MINISTRY OF HOUSING, CONSTRUCTION AND SANITATION
TECHNICAL BUILDING STANDARD
E.030
“EARTHQUAKE-RESISTANT DESIGN”
Lima, April 02, 2003
Approved By Ministerial Decree N° 079-2003 VIVIENDA
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TECHNICAL BUILDING STANDARD E.030
PERMANENT TECHNICAL COMMITTEE NTE E-030 EARTHQUAKERESISTANT DESIGN
Chairman:
Advisor
Technical Secretary:
Dr. Javier Pique del Pozo
Eng. Julio Kuroiwa Horiuchi
SENCICO
MEMBERS
INSTITUTIONS
Japan-Peru Centre for Earthquake
Engineering Research and Disaster
Mitigation (CISMID-UNI)
South American Regional Center for
Earthquake Engineering (CERESIS)
Peruvian Board of Engineers. Lima
Council
Geophysical Institute of Peru (IGP)
Pontifical Catholic University of Peru
National University of Engineering (UNI).
Faculty of Civil Engineering
National Service for Research, Standards
and Training for the Construction Industry
(SENCICO)
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REPRESENTATIVES
Dr. Javier Piqué del Pozo
Dr. Jorge Alva Hurtado
Dr. Hugo Scaletti Farina
Eng. Luis Zegarra Ciquero
Dr. Leonidas Ocola Aquise
Eng. Alejandro Muñoz Peláez
Eng. Roberto Morales
Morales
Eng. Julio Kuroiwa Horiuchi
Eng. Julio Rivera Feijóo
Chapter 1.
Article 1
Article 2
Article 3
Article 4
CONTENTS
GENERAL
Notation
Scope
Philosophy and principles of earthquake resistant design
Presentation of the project
Chapter 2.
Article 5
Article 6
Article 7
SITE PARAMETERS
Zonation
Local Conditions
Seismic Amplification Factor
Chapter 3. GENERAL REQUIREMENTS
Article 8 General aspects
Article 9 Concept of seismic resistant structures
Article 10 Occupancy categories of buildings
Article 11 Structural configuration
Article 12 Structural systems
Article 13 Category, structural system and regularity of buildings
Article 14 Analysis procedures
Article 15 Lateral displacements
Chapter 4. ANALYSIS OF BUILDINGS
Article 16 General
Article 17 Static analysis
Article 18 Dynamic analysis
Chapter 5. FOUNDATIONS
Article 19 General
Article 20 Bearing capacity
Article 21 Overturning moment
Article 22 Isolated footings and caissons
Chapter 6. NONSTRUCTURAL ELEMENTS, APPENDAGES AND
EQUIPMENT
Article 23 General
Chapter 7. EVALUATION AND REPAIR OF STRUCTURES DAMAGED
BY EARTHQUAKES
Article 24 General
Chapter 8. INSTRUMENTATION
Article 25 Recording accelerographs
Article 26 Location
Article 27 Maintenance
Article 28 Data availability
Article 29 Requirements for acceptance of Works
ANNEX
Seismic macrozonation of Peru
41-5
CHAPTER 1
GENERAL
Article 1
C
CT
Di
e
Fa
Fi
g
hi
hei
hn
Mti
m
n
Ni
P
Pi
R
r
ri
S
Sa
T
Tp
U
V
Vi
Z
Q
∆i
Notation
Seismic amplification coefficient
Coefficient to estimate the predominant period of a building
Lateral elastic displacement of level "i" relative to ground
Accidental eccentricity
Horizontal force on the top roof
Horizontal force on level "i"
Acceleration due to gravity
Height above the base to Level "i"
Height of story "i"
Total height in meters of building
Accidental torsional moment on level "i"
Number of modes used in modal superposition
Number of stories in the building
Sum of weights above level "i"
Total weight of the building
Weight of level "i"
Seismic forces reduction coefficient
Maximum expected elastic structural response
Elastic responses corresponding to mode "i"
Soil factor
Acceleration spectrum
Fundamental period of the structure for static analysis or modal period
for dynamic analysis
Period that defines the spectrum platform for each type of soil
Use and importance factor
Base shear
Story shear in story "i"
Zone factor
Stability coefficient for overall P-delta effect
Relative drift of story "i"
Article 2
Scope
This standard establishes the minimal conditions to ensure that buildings
designed according to its requirements will have a seismic behaviour, in
accordance to principles stated in Article 3.
It applies to the design of all new buildings, to the evaluation and reinforcing
of existing buildings, and to the repairing of buildings that have sustained
earthquake damage.
