Reviews and Reports

Bulletin of IISEE, 46, 153-160, 2012

OVERVIEW OF THE
CURRENT SEISMIC CODES IN
CENTRAL AND SOUTH AMERICA
Juan W. CHAVEZ, Ph.D., P.E 1
ABSTRACTThis paper presents an overview of the current (2011) seismic codes in Central and South America.
The main aspects of the various seismic provisions of the local model building codes used in theregion are presented and briefly discussed. The issues presented include code development, sitecharacterization, building classification, design response spectra, seismic forces and reduction factor,
design considerations, construction practice and code enforcement.
BACKGROUND
Many areas of Central and South America are noted for their high seismicity. Recognizing theseismic activity in the region, earthquake-resistant design of structures is a must in these countries.
As such, each country has developed their own seismic codes based on their experience and laws.
The codes also follow aspects of the 1997 Uniform Building Code (UBC-97) and the 2009
International Building Code (IBC-2009).
The traditional design philosophy of most codes in Central and South America is to maintain Life
Safety by avoiding collapse during severe earthquakes. Although different earthquake activity levels
may be used (see Table 1) the design basis earthquake is typically an event with a 475 year return
period used in UBC-97.

Table 1. Earthquake Event Levels
Earthquake

Probability ofexceedance

Period of Interest(years)Return Period(years)Frequent
Occasional
Rare
Very Rare

50%
20%
10%
2%

50
50
50
50

72
225
475
2475

The method of assigning levels of seismicity utilized by most codes in Central and South America ischaracterized by dividing a country into various seismic zones, similar to that used in the UnitedStates prior to 2000. However, Mexico has recently adopted a new building code which has shifted tothe concept of seismic acceleration maps instead of seismic zones (similar to the concept used in USA
since 2000). There are other countries (i.e. Peru), which have begun to develop their own acceleration
maps, but these have not yet been introduced into their current codes.

1

ABS Consulting, Group Manager (jchavez@absconsulting.com). IISEE Peruvian participant- 153 -

SEISMIC CODE DEVELOPMENT
Most countries in Central and South America have published, enforced and updated their seismic
codes over a period of years. The first application of some sort of earthquake regulations goes back to1914 in Costa Rica, 1935 in Chile, 1939 in Venezuela, and 1942 in Mexico. However, the first
application of what are considered to be modern seismic codes in most countries goes back to the1970’s and followed the recommendations for seismic requirements published by the StructuralEngineering Association of California (SEAOC) in 1961. Other countries, such as Bolivia, have amuch shorter history of seismic codes development.
Table 2 lists the current seismic codes in Central and South America (ordered by latitude, from North
to South). Earlier editions of these codes are also noted in this list. Countries and territories of the
Caribbean are not included in this list due to the report space limitations. Paraguay, Uruguay andBrazil in South America are also not included, since they are located in zones of low seismicity.

Table 2. List of Central and South American Countries and their Seismic Codes
Country

Current
Seismic Code

USA [1]

IBC-2009

2009

Mexico [2]MOC-2008

2008

NTCDS-2004

2004

Guatemala
El Salvador
Honduras [4]Nicaragua [5]Costa Rica
Panama

NR-1
NTDS
None
RNC
CRSC-2002
REP-2004

2002
1997
None
1983
2002
2004

Venezuela

COVENIN 1756

2001

Colombia
Ecuador
Peru
Bolivia

NSR-10INEN-5
E.030
NBDS

2010
2001
2003
2006

Chile [6]Nch433.of96

2009Mod

Argentina

CISROC-103

2005

Mexico City
[3]

