of the National Building Code of Canada was needed to complement the assessment. In comparison with its European counterpart, the New Zealand Standard methodology provides the structural designer with efficient tools such as the direct estimation of the floor-by-floor wind loads, cross-wind accelerations and reference to suitable occupant comfort criteria. The article highlights how the structural designer made use of different methods available at different stages of the project and the importance of integrating the wind loading assessment in the design process.
13. Commercial Bay Tower Wind Loading Assessment_an Integrated Approach to Design - SESOC Journal Vol 33 No 2 September 2020.pdf
Case study numerical and wind-tunnel investigation of pedestrian level wind flow in urban areas
Abstract
The study investigates effects of urban areas and structures on pedestrian level wind (PLW) speeds, which is one of the major causes of damage and discomfort in severe wind events in urban areas. The study uses a case study of a location in the Wellington city centre, Te Aro, New Zealand. The flow behaviour, mean and gust wind speedups, and the probability of exceedance of high wind speeds at locations around the target building were evaluated through wind-tunnel experiments, numerical simulations and analysis of long-term Wellington Meteorological wind records. For the wind-tunnel experiments, the erosion technique and Irwin probes were employed to visualise and measure the flow pattern and wind speed, respectively. The numerical simulation was conducted using the steady Reynolds-Averaged Navier–Stokes (RANS) method and the Shear Stress Transport (SST) turbulence model. The study also investigates the feasibility of the use of a relatively low-cost numerical approach to study wind flow in urban areas, particularly for the purpose of commercial projects. The advantages and disadvantages of the employed methods are discussed in detail. It is demonstrated that numerical simulations provide more detailed information about the wind flow in the whole computational domain compared with wind-tunnel measurements, which can only be conducted at limited points. The analysis of wind speedup ratios and meteorological data shows that there are some locations within the investigated area where the annual gust wind speed and probability of exceedance of moderate and strong winds exceed the safety and comfort criteria for Wellington.
14. Case Study_Numerical & Wind Tunnel Investigation of Pedestrian Level Wind Flow - SESOC Journal Vol 33 No 2 September 2020.pdf
SCOSS Alert
Abstract
15. SCOSS Alert - SESOC Journal Vol 33 No 2 September 2020.pdf
MBIE and Standards New Zealand update
Abstract
16. MBIE and Standards - SESOC Journal Vol 33 No 2 September 2020.pdf
News from the Regional Structures Groups
Abstract
17. News from Regional Structural Groups - SESOC Journal Vol 33 No 2 September 2020.pdf
SESOC Emerging Structural Engineers update
Abstract
18. SESOC Emerging Structural Engineers - SESOC Journal Vol 33 No 2 September 2020.pdf
SESOC Membership Report
Abstract
19. SESOC Membership Report - SESOC Journal Vol 33 No 2 September 2020.pdf
SESOC Treasurer's Report
Abstract
20. SESOC Treasurer's Report - SESOC Journal Vol 33 No 2 September 2020.pdf
SESOC President's Report
Abstract
4. SESOC President's Report - SESOC Journal Vol 34 No 1 April 2021.pdf
Notes from the Editor
Abstract
5. Note from the Editor - SESOC Journal Vol 34 No 1 April 2021.pdf
Letters to the Editor - Response to letter John Scarry Vol. 33 No 2. April 2020
Abstract
7. Letters to the Editor - SESOC Journal Vol 34 No 1 April 2021.pdf
Steel Construction NZ (SCNZ) Excellence in Steel Awards
Abstract
8. Steel Construction NZ (SCNZ) Excellence in Steel Awards - SESOC Journal Vol 34 No 1 April 2021.pdf
Chartered professional engineer review - Submission to Engineering NZ
Abstract
Building for climate change - Submission to Ministry of Business, Innovation and Employment
Abstract
10. Building for Climate Change - Submission to MBIE- SESOC Journal Vol 34 No 1 April 2021.pdf
SESOC Task group - Grounted Connections and Drossbachs
Abstract
The following scoping document has been prepared by the SESOC grouted connections task group. The document is open for review and comments by SESOC members prior to the finalisation of the paper –
as discussed in Section 7 of the discussion paper. Should you have any comments please forward them directly to Barry Brown
11. SESOC Task Group - Grouted connections and Drossbachs - SESOC Journal Vol 34 No 1 April 2021.pdf
Proposed Amendments to SNZ TS 3404
Abstract
In February 2018, Standards New Zealand published SNZ TS 3404 Durability requirements for steel structures and components, and later that year (November 2018) it was cited in the NZ Building Code (Clause 3.6.1) as
an Acceptable Solution under Clause B2 (Durability).
Since its publication the technical specification committee members have been collating feedback from practitioners, with the aim of improving this document, which has culminated in the proposed amendments
given below. These amendments were prepared by industry durability specialists, including representatives from HERA, BRANZ and Engineering NZ; with funding from Steel Construction NZ (SCNZ).
