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ACI 374.2R-13
Guide for Testing Reinforced
Concrete Structural Elements under Slowly Applied Simulated
Seismic Loads
Reported by ACI Committee 374
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First PrintingAugust 2013
Guide for Testing Reinforced Concrete Structural Elements under
Slowly Applied Simulated Seismic Loads
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This is a guide for testing reinforced concrete structural
elements under slowly applied simulated seismic loading. The tests
are primarily intended for assessing strength, stiffness, and
deform-ability of elements under earthquake effects. Integrated are
guide-lines on primary stages of structural testing, including
design and preparation of test specimens, materials testing,
instrumen-tation, test procedure and loading regime, test
observations and data collection, and reporting of test
observations and test data. Emphasis is on the correlation of test
data and predetermined structural performance levels to enable
performance-based design practices. Drift ratio is adopted as the
primary performance indi-cator. Increments of drift ratio are used
in describing the loading history. More refined deformation
components are used to describe element performance levels and
assist in establishing whether a given test specimen meets the
requirements of a specific perfor-mance level.This guide summarizes
ASCE 41-06 performance levels as opera-tional, immediate occupancy,
life safety, and collapse prevention. It outlines different types
of structural elements and subassemblies
that may be tested, and identifies specific requirements for
boundary conditions, instrumentation, and test setups.
Unidirectional and bidirectional loading histories are described in
terms of incremen-tally increasing lateral drift ratio cycles.
Methods of recording and reporting essential components of
deformation and force quantities are identified to correlate test
data and target performance levels. This guide is intended to
maximize the usefulness of information that can be acquired from
experimental research. It is intended to complement guidelines for
structural testing with specific focus. This guide is not intended
for seismic qualification by testing agen-cies, though they can be
used as resource materials for the develop-ment of such
qualification protocols.
Keywords: cyclic loading; earthquake effects; instrumentation;
perfor-mance-based design; performance levels; seismic design;
seismic loads; structural concrete; structural testing; structural
testing guidelines.
CONTENTS
CHAPTER 1—INTRODUCTION AND SCOPE, p. 21.1—Introduction, p.
21.2—Scope, p. 3
CHAPTER 2—NOTATION AND DEFINITIONS, p. 32.1—Notation, p.
32.2—Definitions, p. 4
ACI 374.2R-13
Guide for Testing Reinforced Concrete Structural Elements under
Slowly Applied Simulated Seismic
Loads
Reported by ACI Committee 374
Sergio M. Alcocer, Chair Andrew W. Taylor, Secretary
Mark A. AschheimJohn F. Bonacci
Joseph M. BracciSergio F. BreñaPaul J. Brienen
JoAnn P. BrowningJeffrey J. DragovichJuan Carlos Esquivel
Luis E. GarciaMary Beth D. Hueste
Ivan JelicRonald Klemencic
Richard E. KlingnerBrian T. Knight
Mervyn J. Kowalsky*Michael E. Kreger
James M. LaFaveAndres Lepage
Vilas S. MujumdarStavroula J. Pantazopoulou
Chris P. Pantelides*Jose A. Pincheira
Mario E. Rodriguez*Murat Saatcioglu*†
Mehrdad SasaniShamim A. Sheikh*
Myoungsu ShinBozidar Stojadinovic*
John H. TessemJohn W. WallaceFernando Yanez*
ACI Committee Reports, Guides, and Commentaries are intended for
guidance in planning, designing, executing, and inspecting
construction. This document is intended for the use of individuals
who are competent to evaluate the significance and limitations of
its content and recommendations and who will accept responsibility
for the application of the material it contains. The American
Concrete Institute disclaims any and all responsibility for the
stated principles. The Institute shall not be liable for any loss
or damage arising therefrom.
Reference to this document shall not be made in contract
documents. If items found in this document are desired by the
Architect/Engineer to be a part of the contract documents, they
shall be restated in mandatory language for incorporation by the
Architect/Engineer.
ACI 374.2R-13 was adopted and published August 2013.Copyright ©
2013, American Concrete Institute.All rights reserved including
rights of reproduction and use in any form or by any
means, including the making of copies by any photo process, or
by electronic or mechanical device, printed, written, or oral, or
recording for sound or visual reproduc-tion or for use in any
knowledge or retrieval system or device, unless permission in
writing is obtained from the copyright proprietors.
*Subcommittee members who prepared this guide. †Chair of
subcommittee responsible for preparing report.
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CHAPTER 3—STRUCTURAL PERFORMANCE LEVELS, p. 4
3.1—Operational structural performance level, p. 53.2—Immediate
occupancy structural performance level,
p. 53.3—Life safety structural performance level, p.
53.4—Collapse prevention structural performance level, p.
5
CHAPTER 4—TEST SPECIMENS AND TEST PROCEDURES, p. 6
4.1—Specimen types, p. 64.2—Analytical predictions, p.
64.3—Material testing, p. 74.4—Preparation of test specimens, p.
74.5—Test setup, boundary conditions, and loads, p.
74.6—Instrumentation and data acquisition, p. 84.7—Execution of
tests and test control parameters, p. 84.8—Experimental
observations, p. 10
CHAPTER 5—LOADING PROGRAM AND LOADING HISTORY, p. 10
5.1—Monotonic loading, p. 105.2—Unidirectional load reversals,
p. 105.3—Bidirectional load reversals, p. 11
CHAPTER 6—CORRELATION OF TESTS WITH PERFORMANCE LEVELS, p.
12
CHAPTER 7—DOCUMENTATION OF TEST DATA AND TEST OBSERVATIONS, p.
17
CHAPTER 8—REFERENCES, p. 18Authored references, p. 18
CHAPTER 1—INTRODUCTION AND SCOPE
1.1—IntroductionSeismic design practice worldwide is moving
toward
performance-based design of buildings. This approach aims at
producing buildings capable of developing predict-able performance
levels to achieve predefined performance objectives when subjected
to earthquake ground motions. The performance objectives are met by
ensuring the struc-ture and its components achieve target
performance levels associated with different states of damage for
specified seismic hazards. Usually, the seismic hazard is expressed
in terms of the intensity of ground motion for a specified return
period. Performance levels (capacity) that can be devel-oped by
structural components and ground motion intensity (demand) for
which the building is designed form the funda-mental framework of
performance-based seismic design of buildings.
The design of structural components for target perfor-mance
levels requires an assessment of strength, stiffness, and
deformation characteristics typically into the nonlinear
range of elements and subassemblies that make up the
seismic-force-resisting system. Despite advances in compu-tational
techniques and increased computing power, avail-able analytical
approaches and computational models based on the principles of
mechanics may not be sufficiently accu-rate for design. This is
especially true for performance-based design of concrete buildings
for which the knowledge of seismic performance of structures during
loading, unloading, and reloading beyond post-cracking and
post-yielding stages of deformations, including strength and
stiffness degrada-tion under reversed cyclic loading, becomes
vitally impor-tant. For this reason, tests of large-scale specimens
repre-senting actual conditions in the field are needed to generate
fundamental knowledge on inelastic behavior of reinforced concrete
structural components and subassemblies.
Many experiments have been conducted by university research
laboratories, government agencies, and private institutions.
Laboratory testing continues to enhance knowl-edge on
earthquake-resistant behavior and design of concrete structures.
During testing, the selection of loading histories, measurement of
data, and the presentation of test observa-tions and results are
sometimes decided by the researchers without consistency. This
reduces the effectiveness of the research effort. Though consensus
has been reached on certain aspects of seismic structural testing,
and guidelines have been developed for specific applications, the
lack of uniform guidelines continues to create challenges for
experi-mentalists, occasionally necessitating additional tests.
This guide responds to this need and provides a testing protocol
for reinforced concrete structural components to maximize the
usefulness of information acquired from experimental research. This
guide intends to complement those with specific focus, including
ATC-24 for steel structures, Seible and Hose (2000) for bridges,
SEAOSC (1997) for framed wall buildings, ACI 374.1 for concrete
frames, Richards and Uang (2006) for short links in steel frames,
ASTM E2127 for shear resistance of walls, and FEMA 461 for
structural and nonstructural elements.
