ASCE/SEI Standard 43, " Seismic Design Criteria for Structures, Systems, and Components in Nuclear Facilities, " is a consensus US national standard developed by the American Society of Civil Engineers. It provides design criteria for nuclear structures and should be used in conjunction with ASCE/SEI Standard 4. " Seismic Analysis of Safety-Related Nuclear Structures and Commentary ". The two standards are performance based and are written to ensure that structures, systems, and components designed and evaluated in accordance with their provisions meet target performance goals that vary as a function of the seismic design basis. ASCE/SEI 43 was published in 2005, and is currently being revised with the goal of issuing the updated Standard in 2018. This paper presents a summary of the significant changes in the new revision of ASCE 43 and describes the potential impact these changes may have on the design and analysis of nuclear structures. Significant revisions include the characterization of design response spectra, procedures for modeling and analysis, the inclusion of new framing systems, and the addition of a chapter on seismic isolation. The paper will also discuss the integration of ASCE/SEI Standards 4 and 43.
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Transactions, SMiRT-24
BEXCO, Busan, Korea - August 20-25, 2017
Division VI, Paper No. 173
SUMMARY OF CHANGES TO THE UPCOMING REVISION OF ASCE 43
AND IMPACTS ON THE DESIGN AND ANALYSIS OF NUCLEAR
STRUCTURES
F.G. Abatt
1
, Michael W. Salmon
2
, Andrew S. Whittaker
3
1
Senior Engineering Advisor, Becht Engineering; Vice-Chair, ASCE Dynamic Analysis of Nuclear
Structures Committee, USA
2
Lead Engineer, Office of Seismic Hazards and Risk Mitigation, Los Alamos National Laboratory; Chair,
ASCE Dynamic Analysis of Nuclear Structures Committee, USA
3
Professor, Department of Civil, Structural, and Environmental Engineering, University at Buffalo;
Director, MCEER; Chair, ASCE Nuclear Standards Committee, USA
ABSTRACT
ASCE/SEI Standard 43, "Seismic Design Criteria for Structures, Systems, and Components in
Nuclear Facilities," is a consensus US national standard developed by the American Society of Civil
Engineers. It provides design criteria for nuclear structures and should be used in conjunction with
ASCE/SEI Standard 4. "Seismic Analysis of Safety-Related Nuclear Structures and Commentary". The
two standards are performance based and are written to ensure that structures, systems, and components
designed and evaluated in accordance with their provisions meet target performance goals that vary as a
function of the seismic design basis.
ASCE/SEI 43 was published in 2005, and is currently being revised with the goal of issuing the
updated Standard in 2018. This paper presents a summary of the significant changes in the new revision
of ASCE 43 and describes the potential impact these changes may have on the design and analysis of
nuclear structures. Significant revisions include the characterization of design response spectra,
procedures for modeling and analysis, the inclusion of new framing systems, and the addition of a chapter
on seismic isolation. The paper will also discuss the integration of ASCE/SEI Standards 4 and 43.
OVERVIEW
ASCE/SEI 43 (hereafter referred to as ASCE 43) consists of a Foreword plus ten Chapters
arranged as follows:
Foreword
Chapter 1 – Introduction
Chapter 2 – Earthquake Ground Motion
Chapter 3 – Evaluation of Seismic Demand
Chapter 4 – Structural Capacity
Chapter 5 – Load Combinations and Acceptance Criteria for Structures
Chapter 6 – Ductile Detailing Requirements
Chapter 7 – Special Considerations
Chapter 8 – Seismic Qualification of Equipment and Distributions Systems
Chapter 9 – Quality Assurance Provisions
Chapter 10 – Seismically Isolated Structures
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All chapters have been updated. The revisions range from significant to more editorial and
clarifying. First, the changes to the chapters will be summarized and then potential impacts to the design
of nuclear structures will be discussed.
In general, there has been an attempt to more tightly integrate ASCE 43 and ASCE/SEI 4
(ASCE 2017; hereafter referred to as ASCE 4) by more clearly separating seismic design criteria from
seismic analysis topics and removing duplication between the two Standards. In some cases, provisions
have been removed, simplified, or provided by simply incorporating other Codes and Standards by
reference. An example is reference to ACI 349-13 (ACI 2013a) for strength requirements for concrete and
reinforcing steel in Chapter 6 in lieu of independently including such details in this Standard.
SUMMARY OF CHAPTER CHANGES
Chapter 1 introduces one of the more significant changes to the Standard with the inclusion of
Seismic Design Category 2 (SDC-2), which is in contrast to ASCE 43-05 (ASCE 2005), which only
includes SDC-3 through SDC-5. When ASCE 43-05 was written the expectation was that the majority of
nuclear facilities would be categorized as SDC-3 and SDC-4, and thus that the provisions of ASCE 43
(and ASCE 4) would apply to such facilities. This expectation was a natural consequence of the fact that
ANSI/ANS2.26 did not provide a numerical target performance goal for SDC-2 Structures, Systems, and
Components (SSCs) because it was not anticipated that major nuclear facilities would be categorized or
designed as SDC-2. It was thought that SDC-2 SSCs would be designed using ASCE 7 and criteria from
the International Building Code (IBC), and would not include facilities with significant nuclear inventory.