It is envisioned that once the proposed amendments are finalised, SCNZ will liaise with Standards NZ to incorporate these changes when the document is formally revised in due course. In the meantime, the
Committee Members will appreciate your feedback
Construction Sector Accord Aims
Abstract
The Construction Sector Accord is a genuine partnership
between industry and government that is working to fix
many of the issues and challenges facing the construction
sector. Through its three-year Transformation Plan,
the Accord is driving behaviour change to lift overall
performance, achieve a safer, better-skilled and more
productive industry, and share good practice across the
sector.
Residential Portal Frames - An Engineers Perspective
Abstract
can produce very different results. As a result, Engineering New Zealand and the Engineering General Practitioners Group decided to work together to make a simple, reasonably conservative informative document. We highlight
some of the common issues and make suggestions made for resolving them. We hope that the document will aid engineers, reduce Requests for Information (RFIs) from Building Consent Authorities (BCAs), answer common questions, and produce more robust designs.
Senior structural engineers from the Engineering General Practitioners Group and engineers from several BCAs have checked the approach below and judged it to be a simplified example of good practice design.
14. Residential Portal Frames - An Engineer's Perspective - SESOC Journal Vol 34 No 1 April 2021.pdf
Singly Reinforced Walls
Abstract
2006, which are designed as nominally ductile members, has identified a number of shortcomings and anomalies. This review is concerned with the case where these walls are assumed to contribute to the seismic resistance. The
case where precast panels are used solely to provide protection against the weather is not considered, though some of the actions arising from self-strain effects, such as thermal expansion and elongation, should be considered in
design. The design clauses in the Standard contain two different strength reduction factors (Ø), one of which is applied to in-plane actions and the other to out-of-plane actions. The use of two factors does not appear to be
reasonable and it is recommended a single value be used.
The Standard allows the calculation of the flexural strength of the subject walls to be based on the conventional assumptions that the maximum usable strain in the concrete is 0.003 and the equivalent rectangular block (7.4.2.7)
is an adequate idealization of compressive stresses in concrete. These assumptions are in conflict with the material strain limit (2.3.2.2), which limits the level of inelastic deformation that may be sustained at their ultimate strength. An examination of this conventional approach to flexural design shows that its use is inappropriate for singly reinforced walls, as it leads to excessive estimates of deformability and high tensile strains in the reinforcement that are inappropriate for nominally ductile members. The high tensile strains if they develop, would be likely to cause the concrete surrounding the reinforcement to break up, leading to either a premature compression failure of the
concrete or buckling of the reinforcement.
The minimum specified eccentricity of axial loading used to assess stability associated with P-delta actions is shown to be too small to account for construction tolerance and loading conditions not usually considered in design.
No guidance is given in the Standard on the effects arising from interaction of in-plane and out-of-plane actions in these walls. This interaction is shown to have a potentially major adverse influence on the strength and stiffness of
the walls for out-of-plane actions, including the resistance to P-delta effects.
15. Singly Reinforced Walls - SESOC Journal Vol 34 No 1 April 2021.pdf
Time to Cessation of Curing for Precast Concrete Using Equivalent Durabilty Performance
Abstract
Curing of precast concrete has an area of considerable discussion among specifiers and suppliers in recent years, particularly about concerns about durability of the material being affected. Time to cessation of curing of
precast concrete is assessed overseas using either the maturity approach or by comparing the equivalent durability performance. This paper addresses how initial curing temperature and duration affects the microstructure of
concrete and influences the durability of concrete. Results from this study show that measuring equivalent durability performance using accelerated carbonation or chloride resistance can assess when curing of concrete can cease.
Findings show that cessation of curing of precast concrete may be possible after 24 hours without negatively affecting the durability potential of the material. Recommendations are made about how the durability of precast concrete can
be quality assured by suppliers of these products.
16. Time to Cessation of Curing for Precast Concrete Using Equivalent Durabilty Performance - SESOC Journal Vol 34 No 1 April 2021.pdf
Lateral Stiffness cf Composite CFST Columns
Abstract
Concrete-filled steel tubes (CFSTs) columns are used extensively in modern multi-storey buildings and a number of different expressions are available to assess their lateral stiffness for use in design. The lateral stiffness is used
in the determination of the elastic critical buckling load for a slender column, and it is used in analyses of frames to determine likely actions and displacements under lateral loadings including those from earthquake. The different
expressions available to assess lateral stiffness can give significantly different results. This paper describes the background of a number of empirical relationships for composite column stiffness commonly
considered for design. Also, the values of stiffness obtained are compared with those obtained from simple moment curvature analysis. It is shown that the secant lateral stiffness of columns is almost independent of the axial loading
for a specific section in the moment curvature analyses, and this is consistent with some AISC, ACI and NZS3404 design recommendations. Some AISC design provisions developed to determine the member compressive axial
force result in a greater computed stiffness than the other methods. Also, for the limited range of analyses conducted with section slenderness near the NZS3404 slenderness limit, NZS3404 methods, which are similar to ACI methods,
gave similar results to the moment-curvature analysis. Issues relating to design are discussed, and for situations where low stiffness is critical, the NZS3404 method and the ACI method were considered to be both conservative
and appropriate for calculating lateral stiffness for design.
