Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanLESSONS FOR CONCRETE WALL DESIGN FROM
THE 2010 MAULE CHILE EARTHQUAKE
Karl TELLEEN1, Joe MAFFEI2, Michael WILLFORD3, Ady AVIRAM4, Yuli HUANG5,
Dominic KELLY6, and Patricio BONELLI7
1

Associate, Rutherford & Chekene, San Francisco, CA, USA, ktelleen@ruthchek.com
Principal, Rutherford & Chekene, San Francisco, CA, USA, jmaffei@ruthchek.com
3
Principal, Arup, San Francisco, CA, USA, michael.willford@arup.com
4
Senior Staff I - Structures, Simpson Gumpertz & Heger, San Francisco, CA, USA, aaviram@sgh.com
5
Structural Analyst, Arup, San Francisco, CA, USA, yuli.huang@arup.com
6
Associate Principal, Simpson Gumpertz & Heger, Boston, MA, USA, djkelly@sgh.com
7
Professor, Department of Civil Engineering, Universidad Técnica Federico Santa Maria, Valparaiso,
Chile, patricio.bonelli@usm.cl
2

ABSTRACT: Damage to mid-rise and high-rise concrete wall buildings caused by the2010 Chile Earthquake offers a rare and valuable opportunity to study buildings in detailto gain practical lessons for structural design. Observed damage includes concrete
crushing and reinforcing bar buckling in wall boundary elements, overall wall buckling,
and damage resulting from configuration issues such as discontinuities. Through theATC-94 project, a team of researchers and practitioners is developing recommendations
for modifying design practices based on studies of damaged Chilean wall buildings.
Key Words: 2010 Maule Chile Earthquake, concrete wall, boundary element, buckling,crushing, shear, configuration

INTRODUCTION
The Maule Chile earthquake of 27 February 2010 subjected many engineered structures to strong
earthquake shaking, and it presents opportunities to learn from the seismic performance of thesebuildings. The earthquake was large (Mw 8.8) with a long duration of strong shaking (two minutes insome locations), and in many cases buildings performed well. However, severe damage from groundshaking occurred in some buildings, including several mid-rise and high-rise concrete wall structures
housing apartments. Post-earthquake reconnaissance teams reported that most buildings of this typeuse thin concrete walls—typically 200mm thickness for buildings up to 16 stories and 250mm up to 25
stories—as the primary gravity and lateral-force-resisting elements, and that the dimensioning,detailing, and configuration of these walls may have contributed to the damage sustained in theearthquake (EERI 2010, Cowan et al 2011).
The availability of complete structural drawings for many of the damaged buildings, designed tomodern building codes, provides a rare and valuable opportunity for study. Such information has

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typically not been available after earthquakes in the US and other countries. The structural drawingsand damage documentation enable quantitative studies that can be used to advance knowledge in thefield of structural engineering.
Similarities exist between the United States and Chile in terms of many building code provisions,seismic hazards, and urban environment, so collaborative research on these topics offers potential
benefits for both countries. For example, the Chilean building code, in place during the construction ofmany of the earthquake-affected buildings, incorporates many of the concrete design provisions fromthe U.S. standard ACI 318. One notable exception is that the provisions for special boundary elements
in ACI 318 were not included in the Chilean code (INN 1996) until recently.
Following the earthquake, representatives of several U.S. earthquake engineering organizations
met with Chilean researchers and practitioners and produced a list of potential engineering study
topics that could lead to recommendations for improved design provisions based on information fromthe earthquake (Moehle 2010).
To study some of these items, a team of practitioners and researchers is collaborating through theApplied Technology Council (ATC) ATC-94 project “Seismic Performance of Reinforced Concrete
Wall Buildings in the 2010 Chile Earthquake.” The project objective is to evaluate critical issues in thedesign of reinforced concrete walls and recommend revisions to design requirements whereappropriate.
This paper summarizes preliminary findings from the project, including post-earthquake
observations, structural seismic behaviors being studied, and concepts for potential changes tobuilding codes and design practices.

PROJECT ORGANIZATIONThe ATC-94 project team consists of practitioners and researchers organized into working groups to
conduct problem-focused studies on specific topics (Fig. 1). Working group studies draw on observed
damage (or lack of damage) in several different mid-rise and high-rise concrete wall buildings,
available information about detailing and construction in those buildings, past data from related
experimental testing and research, and analytical studies. Studies make use of tools commonly used inengineering design offices as well as more advanced analysis tools. Analytical tasks include studies ofindividual concrete elements, studies of multi-story walls, and studies using full-building analyses.

