SESOC Report – Collapse of the Canterbury Television (CTV) Building

SESOC Report - Collapse of the Canterbury Television (CTV) Building

by

Richard Fenwick - Commissioner, Royal Commission Canterbury Earthquakes, May 2011 to Nov. 2012.
Derek Bradley - Principal, Compusoft Engineering Ltd

Abstract

A detailed structural assessment has been made of the CTV building which was a moderately sized six storey structure located in Christchurch, New Zealand. It was designed in the mid-1980s and it collapsed catastrophically in the 22 February 2011 earthquake, killing 115 people. There are numerous structural components the failure of which could have contributed to the collapse of the building. The failure of the columns in the south-west corner of the building appear to be the most likely action initiating collapse. Other weaknesses, arising from sub-standard detailing account for why the initial local failure resulted in a progressive pancake-type collapse of all floors in the building.

It is shown that the collapse occurred due to several causes. In particular there were:

• errors made in the structural analysis of the building.
• a number of critical clauses in the then-current design codes which were not considered.
• many structural elements which were inadequately detailed.
• a number of numerical errors in the calculations.
• a number of construction errors.

The seismic safety of structures designed in the 1980s was adversely influenced by a number of contradictions, errors and omissions in the then current design standards. Some of these issues are still present in our current design Standards (2020). One of the conclusions from this study is that it is important to check that the structural design and drawings comply with the fundamental requirements on which structural design is based, and not just rely on satisfying code requirements.