In case of special structures, such as reservoirs, tanks, silos, bridges,
transmission towers, docks, hydraulic structures, nuclear plants, and all those
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structures whose dynamic behaviour differs from that of conventional
buildings, additional considerations are required as a supplement to the basic
guidelines contained herein.
In addition to the standards contain herein prevention measures must be
taken against disasters that may occur as a consequence of seismic
movements: fire, leak of hazardous materials, massive landslides and others.
Article 3
Philosophy and Principles of Earthquake Resistant Design
The philosophy of earthquake resistant design consists of:
a) to avoid human life casualties
b) to ensure continuity of vital services
c) to minimize damage to property
It is recognized that to give complete protection against all earthquakes is not
technically neither economically feasible for most structures. In accordance
with this philosophy the following design principles are established:
a) The structure should not collapse nor harm human beings by severe
earthquake ground motions that could occur at the site.
b) The structure should withstand moderate earthquake ground motions
which may be expected to occur at the site during service life of the
structure with damage within acceptable limits.
Article 4
Presentation of the Structural Project
The drawings, description, and technical specifications of the structural
project shall be signed by a chartered civil engineer (a civil engineer
registered at the Peruvian Board of Engineers), who shall be the only person
authorized to approve any modification to the above-mentioned documents.
The specifications and the drawings for the structural project shall contain at
least the following information:
a) Earthquake-resistant structural system
b) Parameters to define the seismic force or the design spectrum
c) Maximum displacement of the uppermost level and maximum relative
interstory displacement.
Projects for buildings over 70m in height shall be backed up with a report
containing data and justifying calculations to be reviewed and approved by
the concerned authorities.
The use of materials, structural systems and construction methods other than
those indicated in this Standard shall be approved by the concerned
authorities appointed by the Ministry of Housing, Construction and Sanitation,
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and such materials, systems and methods must comply with the provisions of
this section and it must be demonstrated that the proposed solution will
produce adequate results in terms of stiffness, seismic resistance, and
durability.
CHAPTER 2
SITE PARAMETERS
Article 5
Zonation
The country is considered to be divided into three zones, as shown in Figure
N° 1. The proposed zonation is based on the spatial distribution of the
seismicity observed, the general characteristics of the seismic movements,
and their attenuation with the epicentral distance; and also on neotectonics
data.
Each zone has a Z factor allocated to it, as shown in Table 1. This factor is
interpreted as the maximum ground acceleration that has a 10% probability
of exceedence in 50 years.
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Table 1
Zone Factors
ZONE
3
2
1
Article 6
Z
0.40
0.30
0.15
Local Conditions
6.1
Seismic microzonation and site studies
a.
Seismic microzonation
This involves multidisciplinary studies which investigate the effects of seismic
movements and associated phenomena such as soil liquefaction, landslides,
tsunamis, etc., on the area of interest. The studies supply information on the
possible modification of the seismic actions by local conditions and other
natural phenomena, as well as the limitations and demands that, as a result
of the studies, are taken into account for the design and construction of
buildings and other works.
It shall be a mandatory requisite that microzonation studies be carried out in
the following cases:
•
•
•
Urban expansion areas
Industrial complexes, or similar
Reconstruction of urban areas destroyed by earthquakes and associated
phenomena.
The results of microzonation studies shall be approved by the concerned
authorities, who may request additional information or justification if they
deem it necessary.
b.
Site studies
They are similar to microzonation studies, although not necessarily so
extensive. These studies are limited to the project site, and they supply
information on the possible modification of seismic actions and other natural
phenomena by local conditions. Their main objective is to determine the
design parameters.
Design parameters below those indicated in this Code shall not be taken into
consideration.
6.2
Geotechnical Conditions
For the effects of this Standard, soil profiles shall be classified taking into
account the mechanical properties of the soil, the depth of the stratum, the
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fundamental vibration period and the velocity of propagation of the shear
waves. There are four soil profile types:
a) Type S1 profile: Rock, or very rigid soils.
This group includes rocks and very rigid soils with a shear wave
propagation velocity similar to that of rock, in which the fundamental
period for low amplitude vibrations does not exceed 0.25 s, including the
cases in which foundations are on:
•
•
•
•
Sound or partially altered rock, with a resistance to non-confined
compression of 500 kPa (5 kg/cm2) or more.
Dense sandy gravel.
Stratum of no more than 20 m of very rigid cohesive material, with a
shear resistance under undrained conditions of more than 100 kPa (1
kg/cm2), on rock or another material with a shear wave propagation
velocity similar to that of a rock.