1.1.1 Experimental research in earthquake
engineering—Experimental research in earthquake engineering has a
broad scope, covering laboratory and field investigations.
Experimental research can be broadly classified under three
categories: 1) tests under slowly applied and incrementally
increasing or decreasing loads (quasi-static loads); 2)
pseudo-dynamic tests; and 3) dynamic tests. The test protocol in
this guide is limited to tests of structural components under
quasi-static loading. Slowly applied load indicates that the load
is applied either in a load-controlled or deformation-controlled
mode, following a predetermined loading regime slow enough so that
the dynamic inertia effects and strain rate effects on materials do
not develop. (For further discus-sion of strain rate effects in
reinforced concrete, refer to Li and Li [2012], Mander et al.
[1988], Pandey et al. [2006], and Paulay and Priestley [1992]).
Tests under slowly applied loads can be grouped into: 1) tests
under cyclic or reversed cyclic loading; and 2) tests under
monotonically increasing load/deflection increments. The former
category forms the primary scope of this document. The latter is
included
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because some of the fundamental knowledge on generic material
and element performance is obtained by performing tests under
monotonically increasing loads.
1.2—ScopeThis guide provides a testing protocol for structural
testing
of reinforced concrete elements and assemblies under slowly
applied simulated seismic loading. Tests of nonstruc-tural elements
are not included. An emphasis is placed on the characterization of
force-deformation relationships of test specimens to quantify
performance indicators for use in subsequent evaluation of seismic
structural performance. These guidelines are primarily intended for
new tests, but they may also be used for interpreting existing test
data. This guide has a broad scope and may not cover all the
details of experimental research programs. Users should exercise
appropriate judgment during the course of research and make
adjustments to the protocol contained herein. It is, however,
encouraged to use as many of the guidelines outlined in this
document as possible. This guide is not intended for the purposes
of seismic qualification by testing agencies, though it can be used
as a resource for developing such qualification protocols.
In the course of developing this document, consideration was
given to creating a standardized format for reporting experimental
data. However, it was recognized that varia-tions in reporting
formats necessarily arise from differences in instrumentation, test
equipment, and test objectives, and that a standardized reporting
format would be impractical. Therefore, this guide focuses on
defining the essential infor-mation that should be recorded.
This guide does not anticipate the varying challenges that could
arise from the varied testing types. Each experimental program is
unique in itself, making it impossible for the authors to
anticipate every problem arising in planning and conducting a
specific test. Instead, solutions to the more common concerns that
might arise during testing are addressed.
Regulatory agencies or building officials may wish to consult
this guide as a resource for approving new forms of design or
construction that are outside the scope of current building codes.
Such approval might be contingent on performance of component
testing following the procedures suggested in this guide. This
guide has refrained, however, from presenting specific seismic
performance criteria that could be applied to qualify a specific
structural component or assembly for use in a particular seismic
design application. This guide does not anticipate the full range
or combina-tions of possible applications, components, and
performance goals. Any attempt to define such specific numerical
goals would certainly not address all situations, and might
inap-propriately constrain or liberalize approval of a particular
structural component or system. This guide presents exam-ples of
possible acceptance criteria, leaving the establish-ment of
program-specific criteria to the regulatory agency.
The document is organized to provide information on:a) ASCE/SEI
41 performance levelsb) Requirements for preparation of test
specimens, support
and boundary conditions, and test setups
c) Instrumentation needs, data acquisition, and test
observations
d) Description of loading regime, including amplitude and
sequence of load, deformations, or both, including the number of
cycles required for each load level, deformation level, or both
e) Documentation, including reporting of test data, test
observations, and correlations with performance levels
CHAPTER 2—NOTATION AND DEFINITIONS
2.1—NotationAg = gross area of concrete section, in.2 (mm2)As =
area of nonprestressed longitudinal tension rein-
forcement, in.2 (mm2)As′ = area of compression reinforcement,
in.2 (mm2)bw = web width, in. (mm)d = distance from extreme
compression fiber to centroid
of longitudinal tension reinforcement, in. (mm)Ec = concrete
elastic modulus, psi (MPa)F = lateral force, lb (N)fc′ = specified
compressive strength of concrete, psi
(MPa)fy = specified yield strength of reinforcement, psi (MPa)h
= overall height of member, in. (mm)Ie = effective moment of
inertia of section, including
the effects of cracking before yielding, in.4 (mm4)Ke =
effective elastic stiffness, lb/in. (N/mm)ℓ, L = member length, in.
(mm)ℓp = plastic hinge length, in. (mm)ℓu = unsupported length of
compression member, in.
(mm)ℓw = wall length, in. (mm)M = bending moment, in.-lb
(N-mm)My = yield moment of a member or a test specimen,
in.-lb (N-mm)P = axial force, lb (N)Po = nominal axial strength
at zero eccentricity, lb (N)tw = wall thickness, in. (mm)Q =
generalized force in a component, lb (N)Qy = yield strength of a
component, lb (N)V = shear force, lb (N)Vn = nominal shear
strength, lb (N)Vs = nominal shear strength provided by shear
reinforce-
ment, lb (N)a = fraction of Qy that is used to define idealized
effec-
tive elastic stiffnessDy = displacement at member yield load,
in. (mm)d, D = displacement, in. (mm)de = elastic displacement
under a load of aQy, in. (mm)dy = yield displacement under a load
of Qy, in. (mm)f = drift ratio (D/L)f1 = drift ratio at half drift
ratio at member yield loadf2 = drift ratio at member yield loadf3 =
drift ratio at two times drift ratio at member yield
loadf4 = drift ratio at three times drift ratio at member
yield
load
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f5 = drift ratio at four times drift ratio at member yield
load
fy = drift ratio at member yield loadqm = total rotation of
plastic hinge region, radiansqp = plastic rotation of plastic hinge
region, radiansqy = effective elastic rotation of plastic hinge
region at
yield, radiansr = ratio of As to bwdr′ = ratio of As′ to bwdrbal
= ratio of As to bwd producing balanced strain
conditions
2.2—DefinitionsACI provides a comprehensive list of definitions
through
an online resource, “ACI Concrete Terminology,”
http://terminology.concrete.org. Definitions provided here
comple-ment that resource.
cycle—a load or deformation history unit consisting of two
sequential excursions, one in the positive, and the other in the
negative direction.
deformation control parameter—the most relevant deformation
quantity representing the primary cause and effect of damage in a
test specimen, used as a reference value in describing the
deformation history or loading program.
deformation controlled test—test conducted under incrementally
increasing or decreasing deformation levels following a
predetermined deformation history or loading program.
force—a generic quantity, including internal forces (force or
moment) and externally applied loads.
force control parameter—the most relevant force quan-tity
representing the primary cause and effect of damage in specimen,
for use as a reference value in describing the loading history or
loading program.
force-controlled test—test conducted under incremen-tally
increasing or decreasing force following a predeter-mined load
history or loading program.
generic test specimen—test specimen designed to inves-tigate a
general behavioral aspect of structural performance.
performance level—a limiting structural and nonstruc-tural
damage state used for establishing building design performance
objective.
performance objective—one or more design goals where each goal
is attained by ensuring the structure and its compo-nents achieve
target performance levels associated with different states of
damage for a specified level of seismic hazard.
primary structural component—structural compo-nent that is part
of a primary lateral-force-resisting system, providing resistance
to specified earthquake effects.
quasi-static test—an incremental static force or deforma-tion
applied slowly to a specimen so that the dynamic inertia effects
and strain rate effects on materials do not develop.
secondary structural component—structural compo-nent that
fulfills structural functions other than those for seismic
resistance.
slowly applied load—loads applied during a test slow enough so
that the dynamic inertia effects and strain rate effects on
materials do not develop.
story drift ratio—relative difference of displacement between
the top and bottom of a story, divided by the story height.
yield force—the computed or measured force or deforma-tion at
which significant yielding occurs.
