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STRUCTURAL & METALLURGICAL
CASE S1 - Failure of Precast Concrete Lintels, M. Yachnis
Problem:  Failure of precast reinforced concrete lintels in a building which
resulted in a great loss of money and construction time.
Symptoms:  Extensive cracking on the bottom on the majority of the precast
reinforced concrete lintels developed shortly after their placement over door
and window openings (see Fig. 1).  The first reaction was that the cause of
cracks was either overloading or poor quality of concrete or inadequate
reinforcement.
Collection of Facts:  This project involved a complex of multi-story apartment
buildings with brick bearing walls, steel columns, beam and joists. A
structural evaluation of the precast reinforced concrete lintels was made from
the design drawings and they were found adequate to carry the design loads.
During the investigation, it became obvious that the location of the
reinforcement was unknown after the fabrication of the lintels.  Therefore, a
great number of lintels were placed over the openings with the reinforcement
on the compression side of the lintel (The top of the lintel. See Fig.2).
This was verified by removing a number of lintels and exposing their
reinforcement.  Removing the cracked lintels and replacing them with new
lintels was a costly process since it was necessary to remove and replace part
of the already constructed brick wall over the lintels.
Solution:  Use top and bottom reinforcement in precast concrete lintels to
eliminate the possibility of misplacement.  See Figure 3.
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