Stratum of no more than 20 m of very dense sand with N > 30, on
rock or another material with a shear wave propagation velocity
similar to that of a rock.
b.
Type S2 profile: Intermediate soils.
Soils classified in this group are those belonging to the sites whose
characteristics fall between those indicated for S1 profile and for S3
profile.
c.
Type S3 profile: Flexible soils or those with very deep strata.
This group contains flexible soils or strata of great depth in which the
fundamental period, for low amplitude vibrations, is over 0.6 s, including
those cases in which the depth of the soil stratum exceeds the following
values:
Cohesive soils
Shear resistance typical in
undrained condition (kPa)
Soft
< 25
Moderately compact
25-50
Compact
50-100
Very compact
100-200
Granular soils
N typical values in standard
penetration tests (SPT)
Loose
4-10
Moderately dense
10-30
Dense
over 30
(*) Soil with shear wave velocity lower than that of a rock
d.
Depth of stratum (m) (*)
20
25
40
60
Depth of stratum (m) (*)
40
45
100
Type S4 profile: Exceptional conditions
This group includes exceptionally flexible soils and sites where the geological
and/or topographical conditions are particularly unfavourable.
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The type of profile that best describes the local conditions should be
considered, using the corresponding values of Tp and of the soil amplification
factor, S, shown in Table 2.
On the sites where the soil properties are unknown, the values corresponding
to S3 profile type may be used. An S4 profile type need only be considered
when the geotechnical studies so indicate.
Type
S1
Table 2
Soil Parameters
Description
Rock or very rigid soils
Tp (s)
0.4
S
1.0
S2
Intermediate soils
0.6
1.2
S3
Flexible soils, or those with very
thick strata
Exceptional conditions
0.9
1.4
*
*
S4
(*) The values of Tp and S for this case shall be established by the expert, but under
no circumstances shall they be lower than those specified for S3 profile type.
Article 7
Seismic Amplification Factor
According to the site characteristics, the seismic amplification factor (c) is
defined by the following formula:
⎛ Tp ⎞
C = 2 .5 * ⎜ ⎟
⎝T ⎠
C ≤ 2 .5
T is the period after it is defined in Article 17 (17.2) or in Article 18 (18.2)
This coefficient is interpreted as the amplification factor of the structural
response respect to ground motion.
CHAPTER 3
GENERAL REQUIREMENTS
Article 8
General considerations
All buildings and each one of their parts shall be designed and built to
withstand seismic forces as determined in this Code.
Consideration shall be given to the possible effect of the nonstructural
elements in the seismic behaviour of the structure, and the analysis and
specification of the reinforcement and anchoring shall be performed in
keeping with this consideration.
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For regular structures, analysis may be made considering the total of the
seismic force acting independently in two orthogonal directions. For irregular
structures the most unfavourable direction for design of each element or
component under study must be used for seismic action.
Vertical seismic force shall be considered to act on the elements
simultaneously with the horizontal seismic force, and in the most
unfavourable direction for the analysis.
It is not necessary to consider simultaneously the effects of earthquake and
wind.
When one single element of the structure, wall or frame resists a force of
30% or more of the total horizontal force at any level, this element shall be
designed for 125% of said force.
Article 9
Seismic resistant structural concepts
The seismic behaviour of a building shall be considered to improve when the
following conditions are observed:
•
•
•
•
•
•
•
•
•
•
Symmetry, both in the distribution of masses and stiffnesses.
Minimal weight, especially on the upper stories.
Selection and adequate use of the building materials.
Adequate resistance.
Continuity in the structure, both in plan and in elevation.
Ductility, as an indispensable requisite for satisfactory seismic behaviour.
Limited deformation, since otherwise the damage to nonstructural
elements could be out of proportion.
Inclusion of successive lines of resistance.
Consideration of the local soil conditions in the project.
Good construction practice and rigorous inspection of structure.
Article 10
Building Categories
Each structure shall be classified according to the categories indicated in
Table 3. Depending on the classification made, the use and importance
coefficient (U) defined in the following table shall be used.
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Table 3
OCCUPANCY CATEGORIES OF BUILDINGS
CATEGORY
DESCRIPTION
Essential buildings whose function should not be
A
interrupted upon occurrence of an earthquake -- such as
Essential hospitals, communication facilities, fire stations, police
buildings stations, electricity substations, water reservoirs; schools
and other buildings that can be used as places of refuge
after a disaster.
Other buildings included in this group are those whose
collapse could pose an additional risk, such as large
furnaces, and warehouses where inflammable or toxic
materials are stored.