17. Lateral Stiffness cf Composite CFST Columns - SESOC Journal Vol 34 No 1 April 2021.pdf
SCOSS Alert
Abstract
18. SCOSS Alert - SESOC Journal Vol 34 No 1 April 2021.pdf
Building Code System and Standards Update
Abstract
19. Building Code System and Standards Update - SESOC Journal Vol 34 No 1 April 2021.pdf
News from the Regional Structural Groups
Abstract
20. News from the Regional Structural Groups - SESOC Journal Vol 34 No 1 April 2021.pdf
SESOC Emerging Structural Engineers Report
Abstract
21. SESOC Emerging Structuiral Engineers Report - SESOC Journal Vol 34 No 1 April 2021.pdf
SESOC Membership Report
Abstract
22. SESOC Membership Report - SESOC Journal Vol 34 No 1 April 2021.pdf
SESOC Treasurer's Report
Abstract
23. SESOC Treasurer's Report - SESOC Journal Vol 34 No 1 April 2021.pdf
SESOC President's Report
Abstract
4. SESOC President's Report - from SESOC Journal Vol 34 No2 Sep 2021.pdf
Notes from the Editor
Abstract
5. NOTE FROM THE EDITOR - SESOC Journal Vol 34 No2 Sep 2021.pdf
Letter to Editor
Abstract
6. LETTER TO EDITOR - SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC 2021 Citations & Awards
Abstract
7. SESOC 2021 Citations & Awards - SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC 2021 Conference
Abstract
8. SESOC 2021 Conference - SESOC Journal Vol 34 No2 Sep 2021.pdf
Three engineering institutions - Three female presidents
Abstract
9. Three engineering institutions - Three female presidents - SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC President meeting with the Minister of Building and Construction - Minister Poto Williams
Abstract
10. SESOC President meeting with... - SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC advice on hollow-core floors
Abstract
11. SESOC advice on hollow-core floors - SESOC Journal Vol 34 No2 Sep 2021.pdf
Occupational regulatory regime for engineers
Abstract
The Structural Engineering Society of New Zealand (SESOC) supports the proposals in the MBIE consultation document and endorses the objectives to improve public confidence in the sector and to ensure engineers are competent, behave ethically and are held to account.
In accordance with our 2019 MBIE submission, SESOC supports:
• A new two tier, two gate regulatory regime that addresses behavioural competence (i.e. professionalism and ethical behaviour) at the lower tier and technical competence at the upper tier. The lower and upper tiers are referred to as ‘Professional Engineer’ and ‘Licenced Engineer’ respectively in this submission.
• A new early career registration scheme (tier 1 – behavioural competence) for all Professional Engineers with up to 2 years of engineering experience, under the guidance of suitable engineers. This timeframe enables the graduate engineer to: – learn and apply behavioural competence through engineering practice in the workplace. – demonstrate behavioural competence in the workplace and through professional training courses.
• A new licencing scheme (tier 2 – technical competence) for Structural Engineers and other high risk practice fields of engineering. We see this licensing regime applying to the types of structural engineering design work outlined in our 2019 submission, i.e. specific design under the verification method of the Building Code.
• The establishment of a new regulator to oversee any regulation and licensing process including the need for sufficient accountability, transparency and independence. For the purpose of clarity, we do not support the continuation of the CPEng scheme for either the lower tier Professional Engineer qualification or the upper tier Licenced Engineer qualification. Our reasons for this position are that:
• It would be confusing to retain CPEng because it covers behavioural and technical competence, whereas the new Professional Engineer mark would cover only behavioural competence and the new Licenced Engineer mark would cover only technical competence.
• The technical competency required to qualify for Licenced Engineer would be higher than for CPEng, so retaining CPEng would devalue the licencing regime.
• CPEng is not well regarded, especially by Building Consent Authorities, so there is little value in retaining this qualification.
• There is currently considerable confusion within the existing dual CMEngNZ and CPEng frameworks which needs to be replaced with a simple and transparent framework. We believe the best way to achieve this is to remove both existing frameworks and we strongly believe that Engineering New Zealand and MBIE need to work together collaboratively in order to achieve this outcome.
As outlined in our 2019 submission to MBIE, SESOC believes the broader objective of improving quality outcomes in the building sector will be achieved only by having a regulatory framework that supports a holistic view of quality. New occupational regulations for structural engineers will lead to improvements in certain areas of the sector, but it will not eliminate problems.
Other areas of the building performance system will need to be addressed in order to achieve better quality outcomes. We strongly recommend improving the building consenting process by strengthening peer reviews and introducing technical design audits.
Two years on from the previous MBIE consultation we see further examples (e.g. 230 High Street, Christchurch and Harington Street Carpark, Tauranga) of unnecessary structural engineering failures in the building sector. Frustratingly, there continues to be a lack of evidence-gathering in relation to the technical quality of engineering design. There remains, to our knowledge, no consistent means by which the technical quality of designs are assessed against the requirements of the Building Code, nor gathering of data to assess quality outcomes.
SESOC would like to be actively involved in helping MBIE shape the detail of the legislation and believe we have an important role to play in any subsequent implementation phases.
Any new system must be of high quality and have sustained investment, support and curation, with input and buy-in from across the entire sector for it to become successful over time – this system will not achieve long term meaningful outcomes if it is treated as a “set and forget” approach.