Fig. 1 ATC-94 project team

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The final deliverable for the project will be a report, expected in late 2012, describing certain
structural seismic behaviors observed in the Chile Earthquake, practical and theoretical understandingof the behaviors studied, and recommendations for modifying design practice and code provisions toimprove the seismic performance of concrete wall buildings.

STRUCTURAL BEHAVIOR MODES STUDIED
Post-earthquake reconnaissance teams observed damage to buildings of a variety of construction types.
In concrete buildings, which constitute most mid- and high-rise buildings in Chile, observed behavior
modes included:• damage to wall boundary areas including bar• coupling of concrete walls from slabs, beams,
buckling, bar fracture, concrete crushing, andand spandrels
overall wall buckling• interaction of stairs with lateral-force-resisting• damage concentrated at wall setbacks andflag-shaped walls
systems• bar splice failure• shear failure of concrete walls and wall piers• wall damage extending into basement levels• damage to walls with irregular openings• apparent plan torsion effects• soil-structure interaction
Certain of these behaviors are less desirable than others in terms of seismic safety, reliability, andrepairability. Several of these behaviors have also been observed in experimental tests, which provide
measured data to complement and compare to earthquake observations. In the ATC-94 project,discussions of study objectives led to questions including the following:• Is it possible, as designers intend, for compression-governed walls to develop distributed yielding(over a certain plastic hinge length)? Should concrete walls be required to be tension-controlled in
flexure (to preclude compression failure from flexure and axial loads)?
• What are the effects of earthquake duration on building performance? Does it depend on the
behavior mode of the building?
• Should the seismic response modification factor (R in U.S. building codes, ASCE 2010) depend on
the expected behavior mode of a structural system rather than just the construction type?
• For pier-spandrel systems, should there be a code requirement to ensure strong-pier/weak-spandrel
behavior, similar to current requirements for strong-column/weak-beam?
• How can engineers and society confront the challenges of demolishing tall buildings in an urban
setting that have suffered severe earthquake damage?
• What causes a building to go from extreme damage to collapse? Are analysis methods capable ofdistinguishing between these limit states?
• What strategies have engineers and building owners used to decide what damage is repairable andwhat requires demolition?
The ATC-94 project focuses on the following selected behaviors, with the objective of taking
meaningful steps to advance the practice of structural engineering:
Damage to wall boundary elements, including concrete crushing and/or buckling of longitudinal
reinforcing bars (Figs. 2a, 3a)
These phenomena result from flexural compression and/or cyclic tension and compression. They canbe undesirable failure modes because they can lead to strength degradation and irreparable damage. To
improve performance, potential modifications to design practice could include providing transverse
reinforcement ties at a close spacing and/or providing an increased area of transverse reinforcement inwall boundary elements. Wall sections could also be designed to be governed by tension yielding.

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Different interpretations of this damage could lead to different design implications, as discussed in thenext section.
Overall wall buckling (Figs. 2b, 3b)This phenomenon consists of buckling of the wall section (as opposed to individual reinforcing bars)
out-of-plane, resulting from flexural compression and/or cyclic tension and compression. Prior to the2010 Chile earthquake this behavior mode had been observed in experimental tests but had not beenreported in an actual earthquake. This behavior was also observed in the 2011 Christchurch, New
Zealand, Earthquake. It can be an undesirable failure mode, particularly in regards to repairability ofstructures. To improve performance, potential modifications to design practice could include providing
a minimum wall thickness at the compression boundary of a wall, as a function of the unsupported
wall height in the region of potential plastic hinging. The thickness requirement could also depend onother variables such as unbraced wall length, axial load, neutral axis depth, or expected strain demand.
Damage resulting from building configuration issues (Fig. 2c)
Coupling from slabs, beams, spandrels, stairs, and other outrigger-type elements can cause damage tothese elements and can also increase shear demand in walls. Potential improvements to design practiceinclude accounting for these elements in the seismic analysis and design, or detailing them tominimize interaction with the designated seismic force-resisting elements.
The following sections describe preliminary investigations related to some of these behavior
modes. Full findings for the project will be described in the project report.

Fig. 2 Damage from Chile Earthquake (a) Damage to a wall boundary element (b) Overall wallbuckling (photo by Prof. Jack Moehle) (c) Damage at wall discontinuity

Fig. 3 Test specimens from Thomsen and Wallace (2004) (a) Wall boundary element with transverse
hoops spaced at 8db exhibited longitudinal bar buckling and concrete crushing at 1.25% lateral drift.
(b) Wall boundary element with hoops spaced at 4db exhibited more ductile behavior until initiating
overall wall buckling at 2.5% drift.

