THE Canterbury TV building that was destroyed in the February 2011 Christchurch earthquake, killing 115 people, should never have been approved, a royal commission report into the collapse has found.
The 300-page report by the Royal Commission into the Canterbury Earthquakes, released on Monday, has criticised the process followed by engineers responsible for creating and signing off the building and identified six reasons for its collapse.
The report is also critical of a rapid assessment by Christchurch City Council building officers after the September 2010 quake, which saw the building given a green sticker, without assessment by an engineer.
Among the findings was that its designer in 1986, David Harding, failed to properly consider the seismic behaviour of the loads the columns and beams had to carry, resulting in “brittle” joints.
The report says Mr Harding was “working beyond his competence” in designing the building, and principal engineer, Alan Reay, should not have left him to work unsupervised or without his work being reviewed.
The building’s design did not comply with local bylaws, in part because of its non-compliant north wall – which was the only part of the building left standing after the quake – and should never have received a permit from Christchurch City Council.
While council engineers had concerns about the design, they were “under pressure to approve it” – including from Dr Reay, even though he “knew very little about the structural details of the building”, the report says.
The building site’s foreman, William Jones, received insufficient guidance from construction manager Gerald Shirtcliff, who did not spend enough time at the site to do his job adequately.
Mr Shirtcliff is under investigation by police in New Zealand and Australia amid allegations he misrepresented his engineering qualifications.
The report also identified errors in the way the floors were connected to walls, and defects in the north and south walls while meant they couldn’t resist lateral movement caused by the quake.
In 1990, when non-compliance of the connections between the building’s walls floors and north wall was identified during a pre-sale inspection, Alan Reay Consultants Ltd installed steel “drag bars” on levels four-six.
However, the drag bars failed in the February earthquake – or possibly even in the September quake – due to their lack of ductility (malleability), the report says.
It also found construction defects identified after the February quake, such as a lack of roughening of construction joints, should have been visible to Mr Harding “if he was carrying out regular site inspections”, as well as to Mr Jones and Mr Shirtcliff, during the building’s construction.
The report makes several recommendations relating to the design, construction and maintenance of other buildings around the country, including better assessment of their seismic performance, especially connections of beams and floors to structural walls.