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The primary truss centre section lift by Grayson Engineering weighing 390 tonnes.

Grayson Engineering Ltd, as the lead steel constructor, fabricated the five 105m long arched roof trusses, each 10m wide and up to 10m tall and weighing more than 200 tonnes. They also fabricated the 140m long South Stand Primary truss weighing more than 700 tonnes, which has chord members 711mm in diameter with a wall thickness of 60mm, the largest on the project. Pegasus, meanwhile, was subcontracted to do the North, East and West Stands, all the stair structures and lift shafts, and would add five prismatic and four planer trusses to the South Stand roof.  In the end, Pegasus contributed 1,827 tonnes of steel to the project and Grayson 2060 tonnes.

All the shop drawings for the project were prepared by Grayson’s subsidiary Cadtec Draughting – a total of 8,578 Strucad drawings for a total of

Fabrication of the South Stand primary truss

 20, 642 members. The 3-D modelling technology was critical to the success of the project as the erection methodology meant that pre-cambers had to be allowed for in the fabrication.  The two external arch trusses of the five had the added complexity of ‘twists’ that were incorporated to compensate for the eccentric loadings of the facades that hung off them.

Since all of the roof steel consisted of Circular Hollow Sections, both Grayson and Pegasus had imported high-tech CNC (Computer Numeric Control) pipe profiling equipment.  In addition to the time that this saved in profiling, the accuracy of the fit-up meant that there were considerable savings to be made in weld time and the cost of consumables.

The sheer size of the steel members and the need for total accuracy in conforming to the demanding geometry compelled both Grayson and Pegasus to invest in more workshop space. Grayson simply added another bay to its new plant in Wiri, South Auckland, while Pegasus rented another factory.  The dimensions and heavy weight of the steel they were fabricating made test assemblies imperative to prove that it would all go together on site without any hitches. All splice points were meticulously pre-planned. Once they were satisfied, the two fabricators would dismantle the large steel assemblies into smaller units and paint them in preparation for shipping to Dunedin.     

Trial assembly in the yard to ensure a perfect fit

Here Pegasus had the advantage of closer proximity to Dunedin, making 128 round trips – a total of 90,880 kilometres. Grayson sent 124 truck loads from Auckland, most of these being over-dimensional, the heaviest weighing 30 tonnes plus. The first route was Auckland to Wellington by road, Wellington to Lyttleton by sea and on by road to Dunedin, but when shipping to Lyttleton was cancelled, the sea-crossing terminated at Picton, thus increasing the distance of the road journey. Each Grayson delivery was a four-day round trip.

“There were several advantages in following this methodology,” says Gavin Lawry, Managing Director of Pegasus Engineering. “It virtually eliminated on-site welding and thus saved time on the construction programme. It was also good practice in terms of safety. Very importantly, it enabled both fabricators to draw up ITPs (Inspection Test Plans) that intensified Quality Assurance and Quality Control activity. Every plate required for bolted flange connections was subjected to a three-stage non-destructive testing, specifically to detect steel delaminations. Ultrasonic testing was then carried out by qualified third party inspectors.”

All told, approximately 71,000 bolts were used on this project. The bolts for the flange connections were Grade 10.9 manufactured to a JIS B 1186 specification and then tested in Australia to determine the tensioning procedure to be adopted. Each flange connection was bolted up by two experienced erectors, closely watched by a supervisor who ensured the correct torque values were applied. The torque values were pre-determined by an engineering algorithm, which also prescribed the exact bolt sequence. Strictly following this sequence, the riggers first tightened the bolts to one third of the required torque value. Then, following the same sequence and using a hydraulic wrench, the riggers tightened the bolts to two thirds of the required torque value. In phase three, the bolts were tightened to the full required torque value. The last stage was to then loosen each bolt off and retighten back to the full required torque value.  A 20-bolt connection took about two hours to complete. By following this procedure, the erection team ensured that no stresses or fractures had occurred in the final bolt assembly.