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WALL FLEXURAL FAILURES—TWO POSSIBLE INTERPRETATIONS

One of the key behaviors observed in the Chile earthquake is damage to multi-story walls near thebase of the building, exhibiting buckled vertical reinforcement and crushed concrete concentrated overa relatively short height of wall. This type of failure was often not concentrated only at the boundaries,
but was instead seen to propagate over much of the length of the wall as shown in Figs. 2a and 3a.
In discussions with various engineers and researchers about the damage to flexure-governed walls
in Chile, two somewhat different interpretations tend to be offered, as summarized in Table 1. As
shown in the table, the two interpretations lead to different conclusions about the cause of this damage
and the implications for code provisions. Both interpretations assume that the damage initiates in theextreme boundaries of the wall section, where strain (either in tension or compression) is highest. In
either scenario the propagation of damage into the wall depth could be the result of subsequent cycles
after the boundaries have lost the capacity to transfer compression force. Because the tension zone of awall is generally deeper than the compression zone, it may be more likely to see this damage
throughout a wall section in the buckling-first scenario.
Some evidence from the Chile earthquake points toward the buckling-first interpretation, in that:• All of the serious flexural damage to walls reported has included buckled bars. The authors are notaware of reports of spalling without buckled vertical bars.
• All of the damaged walls reported had inadequate transverse reinforcement. Some engineers in Chilestate that they do use well-detailed transverse reinforcement and that such walls did not suffer any
damage. In the spalling-first scenario one would expect to see some damage even to well-detailed
walls.
The buckling-first interpretation is also consistent with behavior observed in the test specimen byThomsen and Wallace (2004), shown in Fig. 3a, which showed bar buckling occurring suddenly
without significant prior spalling.
The ATC-94 project will analyze damaged and undamaged walls in an attempt to determine which
scenario most accurately describes the observed damage in Chile and in experimental tests.
Both interpretations lead to a conclusion that inadequate ties in the boundary zones are what leadto the damage. The implications of the spalling-first scenario would lead to requirements for a greater
amount of confinement ties in the compression boundaries. The implications of the buckling-firstscenario would lead to close spacing of ties (not necessarily greater tie area) and would possibly imply
ties further into the section.
If the buckling-first interpretation is validated, the emphasis of design for flexural walls such as
those in Chile should focus on restraining bars from buckling, because if this is done the questions ofstrain demand and strain capacity may be less critical.

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Table 1 Summary of two possible interpretations of the flexural wall failures with longitudinal bar
buckling that were observed in Chile.
Observation

Spalling-first interpretation

Buckling-first interpretation

Cause/
initiation of
failureThe failures are associated with flexural
compression and occur because compression
strain demand exceeds compression strain
capacity of the concrete. Strain capacity may besmaller than traditional assumptions.

Failures begin with buckling of longitudinal bars that
occurs as a result of high tensile strain that stretches
the bars prior to a reversal into compression thatcauses buckling.

Bar buckling occurs after spalling and crushing,as a consequence of the flexural compression
failure.

Bar buckling occurs prior to any significant spalling or
crushing of cover concrete, with the bar buckling itself
helping to spall off the cover concrete.

High axial load contributes to the failures.

A deep neutral axis depth (in both tension andcompression) is a more important variable than highaxial load.

Verticalconcentrationof damage

Strain demand is large because the walls show avery short plastic hinge zone (of highcompression strain in the concrete).

Once bar buckling and spalling occur, compression
strain concentrates in the concrete at the reduced
section caused by the buckling, which is then heavily
damaged by cycles of compression.

Horizontal
propagation ofdamageWith continued cycling, damage progresses
further into the wall section.

A large tension neutral axis depth makes a large depthof the wall vulnerable to bar buckling. With continued
cycling, damage progresses further into the wall
section.

Implication for
designrequirements

The cause of wall damage in Chile is a lack ofadequate transverse reinforcement to provide
confinement. It may not even be possible toprovide enough confinement in thin sections
because core area is small and the pattern ofspalling indicates that plastic-hinge length isshort. Thus moderate amounts of well-detailed
confinement may not improve performance.

