STEVE ELLIOTT, project director of British Association of Reinforcement, reports that the initial investigations into the recent fire that devastated the Windsor Tower in Madrid highlighted a fundamental weakness of steel sections, and underlined a fundamental strength of reinforced concrete structures reports.
The fire, which started on the 21st floor of the 32 storey building quickly spread due, it is believed, to the lack of fire stops between the curtain wall facade and concrete floor slabs. Failure of the structure happened with the collapse of the steel perimeter columns, resulting in the floor slabs collapsing as the edge support was taken away. Structural stability continued to be provided by the internal reinforced concrete cores. The massive concrete transfer slab at floor 17 prevented further progressive failure. However, as the debris fell, the cladding below was smashed and the fire spread to lower floors.
“The internal reinforced concrete core withstood the fire and appears to have remained structurally sound. The same cannot be said of the perimeter steel columns and beams which dramatically failed, despite having some fire protection. This resulted in the partial collapse of the tower,” said Mr Elliott. “The failure of the structure is confined to the steel perimeter section. The concrete frame performed extremely well. We expect this to be confirmed by the investigations now being carried out into the structural performance of the building.”
Designed in the 1970s, Torre Windsor was under going extensive refurbishment at the time of the fire to bring fire standards up to date. Additional fire protection was being applied to the steel frame. “Unfortunately this now seems to be too little too late”, said
Mr Elliott.
