The initial investigation of the Willow Island cooling tower collapse (NBS IR 78-1578)established that the most probable cause of the collapse was the imposition of construction loads on the tower before the concrete had gained adequate strength. The analysis presented herein responds to questions outside the scope of that investigation which considered only actual conditions existing at the time of the collapse. The present investigation show that failure would initiate in lift 28 if the concrete strength in that lift is 1000 psi (6.9 Mpa) or less, and to maintain a safety faction 2.0, the concrete strength in that lift should be 4000 psi (27.6 MPa). This study also reveals that even if an additional bolt had been introduced between each exterior jumpform beam and the tower, the stresses would not have been relieved enough to prevent failure of lift 28. Finally, it is shown, that if the ground anchor point of the static line had been kept at the location occupied just prior to its last move to a location near the center of the tower, the stresses in the shell due to construction loads would have been relieved to the extent that failure of lift 28 would probably not have occurred.
Citation: NIST Interagency/Internal Report (NISTIR) - 80-2010Report Number:
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
collapse, concrete, construction loads, cooling towe