29 July 2021

Wellington: an active earthquake engineering laboratory

Earthquakes may be a way of life for Wellingtonians, but the city has been home to cutting edge engineering developments since the 1960s that have helped keep us safe. So here are four buildings that stand out as globally significant seismic engineering designs – with the wider public that see them every day largely unaware of their significance.

Jerningham Apartments (1968)

First use of ‘capacity design’

Wellington’s post-war baby boom and predictions of enormous population growth unleashed a new generation of high-rise apartments. To the casual observer these 1960s behemoths look relatively indistinguishable, but in the world of seismic engineering the large block at 20 Oriental Terrace is a global icon.

Design work on Jerningham Apartments started in 1964, with the tall structure stepped back from the street to take maximum advantage of the town plan’s height limits. Developers Wilkins and Davies were experienced hands in the Wellington apartment market, having completed Wharenui further along Oriental Parade in 1960, and Hollings & Ferner (a relatively new Wellington engineering practice) was engaged as the project’s structural engineers.

John Hollings was interested in improving the performance of concrete frame buildings in earthquakes, which typically failed in a brittle manner as movement occurred in a single storey low down, ultimately risking a ‘pancake’ collapse. He envisaged the new development as a tall building with movement evenly distributed up the height of the structure, and flexing occurring in carefully specified areas, a concept he described as ‘lead hinges’ protecting the ‘glass-like columns’ from damage.

Jerningham’s concrete columns were strengthened considerably relative to the beams so they would not fail. The connection of the concrete beams to the columns including extra steel reinforcement to allow them to flex and dissipate energy without losing integrity during a big shake. The precision of the calculations in the era before calculators or computers was extraordinary, but Hollings was still not fully satisfied as to the performance of the junction between the floors and internal columns. He had his team build a full-scale rig at the building’s base to undertake testing at the start of construction – the design passed with flying colours.

Holling’s structure had significantly better seismic performance compared to the conventional approach proposed by the developer; it was also commercially more attractive. The revolutionary design reduced the scale of the foundations required, saving $100,000 on the original cost estimate (around $8 million today). And by opting for a low-profile floor system he had fitted in an extra level of apartments for the developer – all of which helped increase the affordability of the high-rise housing needed to accommodate Wellington’s steep population growth.

The strong columns, weak beams design philosophy sounds like common-sense now, but it was a revolutionary concept at the time. It was refined by the University of Canterbury to become known as ‘capacity design’, and is now a fundamental aspect of almost all seismic design codes around the world. Meanwhile recent property listings state Jerningham has been assessed as 84%NBS – better than some apartments a third of the building’s age.

The Beehive (1979)

First use of diagonally reinforced coupling beams

In 1951 a young refugee family arrived in Wellington, sponsored by Catholic students at Victoria University of Wellington. Tom Paulay, 27, had fled Hungary three years earlier, after his two years as a cavalry officer fighting the Red Army on the Eastern Front had put him at odds with the new Communist regime in Budapest. Paulay completed his engineering degree in Christchurch and returned to Wellington, where he spent eight years as a consulting engineer, before taking a 35% pay cut to return to the University of Canterbury as a lecturer on structural design in 1961.

1960s New Zealand was a curious mix of forward-thinking confidence and lingering attachment to the Mother Country – epitomised by plans to replace the rat-infested, earthquake-prone 1871 Government Buildings at the southern end of the Parliamentary Estate. The Parliament Building’s incomplete Edwardian design was viewed as old-fashioned, and Britain’s star architect Sir Basil Spence was engaged to make the case for something more progressive. Construction on his circular, modernist tower (quickly dubbed ‘the Beehive’) started in 1969, just as Paulay was completing his doctorate on the vulnerabilities of interlinked shear walls during earthquakes.

Paulay’s research was perfectly timed: damage from the 1964 Alaska Earthquake had confirmed his hunch that the existing approach to reinforcing the beams coupling shear walls was inadequate, with the side-to-side rocking of the building stretching these links diagonally, producing large X-shaped cracks that significantly weakened the structure. The improvement Paulay landed on was simple: introduce steel reinforcement in an X-shape to mirror the stress from the building’s movement, and allow ductile steel to take the load, rather than brittle concrete.

New Zealand’s reputation for earthquake engineering was growing rapidly – Paulay’s peers would greet him at international conferences by crossing their arms over their heads, imitating his new design. A culture of co-operation between academia, the engineering profession and government was spurred on by the 1968 Inangahua Earthquake on the West Coast, the strongest felt in the capital since 1942, and encouraged by the Ministry of Work’s enthusiasm for seismic design innovation, under Chief Structural Engineer Otto Glogau.

