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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

Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=wer, weqwe

Not for Resale, 01/26/2015 02:02:30 MSTNo reproduction or networking permitted without license from IHS

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First PrintingAugust 2013

Guide for Testing Reinforced Concrete Structural Elements under Slowly Applied Simulated Seismic Loads

Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI.

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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.

1Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=wer, weqwe


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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

American Concrete Institute Copyrighted Material—www.concrete.org

2 TESTING RC STRUCTURAL ELEMENTS UNDER SLOWLY APPLIED SIMULATED SEISMIC LOADS (ACI 374.2R-13)



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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


TESTING RC STRUCTURAL ELEMENTS UNDER SLOWLY APPLIED SIMULATED SEISMIC LOADS (ACI 374.2R-13) 3



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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


Immediateoccupancy

Component typesPrimary Secondary

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.






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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


Immediateoccupancy

Component typesPrimary Secondary

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.






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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


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


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

374.2r-13 guide for testing reinforced concrete structural … · 2020. 5. 12. · this is a guide...

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