12. Occupational regulatory regime for engineers - SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC sustainable design report
Abstract
13. SESOC sustainable design report - SESOC Journal Vol 34 No2 Sep 2021.pdf
Christchurch 10 years on
Abstract
14. Christchurch 10 years on - SESOC Journal Vol 34 No2 Sep 2021.pdf
Innovation - The next big thing or the next big failure?
Abstract
Innovation is a common buzzword that is used to describe new design solutions or technologies. Although intended to have positive connotations, the reality is that the term innovation is often used to describe new ideas that are untested or under development. These innovative solutions do not always succeed, and examples of notable failures are presented for both radical and incremental innovation. The technical causes for these failures are summarised and recommendations are provided regarding evidence and testing required to prove or validate new solutions prior to widespread implementation. The incremental development of seismic design procedures and structural systems has played a critical role in improving the performance of structures during earthquakes. Tried and tested solutions that are reliable, but not necessarily perfect, should not be tossed out in favour of underdeveloped ideas being promoted as the next big thing, when such ideas may instead turn out to be the next big failure.
15. Innovation – The next big thing or... - SESOC Journal Vol 34 No2 Sep 2021.pdf
Post-installed rebars for seismic applications in concrete-to-concrete connections
Abstract
Use of post-installed rebar (PIR) systems is getting more and more common in the reinforced concrete construction practice for both modification/extension of existing buildings and optimisation of processes in new realisations. They find also a widespread application in seismic retrofit solutions involving connections between existing and new reinforced concrete members. In Europe, the use of injection mortar systems for PIR is regulated by qualification procedures issued by the European Organization for Technical Assessment (EOTA). Typically, the qualifications are based on the demonstration of equivalency of the load-displacement behaviour of PIR with cast-in rebars (CIR). A qualified system can be used in applications (i.e. end anchorages and lap joints with straight bars) following the design provisions of Eurocode 2 and Eurocode 8 for static and seismic loading conditions, as well as for fire design. In New Zealand, European Technical Assessments (ETA) issued by EOTA are commonly used. However, for the case of PIR systems the question arises how to interpret it in the view of NZS 3101. The present paper gives a summary of the current state-of-the-art design of post-installed rebar systems as well as the assessment methods of the injection mortar systems for such applications with a special focus on the seismic situation. An outlook and recommendations are also proposed for the next steps needed in New Zealand to utilize PIR for all applications where straight cast-inplace rebars are allowed by NZS 3101.
16. Post-installed rebars for seismic applications... - SESOC Journal Vol 34 No2 Sep 2021.pdf
Observed defects in grouted duct precast panel connections in New Zealand and the potential performance imperfections
Abstract
Grouted duct connections, commonly referred to as “drossbach duct” or “splice-sleeve” connections, have been used in precast concrete construction for more than 50 years in New Zealand. These types of connections allow for direct or indirect splicing of reinforcing across the joints of precast elements, and are typically used to splice the vertical reinforcing of precast wall panels, forming a horizontal construction joint. The components of the connection are typically hidden from view once construction is completed, so defects in the connections are often not apparent without invasive investigation. This paper presents a summary of the investigation of indirect splice grouted duct connections across 22 existing buildings carried out by Fraser Thomas Ltd (FTL) and Concrete Structures Investigation (CSI) between 2014 and 2020. The investigation results show that there are defects that commonly occur in these types of connections, particularly insufficient grout fill which can reduce the capacity of the splice. A Monte Carlo simulation has been carried out to predict the likely effects of the individual defects observed during the investigation on the full panel capacity, with varying wall and duct configurations. The analysis shows that there is significant possible variation in the reduction in wall flexural capacity arising from individual splice defects, which reduces as the length of the wall panels increase. A model is proposed to provide conservative high-level capacity reduction estimates for wall panels where sampling of the grouted duct connections has identified defects. Based on the experience from the investigations and the structural performance implications arising from defective grouted duct connections, it is clear that these connections should be carefully investigated and assessed when identified in existing buildings in New Zealand.
17. Observed defects in grouted duct precast... - SESOC Journal Vol 34 No2 Sep 2021.pdf
CROSS Report
Abstract
18. CROSS Report - SESOC Journal Vol 34 No2 Sep 2021.pdf
Building Standards NZ Update
Abstract
19. Building Standards NZ Update - SESOC Journal Vol 34 No2 Sep 2021.pdf
Emerging Structural Engineers Report
Abstract
20. Emerging Structural Engineers Report - SESOC Journal Vol 34 No2 Sep 2021.pdf
News from the Regional Structural Groups
Abstract
21. News from the Regional Structural Groups - SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC Structural Engineers Report
Abstract
SESOC Membership Report
Abstract
23. SESOC Membership Report SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC Treasurer's Report
Abstract
24. SESOC Treasurer’s Report - SESOC Journal Vol 34 No2 Sep 2021.pdf
SESOC President's Report
Abstract
Notes from the Editor
Abstract
Obituaries - Professor Michael John Pender and Bruce Henry Williams
Letter to the Editor
Abstract
SESOC 2022 Citation - Hamish McKenzie
Abstract
Understanding the Bounds of your Competence
Abstract
The Chartered Professional Engineer mark relies heavily upon an engineer understanding and staying within their bounds of competence. However, how do you know what you don’t know?
