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.”

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.”

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.”

Five teams were selected to take part in the competition, among them Sinclair Knight Merz (SKM), who had engaged Wellington-based Tennent Brown Architects, for architectural design and to support the SKM Environmentally sustainable Design integration into the project. The site is at Cobham Park at the head of Evans Bay, near Wellington Airport. The ground here is reclamation fill with poor bearing capacity; under high seismic loads it is subject to liquefaction.

The solution that won the competition for SKM and Tennent Brown was presented as a gateway to Wellington building consisting of a two-chamber ovoid layout with a splayed central spine, column-free over the playing courts and encircled by a breathing, see-though wall system of precast panels. Over the top is draped a curved and faceted roof resembling the wings of a stingray.

John Mason, leading SKM’s structural team, says a box solution would have been excessively imposing at this very large scale. “The building is 12,500m2 and needs to be able to resist wind uplift and also maintain its integrity during a major earthquake. We defined the interaction between the substructure and the superstructure and separated these elements through articulated pin joints. These allow the expected seismic settlements to occur differentially across the footprint of the building, without causing catastrophic failure to the superstructure. By adopting this approach, we were able to use relatively modest reinforced concrete pads, because these will adequately resist wind uplift while transmitting the gravity loads.”

The roof structure consists of long-span prismatic roof trusses (also known as bowline or fish-belly trusses) that are supported on tapering elliptical columns. The columns are also cranked. Hugh Tennent and Ewan Brown, directors of Tennent + Brown Architects, comment: “They are like figures reaching into the upper space of the two chambers. They shorten the span of the main trusses without interfering with the height requirements of the sporting codes, and assist in compliance with the low height required by Wellington Town Planning,. We wanted the columns to taper so that they got smaller towards the pinned connections of the trusses and also towards the floor. As an expression of the forces involved, architecturally it looks right. The SKM designed steel structure provides the defining character for the vast interior. The structural design team has produced an elegant solution in both concept and detail addressing extremely demanding joint arrangements”

Extending along the centre of the building is a spine structure that contains the main vertical and horizontal load paths for the middle section. Within this form is a mezzanine structure that has been seismically separated from the main superstructure. There are administrative areas and meeting/social spaces at the southern and northern ends. The link between the two ends provides an elevated viewing perspective. On the flanks of the building, the support columns reflect the spine structure for the transmitting of loads. They also allow for the curved façade of the building.

Hugh Tennent and Ewan Brown again: “The staggered precast panels have automatic glass louvres between them, allowing the building to breathe. Passers-by can see in while players can see out. Above each of the bowline trusses designed by SKM are roof-lights that allow the courts to be naturally lit, making for large savings in power when the lights aren’t needed. The building is also naturally ventilated thus sustainability is inherent in the design concepts.”

The Kalzip composite ceiling and roof system, developed by Corus (now Tata Steel), has been assessed as optimal for the centre, given its aggressive coastal environment. A total of 12,257m2 is required. First to go on is the lower sheet of aluminium, then three layers of insulation of varying densities, and lastly the difficult top sheet of continuous, cold-rolled aluminium formed in the air and zipped up from a high-level scaffold.

This is the first time that Kalzip has been used for roofing in New Zealand. It delivers high quality thermal and acoustic insulation, with little or no maintenance needed over its expected 70-year life. That represents a saving of around $22-million over conventional roofing over the course of the building’s lifetime. Kalzip is made from 60% recycled content, and at end of life 90% can be recycled again.

Main Contractor, Mainzeal Property & Construction Ltd’s Senior Project Manager Mike Prince, says: “On the structural steel side, MJH Engineering has been magnificent. Malcolm Hammond and his team have done a lot of work for us in the past, but nothing that matches this high level of complexity. Those elliptical columns had all to be split down the middle from top to bottom, fitted with backing plates and given full-strength welds. Now we’re cracking along at the rate of an 11m bay in a week in one chamber, and the same again the next week in the second chamber.”

Wellington City Council’s Senior Project Manager, Jim Coard, says that for indoor sports facilities to be successful, they must ultimately provide an environment that people enjoy, while at the same time meeting the functional needs of the users. “Multiple sports groups will be able to use the venue simultaneously. The centre will also give Wellington a greater chance of securing regional, national and international sports tournaments.”

The double-quick construction programme saw the learning pod erected efficiently.

In January 2009 Naylor Love Construction was confirmed for the design/build contract for the new school. Although it was agreed that there was very little chance that the school would be finished by the end of the year, the Ministry of Education made its expectation clear: the new school was to be in a position to accept new entrants for the first term of 2010.

