sismo instalaciones industriales _3621-0 - covenin
DESCRIPTION
COVENINVenezuelaTRANSCRIPT
VENEZUELAN
STANDARDS
EARTHQUAKE RESISTANT
DESIGN FOR INDUSTRIAL
FACILITIES
(Interim)
COVENIN
3621:2000
PROLOGUE
This standard was prepared in accordance with directions issued by the Normalizing Technical Committee CT3 Construction by the Technical Subcommittee SC1 Buildings and approved by Fondonorma in the Superior Council Meeting Nº 2000-07 held on 07/26/2000 with a provisional character. The following entities took part in the preparation of this Standard: Venezuelan Institute of Seismic Research (FUNVISIS), Petroleos de Venezuela S.A. (PDVSA); Ministry of Infrastructure (MINFRA); Fund for the Quality Normalization and Quality Certification (FONDONORMA). This COVENIN-MINDUR Venezuelan Standard is equivalent to PDVSA Specifications Nº JA-221
TABLE OF CONTENTS
1 PURPOSE.............................................................................................................................. 1 2 REGULATORY REFERENCES ............................................................................................. 1 3 TERMINOLOGY ..................................................................................................................... 2 3.1 Definitions............................................................................................................................ 2 3.2 Notation ............................................................................................................................... 5 4 GENERAL REQUIREMENTS ................................................................................................. 6 4.1 Design Strategy ................................................................................................................... 6 4.2 Site Surveys......................................................................................................................... 7 4.3 Measurements and Tests for Evaluation Purposes ............................................................... 7 4.4 Superposing on other Actions .............................................................................................. 7 5 HAZARD RATING................................................................................................................... 8 5.1 Reference Scale .................................................................................................................. 8 5.2 Doubtful Cases .................................................................................................................... 9 5.3 Temporary Risks.................................................................................................................. 9 6 FOUNDATION LANDS ........................................................................................................... 9
6.1 Spectral Pattern and Factor ϕ Selection ............................................................................... 9 6.2 Special Cases.................................................................................................................... 10 6.3 Foundations, Walls and Slopes .......................................................................................... 10 7 SEISMIC ACTIONS .............................................................................................................. 10 7.1 Seismic Hazard Maps ........................................................................................................ 10 7.2 Maximum Horizontal Land Acceleration See A.5.2 ............................................................. 10 7.3 Elastic Response Spectrum ............................................................................................... 11 7.4 Accelerations History ......................................................................................................... 15 7.5 Motion Components ........................................................................................................... 15 7.6 Permanent Displacements of Active Faults......................................................................... 15 7.7 Other Seismic Actions........................................................................................................ 16 8 DESIGN SPECTRUMS......................................................................................................... 16 9 MODELING .......................................................................................................................... 17 9.1 Structure-borne Facilities ................................................................................................... 17 9.2 Masses .............................................................................................................................. 17 9.3 Mechanical Properties........................................................................................................ 18 10 ANALYSIS METHODS........................................................................................................ 19 10.1 General Criteria................................................................................................................ 19 10.2 Dynamic Analysis Methods for Elastic Systems ................................................................ 19 10.3 Static Methods for Elastic Analyses.................................................................................. 20 10.4 Inelastic Analysis Methods ............................................................................................... 23 10.5 Scope of Application ........................................................................................................ 24 11 COMBINATION OF EFFECTS BROUGHT BY THE ACTION OF THE THREE SEISMIC
COMPONENTS................................................................................................................. 24 12 SPECIAL SEISMIC PROTECTION SYSTEMS.................................................................... 24 12.1 General............................................................................................................................ 25 12.2 Mechanical Properties...................................................................................................... 25 12.3 Analysis ........................................................................................................................... 25 13 EXISTENT FACILITIES....................................................................................................... 25 13.1 Purpose and scope .......................................................................................................... 25 13.2 Fitting Levels.................................................................................................................... 26 13.3 Information Needed.......................................................................................................... 26 13.4 General Criteria to Evaluate Existent Facilities ................................................................. 26
BIBLIOGRAPHY APPENDIX A: COMMENTS APPENDIX B APPENDIX C REFERENCES TO COMMENTS
FOREWORD
By initiative of the Ad-Hoc Commission appointed by the Venezuelan Institute of Seismic Research (FUNVISIS), to prepare and discuss the final text for the COVENIN-MINDUR Venezuelan Standard 1756-1998 Earthquake resistant Buildings including the following professionals: Arnaldo Gutierrez, Denis Rodriguez. Heriberto Echezuria, Jose Grases (Coordinator), Jorge Gonzalez (Secretary), Oscar Andres Lopez, William Lobo Q., and Manuel Paga (Advisors); the Permanent Commission for Technical Standards of the Ministry of Urban Development, MINDUR, handled, reviewed and approved this PDVSA Specification Nº JA-221 to be considered by the Normalizing Technical Committee CT3 CONSTRUCTION, approved by FONDONORMA Superior Council to be adopted as the COVENIN-MINDUR 3621 Venezuelan Standard - Earthquake Resistant Design for Industrial Facilities. This Standard is an Integral Part of the Engineering Design Manual of Petroleos de Venezuela S.A. PDVSA By the Permanent Commission for Technical Standards of MINDUR Salomon Epelboim Arnaldo Gutierrez Cesar Carreño Carmen Lobo de Silva Caracas August 24th 1999
This COVENIN-MINDUR 3621 Venezuelan Standard shall be INTERIM for one year term counted since its date of publishing in the Official Gazette in order to obtain, and process any remark arising from its usage. Any remark or consultation arising within such year shall be submitted in writing and duly documented, as per guidelines set forth in Annex B hereto, to any of the following entities.
Venezuelan Institute of Seismic Research (FUNVISIS) Prolongación Calle Mara, El Llanito. Caracas 1070; Fax: (0212)257.99.77 e-mail: [email protected] Attention: Dr. Jose Grases, Ad-Committee Coordinator, or Eng. Nuris Orihuela, FUNVISIS President Fund for the Quality Normalization and Quality Certification (FONDONORMA). Final Av. Andrés Bello, Torre Fondo Común, Pisos 11 y 12 Caracas P.O. Box 51116 – Caracas 1050 –A- Venezuela Fax (02) 574.13.12 e-mail: [email protected] Attention: Humberto Vivas Perez, Coordinator of the Technical Normalization Committees for the Construction Sector
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1 PURPOSE
1.1 This Venezuelan Standard sets forth the general earthquake resistant provisions ruling
the analysis and design for oil and non-oil related industrial facilities located within the
territory of Venezuela.
1.2 This Standard does not include buildings whose analysis and design shall be governed
by COVENIN 1756 Standard.
1.3 Appendix hereto includes comments to these specifications explaining their content.
2 REGULATORY REFERENCES
The following standards include provisions that, when mentioned in this document,
become requirements for this Venezuelan Standard. Listed issues were in effect by the
time this standard was published. As any standard is subject to review, we recommend
anyone using it to analyze the convenience of using more recent issues that those listed
hereon:
2.1 COVENIN Venezuelan Standards
Covenin 1618-1998 Steel Structures for Buildings. Ultimate State Method
Covenin 1753-1987 Reinforced Concrete Structures for Buildings. Analyses and Design
Covenin 1756-1998 Earthquake Resistant Buildings
Covenin 2002-1988 Minimum Criteria and Actions for Building Projects
Covenin 2003-1989 Wind actions on Buildings
Covenin 3622:2000 Earthquake Resistant Design for Containers and Structures
Covenin 3623:2000 Earthquake Resistant Design for Structures in Lake and Shallow
Waters
Covenin 3624:2000 Earthquake Resistant Design for Metal Tanks
2.2 PDVSA Engineering Guidelines
Engineering Design Manual, Volume 18, Engineering Specifications, PDVSA
90615.1.008: Foundations for Horizontal Containers
90615.1.013: Seismic Loads on Vertical Containers, Chimneys and Towers
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2.3 Other Standards
Until the relevant COVENIN Venezuelan Standards are not approved, the following
documents can be used as reference:
2.3.1 AISC
LRFD: Manual of Steel Construction. Load & Resistance Factor Design
ASD: Manual of Steel Construction. Allowable Stress Design
2.3.2 ACI
2.3.3 Building Code Requirements for Structural Concrete
3 TERMINOLOGY
3.1 Definitions
3.1.1 Accelerogram
The record of variations shown by land motion accelerations over time, at one point and in
one direction
3.1.2 Damping
Materials and systems capacity as to dissipate energy. It does not include any dissipation
arising from incursions in the inelastic range.
3.1.3 Dynamic Analysis
An analysis made to determine responses before dynamic forces. Frequently, standards
refer to this analysis based on a design spectrum, taking into account the structure modal
properties and reaching the answer by combining values correspondent to each mode.
3.1.4 Permanent Load
The load related to the weight of all structural components, as well as to permanent non-
structural systems and components such as pipelines, platforms, trays, and fixed
equipment.
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3.1.5 Service Load
A combination of most probable loads under normal service conditions the structure shall
have to bear with its own structural elements subject to the admissible stress, lower than
actual capacity.
3.1.6 Creep
A condition featured by the plasticizing of -at least- the region subject to more forces in the
earthquake resistant system, such as the first plastic swivel arising in a major component
of such system.
3.1.7 Seismic Ratio
The ratio between the design horizontal force acting at base level (basal shear stress) and
the total weight on it.
3.1.8 Ductility Demand
The demand for ductility arising in the structure when subject to design seismic motions
described herein (see Ductility and Ductility Factor).
3.1.9 Ductility
The capacity of structural system components to make alternate incursions into the
inelastic domain, showing no considerable loss in their resistance capacity (see Ductility
Factor).
3.1.10 Design Spectrum
The spectrum related to design earthquakes including the response reduction factor
correspondent to the earthquake resistant system.
3.1.11Response Spectrum
Defines the maximum response from oscillators with one degree of freedom and the same
damping ratio, exposed to a given accelerogram, expressed in function of the period.
3.1.12 Site Surveys
An assessment of the seismic hazard made by taking all local site conditions into
consideration.
3.1.13 Ductility Factor
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The value describing the global ductility an earthquake resistant system can tolerate while
keeping its integrity; this factor quantifies the relationship between the maximum actual
displacements and the estimated displacements, assuming a linear elastic behavior for the
structure.