Issues with Residential Hold Down System
Abstract
Bracing systems in New Zealand commonly use hold-down bolts like the MiTek screw bolt/GIB HandiBrac system. Recent conversations with engineers and designers have raised potential issues to be aware of when using them on internal bracing lines with concrete slabs and detailing for timber floors.
While this article uses MiTek as an example, we primarily illustrate the need to follow a reliable load path and consider the requirements of the system specified, regardless of the manufacturer.
SESOC Recast Floors Project Papers Introduction
Abstract
SESOC takes great pleasure in publishing the following papers which have arisen from the ReCast Floors project. These papers relate to the performance of precast concrete floors in New Zealand including related design issues and retrofitting. The papers have been collated to provide comprehensive guidance for structural engineers and as stated in the introductory paper, ReCast Floors Project: Overview and Key Recommendations (Elwood, Brooke, Hogan), the Recast Floors project has two primary aims:
• Improving understanding of the likely behaviour of precast floors during earthquakes, including the performance of earthquake-damaged precast concrete floors, and
• Developing and validating methods for improving the performance of existing precast concrete floors.
Recast Floors Project: Overview and key recommendations
Abstract
Overview of retrofit requirements and techniques for Precast concrete floors
Abstract
Despite development of detailed assessment procedures based on extensive past research, little guidance has previously been available regarding how to retrofit deficient precast floors. Additionally, prior to the ReCast floor project there had been little previous experimental validation of retrofit techniques for precast concrete floors. This paper outlines philosophical requirements affecting design and detailing of retrofits for precast concrete floors, and summarises the efficacy of known retrofits techniques for floors constructed using hollow-core, double tee, flat slab, or rib and infill precast units.
Design recommendations for seating angle retrofits
Abstract
Existing precast hollow-core floors commonly have insufficient seating lengths, which makes them prone to Loss of Support failure when subjected to earthquake-imposed demands. A supplementary seating retrofit, such as a seating angle, can be used to prevent collapse when the floor unseats. The absence of design guidance for such seating retrofits has resulted in a wide range of different design and detailing approaches that often underestimate the demands on the post-installed anchors and seating angles. This paper addresses the lack of design guidance by introducing two design methodologies for seating angle retrofits. The first design approach entails design steps for seating angles installed hard up against the soffit of the floor. Capacity-design philosophy is used to ensure the postinstalled anchors can withstand the force demands arising from earthquake-imposed deformations. The second recommended approach omits these high demands on the post-installed anchors by leaving a gap between the seating angle and the floor soffit and partially filling this gap with a deformable infill strip. Using these two proposed design recommendations ensures that the seating angle and post-installed anchors can safely support the precast
flooring unit if it unseats.
Design recommendations for strongback retrofits
Abstract
Since the early 2000s, it has been widely recognised that existing hollow-core floors can pose a threat to life during earthquakes, but only limited and mostly unvalidated guidance on how to retrofit the many existing hollow-core floors in New Zealand has since been provided. The lack of retrofit validation was emphasised by recent experimental findings showing that seating angles do not necessarily address positive moment failure within the precast floor unit, as has commonly been assumed.
A new retrofit solution referred to as ‘strongback’ retrofit has been developed and experimentally validated. The strongback retrofit consists of short steel beams running longitudinally underneath the hollow-core unit combined with a supplementary support. When the floor loses its gravity load-carrying capacity, the strongback retrofit can provide a robust alternative load path. Thereby, the strongback retrofit can address the majority of known hollow-core floor failure modes, including positive moment failure proximate to the support.
This paper provides design recommendations for the new strongback retrofit and describes the key performance observations from the validation test. The paper also discusses in what situations the strongback retrofit should be used.
Seismic performance of precast hollow-core floors with modern detailing: a case study
Abstract
This paper describes the observed seismic performance of precast hollow-core floors from an instrumented building subjected to design-level ground shaking during the 2016 Kaikōura earthquake. The hollow-core floors in the building incorporated the detailing requirements of the current design standard, NZS3101:2006-A3, which were intended to suppress undesirable failure modes such as loss of support, negative moment failure, positive moment failure, and rupture of non-ductile topping mesh. The structural system was extensively surveyed to document the severity and distribution of the damage sustained in the flooring system. Furthermore, the building response during the earthquake was reconstructed from the acceleration records obtained from instruments installed throughout the building to estimate the demands on the floor units. While the failure modes that the NZS 3101 hollow-core detailing was designed to suppress were not observed in the building, the damage survey showed unexpected poor performance of hollow-core floor units seated within the plastic hinge regions of the supporting beams and in line with columns, which are referred to as “beta units”. It was found that beta units incurred more damage than units seated outside the plastic hinge zone. The susceptibility of these beta units to sustain severe damage is neither recognised in the current design standard, NZS3101:2006-A3, nor in the technical proposal aiming to revise the Assessment Guidelines C5 (Yellow Chapter).