Naylor Love called the first design meeting towards the end of January, inviting Babbage Architecture and other consultants it had engaged before, knowing their ability to fast-track the design so that earthworks could be started in April. To make the co-ordination of design and plans more efficient, Babbage Consultants was sub-contracted as the structural engineers on the project. It was agreed that a three-stage building consent process was needed to get construction underway. This allowed time for the detailed design to be completed for full consent, which needed to be lodged and approved before work could begin on the building envelope in July. John Jones Steel was confirmed as the structural steel and Comflor decking system sub-contractor.

ComFlor 210 forms the decking system.

Remarkable People – Nga Iwi Tumeke”. Architect Michael Bilsborough, who is very knowledgeable about education design, said the Board had a very clear vision of the sort of school they wanted to create: Remarkables Primary School aims to provide world class education to equip and inspire each student to take full advantage of life’s opportunities.

“When we research current education practices,” says Michael, “we find that they place great emphasis on the importance of self-directed learning. The teacher’s modern role is that of facilitator, allowing their pupils to discover knowledge for themselves as individuals. This in turn requires the architect to provide the spaces needed for different individual activities. Hence, camp-fire space, for story-telling; watering-hole space for social collaboration; and small cave spaces for intimate, one-on-one encounters and conversations.

Babbage Structural Engineer Victor Lam says that after examining the seismic considerations of the Frankton site, the Ministry of Education decided to increase the design loading by 30% to achieve a return period of 1,000 years. “In concrete, this would have made the school

The entrance from Lake Avenue to the rooftop walkway.

 buildings excessively heavy. Instead, our design concentrated on steel, relying on the ductility of Eccentrically Braced Frames (EBFs) and the long span properties of Comflor 210 steel decking to keep the structures and the floors as light as possible. ”

Manager, Peter Taylor, comments: “Having worked with John Jones Steel extensively throughout the South Island, we were confident that they had the resources required to meet our very demanding programme and deliver a quality product at the same time. They staged their shop-drawing process to suit our compressed time-table, and they worked proactively with our design engineers to restrict draughting errors. They were also very quick to tell us about potential cost savings. I have to say that their steel detailing and quality assurance documentation were of the highest standard, while the care that they took during the erection process contributed to this project being one of the most stress-free that Naylor Love has been involved with.”

The fabrication was done in the John Jones Steel Timaru workshop. The 3-D model drawings were produced in X-Steel, a Tekla software product, in the company’s Christchurch headquarters. General Manager Dave Anderson reports: “The dialogue between our detailers and the Babbage Structural engineers generated efficiencies and enabled us to progress rapidly with the Comflor 210 (deep profile) decking. At one stage we were a fortnight ahead of the design review. It helps when the main contractor is a company of Naylor Love’s calibre. Liaison with the client and the sub-contractors is always close, with the objective and the deadlines clearly defined and the methodology agreed up front. That this project was delivered on time and within budget is largely the result of Naylor Love’s highly organised approach.”

Between the cedar wood-clad library and the first learning pod, the reading court.

Christchurch-based Murray Aitken, currently the Ministry of Education’s Senior Advisor on Education, Curriculum and Performance, says the school buildings fit the landscape very well. “The low-level profile from the Lake Avenue entrance is an attractive feature of the design that keeps the lake views for the surrounding properties pretty much intact. The design is inspiring, inclusive and welcoming, not imposing, and the indoor spaces connect with and flow naturally into the outdoor areas. Remarkables Primary is a school where pupils and teachers are able to witness learning as it happens.”

Acting SCNZ Manager Alistair Fussell visited Christchurch to meet with some of the local steel constructors to record details of any such repair work and also to inspect first hand a range of steel structures in the region that had been subject to seismically induced ground motion. The observations made in this article are based on the author’s inspection of a limited number of steel structures which consisted of several low rise industrial buildings in the Rolleston area and a couple of multistory eccentrically braced buildings at different locations in Christchurch. The author’s own observations have been supplemented by information provided by local steel constructors.

The epicenter for the magnitude 7.1 earthquake was located approximately 40 km to the west of Christchurch near Darfield. The initial earthquake which was of relatively short duration, 40 seconds, resulted in up to 4metres sideways movement between the two sides of the fault near Darfield. While seismologists use a magnitude scale, which is a measure of the energy released by an earthquake to quantify earthquake events, this is not a good measure of how potentially damaging the earthquake motion is at a specific site to buildings. Structural engineers are more interested in the peak accelerations induced in the ground by the earthquake event. The reason that the ground acceleration is an important parameter is that the forces acting on a structure during an earthquake event are related to the ground acceleration. You will have experienced this phenomena if you ever have tried to stand in the aisle of a bus when it is accelerating from a standing start or breaking before coming to a stop. The direction of the force you experience is dependent on whether you are accelerating or decelerating. Similarly if you drive a sporty car and you have accelerated quickly from a standing start you will find yourself pinned to your seat. Simplistically this is what a building experiences when the ground beneath it is accelerated by earth motion generated by a fault rupture.

Wall collapse—unreinforced masonry building.