However, the ASCE 43 Working Group recognizes that there are now many facilities with significant
nuclear inventory that are categorized and designed as SDC-2 and thus this situation should be addressed
by ASCE 43.
The inclusion of SDC-2 was a straightforward decision by the Working Group, but there was
considerable discussion and debate as to whether the associated target performance goal should be set at 4
10
-4
Annual Frequency of Exceedance (AFE) or if it should be lowered to 2
10
-4
AFE. The argument
for reducing the AFE to 2
10
-4
is based on the recognition that the risk adjusted ground motion in
ASCE/SEI 7 (hereafter referred to as ASCE 7) expressed as MCE
R
corresponds to a 1% probability of
structural collapse in 50 years (i.e. 2
10
-4
annual probability of collapse). Thus, in nominal terms, it is
difficult to accept a model building code with a more stringent target performance goal (2
10
-4
annual
probability of collapse) than a nuclear standard (4
10
-4
hazard AFE). That said, such a comparison is
anything but direct because the procedures for formulating the performance goals in the two Standards are
fundamentally different, namely, performance is judged in ASCE 7 at the system level (building collapse
requires the failure of multiple building components) whereas performance is judged in ASCE 43 at the
component level. This subject is addressed in Houston et al. (2016) via a case study of a low-rise
reinforced concrete shear wall structure.
The argument to lower the target performance goal was ultimately rejected as being based too
much on the optics of (tenuous) comparisons between the performance goals of ASCE 43 and ASCE 7.
The Working Group also noted that if the target performance goal were set to the lower value of 2
10
-4
,
it would be so close to the SDC-3 target performance goal of 1
10
-4
that the difference would be nearly
indistinguishable in risk space. With this background, the target performance goals for the four SDCs to
be included in the next revision of ASCE 43 are shown in Table 1.
Table 1. Target Performance Goals as a Function of Seismic Design Category
Seismic Design Category (SDC)
2
3 4 5
Target Performance
Goal (P
F
) 4
10
-4
1
10
-4
4
10
-5
1
10
-5
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The revision of Chapter 2 on Earthquake Ground Motion introduces a different approach to
generating Design Response Spectra (DRS) from Uniform Hazard Response Spectra (UHRS). In both
cases, the DRS is determined from two UHRS at different hazard annual exceedance frequencies.
ASCE 43-05 defines DRS as the product of a Design Factor (DF) and the UHRS at a specified annual
exceedance frequency.
DRS = DF x UHRS
HD
(1)
In equation (1), UHRS
HD
is the Uniform Hazard Response Spectrum at the mean hazard at a
specified exceedance frequency. The hazard exceedance frequencies for SDC-3, -4, and -5 designs are
given in Table 2. At spectral frequencies for which the UHRS are defined, the DF is determined from the
slope factor (A
R
) and a parameter α as follows:
A
R
= (SA
0.1HD
/SA
HD
) (2)
In equation (2), SA
HD
is the spectral acceleration at the mean hazard annual exceedance frequency
H
D
and SA
0.1HD
is the spectral acceleration at 0.1H
D
. The DF is then defined according to
DF = max(DF
1
, DF
2
) (3)
DF
2
= 0.6(AR)
α
(4)
where DF
1
and α are defined in Table 2.
Table 2. Design Response Spectrum Parameters from ASCE 43-05
SDC Mean Hazard AFE
(H
D
)
Target
Performance Goal
(P
F
)
Probability Ratio
(R
P
)
1
DF
1
α
3 4 x 10
~1 x 10
4 0.8 0.4
4 4 x 10
~4 x 10
10 1.0 0.8
5 1 x 10
~1 x 10
10 1.0 0.8
1
The probability ratio (R
P
) is defined as H
D
/P
F
The working update to ASCE 43 uses a Scale Factor (SF), less than 1.0, rather than a design
factor. The new equation defining the DRS in terms of SF is given by
DRS = SF x UHRS
Hp
(5)
The SF reduces the UHRS
Hp
defined at the target performance goal AFE to get the DRS instead of
the previous method of using a DF, which increased the UHRS
HD
defined at ten times the target performance
goal annual frequency of exceedance to obtain the DRS. This change differs from the previous approach
using a DF in that inclusion of SDC-2 in the revised Standard led to an inconsistency in the probability
ratios (R
P
) used for SDC-2, -3, -4, and -5. Such an inconsistency existed to a lesser degree in ASCE 43-05
as evidenced in Table 2, but inclusion of SDC-2 exacerbated the situation and made it clear that using the
previous method would lead to a different format for the DF for SDC-2 than existed in ASCE 43-05. The
new SF method uses an R
P
of 10 for SDC-2 through SDC-5.
The change in methodology from DF to SF is made for three reasons.