The cause of wall damage in Chile is a lack ofadequate transverse reinforcement to restrain bar
buckling. Moderate amounts of well-detailed
confinement, (e.g., spaced at 6 db) should restrain
longitudinal bars from buckling. If bars can be
restrained from buckling, the compression plastic
hinge length can be longer, and the strain demands
will not be so high. Thus performance would be
improved, with little visible damage.

COMPONENT BEHAVIOR MODES
While post-earthquake seismic evaluation of building structures can involve complex considerationsof site seismicity and soil characteristics, to estimate earthquake demands, studies (Zhang et al 2011)
have shown that it is also possible, lacking an estimate of earthquake demands, to gain an importantunderstanding of a building’s response behavior through consideration of the relative strengths of thevarious structural components and actions. In its simplest application, this process involves evaluating
the hierarchy of strength of the building’s structural elements and identifying the governing
mechanism of lateral deformation by hand calculation. FEMA 306 (ATC 1999) outlines a version ofthis process in which structural components are categorized according to their strength hierarchy andplastic mechanism (Fig. 4, Maffei et al 2000).

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Spandrel
weaker thanadjacent
wall piers

Wall piers
weaker thanspandrelbelow

Fig. 4 Illustration from FEMA 306 of a method for determining the governing mechanism of
non-linear lateral deformation in a concrete pier-spandrel system.
For example, the pier-spandrel system shown in Fig. 5a is a portion of a high rise building that
suffered severe damage and partial collapse in the earthquake. Though not necessarily the cause ofcollapse, it is clear from the photo that wall piers suffered severe shear damage when constrained
between deep spandrels, while the spandrels suffered flexural damage where they connect to heavier
piers at the extreme bays. Based on this observation, engineering calculations of element strength
should confirm that piers are shear-governed, and that the governing plastic mechanism for the system
is as shown in Fig. 5c.
The structural behavior modes considered in this analysis for individual wall piers and spandrels
were flexural yielding, sliding shear, and diagonal tension failure, computed based on strength
equations from FEMA 306. FEMA 306 calculations for diagonal shear strength distinguish between
the capacity corresponding to low and high displacement ductility demands on wall type elements. The
geometry, reinforcement details, and specified material properties were obtained from available
structural drawings for the building, while expected material properties for concrete and steel
reinforcement were estimated based on PEER (2010). The axial load was calculated based on tributaryarea, self-weight, and typical dead and live uniform loads defined for a residential building by the
NCh433Of.96 Chilean code (INN 1996). The resulting axial load ratio on the wall piers represents
approximately 2% of their nominal axial capacity. Axial loads produced by seismic forces weredisregarded in the simple hand calculations presented here. For each wall pier and spandrel beam,
Table 2 presents the shear force corresponding to each of the behavior modes considered; the behavior
mode with the lowest corresponding shear force is expected to govern the element’s seismic response.
These hand calculations confirm that the expected shear strength of individual piers is less than theshear that would correspond to flexural yielding.
In some buildings, pier-spandrel joint equilibrium can help to identify whether damage is expected
to occur in piers or spandrels. However, for this example, a plastic mechanism analysis is necessary
because the stronger end piers affect the overall mechanism of lateral deformation for the system.
For the plastic analysis of the four-story four-bay pier-spandrel system, several plastic mechanisms
were considered, including shear failure of intermediate piers (Fig. 5c), spandrel shear failure between
pier lines (Fig. 5d), and others. Virtual work principles and Lower Bound Theorem were applied toestimate the collapse load, assumed to be applied to the system at the top level of the subassembly.
Indeed, the plastic mechanism shown in Fig. 5c corresponds to a lower plastic load than other possible
mechanisms and is also consistent with the post-earthquake behavior observed.
Given that this behavior mode and mechanism are reasonably predictable by straightforward
engineering calculations, the question could be considered whether design codes should require
engineers to identify the governing behavior mode and mechanism, for example using capacity designprinciples. Currently US and Chilean codes make only a small distinction (via the strength reduction
factor) in the assumed ductility capacity between shear versus flexural behavior. Shear failure of wall
piers is generally less-desirable than flexural yielding because shear failure tends to exhibit lessductility and can be associated with a concentration of lateral deformation and damage.

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US and Chilean codes currently do not require investigation of the governing mechanism for pierand spandrel systems. While codes have “strong-column-weak-beam” provisions for moment frames,
there are no such requirements for walls with openings to avoid strong-spandrel/weak-pier behavior,
which can lead to a story mechanism in some wall structures. Reviewing the damage in Chilecompared to current trends for more transparent “performance-based” code requirements, Bonelli et al(2012) have questioned whether performance-based design can be effectively applied to structures if
the design process does not check explicitly for a suitable ductile mechanism of behavior.
In the ATC-94 project, studies of lateral-force-resisting elements, such as cantilevered and coupledwalls, will be performed to investigate how designers can best evaluate the expected behavior of theseelements.