CHAPTER 3—STRUCTURAL PERFORMANCE LEVELS
Structural testing should be performed to permit the correlation
of results with predetermined structural perfor-mance and to
provide sufficient information for exercising judgment on meeting a
previously established performance level. Therefore, it is
important to introduce the concept of performance-based design and
the expected performance indicators for correlation with structural
testing.
The performance levels used for seismic design were developed in
the 1990s for seismic evaluation and upgrading of existing
buildings (FEMA 273; FEMA 356). These were incorporated in national
guidelines and standards for seismic evaluation and rehabilitation
of existing buildings (ASCE/SEI 41). They are widely accepted by
the structural design community and, though not intended, are
sometimes used for the structural design of new buildings. In such
cases, the performance level for a specific building design is
selected with due consideration given to potential life and
economic losses that may result from such decision, although
sometimes subjective judgments may be exercised on the consequence
of the decision made. The relationship between the performance
level selected and the potential consequence on quantified life and
economic loss, including down time and impact on use and occupancy,
is established through various means.
The performance levels described in ASCE/SEI 41 have been
adopted in this guide to illustrate the correlation between
structural testing and performance levels. These performance levels
can be revised or replaced, as necessary, without altering the
intent of the testing protocol presented herein.
According to ASCE/SEI 41, structural performance is described
with four discrete levels: 1) operational; 2) imme-diate occupancy;
3) life safety; and 4) collapse prevention. These performance
levels have been selected from count-less possible damage states
that buildings could experi-ence during an earthquake. They have
readily identifiable consequences that are meaningful to the
building engi-neering community. Furthermore, they can be
correlated with quantitative structural performance characteristics
that are used in design while providing descriptions relevant to
socio-economic aspects of building use, such as the ability to
resume normal functions, the advisability of post-earthquake
occupancy, and the risk to life safety.
Figure 3 illustrates the four levels of structural performance
as a function of lateral story-drift ratio. Table 3 provides a
summary of damage in structural members associated with each
performance level. The damage description is presented separately
for primary and secondary structural compo-nents. Primary
components provide resistance to specified earthquake effects,
whereas secondary components are not intended for this purpose. The
secondary category includes structural components that fulfill
structural functions other
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than those for seismic resistance. The damage states described
in Table 3 provide an understanding of the global level of damage
that may be associated with each performance level with approximate
drift ratio limits. They are not accurate measures of individual
element performance. Further guid-ance is given in Chapter 6 for
establishing acceptance criteria for each performance level.
Sections 3.1 through 3.4 briefly describe each performance
level.
3.1—Operational structural performance levelThis performance
level reflects very light overall damage.
Structural elements essentially remain elastic with some minor
hairline cracks. They retain their original strength and stiffness
and do not experience permanent drift. Buildings demonstrating
these characteristics can continue operation during and after an
earthquake.
3.2—Immediate occupancy structural performance level
This performance level describes post-earthquake damage where
the building remains safe to be reoccupied. The primary
lateral-force- and gravity-load-resisting systems retain most of
their entire pre-earthquake design strength with light damage. For
example, to characterize immediate occupancy performance, fragility
relations such as devel-oped for FEMA P-58-1-2012 could be used.
Alternatively, ASCE/SEI 41-06, Table C1-3, suggests criteria that
could be used to characterize immediate occupancy performance for
reinforced concrete structures. ASCE/SEI 41-06, Table C1-3,
suggests the following criteria. Minor hairline cracks are expected
in primary frame elements without concrete crushing, and
compressive strains remain below 0.003, though limited yielding is
possible in a few locations. Minor spalling of cover concrete may
occur in a few critical regions of secondary components with
inclined shear cracks less than 1/16 in. (1.6 mm) wide in the
beam-column joints of secondary frames. Crack widths less than 1/16
in. (1.6 mm) are also anticipated in structural walls. Coupling
beams may show wider cracks, with widths not exceeding 1/8 in. (3.2
mm). Lateral transient drift ratio remains within the
elastic range of deformations, not exceeding approximately 1
percent in frames and 0.5 percent in structural walls. The
buildings develop negligible permanent drift, if any. The risk of
life-threatening injury as a result of structural damage is very
low. Minor structural repairs may be appropriate, though these can
be done while the building is occupied.
3.3—Life safety structural performance levelLife safety level
indicates a post-earthquake damage state
in which significant damage to the structure has occurred, even
though some margin of safety remains against partial or total
structural collapse. Structural elements and components may be
severely damaged, resulting in injuries. However, the overall risk
of life-threatening injury due to such damage is expected to be
low. Some residual strength and stiffness is left in all stories.
Gravity-load-carrying elements continue fulfilling their functions.
Extensive damage is antici-pated in beams, with hinge formation in
secondary ductile elements. Crack widths are expected to increase
but remain less than 1/8 in. (3.2 mm) in both the beams and
beam-column connections. Spalling of cover concrete is antici-pated
in ductile columns. Limited damage to structural wall boundary
elements is expected with the possibility of buck-ling of
compression reinforcement and crushing of concrete due to flexure.
Some sliding of walls at joints and damage around wall openings is
expected. Major flexural and shear cracking is anticipated in
coupling beams, accompanied by concrete crushing, but concrete
generally remains in place. Significant inelasticity is expected
with up to 2 percent tran-sient and 1 percent permanent drift in
frames and 1 percent transient and 0.5 percent permanent drift in
structural walls.
3.4—Collapse prevention structural performance level
Collapse prevention performance level means the building is on
the verge of partial or total collapse as a result of earth-quake
damage. Substantial damage to structural elements is expected,
potentially accompanied by significant strength and stiffness
degradation of the lateral-load-resisting system. Large permanent
lateral deformations of the structure and
Fig. 3—Structural performance levels.
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limited degradation of the vertical-load-carrying capacity are
expected. However, the gravity-load-resisting system continues to
function. The structure is not repairable and not safe to reoccupy.
Extensive cracking and hinging of ductile elements is expected.
Severe damage is anticipated in short columns. Extensive spalling
of cover concrete in beams and columns with buckling of some
compression reinforcement in plastic hinge regions is expected.
Structural walls suffer widespread concrete damage with major
flexural and shear cracks leading to voids in the walls. Wall
sliding may occur at the base construction joint with extensive
crushing of concrete, failure around openings, and buckling of
compres-sion reinforcement. Severe boundary element damage is
expected with coupling beams shattered and virtually
disin-tegrated. Frames are expected to exhibit transient or
perma-nent drift ratios of up to 4 percent, whereas structural
walls have transient or permanent drift ratios of up to 2
percent.
CHAPTER 4—TEST SPECIMENS AND TEST PROCEDURES
4.1—Specimen typesA generic test specimen is a representative
sample of
materials and their assemblies such as a concrete cylinder,
reinforcement coupon, or pullout test assembly. A specific test
specimen is a structural element such as a beam, column, wall,
floor diaphragm, or it may be an assembly or subas-sembly of
structural elements such as beam-column joints
or coupled walls. A generic test specimen is designed to
investigate a general behavioral aspect of structural perfor-mance;
for example, concrete confinement, sliding shear, bar buckling, bar
slip, or bond stress. A specific test specimen is a structural
element designed to represent a well-defined element or an assembly
of elements in a seismic-load-resisting system.
4.2—Analytical predictionsAnalytical prediction of specimen
response should be
made before establishing the test program. This may involve
deformation and strength computations at selected stages of
testing. The analytical computations required for generic test
specimens may vary depending on the objective of the research
program and are best judged by the experimentalist. They provide
guidance in terms of the type and location of instrumentation
needed for the specific test specimen at hand while providing
indications of the displacement (stroke) and force capacities of
the equipment and instrumentation to be used, and reduce potential
problems associated with unex-pected behavior or failure at an
early stage during the test.