3.1.14 Response Reduction Factor
The factor by which the elastic spectrum ordinates are divided to obtain the design
spectrum.
3.1.15 Degree of Hazard
Hazard rating scale which depends on the number of people exposed the potential
economic losses and the environmental impact resulting from the structure failure of
malfunctioning.
3.1.16 Base Level
The structure level where seismic actions transfer to the structure are acknowledged.
3.1.17 Seismic Hazard
It quantifies the occurrence potential for future seismic events that could adversely affect
the integrity of facilities and the people in them.
3.1.18 Average Return Period
Average term within occurrences of a given event.
3.1.19 Exceedance Potential
The potential for a specific land motion level, or a specific economic or social effect, arising
from the earthquake to be exceeded at one site or region within a given time.
3.1.20 Seiche
Oscillation of a given amplitude arising in lake waters as effect from earthquakes located
far away.
3.1.21 Useful Life
Number of years representing a facility probable service time.
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3.2 Notation
Sub-indexes i and j are used to indicate any joint or level; letter N is reserved for the last
level. Units are specified only when their use is mandatory.
Ad = Ordinate of the design spectrum expressed as a fraction of acceleration of gravity.
Ao = Maximum horizontal land acceleration expressed as a fraction of acceleration of
gravity.
CP = Effects from permanent loads.
CV = Effects from variable service and operational loads, including thermal effects, internal
pressure, and potential vibrations in the operational regime.
D = Ductility factor.
Fi = Lateral force on i joint.
fi = Lateral force on i joint used to compute the period.
H = Depth at which the material found shows a velocity of shear waves, Vs, higher than
500 m/s.
H1 = Depth from the surface to the stratum top (m) ≥0.25 H.
Ms = Richter magnitude determined as per the amplitude of surface waves.
N = Number of joints where structure weights have been concentrated.
P* = Potential for the land acceleration to exceed value a, within t years.
R = Maximum dynamic response value.
S = Earthquake effects including the three seismic components, duly combined.
T = Fundamental period of the structure, in seconds, also referred to as return time.
To= Value of the period defining part of the normalized elastic spectrum, in seconds.
T+ = Lowest value of the period in the interval where design spectrums have a constant
value, in seconds.
T* = Maximum value of the period in the interval where normalized elastic spectrums have
a constant value, in seconds.
Vo = Shear stress in the base (basal shear stress).
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Vsp = Average velocity of shear waves in the soil profile (m/s).
W = Total weight of the structure above the base level.
Wi = Weight concentrated on joint i.
a = Maximum land acceleration (cm/s2).
a* = Characteristic acceleration of the seismic hazard in each location (cm/s2).
= Maximum displacement of active faults (cm).
g = Acceleration of gravity equal to 981 gals.
gal = Value of 1.0 cm/s2.
h = Height.
p1 = Exceedance potential per annum. It is equal to the inverse of the return period.
q = Coefficient impacting seismic action effects.
t = Useful life or economic life designated for the facility (years).
ß = One parameter defining spectrum patterns.
ß* = Spectral amplification factor.
ϕ = Correction factor of the horizontal acceleration ratio.
γ = Typical value of the seismic hazard in each location.
ξ = Damping ratio referred to the critical damping ratio.
4 GENERAL REQUIREMENTS
4.1 Design Strategy
4.1.1 The dynamic nature of seismic actions and the relevant structural response are
included into this Venezuelan Standard. Such nature is quantified through procedures
showing various complexity degrees as per each facility inherent features. See A.2.1
4.1.2 Designs carried out as per these Venezuelan specifications are based on seismic
actions selected depending on the relevant facility performance and potential
malfunctioning. Such strategy allows, in certain structures, moderating incursions into the
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inelastic deformation ranges. Consequently, designs are only allowed for limited
spectrums.
4.1.3 The point for earthquake resistant designs based on ductility-restricted spectrums is
to create a structure showing the same ductile behavior expected when the ductility factor
was selected. In such sense, checks shall be focused on removing any possible fragile
failure.
4.1.4 Total structure displacements, which include the potential inelastic component, shall
be checked, as they shall not exceed permissible values designated for each facility in
order to protect its integrity and the adjacent facilities integrity.
4.2 Site Surveys
Seismic actions described in this Venezuelan Standard can be applicable both for
designing new facilities and fit existent ones, within the Venezuelan territory. For major
facilities or facilities located near active faults, site surveys must be carried out in order to
include relevant seismic hazards, such as the inherent characteristics of local subsoil. See
A.2.2
4.3 Measurements and Tests for Evaluation Purposes
Whenever a needed, measures and tests shall be carried out to evaluate any facility and
determine the mechanical (static ands dynamic) properties of the relevant facility or facility
section. Likewise, the necessary soil surveys to determine the site subsoil characteristics
shall be carried out. See A.2.3
4.4 Superposing on other Actions
For design or checking purposes, seismic actions effects shall be superposed on effects
from any other action, as follows:
mCP + nCV ± qS (1)
where:
CP = effects from permanent loads.
CV = effects from variables service and operational loads, including thermal, internal
pressure, and potential vibrations in the operational regime.
S = earthquake effects, including combined seismic components (See Chapter 11).
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m, and n = coefficients depending on methods used for elements design; which can
include effects from the earthquake vertical component. These coefficients are set in the
correspondent design standards.
q = 1.0 when methods used are based on ultimate state. For the particular case of fire
fighting systems q = 1.2 shall be used.
In Equation (1) the two following combinations shall be used, as minimum:
1. 1 (CP) + 1. 0 (CV) ± 1. 0 (S) (1a)
0. 9 (CP) ± 1. 0 (S) (1b)
5 HAZARD RATING
5.1 Reference Scale
5.1.1 All and any facility to de designed and/or reviewed shall be rated as per the Hazard
Rating Scale in Table 1, by selecting the Degree of Hazard related to the line showing the
most unfavorable consequences. See A.3.1
5.1.2 Whenever a structure, equipment, or component failure would affect a nearby
structure showing a higher degree of hazard, such higher degree of hazard shall be used
for both structures.
TABLE 1
HAZARD RATING SCALE AND EXCEEDANCE POTENTIAL PER ANNUM OF LAND MOTIONS (P1)
Degree of Hazard
CONDITIONS P1
(10-3
)
Number of People Exposed
Economic Losses Environmental Impact
Material Losses Loss or Profits
A Few < 10) Limited to the facility Negligible Low or none ≤ 2
B Important (11-100) The facility and an adjacent one
Significant From 1 to 50 MM US$
Recovery in ≤ 3 years
≤ 1
C High number of people The facility and multiple adjacent
ones
From 50 to 250 MM US$
Recovery in 3 to 10 years
≤ 0.5
D > 500 people Of catastrophic nature
> 250 MM US$ Irreversible ≤ 0.1
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5.2 Doubtful Cases
Whenever a doubt would arise as to select the Degree of Hazard, the higher one shall be
selected. See A.3.2
5.3 Temporary Risks
5.3.1 When the case relates to temporary service facilities in Group A to be used for less
than three years, the value admitted shall not be higher than P1 = 5 x 10-3.Values shown in
Table 1 will be used for all other cases.
5.3.2 For very short exposure periods, repairs for instance, design values shall be justified
with special risk assessments.
6 FOUNDATION LANDS
This Venezuelan Standard considers four spectral pattern types (S1 to S4) and a
correction factor for the horizontal acceleration ratio (ϕ), which depend on geotechnical
features shown by the foundation soil profile. See A.4
6.1 Spectral Pattern and Factor ϕϕϕϕ Selection
The spectral pattern and the ϕ factor shall be selected as per Table 2, where:
H = depth at which the material found shows a velocity of shear waves, Vs, higher than
500 m/s.
H1 = depth from the surface to the soft stratum top (m) ≥ 0.25 H.
Vsp = average velocity of shear waves in the soil profile (m/s).
ϕϕϕϕ = correction factor for the horizontal acceleration ratio.
See A.4.1
TABLE 2 - SPECTRAL PATTERN TYPES AND ϕϕϕϕ
Material Vsp (m/s) H (m) Spectral Pattern ϕ
Sound/fractured rock > 700 Any S1 0.85
≤ 50 S1 0.90 Soft or moderately weathered soils
> 400
>50 S2 0.95
< 30 S1 0.90
30-50 S2 0.95
Very hard or very dense soils
> 400
> 50 S3 1.00
< 15 S1 0.90
15 - 50 S2 0.95
50 - 70 S3 (b) 1.00
Hard or dense soils
250-400
> 70 S4 1.00
≤ 50 S2 (c) 1.00 Solid/moderately dense soils
170-250
> 50 S3 (b) 1.00
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Material Vsp (m/s) H (m) Spectral Pattern ϕ
≤ 15 S2(c) 1.00 Soft/loose soils
< 170
> 15 S3 (b) 1.00
< H1 S2 1.00 Soft strata interleaved with more rigid soils (a)
< 170 > h1 S3 0.90
(a) the stratum width must be higher than 0.1 H (b) If Ao ≤ 15, use S4 (c) If Ao ≤ 15, use S3
6.2 Special Cases
For soils showing resistance degradation, or suffering volumetric changes when exposed
to seismic forces, particular studies shall be carried out in order to assess the profile
seismic response and set the spectral pattern and horizontal acceleration ratio to use for
the design. Patterns used for analyses shall reflect changes in the relevant soils properties
brought by the cyclic load. See A.4.2.
6.3 Foundations, Walls and Slopes
In this respect, those criteria set forth in the new COVENIN 1756 version shall be followed;
by using seismic actions set forth in Chapter 6 thereby.
7 SEISMIC ACTIONS
7.1 Seismic Hazard Maps
7.1.1 For facilities design and checking purposes, seismic hazard maps shown in Figures
1 and 2 shall be used. Values a* and γ correspondent to the site in question shall be read
in those maps, respectively. If necessary, linear interpolations may be used. See A.5.1
7.1.2 Use of options listed in Section 7.2 is limited to return average periods ranging within
200 and 2,000 years; i.e.: 5 x 10-3 ≥ P1 ≥ 0.5 x 10-3. When the case relates to facilities of
exceptional importance or ranked as with D Degree of Hazard, special studies shall be
carried out (see Section 4.2).