Real world experience of seismic performance and retrofits used in buildings with hollow-core floors
Abstract
Hollow-core floors have been recognised to have a potentially poor seismic performance since the 1994 Northridge earthquake, with subsequent research leading to significant developments in design and detailing requirements. Damage evaluations after the 2016 Kaikōura earthquake confirmed the expected seismic vulnerabilities in existing precast hollow-core floors and also revealed some previously unknown behaviour types. The Kaikōura earthquake provided significant impetus to advance our understanding of seismic performance of existing buildings with hollowcore floors and suitable retrofit solutions. Subsequently, the ReCast floors research programme was initiated. The reported work is one component of the ReCast floors programme in which investigations of the real-world performance of buildings with hollow-core floors was conducted. The objective was to collate information on damage patterns observed in buildings following the Kaikōura earthquake, the engineering characteristics of existing Wellington buildings with hollow-core floors, current strengthening status and the retrofit solutions implemented to help inform the ReCast research activities.
Torsional capacity assessment of precast hollow-core floors
Abstract
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 accuracy of the procedure currently used to assess the torsional capacity of hollow-core floors. This paper discusses the basis and limitations of the procedure adopted in the New Zealand assessment guidelines (C5) for quantifying the torsional capacity of hollow-core floor units, describes potential implications of the limitations of the available methodology on the assessed torsional capacity accuracy and potential impact on other hollow-core seismic failure modes, and provides a twist-limits chart as a simple tool to assess the torsional deformation capacity of typical hollow-core unit depths based on the methodology available in the current assessment guidelines. The twist-limits chart provides a useful assessment tool for engineers, but must be used with due consideration of the limitations of the torsional capacity assessment methodology discussed herein. Informing the judgement of how and when to use this twist-limit information in the assessment process, given the limitations and uncertainty of conditions in the field, remains a key challenge for future research on the seismic assessment of precast floors.
Seismic damage observations of precast hollow-core floors from two full-scale super-assembly tests
Abstract
Serious concerns about the life safety risk of hollow-core floors during earthquakes were raised following the collapse of hollow-core units during the 1994 Northridge earthquake and in subsequent laboratory tests. To enhance the understanding of the seismic performance of existing hollow-core floors, a substantial experimental programme of two large-scale super-assembly tests with hollow-core floors was carried out. Each test specimen consisted of a two-bay by one-bay concrete frame with full-scale hollow-core floors, which were constructed using typical 1980s floor detailing. The specimens were loaded with a simulated earthquake record applied quasi-statically.
This paper discusses the progression of hollow-core floor damage observed in both super-assembly experiments. The main findings include the early onset of cracks in the unreinforced webs of the hollow-core units at 0.5% interstorey drift. The tests also demonstrated the detrimental effect of web cracking on the gravity load-carrying capacity of hollowcore floors. Additionally, hollow-core units that are seated at intermediate columns (so-called ‘beta units’) were found to get damaged more heavily than those supported away from the columns. Moreover, several transverse cracks were observed in the floor soffit away from the support and beyond the provided seating retrofits. Lastly, the extent of floor damage was found to be sensitive to the ground motion, with pulse-type motions (pushing the structure in one direction) tending to cause more severe floor damage than far-field motions with multiple cycles. The paper also outlines key challenges and recommendations for web crack inspections.
Load-path and stiffness degradation of floor diaphragms in reinforced concrete buildings subjected to lateral loading - Part I: Experimental observations
Abstract
An experimental investigation into the degradation of load-paths in damaged diaphragms was conducted to provide answers to the New Zealand structural engineering community following concerns that strut-and-tie load-paths could not cross wide cracks that develop around the floor perimeter during earthquake loading demands. A full-scale super-assembly concrete moment frame specimen with a hollow-core flooring system installed was subjected to realistic drift deformations to induce damage in the floor, followed by in-plane shear deformation demands to assess the ability of the diaphragm to transfer load between frames at different floor damage levels. It was found that compression struts could form across much wider cracks in floors than previously anticipated. This was due to contact compressive stresses forming via loose aggregate that lodged within rugged sinusoidal wide floor cracks. Additionally, it was found that diaphragm compression struts can only transfer to the primary lateral load resisting frame through beam plastic hinges acting in minor axis shear following gaps opening between the floor and columns at moderate drift demands. Smooth floor to column interfaces did not provide the same residual rubble aggregate binding compressive load path observed in cracks within the floor. The primary driver of diaphragm shear stiffness degradation was found to be torsional softening of the perimeter beams of the floor. This was caused by simultaneous bi-directional demands applied to longitudinal beam bars and a phenomenon known as the bowstring effect applying large torsional demands through the beam-floor continuity reinforcement. The diaphragm strength and rate of shear stiffness degradation was found to be highly reliant on earthquake directionality. A set of generalised equations was developed to describe the rate of diaphragm shear stiffness degradation with respect to magnitude and directionality of drift demands. Part I of II in this journal series details the full-scale super-assembly experiment conducted on a floor diaphragm at different damage states and the observed behaviour during testing.