The computations for specific test specimens that represent
structural components should be carried out at a number of control
points. These include flexural crack initiation, shear (diagonal
tension) crack initiation, flexural yielding, maximum flexural
strength, and maximum shear strength, all in the pres-ence of other
accompanying forces. The computation of yield displacement and the
corresponding force capacity is essential
Table 3—Structural performance levels and damage (ASCE/SEI
41)Performance level Structural element type Frame buildings
Structural wall buildings
Operational Minor hairline cracks; no concrete crushing and
permanent deformation.Minor hairline cracks; no concrete crushing
and
permanent deformation.
Immediate occupancy
PrimaryMinor hairline cracking; limited yielding possible at a
few locations; no crushing
(strains below 0.003).
Minor hairline cracking of walls less than 1/16 in. (1.6 mm)
wide; coupling beams experience cracking
less than 1/8 in. (3.2 mm) wide.
Secondary
Minor spalling in a few places in ductile columns and beams;
flexural cracking in
beams and columns; shear cracking in joints less than 1/16 in.
(1.6 mm) wide.
Minor hairline cracking of walls; some evidence of sliding at
construction joints; coupling beams experi-
ence cracks less than 1/8 in. (3.2 mm) wide; minor spalling.
Drift 1 percent transient, negligible permanent 0.5 percent
transient, negligible permanent
Life safety
Primary
Extensive damage to beams; spalling of cover and shear cracking
less than 1/8 in. (3.2 mm) wide for ductile columns; minor spalling
in
nonductile columns; joint cracks less than 1/8 in. (3.2 mm)
wide.
Some boundary element stress, including limited buckling of
reinforcement; some sliding at joints;
damage around openings; some crushing and flexural cracking;
coupling beams: extensive shear and flex-ural cracks; some
crushing, but concrete generally
remains in place.
Secondary
Extensive cracking and hinge formation in ductile elements;
limited cracking, splice
failure, or both, in some nonductile columns; severe damage in
short columns.
Major flexural and shear cracks; sliding at joints; extensive
crushing; failure around openings; severe
boundary element damage; coupling beams shattered and virtually
disintegrated.
Drift 2 percent transient, 1 percent permanent 1 percent
transient, 0.5 percent permanent
Collapse prevention
Primary
Extensive cracking and hinge formation in ductile elements;
limited cracking, splice
failure, or both, in some nonductile columns; severe damage in
short columns.
Major flexural and shear cracks and voids; sliding at joints;
extensive crushing and buckling of reinforce-
ment; failure around openings; severe boundary element damage;
coupling beams shattered and virtu-
ally disintegrated.
SecondaryExtensive spalling in columns (limited short-ening) and
beams; severe joint damage; some
reinforcing buckled.Panels shattered and virtually
disintegrated.
Drift 4 percent transient or permanent 2 percent transient or
permanent
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in establishing elastic and inelastic ranges of testing, and to
help develop a suitable loading history.
4.3—Material testingBasic stress-strain characteristics of
concrete and rein-
forcing steel should be established before testing reinforced
concrete elements. Samples for concrete strength tests should be
taken in accordance with ASTM C172/C172M. Standard cylinder tests
should be molded and laboratory-cured in accordance with ASTM
C31/C31M and ASTM C192/C192M. Standard concrete cylinders should be
tested in accordance with ASTM C39/C39M. Strength-versus-age
relationship may be valuable in determining the strength of
concrete at the time of testing the specimen, but it is preferable
to test cylinders on or around the day of spec-imen testing.
Tension coupon tests should be conducted in accordance with ASTM
A370 to establish the stress-strain relationship of reinforcing
steel. As a minimum, concrete compressive strength and steel yield
strength should be established and documented. The complete trace
of material stress-strain relationships, however, is paramount in
inter-preting the performance of reinforced concrete elements in
the inelastic range of deformations. The strain hardening and
maximum elongation (rupture strain) characteristics of steel
reinforcement are especially important in assessing the post-yield
performance of reinforced concrete and should be established by
following standard material tests.
Depending on the structural testing considered, additional
material tests may become necessary to establish other relevant
properties of materials—for example, modulus of rupture, cyclic
performance, and low-cycle fatigue.
4.4—Preparation of test specimensGenerally, a test specimen is
intended to simulate a
portion, a component, or an assembly within a structure that is
designed and built following standard engineering and construction
practices. Therefore, the specimen should be designed and built
following the applicable codes and stan-dards, field conditions,
construction practices, workman-ship, and quality control employed
for the actual structure that it models. It should be as close to
full size as practicable to minimize possible size effects. If a
scaled model is used, it should be large enough to be built using
actual materials and detailing practices used in construction
practice, including the use of standard-size reinforcement and
aggregate. The construction sequence for preparing test specimens,
as well as concrete casting practices and casting positions, should
reflect those used in actual field conditions.
4.5—Test setup, boundary conditions, and loadsThe test setup
should be designed to permit simulation
of key boundary conditions while facilitating application of
lateral loads that are representative of seismic-induced inertia
forces. Initial and boundary conditions, including supports, should
simulate restraints and stress conditions generated in the actual
structural element modeled by the test specimen. Generic test
specimens usually represent a
portion or a segment of a structural member and, as such,
boundary and initial conditions may not be defined clearly in the
context of the overall structural system. Alternatively, specific
test specimens represent well-defined configura-tions within a
structure of known characteristics in a known seismic environment.
Therefore, support and boundary conditions have significant effects
on these specimens and are important. In two-dimensional specimens,
out-of-plane bracing may need to be provided. Three-dimensional
effects of attached structural elements, however, may need to be
considered—for example, floor slab width and transverse beams
framing into the joint.
It is desirable to select specimens that are statically
deter-minate so that internal forces can be determined from
equi-librium of forces without the need for internal measurements.
This may not always be possible, especially when continuity and
redundancy are prevalent in the structural element that is modeled
by the test specimen. In such cases, statically inde-terminate
specimens should be tested and analyzed with due considerations
given to redistribution of stresses.
Lateral loading may be applied by means of hydraulic or
mechanical actuators or other mechanisms. It is applied on the
specimen either in force-controlled or deformation-controlled mode.
Deformation-controlled tests are prefer-able because it is often
difficult to control loads within the inelastic range of
deformations when specimens exhibit significant deformations
corresponding to small changes in load. Load control becomes more
difficult during strength decay, as specimens experience reductions
in load resistance under increasing lateral deformations. During
the initial loading when elastic deformations are small or for the
appli-cation of constant axial loads to simulate gravity loading,
load-controlled application of loads may be necessary, even in a
deformation-controlled test.
The rate of loading may be controlled manually or
auto-matically. In the latter case, a manual override, automatic
limit shut-down of the hydraulics, or emergency stop should be
available as a safeguard. Even though the strain rate effect is
small in tests conducted under slow cyclic displacements, it is
preferable to execute the test continuously without inter-mittent
stops and pauses, particularly when inelastic defor-mations
occur.
Gravity loads should be simulated during testing when-ever their
effects are deemed important. An important aspect of the
application of gravity loads on columns, and to a lesser extent on
walls, is the P-D effect—that is, secondary moments due to off-axis
displacements. The application of vertical axial loads may result
in P-D moments that become significant under increasing lateral
drift, consuming a signif-icant portion of total moment capacity,
resulting in faster rate of lateral force strength degradation.
Figure 4.5 illus-trates P-D moments in a column specimen. Specimens
that are loaded axially so that the line of action passes through
the centroid of the critical section where maximum moment is
imposed do not experience the P-D moment, even though they are
subjected to axial compression.
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4.6—Instrumentation and data acquisitionTest specimens should be
instrumented to measure all rele-
vant response parameters to allow subsequent assessment of
specimen performance. Deformation components can also be used for
analytical modeling of element response. These readings should be
recorded with a view of relating defor-mations to forces and
stresses causing such deformations throughout the test, but as a
minimum at control points of the loading regime described in
Chapter 5. The deformations can be measured as displacements and
rotations by means of transducers, mechanical gauges, or both, or
in the form of strains, typically by placing strain gauges on
reinforce-ment. These readings often provide sufficient information
to calculate other deformation quantities, such as drift ratios,
shear distortions, curvatures, and segmental rotations, and
deformation components such as flexure, shear, and axial
compression. The most important set of data obtained from a
specific test specimen traces the force-deformation hyster-etic
relationship or primary force-deformation curve under monotonically
increasing load. This relationship provides overall performance of
the specimen, or a portion of the specimen, in terms of strength,
stiffness, inelastic deform-ability, and the energy dissipation
capacity, as well as the rate and degree of strength and stiffness
degradation within the inelastic range of deformations. Therefore,
as a minimum, instrumentation should record the force-deformation
data set.