7.2 Maximum Horizontal Land Acceleration See A.5.2
7.2.1 Option 1
Maximum horizontal land acceleration (a), in cm/s2 is obtained from formula 2 See A.5.2.1:
a = a * [ -In ( 1 -p1)] -1/γ (2)
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where:
p1 = exceedance potential per annum listed in Table 1.
a*, γ= values read in the Seismic Hazard Maps shown in Section 7.1.
7.2.2 Option 2
When P* and t have been set:
a = a * { [ -In ( 1 –p*)] /t } -1/γ (3)
where:
P* = exceedance potential within time t
t = the facility useful life, in years
a*, γ= values read in the Seismic Hazard Maps shown in Section 7.1.
In Equation (3), P* can be obtained from the potential per annum (p1): p1 = 1 – (1–P*)1/t ,
which shall not be higher than the value shown in Table 1. The inverse of p1 is equal to the
average return period (years).
7.3 Elastic Response Spectrum
For each spectrum pattern defined in Chapter 6 of this Venezuelan Standard, Figure 3
shows the relevant response spectrum to be used in the analysis (see A.5.3), where:
Ad : spectral acceleration divided by the acceleration of gravity (g).
g : acceleration of gravity.
Ao : maximum land acceleration ratio; which is equal to acceleration ¨a¨ determined in
Section 7.2 divided by the acceleration of gravity (g).
Ao = a /g
ß, To, T* depend on the subsoil typical profile and are listed in Table 3.
ß* is the spectral amplification factor that depends on the damping ratio of the system
under consideration and results from:
ß* = (0.0853 – 0.739 In ξ) (5)
where ξ is the damping ratio referred to the critical damping ratio. These ratios are set in
engineering specifications for structure and specific equipment design. See 2.2
3.2
β
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Elastic response spectrums are equal to design spectrums listed in Chapter 8 for D = 1.
FIGURE 1 SEISMIC HAZARD MAP, a* VALUES
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Elastic response spectra are equal to design spectra shown in Chaptr 8 for D=1
FIGURE 2 SEISMIC HAZARD MAP, γγγγ VALUES
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TABLE 3
VALUES DEFINING SPECTRUM PATTERNS
Spectral Pattern β To (s) T* (s)
S1 2.4 0.1 0.40
S2 2.6 0.20 0.80
S3 2.8 0.30 1.2
S4 3.0 0.40 1.6
FIGURE 3 ELASTIC RESPONSE SPECTRUM
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7.4 Accelerations History
A seismic action can be defined in terms of the acceleration history (accelerogram) of each
orthogonal component in the seismic motion. In order to do so, either recorded or
simulated accelerograms can be used. The intensity of such accelerograms must be
consistent with elastic response spectrums specified in Section 7.3. Within the typical
frequency range for the facility under consideration, the response spectrum ordinates of
selected accelerograms must be conservatively approximate to the response spectrum
ordinates shown in Section 7.3. The total accelerogram time must be consistent with the
intensity of the seismic action in question. See A.5.4.
7.5 Motion Components
7.5.1 Design seismic motions have a simultaneous action in three directions, which are
mutually orthogonal: two horizontal and one vertical. Their effects are combined as
described in Chapter 11. See A.5.5
7.5.2 Each horizontal direction is described by the elastic response spectrum specified in
Section 7.3. The vertical component spectrum is equal to the vertical components
spectrum multiplied by 0.70. When the case relates to deep foundations, the vertical land
acceleration shall be assumed as 0.70 of the ratio between the maximum horizontal
acceleration Ao and the elastic response spectrum correspondent to characteristics shown
by the stratum prevailing at pile ends.
7.5.3 When the seismic action is defined in terms of acceleration history (See 7.4),
recommendation is that accelerograms for all three (3) directions should be statistically
independent.
7.5.4 When floor plan dimensions related to the structure foundation system exceed 60
meters, analyses shall be carried out in order to consider rotational components in land
motion arising from the difference in arrival times of translational components. As an
option, such analysis can be omitted if the structure and the relevant foundations are
divided into independent portions not exceeding 60 meters long.
7.6 Permanent Displacements of Active Faults
The maximum permanent displacement expected from tectonic faults of transcurrent type
(), as those prevailing in Venezuela, shall be computed as follows:
log = 0. 5 Ms – 1.4 6 ≤ Ms ≤ 8 (6)
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where () is in cm and Ms is the maximum Richter magnitude related to the fault in
question. The (log ) standard deviation is equal to 0.25.
7.7 Other Seismic Actions
Whenever appropriate, site surveys shall assess hazards related to other seismic actions
not deemed as remotely placed, such as sea earthquakes, permanent soil displacements
and seiches.
8 DESIGN SPECTRUMS
Ad ordinates in design spectrums that include inelastic effects are defined as follows:
If
(7)
If
(8)
If
(9)
If
(10)
Where:
Ad = spectral acceleration divided by the acceleration of gravity (g).
T = structure period, in seconds.
Ao = maximum horizontal land acceleration as computed in Section 7.2.
ß*,To, T* = parameters defining the elastic response spectrum (See 7.3).
T+ = period characteristic to the inelastic spectrum, as shown in Table 4.
D = ductility factor, as described in the Engineering Specification relevant to the facility in
question, see 2.2.
c = (11) see A.6
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TABLE 4 - T+ VALUES (SECONDS)
D < 5 0.1 (D-1)
D ≥ 5 0.4
To ≤ T+ ≤ T* must be met
9 MODELING
The mathematical model used to idealize the actual structure shall adequately simulate its
inherent properties such as geometry, masses, element dimensions, materials, etc.
Particularly, the model shall include all elements that, even if deemed as non-structural,
can influence masses, rigidities, and energy dissipation capacities in the actual structure.
9.1 Structure-borne Facilities
For facilities that are borne by structures, or not directly set on the land, the structure-
facility set shall be included in the model as per outlines in Sections 9.2 and 9.3, except in
cases where duly justified floor spectrums are used. See A.7.1
9.2 Masses
9.2.1 The mathematical model shall include all and any mass having a permanent
character, such as structural elements and components, fixed equipment and utilities,
walls and partition walls, paving, fillers, casings and wainscots, as well as permanently
stored materials (see COVENIN 2002 Standard).
9.2.2 Likewise, variable loads related to operational level shall be included. If there is no
information about overloads regarding a specific area, a 25% design loads shall be added
as defined in COVENIN 2002 Standard.
9.2.3 Masses in the model shall be spread in a discrete way, throughout a sufficient
number of joints allowing getting their actual distribution as accurately as possible. In
addition, the number of masses and dynamic degrees of freedom designated to each joint
shall allow for vibration modes showing a significant contribution to the dynamic response.
9.2.4 As for buildings with horizontal diaphragms with high rigidity in their own plane,
masses can be concentrated in the centre of mass of each diaphragm, including the
portion contributed by beams, walls and columns, and non-structural elements, in order to
define their dynamic response before the earthquake horizontal components.
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9.2.5 When the case relates to liquid containers, the influence of hydrodynamic effects
brought by oscillation of the liquid must be assessed.
9.3 Mechanical Properties
9.3.1 Mechanical properties correspond to the structure in perfect conditions, showing no
damages, and are related to a linear and elastic model. The cross elasticity and
deformation modules are those foreseen in the relevant design standards. Inelastic
properties of structural elements shall be considered only when using analysis methods
described in Section 10.4. See A.7.3.
9.3.2 For reinforced concrete elements, the inertia related to the cracked section can be
used, as long as the contribution from all structural and non-structural components that
could have an influence on the structural system global rigidity is also included.
9.3.3 The mathematical model shall include all elements and joints deformations having a
non-negligible influence on the seismic response, such as those arising from flexure, shear
stress, axial forces, and torsion.
9.3.4 The importance of walls and filling bulkheads as for any change in the structure
rigidity and resistance must be evaluated and if such importance is not negligible, it must
be included in the mathematical model. Special attention must be given to discontinuous
walls giving raise to the so called ″short column” effect, which must be avoided as
possible.
9.3.5 Elements defining the foundation-soil ratio must be concordant to soil and structure
deformability properties. Soils mechanical properties must be obtained by carrying out field
studies.
9.3.6 Damping ratios are listed in specifications particular to each facility see 2.2. If such
were not the case, they can be determined through experimental procedures or based on
values shown by similar systems. For facilities needing a safety assessment, the
mathematical model shall use damping ratios based on tests results. If the damping ratios
corresponding to the various system components are known, but the damping ratio for the
system as a whole is unknown, the mathematical model shall include a value leading to
obtain a conservative result.
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10 ANALYSIS METHODS
10.1 General Criteria
10.1.1 The system analysis must include effects from the earthquake two horizontal
components and the vertical component as acting in a simultaneous way and computed as
per Chapters 5, 6, 7 and 8 hereby.
10.1.2 Each one of these methods must include P–∆ effects, and can also include the soil-
structure interaction effects. Total displacements are obtained by multiplying
displacements resulting from the elastic analysis by ductility (D) values. See A.8.1
10.2 Dynamic Analysis Methods for Elastic Systems
In these methods, the structure is modeled through a linear and elastic system, with
dynamic properties (periods and vibration modes) corresponding to the structure and its
initial rigidity; yet taking into account exceptions mentioned in Article 9.2. See A.8.2.
10.2.1 Modal Analysis with Response Spectrum
10.2.1.1 In this analysis method, the maximum dynamic response from the structure is
found by combining maximum responses at each vibration mode. Periods and vibration
modes are determined with elastic rigidities, as described in Section 9.2. See A.8.2.1
10.2.1.2The number of modes (Nm) to include shall be such that the sum of their
participative masses is not lower than 90% total structure mass, for each of the three (3)
translational seismic components.
10.2.1.3 All relevant forces on the structure shall be determined for each vibration mode,
and combined as described below.
The maximum dynamic response value (R) before the action of any seismic component
shall be determined by combining maximum modal values (Ri or Rj) as per the complete
quadratic combination criterion:
(12)
Where: the double summation is made for all relevant Nm modes. Please note that
Equation (12) must include Ri and Rj with their correspondent sign.