Load-path and stiffness degradation of floor diaphragms in reinforced concrete buildings subjected to lateral loading - Part II: Data analysis
Abstract
An experimental investigation into the degradation of load-paths in damaged diaphragms was conducted to provide answers to the New Zealand structural engineering community following concerns that strut-and-tie load-paths could not cross wide cracks that develop around the floor perimeter during earthquake loading demands. A full-scale superassembly concrete moment frame specimen with a hollow-core flooring system installed was subjected to realistic drift deformations to induce damage in the floor, followed by in-plane shear deformation demands to assess the ability of the diaphragm to transfer load between frames at different floor damage levels. It was found that compression struts could form across much wider cracks in floors than previously anticipated. This was due to contact compressive stresses forming via loose aggregate that lodged within rugged sinusoidal wide floor cracks. Additionally it was found that diaphragm compression struts can only transfer to the primary lateral load resisting frame through beam plastic hinges acting in minor axis shear following gaps opening between the floor and columns at moderate drift demands. Smooth floor-to-column interfaces did not provide the same residual rubble aggregate binding compressive load path observed in cracks within the floor. The primary driver of diaphragm shear stiffness degradation was found to be torsional softening of the perimeter beams of the floor. This was caused by simultaneous bi-directional demands applied to longitudinal beam bars and a phenomenon known as the bowstring effect applying large torsional demands through the beam-floor continuity reinforcement. The diaphragm strength and rate of shear stiffness degradation was found to be highly reliant on earthquake directionality. A set of generalised equations was developed to describe the rate of diaphragm shear stiffness degradation with respect to magnitude and directionality of drift demands. Part II of II in this journal series provides analysis of the cause and rate of diaphragm stiffness degradation based on instrument data and visual observations as described in Part I (Parr et al. 2022). Analysis of the formation of residual diaphragm load-paths and the relationship between torsional softening of beams with simultaneous bi-directional demands is also investigated.
Strategies for finite element modelling of precast pre-stressed hollow-core floors
Abstract
As part of the ReCast research programme, research has been undertaken to develop a finite element (FE) modelling approach for precast pre-stressed hollowcare (PPHC) floors. This paper summarises the modelling criteria that is considered key to analysing the behavior of PPHC floors. Comparisons of the numerical predictions with experimental results show that the proposed model is capable of capturing shear and torsional failure mechanisms. Lastly, advances towards a sub-assembly model, developed to investigate the bending behavior of PPHC slab-to-beam connections, are presented. The results indicate that the numerical approach is promising and should be developed further as part of future
CROSS Report
Building Standards NZ Update
Abstract
News from the Regional Structural Groups
Abstract
SESOC Membership Report
Abstract
SESOC Treasurer's Report
Abstract
SESOC President's Report
Abstract
4. SESOC President Report - SESOC Journal Vol 35 No2 Sep 2022.pdf
Notes from the Editor
Abstract
5. Note from the Editor - SESOC Journal Vol 35 No2 Sep 2022.pdf
Fellows Dinner 2022
Abstract
6. Fellows Dinner 2022 - SESOC Journal Vol 35 No2 Sep 2022.pdf
Engineering Tips And Tricks
Abstract
7. Engineering Tips And Tricks - SESOC Journal Vol 35 No2 Sep 2022.pdf
Design Issues for Structural Engineers
Abstract
8. Design Issues for Structural Engineers - SESOC Journal Vol 35 No2 Sep 2022.pdf
Building a design mindset for the 2020 – 2030 decade of disruption, and leadership
Abstract
9. Building a design mindset for the 2020 – 2030... - SESOC Journal Vol 35 No2 Sep 2022
Using P21 tested bracing units outside the scope of NZS 3604
Abstract
SESOC Management Committee has had recent correspondence from building consent authorities and engineers asking for clarification on the use of P21-tested elements. This article from ENZ provides guidance on P21-tested systems and looks at when the use of P21 elements may be appropriate. From questions SESOC has been asked, there is also further guidance needed for practitioners for designs which are outside of the Acceptable Solution B1/AS1. SESOC and the Timber Design Society have agreed to prepare some guidance on this topic. In the meantime, SESOC members are reminded of the following.
• All designs in New Zealand must comply with the New Zealand Building Code and you must understand how you are achieving compliance, i.e. Acceptable Solution, Verification Method or Alternative Solution;
• When you specify products and/or systems these typically have a compliance pathway in either a Codemark Certificate or a BRANZ appraisal;
• P21-tested elements typically have an appraisal. This appraisal will include information on the use of the product and any design constraints; and
• Engineers should be careful to ensure that products and/or systems are specified within the constraints of their appraisal.
While specific guidance is being prepared, I urge our members to be familiar with the appraisals for products or systems they are specifying.
10. Using P21 tested bracing units outside the scope of NZS 3604 - SESOC Journal Vol 35 No2 Sep 2022.pdf
New methodology charts course to reducing embodied carbon in buildings
Abstract
11. New methodology charts course to - SESOC Journal Vol 35 No2 Sep 2022
Experimental investigation of the performance of concrete columns after repair of minor damage by injection of epoxy resin
Abstract
Two column tests were undertaken to investigate the efficacy of epoxy resin as a method to repair minor earthquake damage, i.e., residual cracks of less than 0.5 mm width. The tested columns were nominally identical, and constructed as replicas of a typical 1970s New Zealand prototype.
