ETL 1110-2-365
31 Aug 94
reinforced plates are used for U-frame locks, large
(2) Structural engineers should perform a NISA
pump stations, and powerhouses.
during the early stages of design. This will enable
the design team to use NISA results to make key
design decisions at appropriate times. Usually the
5. Criteria
analysis will occur during the initial stages of precon-
struction engineering and design (PED). However, if
an unprecedented structural configuration is being
a. Design guidance. NISA should be used as a
proposed, it may be necessary to perform a NISA
supplemental tool for the design of MCS. The MCS
during the feasibility phase to identify requirements
must also satisfy applicable criteria contained in other
for design changes and unusual construction proce-
guidance documents. When a NISA is needed to
dures which will significantly affect project costs.
achieve any of the listed objectives presented in para-
Guidance for performing a NISA during the feasi-
graph 5b, it should be performed per the guidance in
bility phase is contained in Annex 1 of Appendix A.
Appendix A. This guidance has been developed from
design experience on several recent civil works pro-
(3) A NISA should be based on test results of
jects. Examples of such designs are provided by
the proposed concrete mixture for the project. There-
Garner, et al. (1992). Excerpts from this reference
fore, when a NISA is expected, it is critical to con-
are included in Appendix B.
duct concrete materials tests at the earliest possible
time. The structural engineer must communicate this
b. Objectives. NISA of MCS should be used
requirement to the materials engineer, since normal
when it is necessary and cost effective to achieve one
thermal studies required by EM 1110-2-2000 may be
or more of the following design objectives.
conducted later in the design process. If test results
are delayed excessively, it may be necessary to initi-
(1) To develop structures with improved perfor-
ate the NISA without the test data. If this undesir-
mance where existing similar structures have
able situation occurs, properties should be selected as
exhibited extensive cracking during construction or
described in Annex 1, Appendix A, for a NISA dur-
operation. This objective is to limit cracking to
ing the feasibility phase. Once testing is completed,
minor occurrences in noncritical areas. It is neither
the performance of the NISA during the feasibility
necessary nor realistic to completely eliminate
phase must be verified with NISA's using the mater-
cracking.
ial properties from the test results.
(2) To more accurately predict behavior of
(4) The structural engineer is primarily responsi-
unprecedented structures for which limited experience
ble for performing the NISA. However, adequate
is available; for example, those with unusual struc-
analysis and evaluation of design alternatives require
tural configuration, extreme loadings, unusual con-
participation of a design team including structural,
struction constraints, or severe operational
materials, geotechnical, cost, and construction engi-
requirements.
neers. This team must ensure that NISA results are
properly incorporated into the overall design of the
(3) To provide cost savings by revising the struc-
MCS. Proper coordination is required for: selection
tural configuration, material requirements, or con-
of concrete properties, foundation properties, and con-
struction parameters.
struction parameters; refinement of the analysis
through changes in structural configuration or con-
c.
Action.
struction parameters, or revised material data for
concrete or foundation; economic evaluation of design
(1) The need to perform a NISA should be iden-
alternatives.
tified during the Feasibility Phase of project develop-
ment. Necessary design studies and resources should
(5) Due to the fact that NISA is a state-of-the-
be included in the Project Management Plan. Proper
art procedure and there are many complex issues
identification of objectives is the key to determining
associated with performing a NISA, periodic review
the required scope of studies. Contact CECW-ED for
meetings should be held throughout the performance
assistance in determining appropriate levels of investi-
of a NISA study to ensure that the plan of action
gation and the necessary resources.
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