A feature of the peak ground accelerations experienced in the Canterbury region is how quickly they reduced away from the earthquake epicenter. The peak ground accelerations in the city centre were in some cases only 20 to 30% of those experienced in the Darfield area. A measure commonly used to quantify earthquake ground accelerations is to quote them in terms of percentage of gravity or gravitational acceleration. If you drop an object it will be fall with an accelerate of 1g or 9.81 ms^-2. Car manufacturers like to quote the time taken to accelerate a car from a standing start to 60 miles an hour (100 km/hr) as a measure of performance. If a car accelerated at 9.81 ms^-2 or 1g, it would reach 60 miles per hour in 2.83 seconds. A Porsche Turbo 911 according to manufacturers data will take 3.4 seconds to achieve 60 miles per hour (0.83g) while the average family car will achieve this speed in the more sedate time of 7.1 to 9.4 seconds (0.3-0.4g). The peak ground accelerations in the Darfield area were nearly 1g while in Christchurch City they were in the order of 0.2 to 0.3g.

Initial reports from the Canterbury region indicate relatively modern commercial buildings in the Canterbury region have performed well with no major structural damage or collapse. The older unreinforced masonry buildings have not fared so well with a number of building so seriously damaged they have already or will have to be demolished and also a number of residential buildings have suffered significant damage due to soil liquefaction. The good performance of modern buildings while pleasing when compared to the recent Haiti earthquake of similar magnitude where hundreds of thousands of people may have perished is to be expected as preliminary findings indicate the earthquake induced actions in the structures for the most part were below the levels required by the New Zealand Loadings Standard (NZS 1170.5).

While there was no major structural damage to modern buildings, there was still significant non structural damage to ceilings, furniture, wall linings and roller shutter doors etc.

Consistent with regional peak ground acceleration records which indicate high ground accelerations (70%g) in the vicinity of Rolleston; there is evidence of yielding and permanent stretch of wall and roof rod bracing in low rise industrial buildings in the area. After the event rod bracing required re-tightening and in some cases the connections of proprietary tension only brace systems failed and needed replacing. While none of these connection failures led to collapse of the structures this is not a desirable mode of behavior for tension only braces.  The cause of failure being the stripping of threads of the screw in connection detail.  Christchurch does not have a large number of multistory steel buildings. These range from several to 22 storeys. Consistent with the variability of ground shaking, there was evidence in one structure of limited yielding of some of the active links while in other buildings the structure appears to have responded elastically. Structures are typically designed for some yielding in designated locations, such as the links of eccentrically braced frames to reduce the design loads the structure must resist. This is known as designing for ductility. These yielding regions act in a similar manner to a fuse in a circuit, they limit the demand on the rest of the braced frame by yielding at a given load level. In the process of yielding they absorb earthquake energy. All these buildings were back in service after the earthquake and have performed as expected during the subsequent aftershocks. An interesting observation from one of the multistory buildings was that there was evidence as suggested by  cracking in the slab over the support beam, that the earthquake had caused vertical motion of cantilevered metal deck flooring.

There was also some spalling of concrete around cast in bolts and plates connecting structural steel to precast concrete elements.  This damage to non-seismic connections is due in part to a lack of connection flexibility to accommodate the interstorey displacements that occurred during the earthquake event.

A meeting organized by Gavin Lawry of Pegasus Engineering was convened with local SCNZ steel constructor members to debrief on what had happened to steel structures in the region during the recent Darfield earthquake. In total 17 people attended the meeting. SCNZ Acting Manager Alistair Fussell opened the session with a brief overview of the seismological data for the earthquake. South Island Manager for Reid Construction Systems Peter Johnston provided a manufacturers perspective on the performance of their proprietary rod bracing system. After this there was an open forum where members could discuss their post earthquake remedial activities. As previous mentioned this consisted of tightening stretched rod bracing, replacing a small number of proprietary rod bracing system connections and replacing some loose bolts in cover plate portal frame rafter splice connections.

Our thoughts are with our Canterbury members who have experienced a very difficult time in the past month with the initial earthquake and the numerous aftershocks. The assistance of Canterbury Steel Constructors Chris Chapman of Chapman Engineering and Gavin Lawry of Pegasus Engineering is acknowledged; Gavin for organizing the members meeting and Chris for giving up a morning to take me to visit a number of low rise building projects in the Rolleston area. The assistance of Dr Charles Clifton in providing earthquake seismological data and some of the photographs is also acknowledged.

What remained after the completion of Stage One of the airport upgrade was a mere 1,000m² pocket of a site, defined by the existing buildings and a fuel compound to the North. What was required in the brief to architects Studio Pacific and Warren and Mahoney, who teamed up to respond, was a design that would be unapologetically “edgy”.