1
2
3
4
5

6

Year
Previous Modern Codes
Published
IBC-2006, IBC-2003, IBC-2000,
UBC-97 to UBC 1967 (modified every three years),
UBC-1964 to UBC-1927.
MOC-1993, MOC-1982, MOC-1969
NTCDS-2004, NTCDS-1994, NTCDS-1987,
NTCDS-1985, NTCDS-1976
NR-1 1996
1994, 1989, 1965
None
Not available
CRSC-1986, CRSC-1974
REP-1994
COVENIN 1756:98, COVENIN 1756:87,
NP-MOP 1967
NSR-98, CCCSR-84
Not available
E.030-1997, 1977, 1970
None
Nch2545.Of2003 (industrial facilities), Nch433.96,
NCh433.Of93, Nch433.Of72
CISROC-103.1991, CIRSOC-1983, NAA 1980,
CONCAR 1972

USA code is included as reference.
The Manual de Obras Civiles (Manual of Civil Works) is discussed in this paper instead of the
Mexico City Building Code. Both Codes are applicable in Mexico.
New provisions have been published in 2010 in Guatemala (these are based on combining the
UBC-97 and IBC-2009). However, these new provisions are not included in this paper.
The author does not have knowledge of a seismic code in Honduras.
The author does not have knowledge of an update of the 1983 seismic code in Nicaragua.
The modified version of the Nch433.of96 Mod 2009 was actually published in 2010 after the2010 Maui Chile earthquake.

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SITE CHARACTERIZATION
Seismic zones are used in all Latin-American countries, with the exception Mexico, to characterize
their local seismic hazards. Ground accelerations (effective peak ground acceleration, acceleration
coefficient) associated with each seismic zone varies from 0.04g to 0.50g, depending of each country
and region. Three to four seismic zones are defined in most countries. Exceptions to this rule are
Venezuela having 8 seismic zones (0 to 7), Colombia having 10 seismic zones (1 to 10), and Bolivia
having 8 seismic zones (1 to 8). The ground acceleration in high seismic zones is approximately 0.4g
in most countries. The ground accelerations of boundary regions between countries are generally not
the same.
Soil type is an important component used in the definition of site hazard within the local building
codes. In most countries site soils are classified as soil types S1, S2, S3 and S4. This classification issimilar to the soil classification used in the Uniform Building Code (UBC-97).
Panama andColombia use the soil classification A to F, which corresponds to the IBC soil classification. Chile
adopted a soil classification based on soil types I to IV. Besides the different notations used to define
the soil types there is no consistency with the approach each country uses to define the soil types. In
some cases shear wave velocities are used, whereas in other cases the standard penetration resistance,
N, or the specific soil description is used for soil classification purposes. Some countries provide
better soil type definitions than others.
Table 3 lists the seismic zones adopted in each country as well as the different soil types. An attempt
has been made in this table to group the seismic zones based on the level of seismicity and similarity
between the different soil types. The peak ground acceleration, effective peak ground accelerationand zone acceleration coefficient was used for this purpose.
Table 3. Seismic Zoning and Soil Characteristics

Not definedNot defined2
3
2
II III

PanamaNot defined. Acc
Coef given by city
0- 3- 562
4
7
1- 4- 6- 83
5
7 10I
II III IV
1
2
3
1
2
3
18
02
3
4
1

Venezuela [1,2]Colombia
EcuadorPeru
Chile
Bolivia [1]Argentina [1]
1.
2.

4
1
IV

SpecialUSA
MexicoGuatemala
El Salvador
Costa Rica [1]Ground Acceleration (g)

Soft
Rock
Stiff
Soil
Soft
Soil

Seismic Zone

RockCountry

Soil Classification
Hard
Rock

Seismicity

Use spectral acceleration
Use spectral acceleration
0.15
0.15-0.40
0.40
0.30
0.40
0.20- 0.300.400.34
0.36
0.44
Aa vary from 0.14 to 0.25
Av vary from 0.14 to 0.34
0.10- 0.200.30
0.350.15
0.25
0.40
00.20- 0.300.400.15
0.25
0.35
0.50
0.15
0.25
0.30
0.40
0.15
0.30
0.40
0.20
0.30
0.40
0.040.12
0.04- 0.160.25
0.35
0.10
0.18

A
-

B
S1
S1
S1
S1

C
S2
S2
S2
S2

D
S3
S3
S3
S3

E
S4
S4
S4

F
-

A

B

C

D

E

F

-

S1

S2

S3

S4

-

A

B

C

D

E

F

-

S1
S1
I
-

S2
S2
II
S1

S3
S3
III
S2

S4
S4
IV
S3

S4
-

-

I

III

-

II

Ground acceleration varies with soil type.
Spectral shapes (S1 to S4) instead of soil types are used to define the response spectrum.

