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Ductile building
The weakest parts of large buildings during an earthquake are the structural joints between columns and beams. In many modern concrete buildings, columns and beams are cast in one piece. This means the frame of the building is rigid. When this frame is forced to move by an earthquake, there is no flexibility, so something breaks – it may be the beams, the columns, or where they meet.
A new approach is to create a flexible joint where a beam meets a column. Steel cables tie the parts together – in an earthquake the cables stretch, which lets the joint open slightly, rather than break.
Photograph courtesy of Robinson Seismic Limited
