ETL 1110-2-344
31 Dec 93
Figure A-13. Vertical displacement profiles at the base of monolith
the monolith and the foundation directly influences
material is competent. For the Locks 27 monolith,
data on the exact condition of the interface bond
the results on the interface.
and foundation does not exist. If it is assumed that
the interface bond is perfect and the monolith and
4. Comparison of Current Practice and
foundation materials are homogeneous and defect
Fracture Mechanics Analyses
free, confining the crack to the interface may not be
realistic. For longer crack lengths, the tendency for
the crack to deviate from the interface becomes
The crack length computed from the finite element
more pronounced.
fracture mechanics based analyses assuming a frac-
ture toughness of zero (KIc = 0) is 13.02 ft. The
b. Analysis consideration. The traditional
percentage of base in compression for a crack
method of analysis appears to be overly conserva-
length of 13.02 ft is 71%, which is near, yet still
tive in comparison to the finite element fracture
does not satisfy the 75% criteria required by
mechanics based method of analysis for this partic-
ETL 1110-2-22. The crack length computed by the
ular monolith geometry and the applied load condi-
traditional method of analysis was 23.13 ft, which
tions. This observation was partially confirmed by
yields a percentage of base in compression of
field measurements when the lock was dewatered
48.6%.
and should be accounted for. As opposed to the
traditional method of analysis, the proposed method
5. Conclusion
of analysis is more realistic for two reasons. First,
the deformation of the monolith and foundation are
a. Mode II consideration. The computed val-
considered through elastic analysis, and secondly,
ues for KII are relatively large, even for shorter
the behavior at a crack tip is more realistically
crack lengths. As the crack length increases, KII is
characterized by fracture mechanics. When expen-
sive rehabilitation procedures are being considered
the dominant stress intensity factor because while
the value KI decreases with crack length the value
solely on the basis of the traditional method of
of KII increases. This trend indicates that the pre-
analysis, a fracture mechanics based solution may
yield a less expensive rehabilitation program with-
ferred path of the crack would be curved, provided
out jeopardizing structural safety.
the bond at the interface is good and the foundation
A-14
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