Ground Motion Measurements from the Demolition of Steel Towers

Steel towers from a decommissioned heavy water plant were to be demolished. Ground motions due to the proposed felling were estimated in order to assess the structural integrity of neighboring buildings and piping systems. The extraction towers were 125 feet (38.1 m) high in two sizes: 6.5 and II feet (1.98 and 3.35 m) inside diameters weighing 215 X 103 and 470 X 103 lb (956 X 103 and 2.1 X 106 N). The total potential energy of the tower collapse was about 15 X 106 and 32 X 106 ft-lb (20.3 X 106 and 43.4 X 106 Nm) for the small and large towers, respectively. The ground motion predictions were based on a credible theoretical relationship with constants estimated from data available for a different location at the site for dynamic compaction with an energy input an order of magnitude less than that for the towers. Due to the uncertainty of prediction of ground motions a coefficient of variation of 2.0 was used in the structural assessment. Ground motion from the collapse of the extraction towers were monitored by several 3- and 6-components seismographs. Recorded measurements indicated that the ground motion was less than the predicted values. Peak radial motions were approximately equal to the vertical ones. Video tapes of the demolition suggested significant internal energy losses. The measurements suggested that the tower potential energy conversion to dynamic impact energy was about 25 percent