Buildings where a large number of people gather -- such
B
as theatres, stadiums, malls, prisons; or buildings with
Important valuable contents, such as museums, libraries, and
buildings special archives.
Granaries and other storehouses important for supplies
are also considered in this group.
C
Common
buildings
D
Minor
buildings
Common buildings, whose failure would cause medium
losses -- houses, offices, hotels, restaurants, warehouses
and industrial installations, whose failure would not result
in additional dangers of fire, leakage of pollutants, etc.
Buildings, whose failure would cause smaller losses, and
where normally the likelihood of causing victims is low,
such as fences lower than 1.50 m, temporary
storehouses, small temporary living units, and similar
constructions.
U FACTOR
1.5
1.3
1.0
(*)
(*) In these buildings, the project designer may make the decision to omit the analysis for
seismic forces, but adequate resistance and stiffness must be provided for lateral actions.
Article 11
Structural configuration
Structures shall be classified as regular or irregular in order to determine the
proper analysis procedure and appropriate values of the seismic force
reduction factor (Table 6).
a.
Regular structures. Structures that have no significant horizontal or
vertical discontinuities in their lateral-force-resisting configuration.
b.
Irregular Structures are defined as those that present one or more of
the characteristics mentioned in Tables 4 or 5.
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Table 4
STRUCTURAL IRREGULARITIES IN
VERTICAL CONFIGURATION
Stiffness-related irregularities - Soft story.
In each direction the sum of the areas of the transverse sections of the
vertical elements resistant to shear in the story, columns and walls, is less
than 85% of the corresponding sum for the story above, or less than 90% of
the average for the 3 upper stories. Not applicable in basements. For
stories of different height the former values must be multiply by (hi/hd),
where hd is the different height and hi is the typical story height.
Irregularity of mass Mass irregularity is considered to exist when the mass of one floor is more
than 150% of the mass of an adjacent floor. Not applicable on roofs.
Vertical geometric irregularity The dimension in plan of the lateral-load-resistant structure is more than
130% of the corresponding dimension on an adjacent floor. Not applicable
on roofs or in basements.
Discontinuity in the Resisting Systems Disalignment of vertical elements, due both to a change of direction, and to
a displacement of greater magnitude than the dimension of the element.
Table 5
STRUCTURAL IRREGULARITIES IN PLAN
Torsional irregularity
This shall be considered only in buildings with rigid diaphragms in which the
average displacement of any interstory exceeds 50% of the maximum
allowable indicated in Table N° 8 of Article 15 (15.1).
In each of the directions of analysis, the maximum relative displacement
between two consecutive floors is greater than 1.3 times the average if this
maximum relative displacement with the relative displacement that
simultaneously occurs in the opposed end.
Re-entrant corners
The configuration in plan and the structure's resisting system have reentrant corners, whose dimensions in both directions are more than 20% of
the corresponding total dimension in plan.
Discontinuity of the diaphragm
Diaphragm with sudden discontinuities or variations in stiffness, including
open areas larger than 50% of the gross area of diaphragm.
Article 12
Structural systems
The structural systems are classified according to the materials used and the
predominant seismic-resistant structural predominant in each direction, as
indicated in Table 6.
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After the classification is made a seismic force reduction coefficient (R) will
be used. For ultimate strength design internal seismic forces must be
combined with factors of one. On the contrary, values of Table 6 can be used
if previously multiply by the corresponding seismic load factor.
Structural system
Table 6
STRUCTURAL SYSTEMS
Reduction coefficient (R)for
regular structures (*) (**)
Steel
Ductile frames: with moment
resisting joints
Other Steel Structures
Excentric bracing
Cross bracing
Reinforced Concrete
Frames (1)
Dual (2)
Structural walls (3)
Limited ductility walls (4)
Reinforced and confined
masonry(5)
Wooden constructions (working
stress design)
9.5
6.5
6.0
8
7
6
4
3
7
(1) System in which at least 80% of base shear is resisted by columns of frames designed
accordingly to NTE E.060 “Reinforced Concrete”. In case there are structural walls they
should be designed to resist the fraction of total seismic action accordingly to its stiffness.
(2) System in which the seismic actions are resisted by a combination of reinforced
concrete frames and structural walls. Frames shall be designed to take at least 25% of the
base shear.
(3) System in which the seismic resistance is provided basically by reinforced concrete
structural walls which resist at least 80% of base shear
(4) Low rise building with high density of limited ductility walls
(5) For working stresses design R would be 6
(*) These coefficients shall be applied only to structures in which the vertical and horizontal
elements allow the dissipation of energy while maintaining the stability of the structure.