20
Cij is the correlation coefficient between i and j as resulting from:
2(1 _ r)r1,5| (13)
Where r = Tj / Ti is the ratio between modes i and j periods.
10.2.2 Dynamic Analysis with Accelerograms
At least three accelerograms must be considered for each seismic action direction. When
using the modal analysis method, the number of modes to include shall be such that the
sum of their participative masses is not lower than 90% total structure mass. The
maximum system response can be obtained from the maximum response average in each
accelerogram. Accelerograms to be used must meet requirements set in Section 7.4. See
A.8.2.2.
10.3 Static Methods for Elastic Analyses
Static analysis methods may be used to determine forces caused by the earthquake
horizontal components acting on the structure, in the following cases:
10.3.1 Rigid Systems
In those structures or systems that - because of their rigidity – move jointly with the land,
such as reciprocating compressors or pumps fixed to massive foundations, seismic forces
should be estimated by multiplying their mass (W/g) by the maximum land accelerations
(Ao.g); Ao value is obtained through Equation (4), Section 7.3.
This force must be spread throughout all system elements, in a way proportional to their
mass distribution. See A.8.3.1.
10.3.2 Flexible Systems
For structures having a limited height or where using a simplified procedure is allowed,
(see A.8.3.2) one of the two methods described below shall be employed:
10.3.2.1 Simplified method
Total seismic forces (Vo) shall be computed as follows:
(14)
where:
(15)
2(1 + r) r1.5
21
Wi : weight of each level or section into which the structure has been divided into.
ß* : value to be computed as per Equation 5.
Vo : basal shear stress, in horizontal direction.
Ao : maximum land acceleration ratio (See 7.3).
D : ductility factor, as defined in the correspondent engineering specification (see 2.2).
W : total weight.
Lateral design forces result from the following expression:
(16)
Where:
Fi = lateral force in level or joint i.
hj = height of level or joint i in respect to the base level.
N = Number of levels or joints.
10.3.2.2. Equivalent Static Method
In this method, the seismic action is modeled through various lateral forces that are
statically applied on joints where the weight they contribute is concentrated.
– Fundamental Period
The fundamental vibration period is determined as per the following equation:
(17)
Where:
T = fundamental period, in seconds.
N = number of joints in the structure.
22
wi = contributed weight related to joint i.
fi = static lateral force acting on joint i, whose magnitude results from Equation (18).
ui = lateral displacement of joint i brought by applying N static forces as defined by
Equation (18).
g = acceleration of gravity.
Lateral forces to estimate the period are determined as follows:
(18)
Where
hi, hj= height of the joint i or j, measured in respect to the structure base level, or the zero
lateral displacement level.
C = arbitrary constant, in power unit, such as – for instance - 1 ton or 1000 kg. The sum of
all lateral forces fi is equal to constant C value.
fi = lateral force in joint i, to compute the period.
– Basal Shear Stress
The shear stress on the structure base is determined as per the following equation:
Vo= µAdW (19)
Where:
Ad = design spectrum ordinate defined in Chapter 8 for the fundamental period T
computed as per Equation (17).
W = total structure weight.
µ = dynamic reconciliation factor, the higher value among those resulting from Equations
(20) and (21).
µ = 1.6 (20)
µ = 0.14 (21)
+
+
14NN2
9NN
70.01*T
T+
−
23
NN= total number of levels where weights are concentrated
T* = characteristic period of the design spectrum defined in Chapter 8.
– Vertical spread of Lateral Forces
Lateral design forces on each structure joint shall be those resulting from the following
Equation:
Fi = Vo (22)
Fi: lateral force on joint i.
i: goes from 1 to N.
N: total number of joints.
Wi Wj: contributed weight related to joint i or j.
hi hj: height of joint i or j, measured in respect to the base level.
Vo: basal shear stress as per Equation (19).
10.3.3 Effects from the vertical component must be included in the design by following
procedure described in Chapter 11.
10.4 Inelastic Analysis Methods
These methods represent a more refined analysis option, which is recommended for cases
relating to special structures where critical zones want to be identified and ductility
demands, both global and local, and structure failure mechanisms want to be computed in
a more realistic way.
10.4.1 Inelastic Static Analysis
The structure is to be subject to a lateral load vector whose magnitude is monotonically
varied from zero (0) up to reaching the structure failure or ultimate state. Distribution of
such loads results from using Equation (18). See A.8.4.
10.4.2 Inelastic Dynamic Analysis
10.4.2.1 Earthquakes or seismic motions are described in terms of accelerograms meeting
requirements set in Section 7.4. Number of accelerograms to be used shall be at least
three (3), and mutually independent.
∑=
N
j
ii
1
5.1
jj
5.1
hW
HW
24
10.4.2.2 The structure shall be analyzed through the direct integration of the differential
equation describing its dynamic response (step-by-step method) for each accelerogram.
The probable dynamic response shall be obtained by averaging all responses obtained for
accelerograms.
10.4.2.3 Response parameters to be controlled shall be the ductility demand, the
dissipated energy, and the number of inelastic cycles.
10.5 Scope of Application
The scope of application for analysis methods is described in the Earthquake Resistant
design Standard particular to each facility.
11 COMBINATION OF EFFECTS BROUGHT BY THE ACTION OF THE THREE
SEISMIC COMPONENTS
Any of the following two criteria can be used to determine effects from the simultaneous
action of the three (3) earthquake components. Both assume that each component is
acting in one main structure direction:
11.1 The ultimate design force on one point and one direction as arising from the
simultaneous action of three (3) earthquake components shall be defined as the square
root of the sum of the squares of forces corresponding to each earthquake component.
Results shall be combined with other design actions, considering figures with both signs
(plus and minus).
11.2 The ultimate design force as arising from the simultaneous action of three (3)
earthquake components is obtained by combining the value of 100% forces arising from
the earthquake in one direction, with 30% forces arising from the earthquake in the other
two (2) orthogonal directions. This criterion implies considering the three (3) cases related
to designating 100% forces in each direction. The combination shall consider all possible
signs. See A.9.
12 SPECIAL SEISMIC PROTECTION SYSTEMS
The special seismic protection systems have been designed to be embedded into the
structure with such function as to reduce seismic forces acting on it; including isolation and
energy dissipating systems, both of active and inactive type. See A.10.
25
12.1 General
12.1.1 The design of structures whose behavior relies on such systems must ensure the
structure safety during earthquakes with 30% more intensity than the one set forth in this
Venezuelan Standard.
12.1.2 Likewise, these systems functioning must be checked for cases when the structure
is subject to design winds (See COVENIN 2003 Venezuelan Standard).
12.1.3 Construction works shall provide for leaving the access needed to carry out
periodical inspections on such systems.
12.2 Mechanical Properties
12.2.1 These systems behavior must be based on tests demonstrating their rigidity and
energy dissipation features under vertical loads and when facing a sufficient number of
alternating deformations, as well as their stability over time and response to temperature
changes, fire, fatigue, geological effects, aging, and chemical exposure.
12.2.2 Particularly, the rigidity and damping properties to be used in structure design and
analysis shall be based on tests carried out on a predefined sample, before starting
construction works. In such tests, those systems must be able to bear loads and
deformations imposed by an earthquake showing 30% more intensity than the one set
forth in this Venezuelan Standard.
12.3 Analysis
12.3.1 When calculating structures including such systems, a spatial dynamic analysis
method shall be used, in harmony with the system and the structure linear and non-linear
properties, including the three earthquake translational components.
12.3.2 In order to compute design forces on structures, the ductility factor D used shall not
be higher than ½ of the value that would result from designing such structure without those
elements, also adopting a maximum rigidity condition for all elements. At the same time, a
minimum rigidity condition shall be adopted for all elements to compute displacements.
13 EXISTENT FACILITIES
13.1 Purpose and scope
This chapter sets the structural assessment criteria to be followed to fit, remodel, restore,
or repair, and existent facility.
26
These criteria shall be taken into account jointly with all other provisions in this Venezuelan
Standard, excepting changes included hereby.
13.2 Fitting Levels
Those facilities ranked with a C or D Degree of Hazard under Chapter 5 shall be fit as to
meet, as minimum, all requirements in this Standard.
In all other cases, cost/benefit surveys can be optionally carried out in order to justify
different values.
13.3 Information Needed
13.3.1 Whenever documents (drawings, calculus, construction work logs, etc.) related to
the original structure are available, such must be checked for accuracy with the actually
built structure. In order to do so, surveys on representative facility areas shall be carried
out.
13.3.2 The history of any exceptional demand or force borne by the facility shall be also
investigated to be able to define current conditions, such as: settlements, excessive
overloads, strong winds, earthquakes, fires, corrosion, structural or non-structural
damages, leaks, and changes or repairs made.
13.3.3 Mechanical properties of materials used shall be based on the original inspection
reports and calculus documentation, which must be duly checked. If necessary, field tests
shall be carried out as set forth in Chapter 17, COVENIN 1753 Standard for reinforced
concrete structures.
13.4 General Criteria to Evaluate Existent Facilities
Seismic assessment of the existent facilities shall be carried out, among other things, in
accordance with the following general criteria:
13.4.1 Once the seismic analysis model is defined, critical sections related to potential
failure mechanisms shall be identified. Particular attention shall be given to potential
premature failures of a fragile type.
13.4.2 The D designated for the facility shall be justified in terms of expected behavior and
taking into account the reliable information about actual current conditions of structure
properties. Ductility values D set in the engineering specifications for similar facilities shall
be considered as maximum values.
27
13.4.3 When checking safety for systems with D >1, the mechanism controlling energy
absorption and dissipation in the system under analysis shall be clearly stated.
13.4.4 The current building or facility conditions shall be considered as for all aspects set
forth in Section 13.3.2.
13.4.5 Whenever, as resulting from a detailed assessment, an element failure is
evidenced, its potential effect on the relevant structural system stability shall be
investigated. If conclusion leads to think that stability is actually compromised, the
pertinent reinforcement measures shall be undertaken or -optionally- inelastic models can
be used jointly with the Dynamic Analysis Method with Accelerogram (See 10.2.2), to
evaluate expected damages and current reliability of the existent system in a more
accurate way.
BIBLIOGRAPHY
PDVSA Nº JA-221 Earthquake Resistant Design for Industrial Facilities. General review,
February 1999. Engineering Design Manual. Volume 18.