It began a new period where we stopped copying what was coming from California and became an innovative world-leading laboratory for seismic design.The Ministry was overseeing the construction of Parliament’s new Executive Wing, and Glogau immediately requested that the new ‘diagonally reinforced coupling beams’ be included for the remainder of the building; the circular concrete lift core was modified to accommodate the new design from Level 5 upwards.

Half a century later, Paulay’s coupling beam reinforcement design is global standard practice. Yet with the steelwork encased in concrete it’s invisible to the general public: a hidden witness to the Beehive’s place in earthquake engineering history. 

The William Clayton Building (1982)

First use of lead rubber bearings

The Wellington Urban Motorway ripped a long gash though Thorndon when it was built in the 1960s. Whole streets disappeared following the government’s compulsory purchase of properties, leaving awkward slivers of land adjacent to the roaring traffic, and too far from the CBD to be attractive to commercial developers – but the perfect location for the new Ministry of Works headquarters, which was to be named after William Clayton, the architect of the 1876 Government Building at the other end of Molesworth Street.

The building was located on the site of May Street, a cul-de-sac off Tinakori Road lost under the motorway, and would have a long, low form sympathetic to the surrounding houses. It was also 100m away from the Wellington Fault – and an ideal candidate for Otto Glogau’s interest in seismic isolation. The Department of Scientific and Industrial Research’s Ivan Skinner devised sacrificial steel dampers: then a conversation in the staff tearoom prompted his metallurgist colleague Bill Robinson to hunt out a metal with better damping qualities. Two hours later Robinson had identified lead: its low melting point could turn pressure from an earthquake into heat, it had the right crystal structure to ensure ductile behaviour at low temperatures, and was cheap to buy at a high purity for consistent performance.

Robinson’s genius lay in using the combined properties of simple materials in his revolutionary ‘lead rubber bearing’, where a lead core is contained by a ‘spring’ formed by layers of rubber and steel, which allows lateral movement. The elastic properties of rubber isolate the building from the ground movement and return the bearing to its original position once shaking has stopped, the steel plates maintains the bearing’s shape, and the lead core damps the action.

The experimental bearings were tested by a second-hand Ministry of Works Caterpillar bulldozer that was modified to power a rig called ‘MASHER’ – the Machine for Simulating Earthquakes. By 1978 the concept had been proven, and 80 isolators were despatched to the construction site at the top of Molesworth Street. The building was something of a prototype, with an overly-strong structure in case the isolators didn’t work, and too little ‘rattle’ space for the building to move in a major shake (this was later rectified by Beca).

Bill Robinson died in 2011 having spent most of his working life in Wellington. Robinson Seismic (still based in Lower Hutt) is a global leader in seismic protection devices, with their lead rubber bearings (like those visible underneath Te Papa) manufactured under licence around the world; their effectiveness has been proven by countless earthquakes. The William Clayton building was refurbished and extended five years ago: one of its 1970s vintage isolators as removed for testing by Robinson Seismic and performed like it’d just rolled off the production line.

8 Willis Street (1987 / 2021)

Breakthrough in modelling fluid viscous dampers

Older Wellingtonians will remember the partially completed steelwork of the BNZ Tower (dubbed ‘Darth Vader’s pencil box’ by Ian Athfield) during the late 1970s. The Boilermakers’ Union’s strikes turned a 48 month construction programme into 11 years, and drove up costs fourfold by the time the building was completed in 1984.

The saga contributed to the Lange Government’s labour market reforms, which in turn fuelled an economic boom. Understandably the 1980s property developers weren’t keen on steel, opting for precast concrete floors made with non-union labour. Quick to install, they were manufactured offsite, lifted into place by crane, and held in situ by the adjacent beams and the building’s structural frame – like very rigid sardines in a tin.

Today central Wellington has dozens of buildings with precast concrete floors. The 2016 Kaikoura Earthquake’s long, powerful shaking hit these structures particularly hard, with flexing in the buildings’ frames damaging the edges of the concrete units. Built in 1987 on rock and to higher ‘investment grade’ standards as Trust Bank’s new home, 8 Willis Street – opposite the BNZ Tower (now the Aon Centre) fared better than many of the CBD’s buildings from the 80s and 90s, and came through the shake undamaged.

So what makes the building next to Stewart Dawson’s Corner so interesting? Many of the structural upgrades incorporated reflect lessons learned from the Kaikoura shake – more concrete to stiffen the building, and improvements to the floor units’ seating. However the building’s new tenants will quickly spot large pistons running diagonally from floor to ceiling. These ‘fluid viscous dampers’ were first developed for NASA’s Apollo moon landers, and work like giant versions of the shock absorbers in a car, stiffening the building when it starts to move.