(**) For irregular structures, the values of R shall be taken as 3/4 of those noted in the Table.
For earthen constructions, refer to Technical Building Standard E.080. This type of
construction is not recommended on S3 soils, and it is not allowed on S4 soils.
Article 13
Category, structural system and regularity of buildings
According to the category of a building and the zone it is located in, the
building should be planned observing the characteristics of regularity and
using the structural system indicated in Table 7.
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Table 7
CATEGORY AND STRUCTURE OF BUILDINGS
Category Structural
Zone
Structural System
of Building Regularity
Steel, Reinforced concrete walls,
A
Regular
3
Reinforced or confined masonry,
(*) (**)
Dual system
Steel, Reinforced concrete walls,
2 and 1 Reinforced or confined masonry,
Dual system, Wood
Steel, Reinforced concrete walls,
B
Regular or
3 and 2 Reinforced or confined masonry,
Irregular
Dual system, Wood
1
Any system
C
Regular or
Irregular
3, 2 and 1
Any system
(*) To meet the objectives indicated in Table 3, the building shall be especially structured to
resist strong earthquakes.
(**) For small rural constructions, such as schools and health centers, traditional building
materials may be used providing that the recommendations of the standards on such
materials are followed.
Article 14
Analysis procedures
14.1 Any structure may be designed using the results of the dynamic
analyses referred to in Article 18.
14.2 Only structures qualifying as regular pursuant to Article 10 and no
higher than 45m and bearing wall structures no higher than 15m may
be analysed by the equivalent static force procedure described in
Article 17.
Article 15
Lateral Displacements
15.1 Allowable lateral displacements
The maximum relative story drift, calculated according to Article 16 (16.4),
must not exceed the fraction of the story height indicated in Table 8.
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Table 8
ALLOWABLE STORY DRIFT
These limits are not applicable to industrial naves
Predominant Material
(∆i/hei)
Reinforced concrete
0.007
Steel
0.010
Masonry
0.005
Wood
0.010
15.2 Seismic separation joint
All structures shall be separated from adjoining structures by a minimum
distance ("s") to prevent contact during a seismic event.
This minimum distance shall not be less than 2/3 of the sum of the maximum
displacements of the adjacent blocks, nor shall it be less than:
s = 3 + 0.004(h-500) (h and s in cm)
s > 3 cm.
where:
h = the height measured from ground level to the level
considered for evaluating s.
The building shall be set back from adjacent property lines of empty plots that
can be built on or from existing buildings, by distances no less than 2/3 of the
maximum displacement calculated according to Article 16 (16.4), nor less
than s/2.
15.3
Stability of the building
The effect of eccentricity of the vertical load produced by the building's lateral
displacements (P-delta effect) should be taken into consideration as
described in Article 16 (16.5).
The stability against overturning of the whole shall be verified as indicated in
conformity with Article 21.
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CHAPTER 4
ANALYSIS OF BUILDINGS
Article 16
General
16.1 Seismic forces and analyses
In keeping with the earthquake-resistant design philosophy, it is accepted
that the buildings will have inelastic incursions in response to severe seismic
actions. Therefore the design seismic forces are considered as a fraction of
the maximum elastic seismic forces.
Analysis may be performed using the reduced seismic forces with an elastic
behaviour model for the structure.
16.2
Models for analysis of buildings
Model for analysis shall consider a spatial distribution of masses and
rigidities suitable for calculating the most significant aspects of the structure's
dynamic behaviour.
For buildings in which it can reasonably be assumed that the floor systems
function as rigid diaphragms, a model may be used with concentrated
masses and three degrees of freedom per diaphragm, associated to two
orthogonal components of horizontal movement and one rotation. In this
case, the deformations of the elements must be made compatible using the
rigid diaphragm condition, and the distribution in plan of the horizontal forces
must be made based on the stiffnesses of the resisting elements.
It must be verified that the diaphragms have sufficient stiffness and strength
to ensure the mentioned distribution, otherwise their flexibility must be taken
into account when calculating the distribution of the seismic forces.
In case the floors do not constitute rigid diaphragms, the resisting elements
shall be designed for the horizontal forces directly corresponding to them.
16.3
Weight of the building
The weight (P) shall be calculated by adding to the permanent total load of
the building a percentage of the live load or surcharge that shall be
determined in the following way:
a) In category A and B buildings, 50% of the live load shall be
considered.
b) In category C buildings, 25% of the live load shall be considered.
c) In storage buildings, 80% of the total weight that can be stored shall
be considered.
d) On all roofs, 25% of the live load shall be considered.