Engineering Specifications. Petroleos de Venezuela , S.A., PDVSA
28
APPENDIX A. COMMENTS
A.1 Scope
This Venezuelan standard is of a general use and can be applied to most oil and non-oil
related industrial structures and facilities such as tanks, offshore platforms, docks,
containers, pipelines, etc. Limitations related to specific cases are set forth in particular
standards for the Earthquake Resistant Design; which state inherent features and
uniqueness of each facility such as: damping, hydrodynamic effects, safety check
procedures, ductility, etc.
Taking into account the need to fit existent facilities deigned and built under less stringent
seismic related specifications, the scope of application for this Venezuelan Standard has
been widened to projects focused on reinforcing, modifying, and/or repairing such facilities
This Venezuelan Standard is not applicable to oil and non-oil related industrial facilities
abroad, unless the owner division requests a seismic hazard survey, so that the risk
shown by the final design is not lower than facilities located in Venezuela.
On the whole, these specifications are intended to set methods and procedures to design
oil and non-oil related industrial facilities able to resist intense earthquakes; thus reducing
the risk for human life loss, materials loss, and catastrophic pollution. When selecting
design parameters we tried to reach a comparable degree of exceedance risk,
independently from the location and site conditions.
Even though the design earthquakes are not necessarily the most intense that could be
expected in areas under study; the exceedance potential during the facilities useful life has
been considered as sufficiently short.
Under the action from design earthquakes some damages can arise, but they are usually
limited to easy to repair elements. For movements exceeding design values, expected ruin
or collapse probability should be very low.
The adequate selection of land motions must be understood as a complement –never a
substitute- for a good design and work performance, and a thorough inspection.
29
A.2 GENERAL REQUIREMENTS
A.2.1 Design Strategy
In accordance with the same philosophy shown by other Standards (See 4.1) seismic
actions to be considered for design depend on the facility expected performance and
potential results from any malfunctioning. That is why, for instance, when designing a
metal cylindrical tank with thin walls, and settled on the ground, seismic actions shall
depend on performance results: actions shall be different if this tank will de used to store
potable water, water for fire-fighting, or flammable products (see A.4.1). Those differences
are even more significant if any potential failure could endanger a high number of people
and properties, or bring a potential catastrophe (see Table 1, Degree of Hazard).
Consequently, facilities showing the highest hazard shall use more intense design
earthquakes related to lower exceedance potentials, in order to reduce probability for such
failure conditions to arise during their useful life. (See COVENIN 3622 and 3623
Venezuelan Standards)
Past experiences have shown that under intense earthquakes, it can be convenient to
tolerate moderate incursions in the inelastic deformations range. Such give raise to limited
and repairable damages, but at the same time allow for energy dissipations and therefore
the response before dynamic actions is lower.
A.2.2 Site Surveys
Seismic hazard maps show an overall assessment at national level, taking into account
the best seismic-tectonic information available (see A.5.1). Local subsoil effects have also
been set as per overall conditions, as shown in Chapter 6 hereby. For such motive, in
significantly important facilities, these actions can be substituted by actions resulting from
studies including both the local seismic hazard and the particular local subsoil features.
Likewise, other seismic actions that could occur at the particular site shall be evaluated,
such as sea earthquakes, landslides, etc.
A.2.3 Measurements and Tests for Evaluation Purposes
When evaluating existent facilities, the relevant modeling can be conveniently
complemented with on site measurements. Some frequent measurements refer to periods
and/or damping, either under an environmental vibration, a free vibration, or a harmonic
vibration regime; or are made to determine material properties.
30
A.2.4 Superposing on other Actions
Superposing criteria set forth herein are consistent with procedures specified to compute
effects from earthquakes. Load factors m and n depend on design or checking methods to
be used in each case, and are set forth in the relevant standards.
Seismic actions mentioned in this Venezuelan Standard refer to the creep level. Therefore,
for section dimensioning methods based on ultimate states, seismic action effects should
not be increased: q = 1. For the particular case of fire-fighting systems, their fixtures and
supports, using q =1.20 is required in order to ensure operational conditions. When the
particular specification allows using methods based on admissible stress, seismic action
effects can be dropped to: q < 1.
A.3 HAZARD RATING
A.3.1 Reference Scale
The degree of hazard used to set the exceedance potential per annum is based on
consequences of an accident caused by a structure mal functioning. Such consequences
include: people exposed, economic losses, and environmental impacts, for which
References 4.1 and 4.2 were considered.
To select the Degree of Hazard, the mandatory condition is to select the most unfavorable
one. So, if a quite limited number of operators are endangered by a facility malfunctioning,
but a spill from such facility could bring direct or indirect huge economic losses, or an
unfavorable environmental impact, it must be ranked in the C or D Degree of Hazard, as
the case might be.
A.3.2 Doubtful Cases
In non-clearly defined situations, or when the facility can be subject to a significant change
in the near future, recommendation is to adopt conservative criteria when selecting the
degree of hazard.
A.4 FOUNDATION LANDS
The fact that local subsoil conditions can change land motion features is widely
acknowledged. Multiple accelerograph logs -both from the surface and various alluvial
deposit depths- have evidenced that spectral patterns can significantly differ, therefore the
expected effects do also differ (see References 6.1, 6.2 and 6.3).
31
Including all aspects having influence on land motions at a given site would be quite
complex and their particular effects must be considered as per a highly thorough criteria.
Factors affecting frequency contents, amplitudes, and motion times include, among others:
presence of alluvial deposits, lack of homogeneity among strata, soils inelastic properties,
distance from sources, and site topography (See References 6.1, 6.2, 6.3 and 6.4).
Inelastic effects can have a major importance under certain conditions and can attenuate -
instead of amplifying- surface motions in respect to the rock layer motion.
Local soils influence in spectral pattern types described in Section 6.1 is considered as
independent from the motion intensity and, consequently, from the seismic zone. As
deposits include a greater amount of softer soils, the influence from motion components
having the longer period increases to the same extent, especially within the period range
from 0.5 to 2.0 seconds.
A.4.1 Spectral Pattern and Factor ϕϕϕϕ Selection
A.4.1.1 Soil profile features and its dynamic response
The dynamic response from a soil deposit depends on its profile -as made through
geotechnical tools- and the seismic area where such is located. Usually, for engineering
purposes, spectral accelerations and maximum surface acceleration are taken into
account.
However, in order to reach the most adequate type selection for a soil profile dynamic
response, response spectrums must be generalized and idealized as per parameters
inherent to the soil and the deposit pattern, as such define the dynamic response. Here we
must point out that soil profile and spectral pattern concepts cannot be considered as
synonyms; many soil profiles may show a similar response while one single deposit may
show different responses to earthquakes occurring nearby or far away from it.
Table A.1 shows the two (2) main parameters controlling the dynamic response from soil
profiles that have allowed setting spectral pattern types. Such table was made by taking
into account:
(i) important effects observed during earthquakes occurred within the last 30
years;
(ii) that set forth in other countries’ Standards; and
(iii) (iii) most recent studies about site effects on the dynamic response from soil
32
profiles (see Comments to Chapter 5, in COVENIN 1756 Standard).
In Table A.1, the velocity of shear waves comes to be the most significant parameter to
define the actual response features related to a profile, and shows some characteristic
values.
TABLE A.1 –CORRELATION BETWEEN VS AND
PENETRATION RESISTANCE SOILS AND ROCKS
Material Description N1(60) (a)
Average Velocity of
Shear Waves (m/s)
Soft or loose soils
(very low rigidity) N1(60) < 10
Vs < 170
Solid or moderately compact soils
(low rigidity) 10 ≤ N1(60) ≤ 20
170 ≤ Vs ≤ 250
Hard or compact soils
(moderately rigid) 20 ≤ N1(60) ≤ 50 250 ≤ Vs ≤ 400
Very hard or highly compact soils
(rigid) N1(60) > 50
Vs > 400
Soft rock - Vs > 400
Hard rock - Vs > 700
Note: N1 (60) is the number of drops made in the SPT, corrected by the confinement rate and the equipment energy efficiency.
A.4.1.2 Spectral Pattern Types
Spectrums used to define spectral pattern types S1 to S4 set forth in Section 6.1 included
both actual spectrums, and spectrums obtained by applying constitutive and semi-empiric
models to the dynamic response from soil profiles (See References 6.5; 6.6; and 6.7).
Spectral pattern types S1 to S4 take into account the typical parameters included in Table
2 and other parameters such as epicentre distance, local elastic-seismic properties, soil
types, direction of seismic waves, deposits depth, and stratigraphy. Analyses carried out
considered actual and synthetic earthquakes.
A.4.1.3 Maximum horizontal surface acceleration
Some evidences indicate that local soil conditions, particularly when related to soft soils,
do modify maximum surface acceleration. Factor φ values were obtained from
comparative analyses made on:
(i) surface accelerations correspondent to different seismic hazard assessments
carried out with similar analytical procedures but different attenuation laws; and
33
(ii) surface accelerations arising from different models used to evaluate
amplification caused by soft soils (See Reference 6.8).
Particular studies shall be carried out on those sites located very near active faults,
because accelerations- and therefore horizontal acceleration ratios- can be higher that
those set forth in these Specifications
A.4.1.4 Determining Average Velocity of the Shear Waves in Soil Profiles
The velocity of shear waves is the most important parameter to evaluate dynamic
response from soil profiles. Table A 1 requires the average velocity of VSP profile, which
shall be estimated as shown below.
The weighed average of the shear waves’ velocity for a soil profile is computed based on
the aggregate of vertical travel times at the various profile strata or sub-strata. If a profile is
homogeneous or the strata thickness is too high and velocities show significant variations
with depth, several sub-strata can be defined as per velocity features or spread arising
from depths. Travel time at each stratum is referred to as te,i and represents the average
time needed for a wave to go through it, as per the basic equation:
Te,i = he,i/Vsp,i (A.1)
Where he,i is the stratum thickness and Vsp,i is the average velocity of the shear waves in
that stratum.