After sandblasting and coating, the journey from Christchurch to Dunedin begins

            As much work as possible was assembled on the ground into large modules, which were then lifted into place with large cranes. David Moore, Managing Director of Grayson Engineering, describes the erection of the primary truss: “At 140m in length, and supported by legs at each end, it weighed a total of 701 tonnes. It was assembled on the ground as three truss sections.  First the legs were raised and supported by temporary props. The two end truss sections were then attached to the tops of the legs and also supported until the long middle section could be lifted and secured. Weighing a total of 390 tonnes, this was the heaviest lift of the entire project. One end was picked up by a 400-tonne crawler crane, while the other end was attended to by two 280-tonne crawlers.  The three cranes, provided and operated by Daniel Smith Industries, were each working close to their capacity as they walked the section into position and completed the lift.”

            From the South Stand primary truss to the North Stand opposite is a distance of 105m, as the gull flies! That’s the length of the five roof arch trusses that span the pitch below. Once again the 400-tonne crawler crane of Daniel Smith Industries was in action, walking each truss into position before lifting to an internal clearance height of 37m. A concrete box drainage culvert built in 1930 presenting an underground obstacle. The crane circumvented this simply by setting down the 200-tonne truss, crossing the culvert and picking up its load on the other side. 

Neither Grayson Engineering nor Pegasus Engineering lost time because of injury or accident.  

The central section about to be bolted to the end truss, which is already secured to the leg.

It would be inappropriate to finish this brief account here without acknowledging the teamwork and contributions made by all the other sub-contractors, from those who drove the 550 piles to the engineers who defined the seismic differences between the stands and the roof while minimising any shadowing of the grass growing on the stadium floor. But their names are legion and have been carried in hundreds of other articles. One company, however, deserves to be honoured because more than all the rest, it bore the full weight of responsibility. That’s how it was for Hawkins Construction, the main contractor, whose Project Director Andrew Holmes endorsed Shakespeare’s words: “Uneasy lies the head that wears a crown”. If it wasn’t 10,000 cubic metres of crushed building concrete to be re-used in haul roads and hard stands, it was the steel supply chain and the need to hit those lift dates. “Our mantra was ‘Plan, plan, and plan again: then check, check, check again and sign off!” says Andrew. “We had to win by reducing our collective risk, which is like the spiritual opposite of the sport and performances that will take place here in the future, yet for those who built this wonderful stadium, it was no less emotional.”

With Auckland City Hospital in the background, a D&H Steel flatback makes a delivery to the new structural steel car park going up on Park Rd, Grafton

The first of these involved meeting the developer’s requirement of full corrosion protection. The Auckland District Health Board wanted the car park to have longevity, with the cost of maintenance kept low. The initial choice of decking would have involved propping double multiple spans and leaving an unpainted strip for the welding of through-deck studs.   To avoid the extra cost and to achieve complete corrosion protection, it was decided that ComFlor 60 x 0.75 (supplied by Tata Steel International) would be the decking system of choice. ComFlor 60 x 0.75 could be installed in unpropped single spans. In addition, Composite Floor Decks Ltd delivered the decking with profiled end-caps that would allow concrete infill to take place on each side of the flange during the pour (see Pic 6 ComFlor close-up). The studs, meanwhile, were welded to the beams and given a full protective coating, including the flanges, in the course of D&H Steel’s factory fabrication.

It’s worth noting that this approach is generally regarded as not essential for all steel-framed car parks. Leaving the top flange unpainted is accepted as good practice since the flange will be covered by the concrete. Designers who specify that the top flange should be pre-studded and pre-painted will need to factor in the additional stud detailing and workshop costs.

