Title:
Critique of a Post-Tensioned Roof Slab Failure
Author(s):
James R. Libby
Publication:
Concrete International
Volume:
7
Issue:
10
Appears on pages(s):
28-32
Keywords:
anchorage (structural); concrete slabs; cracking
(fracturing); failure; post-tensioning; prestressed concrete;
reinforced concrete; repairs; roofs; stresses; tensile stress;
unbonded prestressing.
DOI:
Date:
10/1/1985
Abstract:
After five years of service, a failure occurred in a corner of a post-tensioned, sand-lightweight concrete flat slab roof. The failure at first appeared to have been caused by a single horizontal crack at the level of the tendon appearance of the crack suggested that vertical tensile stresses the concrete were caused by the products of corrosion Of bedded materials. A subsequent investigation revealed * approximately horizontal crack below the original crack and the almost complete absence of corrosion, A factor in forming the mechanism that caused f al ‘1 %lifi. we w that the second crack found was detc rmined to have existed considerably longer period of time than the first Observed a crack Structural analysis led to the conclusion that the failure Was ti. result of fatigue in the concrete in the area where splittasile stresses in the anchorage zone combined with flexural t eQlfj stresses due to the variation in moments in the structural frame.