Then, the average total travel time of the wave throughout the profile will be:
tpt = ∑(he,i/Vsp,i ) (A.2)
And the average velocity VSP is the quotient of the total profile height H = ∑ he,i) by the
aggregate of all partial travel times related to each stratum:
VSP = H/∑(he,i/Vsp,i ) (A.3)
The velocity of shear waves can be measured either directly, or through estimates based
on empiric correlations with such tests as SPT or CPT, yet always taking care of using the
needed correction for each particular case. When a case relates to clays, correlations
based on non-drained shear resistance may be used with the velocity of shear waves.
We must point out that on-site measurements do not exclude the need to carry out soil
drillings, because both methods are complementary.
34
A.4.2 Special Cases
Spectral patterns shown in a Section 7.3 above are valid for stable soil deposits and
therefore are not applicable to soils deposits that can be liquefied. So, those soils shall be
first treated to reduce or remove their liquefaction potential before allotting them as per
typical profiles described in Section 6.1.
A.5 SEISMIC ACTIONS
A.5.1 Seismic Hazard Maps
Maps shown in Figures 1 and 2 are based on the probabilistic quantification of seismic
hazard as per the best information available by 1996 (see updated map in COVENIN
1756:1998 Venezuelan Standard). We can expect that as statistical data regarding strong
land motions brought by local earthquakes increases as well as the understanding about
their origins, and the frequency in which intense earthquakes occur (Cariaco Earthquake in
1997), values and/or curves will be changed or adjusted.
The procedure to estimate seismic hazard described in this Venezuelan Standard differs
from the classical one used by various design standards, as it allows including a higher
number of variables conditioning maximum land acceleration in the relevant site. In the
classical formula, as used in COVENIN 1756 Venezuelan Standard, the user selects
design acceleration based on a zoning map related to a fix return period of the seismic
motion (this is equivalent to setting pairs of values (P*, t), where P* is the exceeding
potential within the building useful life t). In the formulation of this COVENIN 3621
Venezuelan Standard, the two maps related to parameters a* and γ allow determining the
design acceleration in the same way as the classical formulation, or by considering
different return periods and useful life values. As the last option is more comprehensive
and flexible than the first one, decision made was to keep both zoning maps in this
Standard. Both maps have been prepared with the new seismic-tectonic information
developed within the last five years.
When results from the seismic hazard are analyzed in terms of maximum land
acceleration, we can observe that the logarithm of the exceedance rate per annum (λ) and
the logarithm of maximum land acceleration (a) show an approximately linear ratio within
the relevant range of values; as follows:
ln λ = q - γ ln a (A.4)
35
where: q and γ are parameters that characterize the seismic hazard in the site.
Equation (A.4) can be expressed as:
λ = (A.5)
Where variable a* has been included, as resulting from:
a* = eq/γ (cm/s2) (A.6)
A.5.2 Maximum Horizontal Land Acceleration
Under such hypothesis as that the number of earthquakes (Na,t ) exceeding a specific
acceleration level (a) within a period of t years follows a Poisson distribution, the
probability for an event showing an acceleration equal to or higher than “a” to occur in t
years can be found through:
P [ Na,t > 0 ] = P* = 1-e -λ t (A.7)
When we substitute λ for Equation (A.5), we have:
(A.8)
The exceedance potential P* in t years is a way to quantify the seismic hazard for the
facility. Please note that for t = 1, P* =p1 which represents the exceedance potential per
annum as shown in Table 1.
Until the seismic prediction studies show any further progress, models shall be kept with
no memory; i.e. design earthquake selection will be independent from the recent seismic
activity, and the related exceedance potential shall be constant. Obviously, this criterion is
not conservative when the case relates to major active faults that have had no motion
within a term near or exceeding its average return period; as we learn more about seismic
issues and can build valid predictive methods, exceedance potentials will tend to vary over
time.
In this Venezuelan Standard two calculus options for the maximum land acceleration are
defined, as follows:
γ−
*a
a
year
1
36
A.5.2.1 Option 1
Earthquakes exceedance potential per annum p1 is defined as a constant parameter, as
shown in Table 1, in function of the Degree of Hazard. Please remember that the inverse
of p1 is the motion return period (T): p1= 1/ T.
In addition, the non-exceedance capacity within the useful life (t) results from:
1 - P* = (1 - p1) t (A.9)
The design acceleration results from:
a = a* [ - In (1 - p1) ]-1/ γ (A.10)
Where we can see that such acceleration is independent from the facility useful life (t) and
does only depend on the seismic zone (a* and γ) and from p1 (or its inverse, the return
period T).
We must also point out that exceedance potential (P*) within the useful life and the same
useful life are correlated through the following expression:
P*= 1 - (1 - p1) t (A.9a)
Evidencing that p1 is related to variable pairs of P* and t values.
Example 1:
For a seismic zone defined by a* = 62 and γ = 3.6
Considering a facility with preset p1= 0.002 (or a return period of 500 years).
The design acceleration is obtained from Equation (A.10):
a = 348 cm/s2
Using Equation (A.9.a), we can relate this acceleration to the following pairs of useful life
and exceedance potential values:
For t = 30 years P* = 0.0585
For t = 50 years P* = 0.0956
For t = 100 years P* = 0.182
or any other pair of values.
37
Please note that such pairs of values correspond to the same return period of 500 years.
A.5.2.2 Option 2
In this option, the exceedance potential (P*) is defined as constant parameter within the
building useful life. When we know P*, the maximum land acceleration is obtained through
Equations (A.10 and A.9a):
a = a* [ ( - ln (1 - P*) / t ] -1γ (A.11)
Where we can evidence that the design acceleration does depend on the building useful
life (t). Likewise we must point out that the exceedance potential per annum (p1) (or its
inverse, the return period (T) does also depend on the selected useful life.
Example 2:
For the same seismic zone in example above, with a* = 62 (cm/s2) and γ= 3.6
Considering a facility with a preset P*= 0.10
The following design accelerations and return periods (T) are obtained for the three useful
life values selected from Equation (A.11):
For t = 30 years a = 298 cm/ s2 T = 285 years
For t = 50 years a = 343 cm/ s2 T = 476 years
For t = 100 years a = 416 cm/ s2 T = 950 years
A.5.2.3 Comparison
In summary, Option 1 is based on setting a constant earthquake return period, while
Option 2 defines the value of the exceedance potential within useful life. Comparing results
from two examples above we can evidence that equal hypothesis bring equal results. Both
options are theoretically right (under the Poisson model hypothesis) and have been used
as seismic design criterion in several countries.
As example, Table A.2 shows a summary of criteria used by various countries for the
Earthquake Resistant design in several building types; the average return period shown is
just 1/P1. The table reflects that as potential consequences from a failure of malfunctioning
have a catastrophic nature or their significance makes leads to reduce ruin potential, P1
value tends to be lower.
38
Such strategy is also reflected in Table 1 of this Venezuelan Standard.
TABLE A.2
CRITERIA TO SELECT ACCEPTABLE HAZARDS IN EARTHQUAKE
RESISTANT DESIGN (NON-SPECIFIED SOURCES)
FACILITY OR BUILDING TO
BE DESIGNED
EXCEEDANCE POTENTIAL
PER ANNUM (10-3
)
AVERAGE RETURN PERIOD
(years) =
Buildings (α = 0.1) 2.1 475
Buildings (α = 1.25) 1.1 – 0.7 900 – 1430
Bridges (α = 1.0) 1.75 570
Bridges (α = 1.25) 0.76 - 0.51 1300 – 1970
Offshore platforms, elastic response 4.2 238
Offshore platforms, stability check 0.40 2490
High voltage electrical equipment, static response 0.67 - 0.33 1490 – 3000
Dams < 1.0 > 1000
Critical structures 1 – 1.0 1000 – 10000
Nuclear plants, with automated shutdown upon
earthquake detection
0.2 – 0.1
5000 – 10000
Liquefied gas facility 0.1 – 0.001 10000 – 1000000
Radioactive waste storage facilities; useful life: 10,000
years
0.001 – 0.00001
1000000 – 100000000
A.5.3 Elastic Response Spectrums
Procedure set in this subsection is exemplified below by determining the response
spectrum to design a facility which will be located at a site featured by a* = 45 gal, γ= 3.2
and S2 type soil (ϕ = 1.0). As per Option 2 in Section 7.2.2, the useful life has been set in
50 years and selected value for P* = 0.07; the system damping ratio equals 3%. So we
have:
A= 45 = 347 gal
1P
1
2.3/1
50
93.0ln−
−
39
Ao = a/g = 0.354
From Table 3:
β = 2.6
To = 0.20 s
T* = 0.85 s
From Equation (5):
β* = (0.0853 - 0.739 ln 0.03) = 3.03
A.5.4 Acceleration Histories
Standards frequently used to design earthquake resistant structures such as buildings and
bridges some times specify seismic actions through response spectrums that are
decreased by ductility. The option to justify analysis methods within the type domain, with
accelerograms, is left open.
In structures of other type, for instance earth dams located in sites with high seismic
hazard, the seismic action characterization based on accelerograms comes to be
mandatory, so that the non-linear nature of its dynamic response is taken into account.
Using accelerograms can be useful for many structures, such as those located in oil and
petrochemical facilities, as they provide more information about the dynamic response
from a structural system.
Whenever the decision is to use accelerograms to design or assess oil and non-oil related
industrial facilities, at least three accelerograms shall be used, also meeting that set forth
in Section 7.4 hereby1. This minimum of three (3) accelerograms is necessary in order to
include variability featuring the structure maximum dynamic response when subject to
earthquakes; design values must be determined by averaging maximum responses related
to all accelerograms.
The intensity of each accelerogram shall be selected in order for it to be equivalent to the
intensity of earthquakes defined in this Standard. That is why each accelerogram spectrum
is required to be similar to elastic spectrum (D = 1) described in Section 7.3. However,
accelerograms do not have to match throughout the entire periods range; as it will be
1 PDVSA–INTEVEP has a database with acceleration histories.
3.2
6.2
40
enough that they match within the range of those periods inherent to the structural system
under consideration.
A.5.5 Motion Components
Earthquakes have a simultaneous action in three (3) directions which are mutually
orthogonal: two (2) horizontal directions, and one (1) vertical direction. In accordance with
the statistical assessments of vertical response spectrums arising from actual logs, vertical
spectrums whose ordinates are 70% horizontal spectrum ordinates do represent expected
vertical motions (see A.9). When using accelerograms from artificial logs, a fact to be
taken into account is that earthquake orthogonal components shall not be correlated (See
References 10.8). Spectrums for the earthquake rotational components can be obtained
through procedures as those shown in References. 10.10 and 10.11; which include
velocity of waves and foundation sizes.
