ETL 1110-2-365
31 Aug 94
APPENDIX A: NONLINEAR, INCREMENTAL STRUCTURAL
ANALYSIS (NISA) OF MASSIVE CONCRETE STRUCTURES
A-1. Introduction
configuration, extreme loadings, unusual construction
constraints, or severe operational requirements.
a. Purpose. Massive Concrete Structures
(3) To provide cost savings by revising the struc-
(MCS) are constructed using the principles and
tural configuration, material requirements, or con-
methods defined for mass concrete by American
struction sequence. Cost savings may be achieved
Concrete Institute (ACI) Committee 207 (ACI 1992a
through items such as increased placing temperatures,
and b) and EM 1110-2-2000, Standard Practice for
increased lift heights, and reduced insulation
Concrete. MCS should be analyzed in accordance
requirements.
with the guidance contained within this appendix
during the preconstruction engineering and design
b. Project design process. A NISA should be
(PED) phase of the project. Should the performance
of a NISA study become necessary during the feasi-
performed as early in the design process as possible,
bility phase of a project, it should be accomplished in
but it is preferable that the actual performance of a
accordance with Annex 1 of this appendix. There are
NISA not take place until test data are available
three types of MCS commonly used for civil works
which will typically occur during the PED phase. A
projects. Gravity structures are used for dams and
NISA should be performed during the feasibility
lock walls; thick shell structures are used for arch
phase only for unprecedented structures and/or those
dams; and thick, reinforced plate structures are used
with requirements for unusual construction procedures
for U-frame locks, large pump stations, and power-
and when it has been determined that these factors
houses. Thick reinforced plate members are unique
will significantly affect project costs. A NISA during
from typical concrete structures because the horizon-
the feasibility phase is primarily to provide insight
tal flexural members are placed in multiple lifts, and
and information as to whether or not construction of
most members are lightly reinforced (i.e., reinforce-
the structure is viable. If a NISA is performed during
ment ratios less than 1 percent). For any of the
the feasibility phase, then this analysis should be
aforementioned MCS, it may be necessary to perform
verified for accuracy once test data from the project
a nonlinear, incremental structural analysis. A NISA
are available.
should account for the complex geometry of the
structure, the nonlinear behavior of plain or rein-
(1) Planning. During the feasibility phase of
forced concrete members, the interaction of the struc-
project design, the need to perform a NISA should be
ture, foundation, and backfill, and the effects of
evaluated, based on the objectives stated above. Any
sequential construction, thermal gradients, and surface
potential construction savings, historical problems
and gravity forces. A NISA may be necessary and
related to structural behavior, or special unprece-
cost effective to attain any of the following design
dented structural features should be identified. Pro-
objectives:
posed solutions requiring NISA should be presented,
and the necessary design studies along with their
(1) To develop structures with improved perfor-
associated costs and schedule should be included in
mance where existing similar structures have exhib-
the Project Management Plan as described in
ited unsatisfactory behavior (such as extensive
ER 1110-2-1150.
cracking) during construction or operation. Cracking
which requires remedial repairs would be considered
(2) Initial NISA. The initial investigations
unsatisfactory behavior. Cracking which does not
needed to verify the potential cost savings, functional
affect the overall structural behavior or some function
improvements, or predicted behavior should be per-
of the structure would not be classified as unsatisfac-
formed in the early stages of the PED. NISA's
tory behavior.
should include project specific material properties
based on test data. Initial analyses should be used to
(2) To more accurately predict behavior of
investigate typical two-dimensional (2-D) monoliths.
unprecedented structures for which limited experience
These analyses should be used to evaluate the need
is available; e.g., those with unusual structural
for changes in monolith design, material properties,
or construction parameters. These initial analyses
A-1
Previous Page
