The CTV building was born in 1984, when development company Prime West Corporation bought three adjoining sections on the corner of Madras and Cashel streets. Two years later it approached a building company, Williams Construction, about leading a speculative design-build on the site. It wanted a structure that was functional, presentable, and as cheap as possible. Williams managing director Michael Brooks came up with the idea of putting the lift shaft outside the floor plan, maximizing the lettable floor space. Christchurch architect Alun Wilkie was engaged for the design. His client liked the look of a four-storey building on the corner of Durham and Armagh streets, with an offset core, precast concrete spandrel panels, circular columns, and inset glazing. It would be good if the new building looked similar.

CTV was based on the look of the Contours building on Durham St, Christchurch.

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To engineer the building, Williams turned to Alan Reay Consulting Engineer (ARCE). Brooks and Williams’ quantity surveyor Tony Scott had worked with the company on another project and liked the standard and presentation of the drawings. The firm’s principal, Alan Reay, would also provide preliminary drawings for costing purposes at no charge. Reay was a man with a growing reputation. He held a Bachelor of Engineering and a PhD in civil engineering from the University of Canterbury. By the mid-1980s he was prominent designer of low-rise tilt-slab buildings and their production systems. His standing grew further in the 1990s, when he became the first non-American to be awarded for engineering achievement by the Tilt-Up Concrete Association of America. In 1995, he was the engineering advisor to the commission of inquiry investigating the collapse of a viewing platform at Cave Creek on the West Coast, which killed 14 people.

Alan Reay has been a highly-regarded engineer in Christchurch since the 1980s.

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The CTV job would fall to an engineer named David Harding. Reay didn’t have much experience in designing multi-storey buildings and the only engineer at his company who did, John Henry, had abruptly left. Harding had previously worked for Reay in the late 1970s, but left to do civil engineering work. He had never designed a multi-storey building but was keen to broaden his knowledge in the field. Here was a way to do it. He rejoined ARCE in November 1985. “They say you should never go back,” Harding said later, “But I made the mistake of going back.” Harding started work on the CTV project in March 1986. His design, based on the client’s wishes and Wilkie’s drawings, was a shear wall protected gravity load system. This meant that in an earthquake the lateral forces from the shaking would be absorbed by a shear wall, or walls - the strongest part of the building - while the columns that held up the structure were designed to do pretty much just that. The columns were attached to reinforced concrete beams, which in turn supported the floor slabs. In engineering parlance, it was an “eccentric” design because the centre of rigidity and strength - the shear wall - was not at or near the centre of the building. The shear wall was on the north side, outside the floor plan altogether, along with the lift shaft and stairs, just as Brooks had suggested. Because of this, and the fact that the building was more than four storeys high, it was a code requirement to conduct computer analysis to measure earthquake loading. To do this, structural specifications were fed into a program called ETABS, which produced a reading of inter-storey deflection (how much the floors would move laterally in an earthquake). The first time Harding ran the numbers, ETABS predicted deflections greater than what was allowed under New Zealand building standards. Harding increased the wall thicknesses and ran it again. No change. After four or five unsuccessful attempts, he went to see Reay.

David Harding had never designed a multi-storey building before CTV.

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The two men discussed the problem and settled on a solution: a second shear wall on the south side of the building. Until then, the design had been relying only on the north shear wall for earthquake strength. Adding a south shear wall was not straightforward. There was already a firewall there, and the upgrade would have to allow for access to the escape doors and stairs. This meant the new wall would be coupled - split in two and connected by steel beams. Harding ran ETABS again with the new design. It came back with deflections inside the allowable limits.

CTV: Who’s who

Harding’s difficulties had not been helped by his lack of experience with ETABS. With no history working on multi-storey designs, he had never had to use it. His only experience with the program came a couple of months earlier on a project for which Henry had done the bulk of the work before he left. Because of this, Reay gave Harding the file for Landsborough House - another building Henry had designed that was similar to CTV - complete with ETABS calculations his new engineer could use as a “method template”. Harding did so, but his inexperience led to a crucial error. ETABS was a rudimentary program. The deflection data it produced was for a single point at the centre of mass for each storey of a building, not the corners, where movement would be exacerbated. An engineer running ETABS on eccentric buildings like Landsborough and CTV would have to calculate their centre of rotation - which would be somewhere other than the physical centre of the building - and use that point to work out likely deflections at the corners. Henry’s Landsborough file contained extensive notes, but nothing about calculations for corner deflections. Harding didn’t do any, which meant he had numbers telling him the floors in the building would move less in an earthquake than they actually would.

An eccentric building like CTV would move more at the corners than the middle in an earthquake.

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Once ETABS analysis was complete, Harding and ARCE draughtsmen went to work on detailed structural drawings. By the end of the year Harding had logged more than 300 hours on the project, all the while thinking his work was being reviewed by his boss. It wasn’t. Reay thought Harding was up to the job; Harding thought Reay was shepherding him through his first full multi-storey design project. Neither of those things was true, and the end result was that when the drawings were submitted to the Christchurch City Council as part of a building consent application, the engineer who reviewed them didn’t like what he saw.

The application was lodged on July 17, 1986. It was common practice in the 1980s for developers to submit incomplete paperwork to get the ball rolling on consent for a project, and CTV was no different. The council didn’t receive the structural drawings until August 26, and even then they weren’t finished. City council engineer Graeme Tapper responded in writing to ARCE a day later requesting a copy of the calculations supporting the design and outlining numerous omissions in the drawings. One stood out: “Floor connection to shear wall system and general connection between floor slab and walls.”