Marcellus Lilley (Studio) and Rodney Sampson (WAM) talk about their daring, even provocative, concept: “We took our inspiration from Wellington’s wild south coast. From a photographic study of the geomorphology, we extrapolated features and scale, the fissures and raking geometry, into the design development of the building form. In marked contrast to the blandness that typifies most international airports with their mall-like interiors, we wanted a geological theme with a rugged personality, yet one which would at the same time be a haven of warmth and calmness, with carefully crafted views from safe vantage points.”

In fact The Rock is comprised of three parts: the Nose, which is nearest to the runway; the Main Rock, which is closest to the existing terminal; and the Ramp, which is adjacent to the Main Rock. From the Nose, passengers have a spectacular view of aircraft docking at the aerobridges, seen as if from inside a giant boulder. In the Main Rock, there is ample seating for travellers to rest, quiet space on the mezzanine floor and a play area for children, while the Ramp serves as a conduit for arriving and departing passengers.

Structural Engineer Peter Holden of Beca comments on some of the challenging geometry presented by The Rock: “The ground floor and first floor are concrete, which supports portal frames. These have varying geometry and shape to create the form; no two portal frames are the same and there is a wide range of steel sizes and connection types.

“The Rock was one of the first buildings in New Zealand that Beca modelled three-dimensionally using Revit software, which enables us to produce structural drawings from a 3-D model. However, because of the irregular shape of the building, it was impossible at the design stage to foresee all of the clashes that could occur between the steelwork, timberwork and services. This is where the steel contractor, Stevensons, helped resolve matters by allowing its detailed 3-D model to be imported and merged with the drawings of the follow-on trades. By successfully conducting clash checks, Stevensons ensured that potential problems were identified and either rectified or eliminated even before fabrication.

“The unique shape also meant that generic details developed during the design phase could not be used in all situations, necessitating a high degree of specific design. For example, no fewer than four support options were required for the triangulated ceiling panels to node correctly. In addition to the construction of the new building, modifications were made to the existing terminal. In some cases the steelwork details weren’t known until sections of the existing terminal were broken out. Meanwhile, there was also the challenge of ensuring seismic interaction between the Rock structures and the existing terminal, with different shapes and stiffnesses coming into play. But I have to say it’s been a great experience to work on what will surely be one of Wellington’s landmark buildings.”

That certainly was the view shared by Evan Kroll, Managing Director of Stevensons Structural Engineering (1978) Ltd. “When we first looked at this project, we saw that it was unique and expected it to be problematical. As our steel detailers worked with the architects’ 3-D model to produce all the dimensions and angles in Pro-Steel, we began to realise that what seemed like an enigmatic design was going to turn out to be iconic. This wasn’t a series of ho-hum portal frames but a complex, angular structure that asked a lot of us and made us work hard to solve the buildability challenges.”

The Stevensons team attributes at least 50% of its success to the strength of its drawing office and the leadership given by its Manager, Peter van der Made. “Because we had superb co-operation from Beca (whose Revit model made things so much easier), from the main contractor, Mainzeal, and from the architects,” says Peter, “we had clear understanding of what everyone wanted. We were also able to tap the practical experience of our detailers, who  know what dimensions are required and where they should be shown. The shop drawings that they provided to our fabricators led to excellent productivity.” They had to, because of the need for accuracy in the workshop. Once the steel was delivered to the site, there would be no room for even minor adjustments. The site, after all, was a fully operational international airport: it had no room for error.

“Check it twice! Check it again but do it once and get it right!” That’s the mantra of Stevensons’ Production Manager Troy O’Donoghue, 13 years with the company. “Even before we despatched our first delivery, we conducted a test erection in our workshop to get our heads around how a section of the structure would go together on site. Once we felt comfortable, then it was a matter of stringent quality assurance. There were angles for Africa and full-penetration welds of plate 40-50mm thick. Our top guns had to be at their best. And then there were the transport logistics. Because the steel members were not symmetrical, each truck load had to be specially configured. That’s how we ensured that the project ran smoothly. It starts with good drawings and is followed by accurate fabrication, planned transportation and speedy construction – with every member of the team staying alert to everybody’s safety.”

The biggest safety concern was the possibility that building debris might be left air-side, close enough to aircraft  to pose  a threat. “Mainzeal Property and Construction Ltd put a raft of processes in place to minimise every risk,” says Graeme Anderson, Project Manager for Wellington International Airport Limited (WIAL). “Mainzeal worked well with our airside staff to ensure there were no issues.

‘In the count-down to the official opening, (date to be confirmed), various visitors to The Rock are clearly delighted by what one can only describe as the WOW! factor. WIAL is equally delighted that The Rock makes such an impact, as we believe that it expresses Wellington’s individuality. Although only the final component of a two-phase upgrade to our international terminal, it doubles our international processing capacity while at the same time making the visitor experience memorable. Word-of-mouth is powerful and it will probably say we’re trend-setting.