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BUILDING CLASSIFICATION AND IMPORTANCE FACTOR (I)
Buildings are classified based on their occupancy and their structural type (besides theirconfiguration). Building occupancy categories, although different nomenclatures are used in eachcountry, are consistently defined in all codes as: essential, important, common and minor structures.
Buildings containing hazardous materials are included in most codes within the essential category
with few exceptions. The basic structural types account for the construction configuration used, i.e.
frame, shear wall, etc. Table 4 shows occupancy categories, importance factors (I), and structure
types used by the various codes.
Table 4. Building Classification & Importance Factor

Country

CommonMinor

Essential

ImportantCommonMinor

Structural Category

Important

Importance Factor [1]Essential

Occupancy Category

Basic Structural System

USA

IV

III

II

I

1.5

1.15

1

1

A+

A

B

-

1.5

1.5

1

-

Guatemala
El Salvador

I,II
I

III
II

IV
III

V
-

NA
1.5

NA
1.2

NA
1.0

NA
-

Costa Rica

A,B

C

D

E

1.5

1.0

1.0

0.75

Panama [3]

IV

III

II

I

1.0

1.0

1.0

1.0

Venezuela

A

B1

B2

C

1.3

1.15

1.0

NA

Colombia [4]Ecuador
Peru
Bolivia
Chile [5]Argentina

IV
A
A
A
IV
A0

II
B
B
B
III
A

I
C
C
C
II
B

D
D
I
C

1.5
1.5
1.5
1.4
1.2
1.4

1.1
1.3
1.3
1.2
1.2
1.3

1.0
1.0
1.0
1.0
1.0
1.0

NA
0
0.6
NA

Buildings and non-building structures
Type 1 to 13 including buildings, bridges,
tanks, dams, industrial facilities, etc
NA
Frames, dual, wall, others
Frame, dual, wall, cantilever and others.
Bridges, dams not included
Bearing, frame, dual, cantilever, others
Type I (frames), type II (dual systems),
type III (walls and braced systems), IV
Frame, dual, shear wall, others
Frame, dual, shear wall, others
Frame, dual, shear wall, others
Frame, dual, shear wall, others
Frames, shear walls, braced, and others
Frame, dual, wall, others

Mexico

1
2
3
4
5

[2]

Importance factor for minor building structures is left to the designer criteria, and in many cases
these minor structures are not required to be designed for seismic forces.
The Mexico code uses an importance factor of 1.5 for important structures (A). For essentialbuildings (A+), the code is not explicit, but a factor of 1.5 is assumed.
The Panama code does not provide an importance factor for seismic actions (an importance factor
is provided for wind actions only). A factor of 1 is assumed for seismic actions.
The Colombia code incorporates group III for important community structures with I=1.25.
Building categories for Chile (I to IV) have been renamed in the modified code. The Nch433.of96
code listed the buildings as category A to C instead.

DESIGN RESPONSE SPECTRA (Sa)The design acceleration response spectrum represents the site characteristics (seismicity and soil type).
Some of the codes include the importance factor in the definition of the elastic response spectrum.
Other codes (i.e., Costa Rica) also include the building characteristics and directly define the inelastic(design) response spectrum. Figures 1 to 5 show (in no particular order) the response spectrum shapesof the various codes (for 5% damping). For comparison purposes, only the elastic spectrum ispresented in all cases (without including the importance factor or any reduction factor). The notation,
in some cases, has also been modified (from the original codes) in order to compare the various codes.