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Tapper was a meticulous man, but even by his standards this was a long list. Anything less, though, would have been out of the question. Tapper had little tolerance for substandard work. He held strong views, was happy to share them, and reluctant to change them. He periodically had blazing rows with his boss, buildings engineer Bryan Bluck, when they disagreed on a job. Around the ARCE office, Reay referred to him as “Colonel Tapper”. If he ever needed to talk to someone at the council he would deal with Bluck, whom he had known for years.

Graeme Tapper

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The additional calculations and amended drawings were provided to the council nine days after Tapper’s letter. Five days after that the city engineer signed off on the application on behalf of the council’s structural unit. During that time, the CTV building had turned into a battle royal for Tapper and Bluck. Tapper wasn’t happy. He broke the habit of a lifetime and told wife Pat of his concerns about the building’s earthquake risk and the “huge pressure” from Bluck to sign off on the design. He went on and on about it. It was “not a question of if,” he said, “but when”. “When it happened he was concerned the CTV building would not prove to be strong enough,” Pat Tapper said.

News spread through the engineering fraternity. West of the city, Riccarton Borough Council engineer Peter Nichols, formerly a city council engineer, heard about a Tapper-Bluck run-in that was particularly caustic, even by their standards. A few months later, while in the central city, he made a point of visiting the construction site at 249 Madras St to see what all the fuss was about. As Nichols stood on the Cashel St side of the building, he bumped into his old boss, who was taking his midday walk. Bluck told Nichols the building had a “novel technological approach” with two non-symmetrical shear walls. The design initially worried him, he said, but his fears were allayed after talking with Reay. Whatever was discussed in Bluck’s conversation with Reay, it wasn’t enough. Despite the extra calculations and drawings from ARCE, the CTV design was still under code, including the connection between the floor slabs and the north shear wall Tapper had mentioned in his letter. The building shouldn’t have got a consent, but it did. Williams quantity surveyor Tony Scott costed the project at $2.45 million.



The 1986 building permit for 249 Madras St.

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Construction on the CTV building began in late 1986 and did not get off to an auspicious start. Site foreman Bill Jones found it hard to get good workers. Some were hired on a daily or weekly basis, and retained depending on whether or not they were any good. Jones himself was accustomed to smaller projects - light timber structures up to three storeys - and had never managed a design-build contract. He was used to having a clerk of works on site for guidance. Williams was in expansion mode, and Brooks decided to hire a construction manager. The new man, Gerald Shirtcliff, had an engineering background and had worked in Australia and South Africa. He was expected to provide daily oversight and guidance to Jones and the foremen on Williams’ other projects. In fact, he visited the CTV site about once a month. “He just wasn’t up to the job,” Brooks later said. Council site inspections to monitor standards were sporadic too. Between April and August 1987, there were none at all. To complicate things further, Williams was the subject of a takeover bid about the time construction started, and was sold by early 1987. Brooks, Scott and Shirtcliff resigned and formed a new company, Union Construction. Union took over the CTV job and completed the build in early 1988. It later became insolvent.

The CTV building under construction.

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The speculative design-build project sat empty for two years before a prospective buyer emerged in the Canterbury Regional Council (later Environment Canterbury). The council hired engineers Holmes Consulting Group (HCG) to inspect the building as part of the pre-purchase review. Senior engineer John Hare was handed the job and examined architectural and structural drawings to make a seismic analysis. He quickly identified the same problem Tapper did - the ties between the floors and the north shear wall didn’t meet the code. “There appeared to be no connection detailed for the walls on either side of the lift shaft,” he said. The north wall complex was “punctured” by the lift shaft and stairs, leaving few floor-wall connections. In the event of an earthquake, Hare said, the building would “effectively separate from the shear walls well before the shear walls themselves reached their full design strength”. Hare visited the ARCE offices, now trading as Alan Reay Consultants Ltd (ARCL), to tell them about the problem and the need for potentially expensive remedial work. Harding had left the firm, but Reay and engineer Geoff Banks agreed the connections were non-compliant. “A straight blunder,” Reay said. To double check nothing had been added during construction, Hare and Banks inspected several floors of the building with a tool to locate structural elements. They found no significant reinforcement. Soon after HCG sent its report describing the connection problem to the regional council, its services were no longer required. A $14,000 quote for remedial work also went no further. The council would not be buying the building. It was left to Reay and Banks to remedy the situation. Prime West was in receivership so they contacted receivers KPMG Peat Marwick to notify the owner of the problem and confirmed the scope of remedial works with HCG. Hare had not identified any other compliance problems. “[The building] generally complies with current design loading and materials codes,” his report read. That was good enough for Banks and Reay, who did no further structural assessment.

Structural engineer John Hare identified design flaws in the CTV building in 1990.

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In fact, no-one did much of anything for about a year. Reay kept an eye out when he drove up Madras St in case it looked like anyone was moving into the building, but otherwise nothing was done until a story appeared in The Press on February 4, 1991, reporting that the property had been sold. ARCL took legal advice and resolved to contact the new owner - Madras Equities Ltd. It sent the company a letter in April 1991 notifying it of the problem. Then nothing happened for another five months. Finally in October, steel drag bars were fitted on levels 4, 5, and 6, reinforcing the floor-shear wall connection. ARCL should have applied for a permit for their installation, but didn’t. It was a missed opportunity. Although Tapper identified the floor-wall problem at the design stage, a consent application for the drag bars to shore up a non-compliant connection would have brought the issue to the city council’s attention in even starker terms.



The retrofitted drag bars were ripped apart in the collapse.

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