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e) In tanks, silos, and similar structures, 100% of the load they can
contain shall be considered.
16.4
Lateral displacements
Lateral displacements shall be calculated multiplying by 0.75R the results
obtained from the linear and elastic analysis with the reduced seismic forces.
For calculation of the lateral displacements the minimum values of C/R
indicated in Article 17 (17.3) nor the minimum base shear indicated in Article
18 (18.2d) shall not be taken into account.
16.5
Secondary (P-Delta) effects
The secondary effects shall be considered whenever they produce an
increase of more than 10% in the internal forces.
In order to estimate the importance of the secondary effects, the following
quotient may be used for each level as a stability index:
Q =
Ni ∆i
Vi hei R
Secondary effects shall be taken into account when Q > 0.1.
16.6
Vertical seismic loads
These loads shall be considered in the design of vertical elements; in post- or
pre-stressed elements and in the cantilevers or projections of a building.
Article 17
17.1
Static Analysis
General
This method represents the seismic forces by means of a set of horizontal
forces acting at each level of the building.
It should be used only for buildings with no irregularities and of low height, as
described in Article 14 (14.2).
17.2 Fundamental period
(a)
Fundamental period for each direction shall be estimated using the
following formula:
T=
hn
CT
where:
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CT = 35
CT = 45
CT = 60
(b)
for buildings whose force-resisting elements in the direction
under consideration are frames only.
for reinforced concrete building whose force-resisting elements
are frames, elevator shafts and stair wells.
for masonry structures and for all reinforced concrete building
whose force-resisting elements are basically shear walls.
A dynamic analysis procedure which considers the characteristics of
stiffness and distribution of masses in the structure may also be used.
As a simple form of this procedure, the following expression can be
applied:
T = 2π
⎛ n
⎞
⎜ ∑ Pi Di 2 ⎟
⎜ i =1
⎟
⎝
⎠
n
⎛
⎞
⎜ g ∑ Fi Di ⎟
⎜ i =1
⎟
⎝
⎠
Whenever dynamic procedure does not consider the effect of the
nonstructural elements, the fundamental period must be taken as 0.85 of the
value obtained by this method.
17.3
Base shear
Total shear in the base of the structure, in a given direction, shall be
determined from the following formula:
V =
ZUSC
P
R
where the following minimum value for C/R should be considered:
C / R = ≥ 0.125
17.4
Vertical distribution of earthquake shear force
If the fundamental period, T, is longer than 0.7 seconds, a part of the shear
V, called Fa, must be applied as a concentrated force on the upper part of the
structure. This force Fa shall be determined using the following formula:
Fa = 0.07 TV ≤ 0.15V
where the period T in the foregoing formula shall be the same as that used to
determine the base shear.
The rest of the shear, in other words V-Fa, shall be distributed among the
different levels, including the uppermost one, in accordance with the following
formula:
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Fi =
Pi hi
n
∑ Pj hj
(V
− Fa )
j =1
17.5
Torsional effects
The force at each level (Fi) shall be assumed to be acting on the centre of
mass of the respective level.
In addition, the effect of accidental
eccentricities must be taken into account, as indicated below.
For each direction under analysis, the accidental eccentricity at each level (e)
shall be calculated as 0.10 times the dimension of the building in the direction
perpendicular to the direction of application of the forces.
At each level, besides the acting force, the accidental moment called Mti
shall be applied, calculated as:
Mti = ± Fi ei
It may be assumed that the most unfavourable conditions are obtained
considering the accidental eccentricities with the same sign in all the levels.
Only increments in horizontal forces shall be considered not reductions.
17.6
Vertical seismic forces
The vertical seismic force shall be considered as a fraction of the weight. For
Zones 3 and 2 this fraction shall be 0.3. For Zone 1, this effect need not be
taken into consideration.
Article 18
18.1
Dynamic analysis
Scope
Dynamic analysis of buildings may be performed using modal spectral
combination procedures or time-history analyses.
For conventional buildings, the spectral combination procedure may be used;
and for special buildings a time-history analysis must be used.
18.2
Spectral combination analysis
a.
Vibration modes
The natural periods and vibration modes may be determined using an
analysis procedure which takes proper account of the characteristics of
stiffness and the distribution of the masses of the structure.
b.