With propping of the ComFlor 60 x 0.75 unnecessary, Composite Floor Decks was able to establish repetitive decking throughout the seven storey structure.  The columns were Circular Hollow Sections filled with concrete for fire rating. The primary beams on the perimeter were mostly 310UBs with a few 410 and 460UBs. Some Custom Welded beams were required where the span was too long and headroom was required below.  The secondary beams were made up mainly of 200 and 310UBs with a few 360UBs thrown in. Eccentrically Braced Frames (EBFs) were designed for four perimeter bays. These are supported on 600mm diameter concrete piles sunk 15 – 20m and founded in basalt. Lateral bracing is also provided by two concrete block stairwells and two shear concrete elevator shafts.

The Eccentrically Braced Frames were designed for four perimeter bays. The columns are Circular Hollow Sections filled with concrete

The second feature that helped to win the tender for the D&H team was the future-proofing of the car park.  When completed it will have 403 parking spaces, but it’s been designed so that two more floors for car parking can be added at a future date. The steel structure means that this can be done quickly and easily, with no disruption to the operation of the building.  The car park’s concrete roof will become a floor when the time comes. In addition to providing parking spaces for the general public and some hospital staff, the building will have ground floor retail outlets on Grafton’s Park Road, with commercial offices above these. Future-proofing includes adding on an extra four floors of offices, as the need arises. Again the roof is concrete but has a sacrificial long-run roof on steel trusses on top of its, pending the addition of the extra floors with steel framing and composite decks.  

Historically, car park buildings have won few medals for aesthetics, but there are some exceptions; this one at 2 Park Road is set to become the next. The Auckland District Health Board challenged those tendering for this job to design a cladding system that would address the issues of screening, ventilation and aesthetics in a comprehensive solution, cost-effectively. Mainzeal, D&H Steel and Ignite Architects agreed on aluminium as the material, with Ignite developing the detail of the folded panels perforated in tree-like patterns. Fabrication by King Façade was to comply with the aesthetic requirements of the Resource Consent. The folds prevent visual monotony and the punched holes allow for natural ventilation, thus saving on power consumption. The cost of maintenance will amount to an occasional wash.  

It might all seem like plain sailing but that’s because of the navigational expertise in the D&H drawing office. Senior Detailer Guy Jamison describes the challenge presented by the secondary steel for the aluminium cladding. “All the connections of the secondary steel to the primary steelwork had to be modelled and detailed early in the project, and because of the complex geometry this could not be done from the architectural and engineering drawings alone. We managed to integrate the architect’s 3-D model into our structural 3-D model, and only then were we able to detail the secondary steel and integrate the connections to the primary steelwork. We use ProSteel (an add-on to AutoCAD) and it immediately highlighted connection clashes, which I was then able to avoid. It was also apparent that not all of the vertical supports were in the correct locations. However, the accuracy and flexibility of our model enabled us to accommodate the changes prior to producing the shop drawings. D&H’s investment in time and attention to detail added value and saved the client money.”   

ComFlor 60 x 0.75 decking laid on steel beams with pre-welded studs and full corrosion protection

Asked if the design of the Auckland City Hospital Car Park would be a suitable for Christchurch, the engineer, Gordan Brkic, Director of DHC Consulting, said: “The design, in principle, would be the same in Christchurch. The only thing that would need to be addressed is the building’s bracing, as the earthquake loads in Christchurch are significantly higher than would be expected in Auckland. However, this would affect only four EBFs, a relatively small part of the whole structure.”

Mainzeal’s Project Manager Stewart Lovelock says despite the traffic congestion associated with a hospital environment, and the limited amount of setting down space, the Auckland City Hospital Car Park made good progress through its construction programme and will be completed and handed over before the end of December 2011. “Mainzeal has more than 40 years’ construction experience under its belt, “ says Stewart, “and this enables us  to tackle a wide array of projects of every shape and size. We do so with skill, focus and enthusiasm, qualities that D&H’s General Manager, Wayne Carson, also brought to our weekly project meetings. These underlined the importance of excellent communications, by means of which Wayne enabled us to steer this project steadily towards its scheduled completion.”