A.6 DESIGN SPECTRUMS
Analytical studies and performance interpretations made on structures affected by
earthquakes evidence that dynamic responses to seismic forces from systems with one (1)
degree of freedom showing non-elastic links between forces and displacements lead to
lower maximum accelerations than those corresponding to strictly elastic responses.
Conclusions for systems with one (1) degree of freedom can be extended to systems with
several degrees of freedom, as long as the system shows no significant discontinuities in
mass and rigidities spread.
For reasons above, elastic spectrums listed in Section 7.3. can be decreased dividing
them by the ductility factor. Please note that to obtain actual displacements arising from
the seismic action, such displacements obtained from elastic analyses made on decreased
spectrums forces shall be multiplied by D.
Criteria set forth above to obtain design spectrums from the elastic spectrum are based on
results shown in See References 8.2.
Figure A.1 shows the design spectrum for a Ductility Factor D = 4 obtained for the example
described in Section A.5.3. For this case T+ = 0.30 s.
41
´
FIGURE A. 1 –DESIGN SPECTRUM
A.7 MODELING
A.7.1 Structure-borne Facilities
The option to use floor spectrums shown in Section 9.1 can be appropriate and
advantageous for cases relating to facilities with a significantly lower mass than the
bearing structure. Such would be the case for huge platforms bearing flexible facilities with
limited mass or structure additions.
A procedure, usually quite conservative, but essentially valid to use for bearing structures
where a significant portion of mass is concentrated at the level where the structure
addition is fixed is shown below. This procedure is valid when one of the following
conditions is met:
µ < 0.1 for τ < 0.8 or τ > 1.25 (A.12)
µ < 0.01 for 0.8 ≤ τ ≤1.25 (A.13)
42
Where:
τ= Ta/Ts
µ = Ma/Ms
Ts = bearing structure period
Ms = bearing structure mass
Ta = structure addition period
Ma = structure addition mass
Obviously, to carry out the analysis, the structure addition mass shall be included into the
bearing structure mass; the bearing structure- addition interaction can be neglected even if
they meet conditions set in A.12 or A.13.
The spectrum to be used for the structure addition base to determine forces would be the
following:
a. For Ta < T*, the same Equations (7 and 8) in Chapter 8 hereby shall be used with the
following changes:
Ad = Ad,a = the structure addition design spectrum ordinate
ϕAo =Ad,s = design spectral acceleration correspondent to the bearing structure
fundamental mode; assuming that the first translational mode is the prevailing one, with a
response history of a debatements type.
β* = 1/ (4 ξa)
T = Ta
D = Da = Structure addition ductility factor
T* = 1.15 Ts
To= 0.85 Ts
ξa = Structure addition damping ratio (%)
2. For Ta ≥T* (τ ≥1.15):
Ad,a = [ (1 - τ 2) 2 + (2τ ξa)2
] -0.5 (A.14)
D
A sd ,342.0
43
A.7.2 Masses
The mathematical model used to compute seismic forces must necessarily represent the
actual structure, both with regard to dimensions and mechanical properties, as well as
masses included therein and their spread, in case of an earthquake. Therefore, materials
and elements giving shape to the facility must be modeled and the most probable weight
under operating conditions must be estimated. It is not likely for the design earthquake to
be superposing on accidental overloads such as hydrostatic and pressure tests lasting for
a very short time if compared to the useful life.
A.7.3 Mechanical Properties
The selection of properties to consider when designing new facilities can be based on the
information available about similar facilities such as; for instance, the damping value
referred to the critical damping to be used in Equation (5). Usually, when existent facilities
are assessed, their dynamic properties are measured: damping, eigen frequencies and
modal patterns. Experimental methods can be ranked as free vibration and forced
vibration procedures. With regard to instrumentation, related procedures and calculus, see
References 10.5, 10.6, and 10.7. The potential to match eigen frequencies and modal
patterns measured against analytical values allow making any potential correction needed
in the mathematical model, thus enhancing reliability on forecasts regarding earthquake
effects. However, we must take into account that rigidity values obtained from dynamic
tests made with low amplitude vibrations can overestimate values representing a response
before earthquakes which is featured by higher amplitudes.
A.8 ANALYSIS METHOD
A.8.1 General Criteria
As set forth in Sections 7.5 and 11, the system analysis must take into account that
earthquakes do simultaneously act in three (3) mutually orthogonal directions, and must
include their effects.
A.8.2 Dynamic Analysis Methods for Elastic Systems
These methods determine inertial forces on the structure by considering its dynamic
properties. Reference 9.5 shows the theory of the structural dynamic analysis and
describes calculus methods most commonly used.
44
Procedures described in Sections 10.2 and 10.3 are based on the hypothesis that inelastic
effects can be duly included by carrying out a linear analysis of the earthquake resistant
system with decreased elastic response spectrums (See Reference 10.1).
Applicability for this method is conditioned to a regular resistance spread. In fact, an
irregular spread can lead to ductility demand concentrations and consequently, results
from this method tend to be out of the safety range.
The mode “i” participative mass for an earthquake in direction “l” is obtained from:
(A.15)
Where:
= mode “i” eigen vector
= vector defining seismic component “l”
M = mass matrix
l = x, y, or z
A.8.2.1 Nodal Analysis with Response Spectrum
The dynamic analysis method is intended to evaluate the maximum probable response
and can be an option of general use for the analysis related to all structure types. Its use
has been prescribed for facilities where the method described in Section 10.3 is not valid.
The seismic response values shall be computed for earthquakes in directions X, Y, and Z,
acing in an independent way.
As modes resulting from the analysis can have frequencies that are near between them,
combination methods used must take their coupling into account.
(See References 10.2 and 10.3).
A.8.2.2 Dynamic Analysis with Accelerograms
A fact to bear in mind is that the only way to have reliable results is if response statistics
are studied under several land motion histories, either actual or simulated, in a number
usually recommended as 3, and consistent to response spectrums listed in Section 8.2. To
such respect, see Reference 10.4.
45
A.8.3 Simplified Methods
Simplified methods are aimed at determining lateral forces to be applied on each joint or
level adopted in the mathematical model for the structure.
A.8.3.1 Rigid Systems
Facilities or structures rigidly linked to the land are deemed as rigid systems if their
fundamental period is shorter than 0.05 seconds, approximately. Such as equipment or
utilities like pumps or compressors bolted to massive foundations which do not amplify
land excitation. Forces spread mentioned in this section can be applicable, for instance, to
shear stress and overturning effects on anchoring bolts.
A.8.3.2 Flexible Systems
Like other simplified methods, we can expect that total seismic forces obtained through the
procedure described in this section come to be somewhat conservative; this is particularly
valid for highly flexible systems. That is why it is only recommended for structures of
limited height.
A.8.4 Inelastic Static Analysis
This method is recommended for structures which are special because of their irregular
nature or their importance. Here, we must point out that this method provides more
realistic information about the structural behavior and allows identifying critical areas. The
importance of the information provided by this analysis justifies efforts made to prepare
additional data on structure properties.
A.9 COMBINATION OF EFFECTS BROUGHT BY THE ACTION OF THE THREE
SEISMIC COMPONENTS
The combining criteria used for effects brought by the three land motion components are
base on Section 2.7.5, See Reference 10.1.
Please note that these combining criteria assume the statistical independence of the three
(3) earthquake components, and that is why their correlation ratios are accepted as of
value zero. The same criterion can be applicable if land rotational components are added.
For structural elements where probable maximum value of each individual actuating force
on a section (obtained through criterion 10a), could not define the critical design case, all
possible combinations related to forces arising from earthquakes shall be used. For
instance, in columns subject to a bi-axial flexure: + P, ±Mx, ±My, there would be eight
46
possible sign combinations to detect the design critical case. Likewise, we must take into
account that this recommendation can lead to obtain highly improbable cases from a
physical standpoint.
Application of criterion 10b is depicted in the following example related to combining
effects from gravity (permanent load + variable load) with effects from earthquake x,
earthquake y, and earthquake z:
gravity ± 1.00 earthquake x ± 0.30 Earthquake y ± 0.30 Earthquake z
gravity ± 0.30 Earthquake x 1.00 Earthquake ± 0.30 Earthquake z
gravity ± 0.30 Earthquake x ± 0.30 Earthquake y ± 1.00 Earthquake z
This last criterion is recommended in References 10.9, 10.12, and 10.13. When effects
from the vertical component are ignored, combinations above shall be limited to both
horizontal components. Forces resulting from the seismic action are combined with service
and operating actions, as set forth in Section 4.5.
A.10 SPECIAL PROTECTION SYSTEMS
Recently, some international standards have included recommendations for structure
seismic design including special systems, as mentioned in See References 12.1.
Reference 12.2 includes some works on passive systems.
47
APPENDIX B
(Informative)
B GUIDE FOR TECHNICAL CONSULTATIONS TO MINDUR TECHNICAL
STANDARDS COMMISSION
B.1 FOREWORD
The MINDUR Technical Standards Commission has agreed that all official interpretations
regarding its standards shall be treated in the same formal way. For such an effect, all
consultations shall be addressed in writing to the Commission premises.
Consultations shall be handled as soon as possible but due to the complexity of work and
procedures to be followed some interpretations and responses can take a considerable
time. The Commission shall not answer to consultations made over the telephone or those
omitting any of the following requirements.
B.2 COMMISSION RESPONSIBILITIES
Commission activities in that regarding the official interpretation of the norms under its
competency, shall be strictly limited to interpret requirements set forth in its standards or
consider reviews for current provisions based on new data or technologies. Neither the
Commission, nor its members as such, are authorized to provide any interpretation or
consulting service on particular problems related to an engineering work, or on standards
requirements applicable to a building which are not included in the same, or issues not
specifically covered by standards. In such cases, the requester shall seek the help from an
experienced engineer in the particular field in question.