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Ao (acc)
=
β=
p=
To =
Ta =
Tb =
Tc =
Note: The spectrum equations for Mexico are valid
for a damping of 5%. The k factor in the Mexico
code is equal to 2 for rock.

MexicoUse software
PRODISIS
2.5 in rock
0.5 to 10NANA<= 2sec

El Salvador
See Table 3
2.5 to 3
2/3
00.10
0.3 to 0.9
4 sec

Costa Rica
See Table
3
2.5
1
0
0.03
0.4 to 1.07
2.6 to 5

Note. Elastic and inelastic spectral acceleration plots(in logarithm scale) are given in the Costa Rica code.
The valúes shown are for the elastic response spectrum

Figure 1. Elastic Design Spectrum for Mexico, El Salvador and Costa Rica

Aa = acceleration =Av = acceleration =Fa = f(soil type, Aa) =Fv = f(soil type, Av) =
To =
Ta =
Tb =
Tc =

Colombia
See Table 3
Aa
1 (soil B)
1 (soil B)
00.10 Cv/Ca
0.48 Cv/Ca
2.4 Fv

PanamaSee Table 3
See Table 3
1 (soil B)
1 (soil B)
00(0.48Cv/Ca)1.5
4 sec

Figure 2. Elastic Design Spectrum for Colombia and Panama

Ao = ground acceleration (in Table 3)
α A A, α V V, α D D = f(soil type, seismic zone)
α A A = 1.10Ao (for soil type I, seismic zone 3)
p = 0.8 to 0.6 (larger value for soil type I)
To = 0(all cases)
Ta = 0.13 to 0.37 (larger value for soil type I)
Tb = 0.22 to 0.68 (larger value for soil type l)
Tc = 1.53 to 1.75 (smaller value for soil type I)

Figure 3. Elastic Design Spectrum for Chile
GuatemalaVenezuela
Bolivia
Argentina
Ao = See Table 3 See Table 3 See Table 3 See Table 3
2.5
2.4 to 3
2.5
3.0
β=
p=
2/3
1 to 0.8
0.5 to 1
2/3
To = 0000
Ta = 0.12
Tb/4
0.4 to 0.8
0.1 to 0.4
Tb = 0.4 to 1.0
0.4 to 1.3
1.0 to 3.0
0.35 to 1.6
Note. The acceleration values in the Venezuela code needfurther to be modified by a correction factor, φ. This factor
varies between 0.65 to 0.85 for seismic zones 1 to 4 andbetween 0.7 to 1.0 for seismic zones 5 to 7.

Figure 4. Elastic Design Spectrum for Guatemala, Venezuela, Bolivia, Argentina- 157 -

Z (zone factor) =Cm = f (soil type,seismic zone) =S (soil factor) =
To =
Tb =

EcuadorSee Table 3
2.5 to 3

Peru
See Table 3
N.A.

1 (soil S1)
1.5 (soil S3)0
0.5 to 0.82 forsoil S1 to S3
2.0 for soil S41 (soil S1)
1.4 (soil S3)0
0.4 to 0.9 forsoil S1 to S3