-        An update on the Christchurch rebuild

-        Upcoming SCNZ Steel Structures Seminars           

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-        SCNZ Elections          

-        Steel Advisor Latest Issue    

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-        Help spread the word about Steel 

-        Material Requirements for Seismic Applications  

-        NZIOB Awards 2011  

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Roofing infill being hoisted with the soffit visible

But first the New Zealand Institute of Geological and Nuclear Science conduced a site specific seismic hazard assessment to ensure the earthquake threat was addressed. Aurecon’s Lana Duboka reports that the new structure complies with the New Zealand Building Code Standard for a 1,000 year return period for both earthquake and wind loadings. “Aurecon then built a model of the stadium and its surroundings in order to conduct wind tunnel tests for loadings. The Aurecon engineers were then able to refine the design of the girders and other roof and façade members.”

The rear section of a box girder showing cigar-shaped bracing and bolt holes for a splice

Grayson’s Commercial Manager Colin Berger says some 900 tonnes of steel were used. “In addition to the girders, we fabricated the steelwork between them and the cigar-shaped braces. These were painted and transported to the site in sections for assembly. For accuracy we used a jig, in which we assembled the bracing. This was then lifted into position and secured. We then lifted the mid-section straight off the back of a truck and bolted the splice from inside the box girder. This required 28 M36 and M20 grade 8.8/TB bolts to resist the significant bending moments.

“The positioning at the back end of the girder was critical because an error of one degree would result in more than half a metre’s displacement at the other end of the girder.  So we used surveyors to make sure that our positioning was correct. In the concrete beam to which the steel had to be attached there was a pocket that allowed the cigar-shaped braces to be adjusted to within the required tolerance. The shape of the braces was entirely the architect’s choice.”

Architect Daryl Maguire of Populous wanted a slim and elegant look. “It was purely a matter of aesthetics. Tapering the bracing elements into cigar shapes makes them appear more elegant than a straight shape, and it also reflects the loads the member will take. One of the beauties and challenges of working on a stadium is that the structure is exposed, making the visual aspects as important as the structural performance. Sometimes the architect has to fight hard to prevent creative concepts from being cut or compromised. Maybe it’s easier to challenge an architect in matters of taste, but it’s not so easy to argue with an engineer, because then you need the Maths! Early in the design work, Populous and Aurecon collaborated in developing the big picture concepts, and worked closely with the cost planners to keep the structure within budget. For both the architect and the engineer, it was a very positive experience.”

Jasmax’s Tim Hoosen says the architects had worked with FSS before on deployable structures and quickly re-established their creative partnership. “We were thinking of Aotearoa, the Maori for New Zealand, land of the long white cloud, and began to design an amorphous roof, conceived as an opaque fabric membrane that would softly touch the wharf, curving, shifting and lifting in places to reveal clear transparency underneath.”

Trying to keep it simple to engineer and fabricate, FSS pursued the possibility of taking identical truss shapes and rotating them about the central axis. However, when Red Steel of Napier was awarded the fabrication sub-contract, chief detailer Hugh Paterson quickly figured out that, far from having an easy ride with repetitive identical shop drawings, his Tekla software was showing a 3-D model in which all the connection plates were on three different angles. “The cleats are the connection points for the struts and various other members. Because of the three different angles, all of the 2-D fabrication drawings would be slightly different and more complex. By the end of April, less than two months after starting, I had produced

In front of the landmark Ferry Building, stunning steelwork fabricated in Napier.

 more than 1,000 individual drawings, with some 400 of them assembly drawings – an awful lot of drawing for this size of building.”