One of the columns, designated Y1, was tested progressively until failure occurred, while the other (Y2) was tested until minor damage occurred, repaired using epoxy resin, and then tested further until failure. Only cracks of 0.3 mm or greater maximum width were repaired, which resulted in several cracks remaining unrepaired.
As expected based on calculation, the behaviour of the columns was flexurally dominated, and controlled by the presence of lap splices adjacent to the critical section. Comparison showed that a reasonable estimate of the force-displacement response of the columns was obtained from calculations based on either moment-curvature analysis or other relevant assessment guidance.
The behaviour of the repaired specimen Y2 was similar to that of specimen Y1 which was to failure without any repair and retesting, although the post-repair small displacement secant stiffness was approximately 15% lower than the original stiffness of the previously-uncracked specimens. This difference was attributed to the presence of unrepaired cracks. The post-repair stiffness exceeded the stiffness estimated using relevant assessment guidance.
12. Experimental investigation of the performance of concrete... - SESOC Journal Vol 35 No2 Sep 2022.pdf
Interface shear-friction in seismic conditions: What’s beyond NZS 3101?
Abstract
Experimental research of load transfer across concrete-to-concrete interfaces started in the early 1960s. Numerous experimental programmes have been conducted and more than fifty different physical models have been proposed. The most complete models engage three interacting mechanisms of the load transfer (i.e., 1. adhesive bonding/mechanical interlocking; 2. shear-friction; 3. dowel action). However, models proposed for seismic loading are very limited in the literature.
This paper gives a general overview of the load transfer across concrete-to-concrete interfaces, together with the introduction of the European Organisation for Technical Approvals (EOTA) Technical Report 066 model, and the most recently proposed physical model based on the research conducted at the National Technical University of Athens (NTUA), for load transfer across concrete-to-concrete interfaces under cyclic seismic loading.
An outlook and comparison to NZS 3101 is also presented.
13a. Interface shear-friction in seismic conditions - SESOC Journal Vol 35 No2 Sep 2022
An experimental study of fire performance of hollowcore floors
Abstract
Since 2006, numerous seismic requirement changes have been introduced to hollowcore floor construction with no consideration given to the impact on fire performance. One change of concern was the introduction of a link slab between the hollowcore unit and the adjacent beam. Because of this, BRANZ established a research project to investigate the fire performance of hollowcore floors constructed according to the current practices. The objectives of this project are (1) to confirm or dismiss the concern raised about the impact of inserting a link slab on the fire performance of hollowcore floors; and (2) to provide insight into the potential fire issues associated with hollowcore floors to ensure that future proposed seismic retrofit solutions or code revisions will not compromise fire performance of hollowcore floors.
The first part of the BRANZ project involved a fire test of a precast hollowcore floor system at the systems level. The test was undertaken with the furnace conditions required by AS1530.4 (AS 2014) and a superimposed load of 5.3kPa, and it was terminated soon after the insulation criterion, measured on the unexposed surface, was reached at 116 minutes. Floor system deflections were insignificant throughout the entire 120 minute furnace exposure duration. However premature web shear failure and tendon exposure in the hollowcore unit adjacent to the link slab was observed only 29 minutes into the test. This observation is a concern for the structural adequacy of hollowcore floor systems of greater spans typically in real buildings.
The preliminary findings from the test provide insight into the potential fire issues of hollowcore practices and they are summarised as follows: (1). Conventional fire rating test methods of precast floors do not allow for the restraining actions imposed to the floor and this could sometimes overestimate fire ratings and/or wrongly identify critical structural fire issues; (2). When restrained from expanding longitudinally in the horizontal direction, the hollowcore units could experience significant sectional distortion due to the exacerbated transverse expansion. In addition, hollowcore units could also experience significant thermal gradient across the depth. All these could lead to web shear failure, jeopardising the structural stability of the buildings with hollowcore floors; and (3). The introduction of the link slab in hollowcore floors could significantly exacerbate the sectional distortion of the hollowcore units and horizontal web cracking due to the web shear failure, leading to a greater possibility of partial collapse of hollowcore units.
14. An experimental study of fire performance of hollowcore floors - SESOC Journal Vol 35 No2 Sep 2022.pdf
CROSS Report
Abstract
15. CROSS Report - SESOC Journal Vol 35 No2 Sep 2022.pdf
Building Code System and Standards Update
Abstract
16. Building Code System & Standards Update - SESOC Journal Vol 35 No2 Sep 2022.pdf
MBIE Updates
Abstract
17. MBIE Updates - SESOC Journal Vol 35 No2 Sep 2022.pdf
News from the Regional Structural Groups
Abstract
18. News from the Regional Structural Groups - SESOC Journal Vol 35 No2 Sep 2022.pdf
Emerging Structural Engineers Report
Abstract
19. SESOC Emerging Structural Engineers Report - SESOC Journal Vol 35 No2 Sep 2022.pdf
SESOC Membership Report
Abstract
20. SESOC Membership Report - SESOC Journal Vol 35 No2 Sep 2022.pdf
SESOC Treasurer's Report
Abstract