Spectral acceleration
41-21
For each of the horizontal directions analysed, an inelastic spectrum of
pseudo-accelerations shall be used, defined by:
Sa =
ZUSC
g
R
For the analysis in the vertical direction, a spectrum with values equal to 2/3
of the spectrum employed for the horizontal directions may be used.
c.
Combination criteria
When use of the combination criteria indicated below it will be possible to
obtain the maximum expected response (r) both for the internal forces in the
structure's component elements, and for the overall parameters of the
building, such as base shear, story shear, overturning moments, and total
and relative story displacements.
The maximum expected elastic response (r) corresponding to the combined
effect of the different modes of vibration employed (ri) may be determined
using the following formula:
r = 0.25 ∑ (ri ) + 0.75
m
i =1
n
∑ ri
2
i =1
Alternatively, the maximum response may be estimated by means of a
complete quadratic combination of the values calculated for each mode.
In each direction those modes of vibration whose sum of effective masses is
at least 90% of the mass of the structure shall be considered, but at least the
first three predominant modes in the direction under analysis must be taken
into account.
d.
Minimum base shear
For each of the directions included in the analysis, the building's base shear
must not be less than 80% of the value calculated as described in Article 17
(17.3) for regular structures, and it must not be less than 90% for irregular
structures.
If it is necessary to increase the shear to comply with the indicated
minimums, all the other results obtained must be scaled proportionally,
except displacements.
e.
Torsional effects
Uncertainty in the location of the centers of mass at each level shall be
incorporated by means of an accidental eccentricity perpendicular to the
direction of the earthquake equal to 0.10 times the dimension of the building
in the direction perpendicular to the direction under analysis. In each case
the most unfavourable sign must be considered.
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18.3
Time-history analysis
Time-history analysis may be carried out assuming linear and elastic
behaviour, and no less than five records of horizontal accelerations must be
used, corresponding to real or artificial acceleration records. These records
shall be standardised in such a way that the maximum ground motion
corresponds to the maximum expected value at the site.
For particularly important buildings, the dynamic time-history analysis shall
be performed considering inelastic behaviour of the elements of the structure.
CHAPTER 5
FOUNDATIONS
Article 19
General
The assumptions made for the structure supports shall be in concordance
with the characteristics of the foundation soil.
The design of the foundations shall be compatible with the distribution of
forces obtained from analysis of the structure.
Article 20
Bearing capacity
All soil mechanics studies shall include the effects of seismic movements for
the determination of the bearing capacity of the foundation soil. In sites
where soil liquefaction could occur, a geotechnical investigation shall be
made to evaluate this possibility and determine the most appropriate solution.
For the calculation of the admissible pressures on the foundation soil under
seismic actions, the minimum safety factors indicated in Technical Building
Standard E-050 "Soils and Foundations" shall be used.
Article 21
Overturning moment
All structures and their foundation shall be designed to resist the overturning
moment produced by an earthquake. The safety factor shall be 1.5 or more.
Article 22
Isolated footings and caissons
For isolated footings with or without piles in soil profiles S3 and S4 and for
Zones 3 and 2, connecting elements shall be provided, which must support,
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in tension or compression, a minimum horizontal force equal to 10% of the
vertical load borne by the footing.
In the case of piles and caissons connecting beams shall be provided; or the
overturning and deformations caused by horizontal force shall be taken into
account and piles and footings must be built for these stresses. The piles
shall be considered to have reinforcement in tension equivalent to at least
15% of the vertical load they support.
CHAPTER 6
NONSTRUCTURAL ELEMENTS, APPENDAGES AND EQUIPMENTS
Article 23
General
Elements which, regardless of whether or not they are connected to the
horizontal-force-resisting elements, provide a negligible contribution to the
system's stiffness are considered nonstructural elements.
In the event that the nonstructural elements are isolated from the principal
structural system, they shall be designed to resist a seismic force (V)
associated with their weight (P), as indicated below:
V = ZUC1 P
The values of U correspond to those indicated in Chapter 3, and the values
of Ci shall be taken from the following table:
Table 9
VALUES OF C1
Elements which when failing can fall
outside the building in which the direction
of the force is perpendicular to their plane.
Elements whose failure implies a threat for
individuals or other structures.
Walls inside a building (direction of force
perpendicular to plane).
Fence walls.
Tanks, towers, lettering and chimneys
connected to a part of the building
considering the force in any direction.
Floors and roofs that act as diaphragms
with the direction of the force in their
plane.
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1.3
0.9
0.6
0.9
0.6
For nonstructural elements attached to the principal structural system and
which should accompany the deformation of the principal structural system, it
shall be ensured that in the event of failure they will not cause bodily harm.