B.3 PROCEDURE
B.3.1 Addressee and Sender Details
All consultations shall be made in writing and sent to the Technical Standards
Commission:
48
Technical Standards Commission, Ministry of Infrastructure, Projects Direction, Torre
Oeste, Piso 48, Ave Lecuna, Parque Cantral, Caracas 1015. Telephone: (02) 576.4322,
571.1222 ext: 9551; Fax: 575.4268
Consultations shall include the name of requester(s), their profession, the agency they
represent, whenever relevant, address, telephone and telefax numbers, electronic mail
address, as well as enough information for the Commission to fully understand the issue
under consultation. In order to facilitate the organization and handling, it is very important
that each problem or issue is isolated, enclosing all pertinent documentation, so that it can
be consulted in a separate way. Whenever the consulted issue is not clearly defined or
mixed questions are set forth, the consultation shall be retuned for clarification.
In order to ensure an efficient handling, all consultations shall be submitted in the order
and form described below:
1- Scope
Each consultation shall be focused on one standard provision, unless the matter is related
to two or more documents. The scope of the question shall start by identifying the
COVENIN-MINDUR Venezuelan Standard, year, issue, and the Article(s), Section(s),
Subsection(s) covering the consulted issues.
2- Purpose for the Consultation
The purpose for the consultation shall be clearly stated, whether it seeks to obtain an
interpretation of standard requirements, or request reviewing a particular provision as
based on new criteria, data or technologies.
3- Content of the Consultation.
The consultation shall be precise but complete, in order to allow the Commission to quickly
and fully understand the issue in question. Whenever appropriate, drawings and sketches
shall be used, stating all identifying data related to paragraphs, drawings, and tables
pertinent to the consultation. If the consultation seeks a review of the standard, the
relevant technical justifications and documentation shall be enclosed.
49
4- Suggested Solution.
The requester, in accordance with the purpose for the consultation, shall write a suggested
solution stating his/her interpretation of provisions relevant to the questioned matter, or
write the text of the review proposed.
B.4 INTERPRETATION AND REVIEW OF STANDARD PROVISIONS
The official interpretations of provisions in the COVENIN-MINDUR Venezuelan Standard
shall be made by the Commission. The Commission President shall refer the consultation
to those members having more experience on the matter. Once the answer is written, it
shall be submitted to the Commission in full meeting for review and approval. Upon
approval, the text shall become an official interpretation and Commission Secretariat shall
send the answer to the requester, the official agencies involved, and FONDONORMA for
its publishing.
B.5 PUBLICATION OF INTERPRETATIONS
All official interpretations shall be included and published in the next issue of the relevant
COVENIN-MINDUR Venezuelan Standard by Venezuelan Standard by Fund for the
Quality Normalization and Quality Certification (FONDONORMA), and in the Commission
Annual Report.
50
APPENDIX C
(Informative)
PRINTING FROM THE PERMANENT TECHNICAL STANDARDS COMMISSION
C.1 COVENIN-MINDUR TECHNICAL STANDARDS
1618-1998 Steel Structures for Buildings. Ultimate State Method.
1753-1985 Reinforced Concrete Structures for Buildings. Analyses and Design.
1755-1982 Code of Normalized Practices to Manufacture and Build Steel Structures.
1756-1998 Earthquake Resistant Buildings
2000-1992 Construction Sector. Measurements and Coding of Allotments for Studies, Projects,
and Construction Works. Part II-A Buildings.
2000-2:1999 Construction Sector. Measurements and Coding of Allotments for Studies, Projects,
and Construction Works Supplement to COVENIN-MINDUR 2000/II a-92 Standard.
2002-1988 Minimum Criteria and Actions for Building Projects.
2003-1987 Wind actions on Buildings.
2004-1998 Terminology of COVENIN-MINDUR Standards for Buildings.
2733-1990 Project, Construction Works and Fitting of Public Usage Buildings accessible for
Physically Handicapped People.
3400-1998 Buildings Waterproofing Process.
3621:2000 Earthquake Resistant Design for Industrial Facilities
3622:2000 Earthquake Resistant Design for Containers and Structures
3623:2000 Earthquake Resistant Design for Metal Tanks
3624:2000 Earthquake Resistant Design for Structures in Lake and Shallow Waters
C.2 Manuals
Epelboim, Salomon; Arnal Henrique. Manual to project reinforced concrete structures for buildings.
2nd
Edition. 1996. 950 pages
Marin, Joaquín, Guell, Antonio. Manual to calculate reinforced concrete columns. 2nd Printing –
Reviewed. 1991. 22 pages
Distribution and Sale: Fondo para la Normalización y Certificación de la Calidad, FONDONORMA, Torre Fondo Común, Av. Andrés Bello, Piso 12 Caracas Telephone (0212) 575.44.98 , (0212) 575.41.11 Email: [email protected]
51
REFERENCES TO COMMENTS
4.1 New Zealand National Society for Earthquake Engineering. Seismic Design of Storage Tanks. December, 1986.
4.2 Petroleos de Venezuela S.A. Corporate Integral Protection management. Guía de Análisis de Riesgos (A Guide to Risk Analysis). Caracas, May 1990. 28 p + Appendixes.
6.1 SEED, H.B; UGAS, C. and LYSMER, J. Site dependent spectra for earthquake resistant design. Bulletin of the Seismological Society of America, Vol. 66, # 1, February. pp. 221–144,1976.
6.2 UGAS, C. Espectros para diseño antisísmico en función de las condiciones locales del suelo. (Spectrums for earthquake resistant design in function of local soil conditions) IMME Bulletin, # 48, October–December, 1974. Caracas.
6.3 National Earthquake Reduction Program. Recommended Provisions for the Development of Seismic Regulations for New Buildings. FEMA, Washington 1988.
6.4 OHTSUKI, A. and HARUMI, K. “Effect of Topography and Subsurface Inhomogeneites on Seismic SV Waves”. EESD. Vol.–11 441–462 (1983).
6.5 ECHEZURIA, H. (1997). Efectos de sitio. En: Diseño Sismo Resistente. Especificaciones y Criterios Empleados en Venezuela. (Site Effects In Earthquake Resistant Design. Specifications and Criteria Used in Venezuela). Academy of Physics, Mathematics and Natural Sciences of Venezuela. Edit J. Grases, pp 91–111, Caracas.
6.6 RIVERO, P. (1996). Respuesta espectral del sitio considerando comportamiento inelástico del suelo. (Spectral Response of a Site, taking into account an Inelastic Soil Behaviour) Degree Thesis for the Magister Scientearum, Los Andes University, Merida.
6.7 PAPAGEORGIOU, A. and KIM, J (1991). “Study of the Propagation and Amplification of seismic waves in Caracas Valley with Reference to the 29 July 1967 Earthquake: SH Waves”. Bulletin of the Seismological Society of America,Vol. 81, No. 6, pp 2214–2233.
6.8 ECHEZURIA, H. (1998). Análisis de las Aceleraciones Máximas del Terreno Ocurridas Durante el Sismo de Cariaco–97 (Analysis on maximum horizontal soil acceleration during the Cariaco Earthquake-97. Accepted for publishing in the IMME Technical Magazine, UCV, 1998.
8.1 N. NEWMARK and W.J. Hall. Earthquake Spectra and Design. Earthquake Engineering Research Institute. Berkeley, California. 1982.
8.2 R. RIDELL, P. HIDALGO and E. CRUZ. Response Modification Factors for Earthquake Resistant Design of Short Period Buildings. Earthquake Spectra, Vol. 5, # 3, 1989.
10.1 CHOPRA A.K. and NEWMARK N.M. Analysis. In: Design of Earthquake Resistant Structures, edited by E. Rosenblueth, John Wiley & Sons, New York, 1980.
10.2 ROSENBLUETH E. and ELORDUY J. Responses of linear system to certain transient disturbances. Proc. IV WCEE, Santiago de Chile, 1969, Vol. 1, pp.185–196.
10.3 KAN C. and CHOPRA A. Coupled lateral torsional response of building to ground shaking. Berkeley, University of California, EERC 1976, 76–13.
10.4 BIGGS J., HANSEN R. and HOLLEY M. On methods of structural analysis and design for earthquake. In: Structural and Geotechnical Mechanics, a volume honoring N. M. Newmark, W.J. Hall Editor, Prentice Hall 1977, pp. 91–101.
52
10.5 CLOUGH, R.W. and PENZIEN, J. Dynamics of Structures. Mc Graw–Hill Book Co., 1975.
10.6 WIEGEL, R.L. Editor. Earthquake Engineering. Prentice–Hall, Inc, 1970.
10.7 NEWMARK, N. and ROSENBLUETH, E. Fundamentals of Earthquake Engineering. Prentice–Hall, Inc, 1971.
10.8 ROSENBLUETH, E. Characteristics of Earthquakes. In Design of Earthquake Resistant Structures, edited by E. Rosenblueth, John Wiley & Sons, New York,1980.
10.9 FEMA. NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings. Building Seismic Safety Council, 1991 Edition.
10.10 NEWWARK N., “Torsion in Symmetrical Buildings”, 4th World Conference on Earthquake Engineering, Chile, (1969).
10.11 HSO W. K., & HSU T. I., “Torsional Spectrum for Earthquake Motions”, Earthquake Engineering and Structural Dynamics, Vol. 6, (1978).
10.12 EUROCODE Nº 8. Structures in Seismic Regions. Design. Part 1. May 1988 Edition.
10.13 French Association of Earthquake Engineering. Recommendations AFPS 90 for the Elaboration of Rules relative to the Structures and Installations Built in Regions Prone to Earthquakes, 1990.
12.1 UBC. Uniform Building Code, 1994.
12.2 R.D.Hanson (Editor). Passive Energy Dissipation. Earthquake Spectra, Vol. 9, No 3, August, 1993.
53
COVENIN 3621:2000 CATEGORY
FONDONORMA,
Av. Andrés Bello, Torre Fondo Común, Pisos 11 y 12
Telephone 575.41.11 Fax 574.13.12
Caracas
I.C.S. 91.120.25 published by
I.S.B.N. 980-06-2542-9 ALL RIGHTS RESERVED The total or partial reproduction through any mean is forbidden
Descriptors: Earthquake resistant design, industrial facility, oil facility, earthquake,
earthquake resistant civil engineering, seismic engineering.