The type of instrumentation used for data collection is
unimportant as long as the instrumentation allows for read-ings at
control points during loading, preferably continu-ously during the
entire test. Technology has evolved from mechanical gauges and
transducers to fiber optic sensors and image processing; therefore,
more accurate devices and sensors are available for structural
testing and should be used. Loads are often measured through load
cells built into actuators. The use of conventional load cells at
selected load application points or reaction points may become
necessary, however, especially for testing statically indeterminate
spec-
imens. Strain gauges provide readings for localized effects, and
their use should be carefully planned. Furthermore, they may debond
and stop functioning in high strain ranges.
Force and deformation data should be recorded by means of data
acquisition systems that are compatible with the type of
instrumentation employed, either continuously or digitally with
sufficiently close intervals to capture all the important features
of response without delay between first and last reading of a set.
It is preferable to use a data acquisi-tion system that permits
real-time display of the force-defor-mation trace during testing
for observations and potential intervention if necessary.
4.7—Execution of tests and test control parameters
This guide is intended for quasi-static tests where the loads or
deformations are applied incrementally and suffi-ciently slowly so
that the dynamic inertia effects and strain rate effects on
materials do not develop. Tests under reversed cyclic loading are
conducted under repeated and incremen-tally increasing force or
deformation reversals following a predetermined loading program and
loading history described in Chapter 5 until significant strength
decay occurs as defined in 4.7.1. Tests under monotonically
increasing loads are conducted by applying incrementally increasing
forces or deformations in the same direction until significant
strength decay is recorded.
4.7.1 Tests under lateral forces and deformations—Tests should
be conducted by applying the most relevant deforma-tion or force
quantity selected as the control parameter. The control parameter
will describe the loading history, as shown in Chapter 5. The
deformation control parameter should be selected to be the most
relevant parameter representing the primary cause and effect of
damage in the specimen that can be related to the global building
response. Drift ratio is an appropriate deformation control
parameter for most speci-mens. Plastic hinge rotation and shear
distortion may be used for some specimens, as appropriate. The
force quantity
Fig. 4.5—(a) Typical column specimen; and (b) Hysteretic
moment-drift relationship. (Note: 1 kN.m = 0.74 kip-ft)(Saatcioglu
and Baingo 1999).
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that can be best related to the deformation control parameter
should be used as the force control parameter. Testing within the
elastic range of deformations may be conducted either in force or
deformation control mode. Testing in the post-yield range of
deformations should be performed in the deforma-tion control mode,
however, as it is often difficult to control the load within this
range of deformations.
Force and deformation control parameters can be applied either
in absolute values or increments of normalized values. If
normalized values of control parameters are used, the normalization
should be done relative to a drift ratio that is representative of
yielding. This drift ratio should also be selected such that the
outcome of the test can be correlated with the performance levels
described in Chapter 3, and used as the deformation control
parameter. The corresponding force can be used as the force control
parameter.
The yield value used to identify the deformation control
parameter should be associated with significant change in the rate
of deformation with little change in force. The yield value can be
computed analytically using measured mate-rial properties, or
experimentally by performing monotonic tests using companion
specimens or during the actual test under reversed cyclic loading.
With appropriate planning, it is possible to identify the yield
point during a test and adjust the loading protocol without
interrupting a test. In either case, judgment should be exercised
in picking the yield value asso-ciated with significant yielding.
This is especially important for establishing force and deformation
control parameters, though other measures of yielding, such as
initial yielding of the critical section, may be useful for the
interpretation of test results. A convenient procedure for
determining the yield point for establishing the control parameters
is illustrated in Fig. 4.7.1. Accordingly, force and deformation
values corre-sponding to aQy are obtained during testing, where a
varies between 0.65 and 0.75 depending on the level of
accompa-nying axial load, the reinforcement pattern, and the
predom-inant stress under which the yielding phenomenon occurs. For
flexure-dominant elements with axial loads below the balanced
point, yielding of longitudinal tension reinforce-ment triggers the
yield point. For these members, it may be appropriate to take a =
0.75. For columns under higher levels of axial compression, the
yield point may be triggered by gradual crushing of compression
concrete as the core concrete confined with properly designed
transverse rein-forcement may continue providing post-yield
response with relatively constant restoring force characteristics.
For these members, a approaches 0.65. The slope of the line between
the aQy point and the origin gives an estimate of the effec-tive
elastic stiffness Ke for the test specimen. The intersec-tion of a
horizontal line drawn at Qy and the line drawn from the origin with
a slope of Ke provides the yield deforma-tion dy. Shear-dominant
members also exhibit yielding as transverse reinforcement
controlling diagonal tension cracks reach yield strain. Following
the yielding of transverse rein-forcement, the member experiences a
faster rate of deforma-tion increase as aggregate interlock along
the inclined crack is lost. This produces a significantly reduced
post-yield stiff-ness and brittle behavior.
As an initial approximation, a researcher can use infor-mation
from prior test programs as a basis to estimate yield deformation.
For example, for relatively slender beams and columns (ℓu/h > 5)
with low axial stress (P < 0.10Agfc′), the first yield point is
typically approximately 1.0 percent of the member length/height.
For moderate-aspect-ratio beams, columns and structural walls (ℓu/h
< 3) and shear-domi-nant elements, the first yield point is
typically less than 1.0 percent—in the range of 0.5 to 0.75
percent—and possibly lower. These estimates are useful to help with
initial plan-ning of the test program—for example, in Chapter 5
where stroke requirements for actuators and displacement sensors
are determined. Prior to testing, more detailed estimates based on
expected behavior (models) and calculations may be performed. The
loading protocol can also be modified during testing based on the
measurements. Vertical elements under high axial compression may
exhibit reduced yield deformation. Shear-dominant members may show
brittle response and develop significant inelasticity at smaller
drift ratios, depending on their shear strength. These members may
have to be tested using a smaller drift ratio established as a
deformation control parameter. Deformation and force control
parameters for such members should be established on the basis of
their shear strength.
The deformation control parameter should be employed in applying
the deformation history specified in Chapter 5 until severe
strength deterioration becomes evident. Test termination may occur
well beyond a deformation level that is likely to be reached during
a maximum credible earth-quake. The maximum strength decay that is
permissible in establishing inelastic deformation capacity depends
on many different parameters. In many previous test programs, the
lateral displacement or drift capacity of the member has been
defined as that corresponding to a strength decay of 20 percent of
the measured peak lateral resistance. For many years, it has been
assumed that exceeding the drift defined previously may result in
lateral instability and lead to partial or total collapse.
Researchers should generally record the point at which 20 percent
strength loss occurs, but should not necessarily adopt this point
as a definition of the collapse state for the structural system.
For example, in bridges with
Fig. 4.7.1—Determination of yield values Qy and dy.
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single-column bents, the lateral displacement associated with 20
percent strength loss may be far beyond the global stability limit
of the structure. Conversely, in a multi-story, multi-bay frame
building with significant redundancy in the structural system, an
individual structural component may be able to carry gravity loads
if it develops more than 20 percent of lateral strength decay.
Furthermore, loads may be redis-tributed among other members of the
lateral-force-resisting system. Figure 4.5(b) illustrates the
hysteretic relationship of a column specimen that sustained
deformation reversals at 4 percent drift ratio, though the moment
strength during the second cycle of this deformation level dropped
below 80 percent of peak moment resistance and is considered to
have 3 percent drift capacity in the positive direction. Because
the 20 percent strength decay deformation level cannot always be
precisely attained during testing, the interpolation of deformation
data may be necessary in interpreting test results. The test should
continue well beyond this 20 percent strength decay level to at
least a 50 percent strength decay point, but preferably more to
assess performance during collapse. If the force or stroke
(displacement) capacity of the test setup or the instrumentation is
attained before the development of significant strength degradation
(beyond 20 percent strength decay), then the specimen should be
cycled at the limit of the test setup or instrumentation, and these
limits should be noted in reporting the test data.