16

Shear
failure15

14
Flexuralhinging

13

12

(a)

(b)

(c)

(d)

Fig. 5 Pier-spandrel system: (a) observed damage (photo from EERI team) (b) idealized structuralelements (c) plastic mechanism observed and validated by calculation (d) example of a plastic
mechanism considered and shown by calculation not to govern.

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Table 2 Wall pier and spandrel beam strength and expected behavior mode
Element
Type

Line

External
Pier

B1,F

Internal
Pier

CInternal
Pier

D1,E

Spandrel

B1-F

Level
12
13
14
15
12
13
14
15
12
13
14
15
13-16

Behavior modes considered, and corresponding shear force (kip)Diagonal Tension
Governing
Sliding
Flexurebehavior,
ACI
FEMA 306, low FEMA 306, highshear
FEMA 306
318
ductility
ductility
290
435
280
230
139
235
372
280
228
137
Diagonal
Tension
235
372
280
226
134
235
372
280
224
132
401
365
206
182
115
318
318
206
179
113
Diagonal
Tension
318
318
206
177
110
318
318
206
175
108
304
298
168
146
92
239
292
168
144
90
Diagonal
Tension
239
292
168
143
88
239
292
168
141
87
236
155
199
144
76
Diag. Ten.

BUILDING BEHAVIOR
To complement studies of specific component behavior, whole building studies examine how
structural elements interact with each other and how component behavior affects overall building
performance. Working groups on the ATC-94 project are evaluate whether computer analysis models
can accurately represent the location, type, and severity of damage observed in buildings that wereaffected by the earthquake. These studies include detailed non-linear dynamic finite element models aswell as simpler models with tools that are more widely used by design practitioners. Objectives are toprovide recommendations for what structural elements are important to consider in seismic analysis,
such as coupling slabs or other elements not designated as primary lateral force-resisting elements, andfor calibrating simpler models based on the findings from detailed models in this study.
Some good agreement has been found between results from sophisticated nonlinear finite element
models and the apparent failure mechanisms observed in certain buildings. A preliminary study has
been conducted using a three-dimensional finite element model of a representative slice of a concrete
wall building affected by the earthquake, using the model shown in Fig. 6. The walls and floors of thebuilding are represented by a detailed mesh of non-linear shell elements with an advanced constitutive
formulation for reinforced concrete available in the LS-DYNA software. The shell elements havematerial zones defined through their thickness such that unconfined and confined concrete and thereinforcement planes are correctly positioned; this enables interaction of in-plane actions and out ofplane bending (and wall buckling) to occur. This type of model does not require ‘plane sections toremain plane’ along a wall, and simulates the in-plane axial-flexure-shear interaction without empirical
combination. LS-DYNA’s large-deflection explicit solver enables softening behavior, buckling andincipient collapse to be captured without numerical convergence problems. The model captures thestrain history of the wall longitudinal reinforcement and accounts for prior tension strain and
Bauschinger softening that contributes to wall buckling or bar buckling. At this point the model does
not address bar buckling in a fully explicit manner, but this capability could be added.
The ‘slice’ model (Fig. 6a) of the building was built based on the structural drawings. Few‘engineering’ decisions and pre-calculations need to be made in assembling models of this type since
all the walls, floors, reinforcement, openings, discontinuities etc. are represented explicitly. Almost all
the concrete is unconfined since the reinforcement has few cross-ties and the bar spacings are large.
The base of the model was subjected to the tri-directional motion time histories from the nearest
recording station in Concepcion (Boroschek et al 2010).
Under seismic excitation this model predicts concrete crushing failure, initiated where1774concentration of compression strain occurs in the extreme fiber of the wall at ground level. The
compression failure zone does not spread vertically, but propagates across the width of the wall insuccessive cycles, during which the sway period of the building also elongates. Eventually, as verticalcarrying capacity is lost at both ends of the wall the building topples under gravity (Figs. 6a and 6b).
Fig. 6c shows a close-up of the lower stories of the wall at the initiation of collapse, with aconcentration of vertical compression strain occurring at the first floor level. As shown in Fig. 6d, thestrain distribution along this section of the wall is not linear in the compression zone; compression
strains increase sharply near the extreme fiber. This preliminary analysis supports the hypothesis thatcompression failure in wall boundary elements can lead to collapse in certain cases.
The concentration of strain at extreme fibers is observed in laboratory tests on walls, but is notpredicted by a traditional analysis that assumes that plane sections remain plane. The observation ofcompression damage over only a short height of the wall is also predictable for ‘strain softening’
failure associated with unconfined concrete and low reinforcement ratio. Further studies will bedirected at refining models to determine what types of conditions are most vulnerable and what
adjustments can be made to practical analysis methods and design practices to account for thisbehavior. Possible recommendations could include avoiding vertical discontinuities in compression
critical areas of wall, adjusting analysis assumptions or limits on concrete compression strain, or using
special detailing requirements to improve compression and cyclic behavior of wall boundaries.