Compared with the simple concept of base isolation, configuring the optimum damper arrangement in a relatively tall structure like 8 Willis Street is complex. Install too many dampers and you risk creating unwanted forces in the structure; too few will leave the building vulnerable during a large shake.

Previously the modelling approach would have been trial-and-error: running different configurations through a range of historical earthquakes, adjusting the damper arrangement, and rerunning the tests. The breakthrough is engineering firm Beca’s work to automate the process to determine the best damper layout – which is then tested against dozens of historic earthquake models. This world-leading approach enables a level of evaluation that would previously have been impracticable.

The optimised damper configuration means the building, now rated at 130%NBS (IL2), has significantly increased resilience to shaking than conventional strengthening work, without the complexities of costly retrospective base isolation – unrealistic for many of Wellington’s tightly packed buildings. It has also paid a large sustainability dividend, with the materials used in construction substantially reduced and thousands of tons of concrete retained, rather than sent to landfill – demonstrating a low carbon way of delivering high performance structural retrofits.

First published in Capital (Issue 77). Illustrations by Kumiko Matsumoto.

11 April 2021

Concrete dreams

The rise of private car ownership, the baby-boom and post-war reconstruction were catalysts for drastic urban planning interventions around the world, a fashion that inevitably reached New Zealand. Metropolitan Wellington’s population increased by 63% in the space of two decades from 1945 – and was projected to reach 398,000 in 1981 (wildly inaccurate – this did not happen until 2014).

This growth, largely concentrated in the Hutt Valley and Porirua, was a headache for planners, but it also gave the civic leadership confidence to invest. It stimulated a decade of radical proposals for the capital, and came close to destroying much of what Wellingtonians now love about the city.

Comprehensive Transport Plan for Wellington (1963 / 1966)

By the late 1950s rapidly increasing traffic volumes on the Hutt Road (comparable to Adelaide Road today) caused a fear of gridlock, and work on the first part of the Urban Motorway from Ngauranga to Aotea Quay started in 1959.

There was bitter debate about the next phase of the road, between a ‘foothills motorway’ route through Thorndon, and one along the waterfront – the latter preferred by the City Engineer and the Ministry of Works. In 1960 American transport consultant De Leuw, Cather & Company was commissioned by the Wellington Regional Planning Authority (a predecessor of the Regional Council) to resolve the matter and create Wellington’s first Transportation Master Plan.

Despite its being the cheaper option (at £13,000,000 cost – close to $570 million today) the initial report in 1963 made the waterfront route look as unpalatable as possible. Projected traffic volumes would require ‘a double-decked structure approximately 40 feet [four storeys] in height with three lanes in each direction’. This would have run from Bunny Street to Cable Street, with offramps required at Kings Wharf, Post Office Square and Mercer Street. The report warned of conflict between the motorway and what was still a working inner harbour, and the impact on the amenity of the waterfront, pointing out how quickly San Francisco’s officials had come to regret building their new freeway above the Embarcadero.

The foothills route was duly recommended, even though it was projected to cost almost 50% more and need streets of houses demolished, with the Mount Victoria tunnel to be duplicated during the first phase of works. The time required to dig the Terrace Tunnel meant Te Aro would need a one-way system to speed up traffic (half a century later the Council has voted to slow traffic down), with southbound vehicles routed up Cuba Street.

Public transport was also considered, with a recommendation that once the motorway was completed the railway should be extended in a 3km subway to the end of Courtenay Place – with underground stations at Parliament, Lambton (located under Boulcott Street), Cuba Street and Courtenay Place – all for £11,000,000 ($480 million in 2020).

As proposed the complete the motorway would have buried half the Basin Reserve under motorway offramps, a deep trench cut across the top of Te Aro and a ‘full-diamond interchange’ at Taranaki Street – designs familiar to Wellingtonians who successfully defeated the Tunnel Link proposals a quarter of a century later.

The focus on roads alarmed Wellington’s retailers. They feared that greater mobility would send shoppers to more convenient destinations outside the city, and commissioned a rival proposal from architects Gabites and Beard. ‘Precinct Planning for Wellington’ (released in 1965) had some bold predictions, with ‘public transport vehicles running on air cushions rather than rails’ and ‘combined air and ground vehicles in general use’ by the year 2000. But the pedestrianisation of large parts of the CBD, rather than a focus on cars, proved popular with Wellingtonians, and this influenced the final version of the Comprehensive Transport Plan in 1966, including retaining the Basin Reserve.