Tests under monotonically increasing lateral forces and
deformations provide fundamental information on element behavior,
including verifications for inelastic static (push-over) load
analysis. Therefore, they may be classified as generic test
specimens. Such specimens are not intended to simulate seismic
action under reversed cyclic loading. As such, the results may not
be directly correlated to the performance levels discussed in
Chapter 3. The initial loading within the elastic range of
deformations may be applied either in the force control or
deformation control mode, in increments of yield force or yield
deformation. The test beyond the elastic range should continue in
deforma-tion control mode, as it is difficult to control the load
within the inelastic range of deformations. The test should
continue well into the strength decay range, with as much imposed
inelastic deformation as practicable, as permitted by the safe
operation of the test, and as limited by the stroke capacity of the
test setup.
4.7.2 Tests under axial forces and deformations—Tests under
monotonically increasing axial force, deformation increments, or
both, are often performed to investigate a general behavioral
aspect of structural performance through tests of generic test
specimens. A good example is a rein-forced concrete column, tested
to establish the characteris-tics of confined concrete or bar
buckling. These tests may be conducted under incrementally
increasing concentric or eccentric compression until substantial
strength degradation is experienced. The initial loading within the
elastic range of deformations may be applied either in the force
control or deformation control mode in increments of computed
specimen capacity. The test beyond the elastic range should be
continued in the deformation control mode, as it is diffi-
cult to control the load within this range of deformations,
especially beyond the peak resistance of specimens under
compression. The test should continue well into the strength decay
range with inelastic deformations as large as prac-ticable, as
permitted by safety considerations to provide data on inelastic
characteristics of the parameter(s) under investigation.
4.8—Experimental observationsInstrumentation and data
acquisition form essential
components of data collection. These data, however, should be
supplemented by observations made during different stages of
testing, to better assess the progression of damage and overall
specimen performance. Therefore, prevalent features of specimen
performance should be observed and recorded during the test. The
magnitude of load at crack initiation should be marked. This may be
the initiation of flexural cracking, diagonal tension cracking due
to shear or torsion, longitudinal splitting cracks associated with
rein-forcement bond or cover spalling, or a combination of these.
Crack widths at maximum deformation of each deformation increment
may be recorded. Marking the cracks and tracing crack patterns may
provide insight into the dominant mode of deformation and the level
of concrete damage. Progres-sion of damage should be recorded in
terms of crack widths, the extension of cracking, and the spalling
and crushing of concrete under compression. Residual crack widths
should be recorded after the first and last cycles for damage
assess-ment. Overall specimen behavior and observed damage should
be recorded while marking significant changes in specimen
performance with references to the corresponding control
deformation and load parameters.
CHAPTER 5—LOADING PROGRAM AND LOADING HISTORY
The test protocol contained in this document is limited to tests
of structural components under slowly applied quasi-static loading,
either as monotonically increasing, or reversed cyclic loading. The
selection of a loading program depends on the objective and type of
experiment and the test specimen.
5.1—Monotonic loadingTests under monotonically increasing loads
are conducted
under incrementally increasing axial or lateral forces or
deformations. These forces and deformations are applied as
increments of computed strength until severe strength degra-dation
occurs. The size of the loading increment should be sufficiently
small to capture the control points in the experi-ment, and may
affect the duration of the test, but is otherwise unimportant.
5.2—Unidirectional load reversalsThe loading history recommended
for tests under unidi-
rectional reversed cyclic loading is shown in Fig. 5.2 in terms
of the deformation control parameter described in 4.7, that is,
drift associated with yielding, fy. Two parameters are significant
in defining the loading history: 1) the increment
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of deformation control parameter to define each deforma-tion
level; and 2) the number of cycles at each deformation level. The
drift ratio is selected such that significant changes in specimen
behavior can be captured and related to the performance levels
described in Chapter 3. A minimum of two cycles at each deformation
level is sufficient to incur damage associated with the number of
cycles at a given drift level, although three cycles have been used
commonly in the past and can be used when appropriate. The
selection of number of cycles at each deformation level depends on
the judgment of the researcher and the particular degrada-tion
characteristics of the system being tested. If degradation with
each cycle tends to be gradual, then three cycles at each
deformation level may be appropriate. If degradation tends to be
rapid, then two cycles at each deformation level may be appropriate
to allow study of performance at a wider range of deformation
levels before most strength of the specimen is lost. Approximately
one-half of fy, which corresponds to approximately one-half the
computed strength, is often sufficient to capture performance
within the elastic range of deformations. The increase in
subsequent drift levels is recommended to be in increments of fy,
as illustrated in Fig. 5.2. Testing should continue until severe
strength degrada-tion is observed as defined in 4.7.
A different loading history may have to be employed for tests
with different objectives. These include tests that incor-porate
near-field effects of earthquakes. Tests performed to investigate
hysteretic features of elements, as well as those conducted to
develop hysteretic models, may require a different loading history
or multiple load histories. These load histories may incorporate
one or more smaller deforma-tion reversals within each deformation
level.
5.3—Bidirectional load reversalsTests of structural elements and
assemblies are often
conducted under unidirectional loads and deformations. When
significant damage associated with bidirectional loading is
anticipated, the test should be conducted under bidirectional
deformation reversals. Bidirectional deforma-tions may be applied
following the orbital pattern suggested
in FEMA 461. Accordingly, bidirectional testing should start
with the application of initial uniaxial drift ratio shown in Fig.
5.2 (1/2fy), followed by the orbital pattern depicted in Fig. 5.3.
The reversal from Point a should accompany an orthogonal drift
equal to one-half the initial uniaxial drift (Points b and c).
Bidirectional loading should then continue following the orbital
pattern of Fig. 5.3 with maximum drift ratios at Points a and d
equal to the drift ratios of unidirec-tional loading history shown
in Fig. 5.2.
The bidirectional loading pattern shown in Fig. 5.3 may be
interpreted as follows. First, determine the displacement amplitude
between the center of the diagram and Point a by consulting the
uniaxial loading diagram in Fig. 5.2 and deter-mining the uniaxial
test amplitude for the first two cycles of uniaxial testing. In
this case, Fig. 5.2 shows that the displace-ment from the origin to
Point a in Fig. 5.3 should correspond to fy/2 for the first two
cycles of biaxial loading. Once the specimen is displaced to Point
a, proceed to Point b, which is to the right of the origin a
distance corresponding to fy/4, and above the origin a distance
corresponding to fy/4. Similarly, proceed to Points c through f
sequentially and return to Point a. Then repeat the entire biaxial
loading cycle at the same ampli-tude. Once the specimen has reached
Point a for the second time, consult Fig. 5.2 for the amplitude
value of the next two cycles, which is the lateral displacement
corresponding to fy. Increase the amplitude to this value, which is
indicated by the Point i.3 in Fig. 5.3. Then, using this new
amplitude value, apply the next two biaxial load cycles, as shown
in Fig. 5.3. After these two cycles are completed, consult Fig. 5.2
again for the next lateral displacement value, and so on.
Fig. 5.2—Deformation history for tests under unidirectional load
reversals.
Fig. 5.3—Orbital pattern for bidirectional loading (FEMA
461).
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CHAPTER 6—CORRELATION OF TESTS WITH PERFORMANCE LEVELS
Structural testing should provide information that can be
compared to previously established performance levels. The
performance levels described in Chapter 3 provide useful
information on global building response while describing the
severity of damage expected at each level, and may be used as a
basis for establishing element and component deformation limits for
each performance level. FEMA 356 and ASCE/SEI 41 provide refined
deformation limits for different structural elements subjected to
different stress conditions for each performance level. These
deformation limits are intended to assess the results of nonlinear
seismic analysis of existing buildings. Therefore, they may provide
conservative values when used to assess test results intended for
new construction. They may, however, assist in estab-lishing
whether a given test specimen meets the require-ments of a specific
performance level.