Connection of equipment and installations within a building shall be the
responsibility of the concerned specialist. Each specialist shall guarantee
that the equipment and installations do not represent a risk during an
earthquake and, in the case of essential installations, he or she shall
guarantee the continuity of the building's functions.
CHAPTER 6
EVALUATION AND REPAIR OF STRUCTURES DAMAGED BY
EARTHQUAKES
Article 24
General
Structures damaged by earthquakes shall be evaluated and repaired in such
a way as to correct possible structural defects that produced the failure and
to recover the capacity to withstand a future seismic event, in accordance
with the objectives of earthquake-resistant design noted in Chapter 1.
Once the earthquake has occurred, the structure shall be evaluated by a civil
engineer, who shall determine whether the state of the building calls for
reinforcement, repairs, or demolition. The study shall necessarily include the
geotechnical features of the site.
Repair work must be able to give the structure the right combination of
stiffness, resistance and ductility to guarantee its good behaviour in future
seismic events.
The repair or reinforcement project shall include the details, procedures and
building systems to be followed.
For seismic repair and retrofitting of existing buildings criteria different than
those indicated in this standard may be used, with due justification and
approval from the concerned authorities.
CHAPTER 8
INSTRUMENTATION
Article 25
Recording accelerographs
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In all seismic zones, all buildings projects with an area equal to, or greater
than, 10,000 m2, shall be equipped with at least one recording
accelerographs.
Article 26
Location
The instruments shall be placed in a room of at least 4m2 located in the lower
level of the building, bearing in mind that they must be easily accessible for
maintenance purposes, and must have suitable lighting, ventilation, electricity
supply, physical security and should be clearly identified in architectural
drawings.
Article 27
Maintenance
Operative maintenance, parts and components, consumable supplies, and
service of the instruments shall be provided by the owners of the building
under the supervision of the Peruvian Geophysical Institute.
This
responsibility shall remain in force for ten years.
Article 28
Data availability
The accelerograms recorded by the instruments shall be processed by the
Peruvian Geophysical Institute and incorporated into the National
Geophysical Data Bank. This information is in the public domain and shall be
available to users at request.
Article 29
Requirements for Acceptance of Works
In order to obtain approval of works, and under the responsibility of the
concerned official, the owner of the building shall present a certificate of
installation, issued by the Peruvian Geophysical Institute, as well as a
contract for the service of operational maintenance of the instruments.
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ANNEX
SEISMIC MACROZONATION
Seismic zones in which the Peruvian territory has been divided, for use with
this Standards is shown in Figure 1 of Article 5. In what follows provinces of
each zone are listed.
Zone 1
1. Department of Loreto. Provinces of Mariscal Ramón Castilla, Maynas
y Requena.
2. Department of Ucayali. Province of Purús.
3. Department of Madre of Dios. Province of Tahuamanú.
Zone 2
1. Department of Loreto. Provinces of Loreto, Alto Amazonas y Ucayali .
2. Department of Amazonas. All Provinces.
3. Department of San Martín. All Provinces.
4. Department of Huánuco. All Provinces.
5. Department of Ucayali. Provinces of Coronel Portillo, Atalaya y Padre
Abad.
6. Department of Pasco. All Provinces.
7. Department of Junín. All Provinces.
8. Department of Huancavelica. Provinces of Acobamba, Angaraes,
Churcampa, Tayacaja y Huancavelica.
9. Department of Ayacucho. Provinces of Sucre, Huamanga, Huanta y
Vilcashuamán.
10. Department of Apurimac. All Provinces.
11. Department of Cusco. All Provinces.
12. Department of Madre of Dios. Provinces of Tambopata y Manú.
13. Department of Puno. All Provinces.
Zone 3
1. Department of Tumbes. All Provinces.
2. Department of Piura. All Provinces.
3. Department of Cajamarca. All Provinces.
4. Department of Lambayeque. All Provinces.
5. Department of La Libertad. All Provinces.
6. Department of Ancash. All Provinces.
7. Department of Lima. All Provinces.
8. Constitutional Province of Callao.
9. Department of Ica. All Provinces.
10. Department of Huancavelica. Provinces of Castrovirreyna y Huaytará.
11. Department of Ayacucho. Provinces of Cangallo, Huanca Sancos,
Lucanas, Víctor Fajardo, Parinacochas y Paucar of Sara Sara.
12. Department of Arequipa. All Provinces.
13. Department of Moquegua. All Provinces.
14. Department of Tacna. All Provinces.
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