Draft Town Plan (1965)

With the transport masterplan complete the City Council was free to focus on transforming the CBD. In 1957 Robert (‘Terry’) Kennedy arrived at University of Auckland to take the first Chair of Town Planning. He was retained as a consultant by Wellington City Council from 1965-75, and the 1965 Draft Town Plan clearly reflected his previous job remodelling Britain’s blitzed cities.

Some ideas were developed from the De Leuw report and ‘Precinct Planning’, including Cuba Mall, and the Farish Street Extension which pushed Victoria Street through to the top of Te Aro – to feed a future Western Suburbs motorway running through a tunnel from the top of Aro Street to Karori.

The plan was also critical of central Wellington’s small commercial plots and streets laid out for the era of deliveries by horse-drawn vehicles, now resulting in increasing conflict between vehicles and pedestrians. European cities were able to ‘take advantage of’ extensive bomb damage to unleash ambitious redevelopments – and Wellington was to follow suit with the ‘Willis Street redevelopment area’, a three tier ‘superblock’ similar to London’s Barbican, to tackle ‘the bottleneck between Stewart Dawson’s corner and the sea’.

The development would have been enormous, stretching between the top of Plimmer Steps and the waterfront. The existing street layout was to be maintained but built over, with garaging and warehouses at ground level, and car parking above them, accessed via ramps from Jervois Quay and a Willis Street flyover connecting Victoria and Boulcott streets. Above that to be a pedestrian deck, with shops, offices and hotels.

The sheer chutzpah of the Town Planning Committee’s report was admirable: the Willis Street superblock was ‘economically feasible’ and would ‘rehabilitate the centre of Wellington’ in combination with the proposed Civic Centre and new Cuba Mall. The City Engineer pointed out to doubters ‘this sort of integrated development is already taking place in larger cities overseas’.

The project stumbled at the first hurdle: the population growth projection was criticised as overly optimistic (a failing among Council officials), and the indicative £50,000,000 cost ($2.1bn in 2020) was seen as wildly unaffordable. Councillor Turk called the proposal ‘a Utopian flight of fantasy’ – and by the mid-1970s Kennedy’s departure from WCC’s payroll and the city’s stagnation meant the idea mercifully faded into the long list of municipal what ifs.

Report and Development Plan for the Wellington City Council Civic Centre (1974)

The idea of a municipal precinct dates back to the 1942 Wairarapa Earthquake, which led to the demolition of the old city library building and technical college buildings on Wakefield Street – now the site of the Council’s closed Civic Administration Building and empty Municipal Office Building (or MOB). Work started on MOB in 1946, and the popular lawn in front of the building was referred to as the Civic Centre.

The Council had gradually acquired land at the harbour end of Cuba Street from the 1960s, and the section of Mercer Street between the Town Hall and Central Library was often closed for civic festivities, so it was a small leap of imagination to pedestrianize the space. Terry Kennedy and Ken Clarke (the council’s City Planner) embarked on a scheme to banish vehicles and create a ‘true and pleasant centre of the City of Wellington’.

The masterplan that emerged had all the hallmarks of European post-war design. The demolition of the seismically prone Town Hall would clear the way for a decidedly Soviet looking 10,000m² office building; a conference facility was to be built on the corner of Harris Street and Jervois Quay; and pedestrian subways would give access to the waterfront and the new shopping arcade that was to be built over Mercer Street through to Willis Street. Kennedy realised changes in opinion and finances would alter the plan, but he suggested a 15 year development programme – the new library and conference centre were to have been completed by 1986.

Instead Mayor Michael Fowler championed the construction of the new concert hall: it was commissioned in 1975, but the challenging ground conditions delayed work. The building was opened in 1983, by which time campaigns to promote the heritage and acoustic value of the old Town Hall had made its removal untenantable, leaving the two buildings uncomfortably close to each other. The waterfront had been transformed from potential motorway route to an increasingly popular open public space – and a rethink for the precinct was required.

While the development Kennedy proposed would have been built at the height of Brutalism in New Zealand, some of the core ideas from the 1974 masterplan shaped today’s Civic Square, including turning the 1937 library building into a ‘City Gallery’. This stimulated the council in 1980 to create exhibition space at 65 Victoria Street, before demolishing the building and using the site for the new Central Library (another Kennedy recommendation). Interconnected elevated walkways linked the library and council buildings – until they were deemed seismic risks earlier this decade – and the space enjoys good sunlight.

Kennedy died in 1997, with his superblock vision for Wellington’s civic precinct largely realised, and especially the underground parking and wide pedestrian expanses. With the Civic Administration Building likely to be demolished, perhaps the lawn in front of the municipal offices which coined the precinct’s name could be restored – bringing the Civic Centre concept full-circle?

First published in the Summer 2021 issue of Capital.