The deformation limits specified in ASCE/SEI 41 are given either
in the form of plastic rotations or drift ratios, depending on the
type of structural element or component under consideration (refer
to Fig. 6). Drift capacities of specimens can be obtained from
displacement measure-ments. The maximum displacement shown in Fig.
6 (Point B) corresponds to the inelastic drift capacity of
specimens with due considerations given to the permissible
strength
decay under cyclic loading as described in 4.7.1. Therefore,
this quantity is readily available from test data. Plastic hinge
rotation may have to be computed from experimental rota-tion
measurements. Total rotation of the plastic hinge region at member
ends may be measured during testing. The plastic hinge region for
shear walls may cover the entire wall in lower stories. Plastic
hinge rotations form a significant portion of segmental or element
rotations, and may be computed from total rotations by subtracting
the elastic components (rotations at yield). The yield rotation of
plastic hinge region may be measured during tests, and may be
available experimentally. Otherwise, it can be computed as shown
below in Eq. (6).
θy
y
c ep
M
E I=
l (6)
The plastic hinge length ℓp may be taken as 0.5 times the
flexural depth of the element, except for walls where ℓp will be
limited to story height or 50 percent of the element length for
wall segments. Tables 6a through 6e provide examples of acceptance
criteria developed to assess the results of nonlinear seismic
analysis of existing buildings (ASCE/SEI 41). These tables are
included only as examples of possible results following the
guidelines described in this guide. They are not intended to convey
values of acceptance criteria
Table 6a—Example of acceptance criteria for reinforced concrete
beams based on plastic rotation limits (ASCE/SEI 41)
Conditions
Plastic rotations, radiansPerformance levels
Immediateoccupancy
Component typePrimary Secondary
Life safetyCollapse
prevention Life safetyCollapse
preventioni. Beams controlled by flexure*
ρ ρ
ρ
− ′
bal
Transversereinforcement†
V
b d fw c
′
≤ 0.0 C ≤ 3 0.010 0.02 0.025 0.02 0.05≤ 0.0 C ≥ 6 0.005 0.01
0.02 0.02 0.04≥ 0.5 C ≤ 3 0.005 0.01 0.02 0.02 0.03≥ 0.5 C ≥ 6
0.005 0.005 0.015 0.015 0.02≤ 0.0 NC ≤ 3 0.005 0.01 0.02 0.02 0.03≤
0.0 NC ≥ 6 0.0015 0.005 0.01 0.01 0.015≥ 0.5 NC ≤ 3 0.005 0.01 0.01
0.01 0.015≥ 0.5 NC ≥ 6 0.0015 0.005 0.005 0.005 0.01
ii. Beams controlled by shear*
Stirrup spacing ≤ d/2 0.0015 0.0020 0.0030 0.01 0.02Stirrup
spacing > d/2 0.0015 0.0020 0.0030 0.005 0.01
iii. Beams controlled by inadequate development or splicing
along the span*
Stirrup spacing ≤ d/2 0.0015 0.0020 0.0030 0.01 0.02Stirrup
spacing > d/2 0.0015 0.0020 0.0030 0.005 0.01
iv. Beams controlled by inadequate embedment into beam-column
joint*
0.01 0.01 0.015 0.02 0.03*Where more than one of the conditions
i, ii, iii, and iv occur for a given component, use the minimum
appropriate numerical value from the table.†C and NC are
abbreviations for conforming and nonconforming transverse
reinforcement. A component is conforming if, within the flexural
plastic hinge region, hoops are spaced at less than or equal to
d/3, and if, for components of moderate and high ductility demand,
the strength provided by the hoops (Vs) is at least three-fourths
of the design shear. Otherwise, the component is considered
nonconforming.
Note: Linear interpolation between values listed in the table
should be permitted.
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Fig. 6—Component deformations used for assessing performance
levels.
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Table 6b—Example of acceptance criteria for reinforced concrete
columns based on plastic rotation limits (ASCE/SEI 41)
Conditions
Plastic rotations, radiansPerformance levels
Immediateoccupancy
Component typesPrimary Secondary
Life safetyCollapse
prevention Life safetyCollapse
preventioni. Columns controlled by flexure*
P
A fg c
′ Transversereinforcement†
V
b d fw c
′
≤ 0.1 C ≤ 3 0.005 0.015 0.02 0.02 0.03≤ 0.1 C ≥ 6 0.005 0.012
0.016 0.016 0.024≥ 0.4 C ≤ 3 0.003 0.012 0.015 0.018 0.025≥ 0.4 C ≥
6 0.003 0.01 0.012 0.013 0.02≤ 0.1 NC ≤ 3 0.005 0.005 0.006 0.01
0.015≤ 0.1 NC ≥ 6 0.005 0.005 0.005 0.008 0.012≥ 0.4 NC ≤ 3 0.002
0.002 0.003 0.006 0.01≥ 0.4 NC ≥ 6 0.002 0.002 0.002 0.005
0.008
ii. Columns controlled by shear*‡
All cases§ — — — 0.0030 0.0040iii. Columns controlled by
inadequate development or splicing along the clear height*‡
Hoop spacing ≤ d/2 0.005 0.005 0.01 0.01 0.02Hoop spacing >
d/2 0.0 0.0 0.0 0.005 0.01
iv. Columns with axial loads exceeding 0.70Po*‡
Conforming hoops over the entire length 0.0 0.005 0.01 0.01
0.02All other cases 0.0 0.0 0.0 0.0 0.0
*Where more than one of the conditions i, ii, iii, and iv occur
for a given component, use the minimum appropriate numerical value
from the table.†C and NC are abbreviations for conforming and
nonconforming transverse reinforcement. A component is conforming
if, within the flexural plastic hinge region, hoops are spaced at
greater than d/3, and if, for components of moderate and high
ductility demand, the strength provided by the hoops (Vs) is at
least three-fourths of the design shear. Otherwise, the component
is considered nonconforming.‡To qualify, columns should have
transverse reinforcement consisting of hoops. Otherwise, actions
should be treated as force-controlled§For columns designated as
primary components and for which calculated design shears exceed
design shear strength as defined by the Vc equation given in
ASCE/SEI 41, the permissible deformation for the collapse
prevention performance level should not exceed the deformation at
which shear strength is calculated to be reached; the permissible
defor-mation for the life safety performance level should not
exceed three-fourths of that value.
Note: Linear interpolation between values listed in the table
should be permitted.
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Table 6c—Example of acceptance criteria for reinforced concrete
beam-column joints based on plastic rotation limits (ASCE/SEI
41)
Conditions
Plastic rotations, radiansPerformance levels
Immediateoccupancy
Component typesPrimary Secondary
Life safetyCollapse
prevention Life safetyCollapse
preventioni. Interior joints*†
P
A fg c
′ Transversereinforcement‡ V/Vn†
≤ 0.1 C ≤ 1.2 0.0 0.0 0.0 0.02 0.03≤ 0.1 C ≥ 1.5 0.0 0.0 0.0
0.015 0.02≥ 0.4 C ≤ 1.2 0.0 0.0 0.0 0.015 0.025≥ 0.4 C ≥ 1.5 0.0
0.0 0.0 0.015 0.02≤ 0.1 NC ≤ 1.2 0.0 0.0 0.0 0.015 0.02≤ 0.1 NC ≥
1.5 0.0 0.0 0.0 0.01 0.015≥ 0.4 NC ≤ 1.2 0.0 0.0 0.0 0.01 0.015≥
0.4 NC ≥ 1.5 0.0 0.0 0.0 0.01 0.015
ii. Other joints*†
P
A fg c
′ Transversereinforcement‡ V/Vn†
≤ 0.1 C ≤ 1.2 0.0 0.0 0.0 0.015 0.02≤ 0.1 C ≥ 1.5 0.0 0.0 0.0
0.01 0.015≥ 0.4 C ≤ 1.2 0.0 0.0 0.0 0.015 0.02≥ 0.4 C ≥ 1.5 0.0 0.0
0.0 0.01 0.015≤ 0.1 NC ≤ 1.2 0.0 0.0 0.0 0.0075 0.01≤ 0.1 NC ≥ 1.5
0.0 0.0 0.0 0.0075 0.01≥ 0.4 NC ≤ 1.2 0.0 0.0 0.0 0.005 0.0075≥ 0.4
NC ≥ 1.5 0.0 0.0 0.0 0.005 0.0075
*P is the design axial force on the column above the joint, and
Ag is the gross cross-sectional area of the joint.†V is the design
shear force and Vn is the shear strength for the joint. The design
shear force and shear strength should be calculated according to
6.4.2.3 of ASCE/SEI 41.‡C and NC are abbreviations for conforming
and nonconforming transverse reinforcement. A joint is conforming
if hoops are spaced at less than or equal to hc/3 within the joint.