Figure 5. Elastic Design Spectrum for Ecuador and Peru

SEISMIC DESIGN FORCE AND REDUCTION FACTOR (R)The design seismic forces (V) are calculated as the product of the seismic coefficient (Cs) times theseismic weight (W)V = Cs. W
The seismic coefficients in the various countries are expressed by different equations and notations.
However, in all cases the following ratio can be used to determine the seismic forces.
Cs = Sa / (R/I)
The R value is the reduction factor used by the codes to decrease the elastic seismic forces. Thisfactor accounts for (a) the global ductility capacity of the lateral force resisting system, and (b) theover-strength inherent in the lateral force resisting system. The R factor is also a function of thestructural system and the expected design level or design category.
The definition and application of the “R” factor varies between the various codes, as follows:• In most codes the R factor is a single and constant value used to reduce the elastic forces in aconstant manner, regardless of the period of the structure.
• In countries such as Venezuela the elastic forces are reduced in a non-uniform manner. The R
factor is modified with the period of the structure.
• In some countries, including Costa Rica and Argentina, a global ductility concept is usedinstead of the typical R factor.
• Colombia and Ecuador use an additional reduction factor, Φ (always <1) to account for any
structure irregularities.
There appears to be good agreement between codes with the reduction factors for concrete andmasonry structures, a building type common in Central and South America. However there is little
consistency among the local seismic codes in the use of the R factor for steel structures. Some codes,
like the recent NSR-10 (Colombia), include a large variety of steel structural systems and associatedreduction values. Other countries, such as Ecuador and Peru, use one or two group types to define all
steel structures. For instance, ordinary concentric brace frames (OCBF) have a value of R=3.25 in the
IBC-2009 and there are height limitations in their use. The same structure according to the Peruvian
code has a value of R=6 with no height limitations. Note also that the 2009 modified Nch433 code
(Chile) appears to indicate an R value of 3 for OCBF compared to a value of 7 used in the previous- 158 -

edition of this code. It may be desirable that more consistent structural systems and R values be
defined in new versions of the local codes.
DESIGN CONSIDERATIONS
The majority of codes in Central and South America make reference or are based on the provisions of
the Building Code Requirements ACI-318, and the American Institute of Steel Construction (AISC)
for the design of reinforced concrete and steel structures, respectively. There are some exceptions,such as the CIRSOC (Argentina) that has based concrete design on a different approach; however, the
new edition of this CIRSOC has been adjusted to also follow ACI-318. Masonry design (reinforced
masonry and confined masonry) typically follows the local practices in the various countries.
Attention should be paid to the following issues:• Load combinations in the various codes are not consistent. Many codes use LRDF-type load
combinations, but other codes still have their own particular set of load combinations. It is
important to keep this in mind when comparing seismic effects between local codes andinternational codes.
• Seismic detailing is important. Some countries make exceptions to ACI-318 detailing
requirements based on their own experience. For instance, the previous edition of the Nch433(Chile) permitted designers to not satisfy ACI requirements for boundary elements instructural walls. This may have contributed to the damage to concrete structures during the2010 Chile earthquake. The modified version of Nch433 appears to have corrected this issue.
• Application of the current versions of the seismic codes is important. Local (country) codes
require satisfying the available versions of the ACI and AISC standards at the time the local
code was issued. This creates a gap with current ACI and AISC codes which are mostly
revised every three years.

CONSTRUCTION PRACTICE AND CODE ENFORCEMENT
The codes, in general, require that construction documents (calculations, drawings, and specifications)need to be submitted for approval to the local authorities. However the review and approval practices
vary from country to country and from city to city. Some countries, like Chile, require that theconstruction documents regarding public utility buildings (schools, hospitals, police stations, firefighting stations, communication centers, etc.) and residential buildings of more than 5 stories need toalso be approved by an independent reviewer. Peer-review approach is not applied in all countries.
Inspection during construction is another issue that may be different in each country. There is no
guarantee that a well designed project is executed as per design intent if adequate inspection is not
performed during construction. Lack of inspection is also not uncommon, especially in housing
construction.
The most recent codes (i.e., Colombia, Mexico) appear to put greater emphasis on the necessity ofproper construction documents review and inspection during construction that includes providing
instrumentation for building monitoring for future earthquakes.

CONCLUSIONS
A general overview of the provisions of the various seismic codes utilized in Central and SouthAmerica was presented. Since the seismicity and local site conditions differ from country to country,
it may be not possible to find a common ground to develop similar design spectra for all countries.

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However, it may be desirable to make an effort to provide for greater uniformity of some aspects ofthe codes, such as definition of structure types, used in all countries. The inclusion of non-building
structures in the codes is also desirable. Construction quality control (inspection) requirements areanother issue that may be improved in current codes.

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