Concrete in Christchurch's deadly Canterbury Television (CTV) building was clearly below strength and had been weakened by a series of earthquakes before the February 22 disaster, the Canterbury Earthquakes Royal Commission has been told.
Workers had described the building as being "more lively" following the Boxing Day, 2010, quake but their concerns fell on deaf ears, Professor John Mander of Texas A&M University's civil engineering department told the hearing on Thursday.
The CTV building collapsed and caught fire, killing 115 people in the most deadly building collapse of the 2011 quake, which claimed 185 lives.
Dr Mander said he carried out tests on building column debris retrieved from a landfill and the concrete was clearly below strength.
Other evidence showed it was likely the building concrete strength was weakened during the first earthquakes in late 2010 and especially Boxing Day.
There were about five major earthquakes before the most destructive in February, when the 6.3-magnitude quake, characterised by major vertical uplift, finished off the building.
This was consistent with the reports from workers in the building that it was more "lively" after the Boxing Day earthquake, he said.
Dr Mander said that human senses would be heightened among workers, but they were able to make comparative judgments.
He had been surprised by the accuracy of Christchurch residents who could estimate the strength of earthquakes when they occurred.
But the comments and complaints of workers had fallen on deaf ears, he said.
Thursday is the last scheduled day of the eight-week hearing into the building collapse.
A final commission hearing into post-quake building assessment will be held next month.