The Cloud is almost 180m long, 11m high and has 33 main frame trusses.  The feet of the trusses have a 21.9m spread and are bolted to the wharf with ground anchors. The trusses are positioned along two straight grid lines at intervals of 5.75m.  There are only two symmetrical frames on grid 13 and 29. Each frame comprises two 250 x 150mm Rectangular Hollow Section columns, connected to a curved truss fabricated from 150mm Square Hollow Section chords with 100mm webbing. The undulations are achieved by making one column leg longer and its opposite leg shorter, progressively along the grids. All of the RHS members are fully sealed to prevent moisture penetration and they are protected with Interthane 990.

Red Steel used truss jigs to speed up the fabrication of the trusses while maintaining accuracy, but the complexities of the connections required intensive detailing and constant communication with Wade Design Engineers Pty Ltd, whose consulting engineer Steve Rode-Bramanis is based in Brisbane. Hugh Paterson found him “very open to problem solving the connection details. We used Skype so that Steve could view our 3-D model and in real time I could show him what things would look like as we talked.”

A cloudy sky provides a suitable backdrop to the construction talking place on Queens Wharf.

The plan for The Cloud was to construct a mezzanine floor at the northern seaward end, to be used by VIPs and the media during the Rugby World Cup. There was a pause in the erection programme while the design was modified to create more legs, thereby reducing the weight per leg impacting the wharf at the mezzanine end of the building.

The cladding consists of two materials: 6,000m² of polyvinyl chloride (PVC) and 1,250m² ethylene tetrafluoroethylene (ETFE) for the see-through walls. Used at the Beijing Olympics for the Aquatics Centre, ETFE is inflammable, 95% transparent, weighs only 1% the weight of glass and extremely tough.  

Bob Hawley, Red Steel’s Managing Director, is particularly pleased with his company’s performance on this project. “It called for total accuracy, which the Tekla software and our skilled team of fabricators enabled us to achieve. But

Beside Shed 10,The Cloud is clad in PVC and will have transparent walls of ETFE.

 there were more than 3,000 laser-cut cleats of 80 x 30 x 10mm mild steel. Each one had to be drilled for two bolts and then welded by hand. In all there were literally thousands of welds but no on-site corrections.”

• Rebuilding Christchurch: The role of the steel construction industry
• SCNZ Regional get-together
• The SCNZ Excellence in Steel Construction Awards
• Steel Industry forms Sustainability Council
• Steel Focus about to Launch
• SCNZ Manager speaks at 2011 NASCC
• Introducing SCNZ newest Councillor
• Steel Advisor latest issue
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A steel girder with a web of 2.8m is loaded at Eastbridge in Napier for the 50km journey to Matahorua Gorge

advantage of sandstone was that it could be prepared for piling using hand-held compressed air tools. This obviated the need for heavy plant, which would have necessitated installing temporary concrete benches. Instead, Concrete Structures was able to install 10.5m-long reinforced concrete piles at 45º angles, in preparation for the raked piers.”

Once in place, the centre span effectively props the raked piers on either side

The design of the bridge drove not only the method of erection but also the steel fabrication. Eastbridge General Manager Andre Van Heerden says the use of long-span steel kept the structure relatively light in weight, a total of 420 tonnes. “One of the main advantages from this is that less concrete is needed to anchor the bridge piers. By eliminating a central pier, we made little impact on the environment. The steel took only 12,700 hours to fabricate and 4,800 bolts to erect. It was given a protective coating of zinc, and this allows at least 25 years to first maintenance. We are confident the bridge will have no trouble fulfilling its 100 year design life. As Ian Hills put it: Simplicity of form usually gives the best value for money. We’ve commissioned him to design our next two steel bridges, for the Eastern Highlands of Papua New Guinea.”

Minister Steven Joyce officially opened the new bridge on 11 March 2011. It will shorten the route from Napier to Wairoa and cut 12 minutes from the daily journey. NZTA’s Regional Manager Mark Kinvig says: “It will save time and petrol, but more importantly it will reduce the accident risk. Wairoa is the gateway to Te Urewera Natioanal Park. For the town’s 8,500 residents, this project will inject millions into the local economy over and above the value of its 60, 000 hectares of pine forests.”