Otherwise, the component is considered nonconforming.
Note: Linear interpolation between values listed in the table
should be permitted.
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Table 6d—Example of acceptance criteria for reinforced concrete
shear walls and associated components controlled by flexure
(ASCE/SEI 41)
Conditions
Acceptable plastic hinge rotations, radiansPerformance
levels
Immediateoccupancy
Component typesPrimary Secondary*
Life safetyCollapse
prevention Life safetyCollapse
preventioni. Shear walls and wall segments
( )A A f P
t fs s y
w w c
− ′ +′l
V
t fw w cl ′
Confined boundary†
≤ 0.1 ≤ 3 Yes 0.005 0.010 0.015 0.015 0.020≤ 0.1 ≥ 6 Yes 0.004
0.008 0.010 0.010 0.015≥ 0.25 ≤ 3 Yes 0.003 0.006 0.009 0.009
0.012≥ 0.25 ≥ 6 Yes 0.0015 0.003 0.005 0.005 0.010≤ 0.1 ≤ 3 No
0.002 0.004 0.008 0.008 0.015≤ 0.1 ≥ 6 No 0.002 0.004 0.006 0.006
0.010≥ 0.25 ≤ 3 No 0.001 0.002 0.003 0.003 0.005≥ 0.25 ≥ 6 No 0.001
0.001 0.002 0.002 0.004
ii. Columns supporting discontinuous shear wallsTransverse
reinforcement‡
Conforming 0.003 0.007 0.010 NA NANonconforming 0.0 0.0 0.0 NA
NA
iii. Shear wall coupling beams
Longitudinal reinforcement and transverse reinforcement§
V
t fw w cl ′
Conventional longitudinal reinforcement with conforming
transverse reinforcement
≤ 3 0.010 0.02 0.025 0.025 0.050≥ 6 0.005 0.010 0.020 0.020
0.040
Conventional longitudinal reinforcement with nonconforming
transverse reinforcement
≤ 3 0.006 0.012 0.020 0.020 0.035≥ 6 0.005 0.008 0.010 0.010
0.025
Diagonal reinforcement NA 0.006 0.018 0.030 0.030 0.050*For
secondary coupling beams spanning less than 8 ft (2.4 m), with
bottom reinforcement continuous into the supporting walls,
secondary values should be permitted to be doubled.†Requirements
for a confined boundary are the same as those given in ACI
318.‡Requirements for conforming transverse reinforcement in
columns are: (a) hoops over the entire length of the column at a
spacing less than or equal to d/2; and (b) strength of hoops Vs
greater than or equal to the required shear strength of
column.§Conventional longitudinal reinforcement consists of top and
bottom steel parallel to the longitudinal axis of the coupling
beam. Conforming transverse reinforcement consists of: (a) closed
stirrups over the entire length of the coupling beam at a spacing
less than or equal to d/3, and (b) strength of closed stirrups Vs
greater than or equal to three-fourths of required shear strength
of the coupling beam.
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recommended by ACI Committee 374. Possible applications of
testing guidelines described in this guide could include
verification or recalibration of the values in them, or
devel-opment of entirely new tables for other structural systems.
Note that acceptance criteria developed for existing struc-tures,
such as the examples shown in Tables 6a to 6e, are typi-cally not
applicable to new structures. When using published performance
criteria tables, such as the examples in Tables 6a to 6e, it may be
necessary to interpolate the deformation data among the drift
levels applied during testing.
The test data can also be used to verify analytical models. The
assessment of global structural performance may require nonlinear
analysis of the structure. The test data provide useful guidance to
the analyst in refining element properties in the global analytical
model for improved assessment of global performance of the
building.
CHAPTER 7—DOCUMENTATION OF TEST DATA AND TEST OBSERVATIONS
The following information should be documented for each
experiment:
a) Specimen geometry, including cross-sectional and
rein-forcement details, with clearly drawn elevation, plan, and
cross-sectional views
b) Details of specimen preparation, including the assembly of
reinforcement cages, position of casting, and other spec-imen
fabrication details of significance, including as-built
conditions
c) Locations, positions, resolutions, limits and descriptions of
instruments, and relevant specifications of the data acquisi-tion
system used for the measurement of response parameters
d) Details and geometry of test setup, boundary and support
conditions, and applied loads, including the loading program
e) Material properties, including the traces of stress-strain
relationships of concrete (preferably at the time of specimen
testing), reinforcing steel, and other materials such as
fiber-reinforced polymer composites
f) A trace of force-deformation hysteretic relationship under
reversed cyclic loading, or force-deformation relation-ship under
monotonically increasing load
g) Numerical values of force and corresponding defor-mation at
first yield or at first significant deviation from the initial
loading curve within the post-cracking range, in both positive and
negative directions. The method used for defining the yield point
should be indicated. Test records should include documentation of
any derived or calculated test control parameters, including the
methods and equations used to develop the parameters
h) Maximum values of force and deformation at the end of each
loading cycle, both in positive and negative directions
i) Force and corresponding deformation at the initiation of
flexural and diagonal tension cracking
j) Forces and corresponding deformations at the onset of
longitudinal splitting cracks, cover spalling, and the crushing of
concrete, as well as at any significant change in specimen
performance
k) Forces and corresponding deformations at first yield,
buckling, and fracture of longitudinal and transverse
rein-forcement, with relevant information on potential slippage of
reinforcement, as well as splice and hook performances
l) Data similar to those listed under items g through i for
other primary response parameters, such as strains, rota-tions, and
distortions
m) Crack mapping with corresponding crack widths at zero load
and peak deformations of incrementally increasing deformation
reversals and associated damage
Table 6e—Example of acceptance criteria for reinforced concrete
shear walls and associated components controlled by shear (ASCE/SEI
41)
Conditions
Acceptable total drift (%) or chord rotation (radians)*
Performance levels
Immediateoccupancy
Component typePrimary Secondary
Life safetyCollapse
prevention Life safetyCollapse
preventioni. Shear walls and wall segments
All shear walls and wall segments† 0.40 0.60 0.75 0.75 1.5ii.
Shear wall coupling beams‡
Longitudinal reinforcement and transverse reinforcement§
V
t fw w cl ′
Conventional longitudinal reinforcement with conforming
transverse reinforcement
≤ 3 0.006 0.015 0.020 0.020 0.030≥ 6 0.005 0.012 0.016 0.016
0.024
Conventional longitudinal reinforcement with nonconforming
transverse reinforcement
≤ 3 0.006 0.008 0.010 0.010 0.020≥ 6 0.004 0.006 0.007 0.007
0.012
*For shear walls and wall segments, use drift; for coupling
beams, use chord rotation (refer to Fig. 6).†For shear walls and
wall segments where inelastic behavior is governed by shear, the
axial load on the member should be less than or equal to 0.15Agfc′;
otherwise, the member should be treated as a force-controlled
component.‡Conventional longitudinal reinforcement consists of top
and bottom steel parallel to the longitudinal axis of the coupling
beam. Conforming transverse reinforcement consists of: (a) closed
stirrups