(a)

(b)

(c)

(d)

Fig. 6 Analysis of wall with vertical discontinuity (a) model deformed shape at failure (b) close-up of
lower stories (c) vertical strain concentration at ground floor (c) strain distribution on wall section

CODE IMPLICATIONS
Chilean engineers have proposed several changes to building codes to address behaviors observed in
the earthquake. The following is a partial list of proposals that have been considered (Bonelli et al2012):• Apply a correction factor to increase the design displacement δu used to determine confinement
requirements for walls.
• Consider longitudinal reinforcement in the entire flange width when determining thestrength/behavior of flanged walls under flexure and axial loads.
• Limit the longitudinal bar diameter to 1/9 of the least dimension of the wall thickness.
• Require that the bar diameter of transverse reinforcement be at least 1/3 the diameter of the confined
longitudinal bar.
• Require that transverse reinforcement be anchored with standard hooks to extreme longitudinal bars
in the wall.

1775• Limit extreme compressive strain to 0.008 under design displacement δu. (Or, more directly in linewith principles of capacity design, require that extreme steel tension strain be at least 0.004 whenconcrete reaches assumed strain of 0.003.)• Require a minimum wall thickness of 1/25 the unsupported wall height; if less than 1/16 theunsupported height, then out-of-plane buckling must be studied. (Or, more conservatively, require aminimum wall thickness of 1/16 the unsupported wall height.)• Apply a shear amplification factor of 1.4 to the code-prescribed earthquake loads for designing wall
web transverse reinforcement, unless principles of capacity design are used to protect against shear
failure.
• For sections with large longitudinal reinforcement ratios or limited cover, require that the totaltransverse reinforcement area in the lap length to be equal or greater than the area of the lapped bar.
The ATC-94 project will also be considering areas where US code changes are warranted, both to
the ACI 318 requirements for concrete, and to the ASCE-7 requirements for the classification of
concrete seismic force-resisting systems and the specification of earthquake force and displacement
demands.

CONCLUSIONS
Damage to mid-rise and high-rise concrete wall buildings caused by the 2010 Chile Earthquake offersa rare and valuable opportunity to study buildings in detail to gain practical lessons for structuraldesign. Observed damage such as concrete crushing and reinforcing bar buckling in wall boundary
elements could be interpreted in different ways with different implications on design. Overall wallbuckling, pier-spandrel wall behavior, and damage from discontinuities and configuration effects arealso key issues. Sophisticated three-dimensional non-linear finite element models of Chilean buildings
have been built and initial response-history analysis results show good agreement with damage
observations. Through the ATC-94 project, a team of researchers and practitioners is developing
recommendations for modifying design practices based on studies of damaged Chilean wall buildings,
leading to efforts to address undesirable behavior modes and improve the seismic performance ofconcrete wall buildings.

ACKNOWLEDGMENTS
The authors gratefully acknowledge the NEHRP Consultants Joint Venture (a partnership of the
Applied Technology Council and Consortium of Universities for Research in Earthquake Engineering),
under Contract SB134107CQ0019, Earthquake Structural and Engineering Research, issued by the
National Institute for Standards and Technology (NIST), for funding the ATC-94 project described inthis paper. In particular, we appreciate Jon Heintz, Steve McCabe, and Jeff Dragovich for providing
leadership and valuable insight for pursuing project objectives. The authors also appreciate the close
collaboration with project team leaders including Professor Jack Moehle, Professor John Wallace,
Professor Laura Lowes, Professor Dawn Lehman, and their team members, as well as projectreviewers Professor Helmut Krawinkler, S.K. Ghosh, Professor Mete Sozen, Derrick Roorda, andProfessor Tara Hutchinson. We appreciate the cooperation and insights provided by Professor Leo
Massone and Sergio Contreras.

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