Vol. 31 – 35

President's Report

Jason Ingham
Abstract
 

Note from the editor

Stewart Hobbs
Abstract
 

Letters to Editor

Barry Davidson
Abstract
 

Simplified Capacity Design Procedure

Hamish Brookie
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. 

Seismic Assessment and Strengthening of the Majestic Centre, Wellington

J. G. White , H.S. McKenzie, A.E. Philpott , D.K. Bull , B.D. Galloway , R. van Ballegooy
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. 

Performance of Panel-to-Foundation Connections in low-rise precast concrete buildings

Lucas Hogan, Rick Henry and Jason Ingham
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 

Adopt a Ductility for Steel Portal Frame Structures

M. Grant and S. Lanser
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. 

An Overview of the Use of Glass Fiber Reinforced Polymer Bars as Reinforcement in Concrete Structures

V. Worner, H. Auman, A. Palermo, A. Scott
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. 

Improving City Resilience - The Role of Structural Engineering

David Hopkins
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. 

BRBF and CBF Gusset Plates: Out-of-Plane Stability Design using a implfied Notional Load Yield Line (NLYL) Method

B. Zaboli, G.C. Clifton, K. Cowie
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. 

Book Review - Tall Wood Buildings - Design, Construction and Performance by Michael Green, Jim Taggart

Andy Buchanan
Abstract
 

SCOSS Report


Abstract
 

MBIE and Standards New Zealand Update


Abstract
 

News from the Regional Structural Groups


Abstract
 

The Institute of Structural Engineers Report


Abstract
 

SESOC President's Report

Jason Ingham

Abstract

 

Note from the Editor

Stewart Hobbs

Abstract

 

Obituaries - Esli J Forrest



Abstract

 

Obituaries - Carl Robert O'Grady



Abstract

 

Letters to the Editor

Barry Davidson, Derek Bradley, Tony Stuart, Nicholas Brooke; Dean Cook

Abstract

 

Sourcing reliable large structure steel hollow sections

Editor

Abstract

 

SESOC Reflctions - 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’.
 

SESOC Reflectinos - 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.
 

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.
 

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.
 

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.
 

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.
 

Fresh concrete performance guideline in New Zealand

James R. Mackechnie

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.
 

An Example procedure for preliminary sizing of Resilient Slip Friction Joints (RSFJs) in seismic resistant structures

Ashkan Hashemi, Hamed Bagheri Mehdi Abadi, Farhad Mohammadi Darani, Seyed Mohammad Mahdi Yousef-Beik, Pouyan Zarnani, Pierre Quenneville

Abstract
The innovative Resilient Slip Friction Joint (RSFJ) technology has recently been developed and introduced to the New Zealand construction industry. This self-centring 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.
 

Steel Compliance

Rob Penny

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?
 

Structure Engineering CPEng Level Body of knowledge and skills (BOKs)

Editor

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
 

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.
 

MBlE and Standards New Zealand Update



Abstract

 

Seismic Designs for Suspended Ceilings

Hedda Maria Oosterhoff

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.
 

News from the Regional Structural Groups



Abstract

 

SESOC Membership Report



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SESOC Treasurer's Report



Abstract