ETL 1110-2-365
31 Aug 94
APPENDIX B: EXAMPLES
B-1. General
heat transfer analysis, a criterion for the element size
is given in paragraph 5c(5), Appendix A. Based on
The information in this appendix is provided to assist
this equation, a minimum timestep of one-quarter day
the designer in understanding certain aspects of per-
and the other necessary data from the Olmsted pro-
forming a nonlinear, incremental structural analysis
ject, the maximum element size which may be used
(NISA). Included are discussions on mesh size and
in the heat transfer analysis is 26.9 in. As can be
selection, evaluation of cracks and crack potentials,
seen in Figure B-1, the majority of the mesh adheres
and a parametric study of varying the placing temper-
to the criterion given in paragraph 5c(5), Appendix A.
ature of the concrete. The information presented in
It is only toward the center of the slab that the crite-
this enclosure was taken from the report on the
ria is exceeded and it is exceeded only in the horizon-
Olmsted project "Nonlinear, Incremental Structural
tal direction. Truman, Petruska, and Ferhi (1992)
Analysis of Olmsted Locks and Dam, Volume I"
(listed in Reference section of Appendix A) show that
((Garner et al. 1992) listed in Reference section of
it is acceptable to exceed the criteria in the direction
Appendix A).
perpendicular to heat flow. Since the direction of
heat flow in the slab, away from the walls, is vertical,
then it is acceptable to increase the element size
B-2. Mesh Size and Selection
above the criterion in the horizontal direction.
a. General. As described in paragraph 5c,
(2) Stress analysis considerations. As stated in
Appendix A, there are certain restrictions on element
paragraph 5c, Appendix A, conventional FE modeling
size which must be maintained when developing a
techniques should be adhered to when developing a
mesh for a NISA. Considerations must be given for
mesh for a NISA. In addition, paragraph 5c(2) dis-
certain restrictions in the heat transfer analysis as
cusses some specific areas where these techniques
well as ensuring that enough elements are present in
can be supplemented. As can be seen in Figure B-1,
the model to capture the structural response in the
the mesh for the Olmsted chamber monolith follows
stress analysis, which includes using two rows of
these suggested guidelines. There are at least two
elements per lift of concrete and at least two elements
elements in every lift and at least two elements
through the thickness of any given member. While it
through the thickness of every member.
is important to adhere to the requirements listed in
Appendix A, in some instances it may become neces-
c. Additional considerations. While the cham-
sary to exceed the criteria with respect to the number
ber monolith from the Olmsted project followed the
of elements and the size of elements to reduce com-
guidelines for mesh size and selection as outlined in
puting time and the amount of output data. The
Appendix A, following these guidelines may not
following discussion provides insight into the mesh
always be practical, particularly in three-dimensional
development for the NISA which was performed on
analyses. Any deviation from the criteria and guide-
the typical chamber monolith of the Olmsted Locks.
lines outlined in paragraph 5c, Appendix A, should be
evaluated on a case-by-case basis. Parametric studies
b. Olmsted chamber monolith. Figure B-1 is a
may be appropriate to justify exceeding the restric-
sectional elevation of a typical chamber monolith of
tions in some cases, where in other cases past experi-
the Olmsted Locks and the finite element (FE) mesh
ence and engineering judgement can be used.
used in the NISA study of the monolith. The
Olmsted project implemented the innovative concept
of a W-frame lock which has a common wall
B-3. Evaluation of Cracks and Cracking
between the two lock chambers and is a variation on
Potentials
the more common U-frame type lock. The dimen-
sions of the monolith are typical for a massive rein-
a. General. Due to the low tensile capacity of
forced concrete structure.
concrete, cracking is likely to occur in any concrete
structure. While cracking can be expected on mas-
(1) Heat transfer analysis considerations. Due to
sive concrete structures, it is the size and location of
the algorithm used in ABAQUS for performing the
B-1
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