In Christchurch, New Zealand, there is currently an investigation underway into the collapse of the Canterbury Television (CTV) building which occurred during last year’s devastating earthquake. The inquiry is looking to discover why the building collapsed so quickly, trapping and killing 115 people. Eyewitness reports told how the building collapsed down into itself rather than out into neighbouring streets, suggesting weak internal structure.
The inquiry has heard from forensic structural engineer Rob Heywood that he was surprised by how the concrete disintegrated and crumbled during the rescue effort. It was originally believed that the fire that engulfed the building after its collapse was the cause for the weak concrete, however all areas of the building - even those not damaged by the fire - also showed this property. Findings have shown that the floor slabs broke away from the connecting columns very early on during the violent shaking caused by the 6.3 magnitude earthquake.
Heywood has collated evidence for eyewitness reports that told how the building collapsed with many parts of the building breaking away and detaching themselves from the main structure, suggesting a brittleness to all of the structural materials. This brittleness of the concrete structure has given rise to comparisons with chalk, with Heywood suggesting that the concrete on site behaved in a similar manner: "One moment the chalk is carrying the load, and the next moment it crumbles without warning."
As further evidence to the weak structural integrity in the load-bearing elements of the building, the top floors of the building collapsed with relatively little damage, with the floor plates and columns still connected. The lower half of the building had completely disintegrated into rubble and the fire that ensued is believed to have been started from 6 cars that were in the underground parking area, not from a gas cylinder in the building as previously thought.
The investigation is set to continue with further expert reports and testimonials from eye witnesses over the next 8 weeks. The general opinion is that the building failed catastrophically and the inquiry is seeking to determine the exact cause for its failure to withstand the shocks from the earthquake and the speed of its demise.