The underside of the deck affords safe access. With a protective coating of zinc, it will be at least 25 years to first maintenance.

The elevated walkway serves as a meeting point and bridge between the wings.

Shannon Jeory was the lead ASC architect assigned to the college project. “We are currently completing Round 2 of the submission for certification. The design must be awarded points by the New Zealand Green Building Council for initiatives such as sustainable management practices both in the construction of the building and in its ongoing operation and maintenance. Other Greenstar criteria include sustainable water management, eco materials selection (the steel, for example, imported from Asia had been recycled), sustainable transport initiatives, emissions reduction, improved indoor air quality, reduced energy consumption and measures to reduce the ecological impact. All of these have been incorporated into the design of Papamoa College to a varying degree.”

The rendering of the college structure is taken directly from Buller George Turkington’s 3-D model. The ground conditions in an area of high seismic activity meant there is a potential for liquefaction. The solution was to sink 6m timber piles and encase these at ground level in concrete pads. The pads carry the normal vertical load while the piles resist the horizontal loading. Shaped like an inverted “Y’, the two storey structure has two single storey buildings that are contiguous: the nearer and larger of the two is the gymnasium and beyond this is the theatre. Roughly at the centre of the “Y” is the bridge connecting the wings via an elevated walkway.

Buller George’s project engineer was Karl Dawe. “I describe the building as consisting primarily of limited ductility moment resisting frames. The columns consist of custom-fabricated box sections, which are concrete filled for fire-rating considerations. Custom welded beams 1m deep are passed through the columns, haunched and welded, with penetrations for building services already in place. The design is a reverse of the norm that, in the event of a major earthquake, would see the interaction of strong columns and weak beams. Here we have strong beams taking on the loading while the weakened columns play a hinge role, dissipating earthquake energy to the piling.  Above the first floor, there are light-weight portal frames.”

Essentially Papamoa College has four main components: the learning commons occupying the wings of the “Y”, the bridge and elevated walkway, and the two single story buildings, the gym and the theatre. All of these have been designed to be seismically separate. In the long direction of the wings, the loading is catered for by the action of moment resisting frames. In the transverse direction, the deep, haunched beams take the load.  Both the gym and the theatre have intense steel bracing because of the sheer height of their ceilings and that ever-present possibility of liquefaction.

Papamoa College currently has 660 teaching places, expandable to 1,100 when the “Y” will grow into an “X”. Al the necessary infrastructure is already in place. It is a combined Intermediate and High School without cellular classrooms; here, learning is not subject-based but inquiry-based. Six teachers and 100 pupils occupy a single Learning Common. One piece of knowledge they will be glad to share is the fact that their school has been designed to withstand a one in 1,000 year earthquake, and remain functional after the event.

There is an elevator for students with physical disabilities. Foot traffic between floors is via these stairs.

Hawkins’ Project Manager was John Overton. “With a design/build project, you get closer to the consultants. They tackled the ground conditions with great design solutions, enabling Jensen Steel Fabricators to get cracking in their workshops, locating optional splice points and pre-assembling complex units of steel before taking them on site for rapid erection. They also expedited matters by filling the box sections with concrete to avoid pouring on site. That set the pace and nobody was going to let the team down. We came in on time and on budget. I heard Shannon Jeory say that Jensen Steel Fabricators and the other sub-contractors went ‘above and beyond’. I’d agree. Because they were mostly local, they took real Tauranga pride in their work, making this school project outstanding.”

- Upcoming SCNZ Steel Structures Seminars
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- Good Reasons to Attend Conference 
- Steel Focus is on Track   
- Steel Construction in Building Today Magazine 
- 2011 SCNZ Awards for Excellence in Steel Construction   
- Steel Advisor Latest Issue
- Updated material Supply Standards Target Product Compliance
- Metals NZ Launch at Industry Event 

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