1. The SF approach more clearly indicates the relationship between the DRS and the UHRS
HP
at the
target performance goal AFE. The SF is less than 1.0 and its value decreases with an increasing
slope on the seismic hazard curve. This relationship was not obvious with the DF approach.
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2. The SF is less sensitive to A
R
than is the D
F
, particularly over the most likely A
R
ranges from 2.0
to 4.0.
3. Some hazard curves at low seismic hazard sites have very low ground motions at mean annual
hazard AFEs at ten times the target performance goal (H
D
=10*P
F
) and at hazard-curve ratios
exceeding about 4.5. In such cases the hazard curves cannot be approximated as linear between
the H
D
=10*P
F
and H
PF
AFEs when plotted on a log-log plot. Because the ratio is based on a linear
approximation, this makes the estimate unreliable. To avoid such problems, a lower bound for the
SF is introduced. This constraint is more easily expressed in terms of SF than in terms of DF.
When the slope factor is cast in the form
A
R
= SA
HPF
/SA
HD
(6)
In equation (6), SA
HD
is the spectral acceleration at the mean AFE H
D
and SA
HPF
is the spectral
acceleration at the mean AFE H
P
corresponding to the target performance goal (P
F
). The SF for this
spectral frequency is given by:
SF = max(SF
1
, SF
2
, SF
3
) (7)
SF
1
= A
R-1.0
(8)
SF
2
= 0.6(A
R
)
-0.2
(9)
SF
3
= 0.45 (10)
The change in methodology makes essentially no difference in the computed DRS for SDC-4 and
SDC-5, and for typical seismic hazard curves makes less than a 5% difference in the DRS for SDC-3. It is
easily shown that when R
P
=10, the scale factor and the design factor are related according to Equation 10.
SF = DF/A
R
(11)
The revised DRS parameters are shown in Table 3.
Table 3. Revised Design Response Spectrum Parameters
SDC Mean Hazard AFE
(H
D
) Target Performance Goal (P
F
) Probability Ratio (R
P
)
1
2 4 x 10
~4 x 10
10
3 1 x 10
~1 x 10
10
4 4 x 10
~4 x 10
10
5 1 x 10
~1 x 10
10
The revision to Chapter 3 illustrates the tighter integration between ASCE 43 and ASCE 4 in that
several sections in 43-05 describing linear and nonlinear analytical methods have been moved from
Standard 43 and placed more properly in ASCE 4-16. Also moved to ASCE 4 is the table providing
effective stiffness values for reinforced concrete members. Chapter 3 provides the first inclusion of steel
concrete composite elements in that damping values for such elements are added to the table of damping
values for structural elements as a function of response level. Steel-plate concrete composite elements are
also introduced in Chapters 4, 5, and 6 as noted below and the technical basis for inclusion of these
structural elements is documented in Epackachi et al. (2015a, 2015b, and 2015c), Seo et al. (2016),
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Varma et al. (2011) and Varma et al. (2013). Requirements for steel-plate composite walls in safety-
related nuclear structures are provided in Appendix N9 of ANSI/AISC N690 (AISC 2015).
Chapter 4 now includes steel-plate concrete composite elements as an acceptable structural
component for new nuclear facilities. The seismic behavior of this newer framing system for nuclear
structures is comparable to reinforced concrete walls provided the reinforcement ratio is similar and the
faceplate slenderness ratio (for the SC walls only) comply with limits in Appendix N9 of
ANSI/AISC N690. The chapter provides better integration between ASCE 43 and other national codes
and standards by removing detail on structural capacities that had been in ASCE 43-05 and instead
referring directly to other codes and standards for such information. The design and detailing of
reinforced concrete is now by reference to ACI 349-13 with a few exceptions, including new provisions
for the out-of-plane shear strength of reinforced concrete walls and slabs. These new provisions update
the nominal shear stress of unreinforced concrete in ACI 318-14 (ACI 2014), namely,
2
f
c
, to account
for the effects of section depth, longitudinal reinforcement ratio, and non-exceedance probability on shear
strength required of safety-related nuclear structures. Mertz and Whittaker (2018) provide the technical
basis for this change, which will affect (and possible increase) the out-of-plane shear reinforcement of
reinforced concrete walls and slabs.
The capacity of structural steel components is by reference to ANSI/AISC N690 for carbon steel
components, ASCE/SEI 8 for stainless steel components, AISI S100 for cold-formed carbon steel
components, and ACI 530/ACI 530.1 (ACI 2013b) for reinforced masonry components. The reference to
Section 2108 of the IBC in the context of reinforced masonry has been removed from the Standard.
The design and detailing of carbon steel components is to be performed according to the provisions
of ANSI/AISC 341. The revised section on the capacity of structural steel places more emphasis on the
LRFD approach and no longer includes individual factors for converting between ASD and LRFD
capacities.
The revised Chapter 5 clarifies the delineation between the component level and system level
inelastic energy absorption factors (F
µ
factors). The provisions give additional guidance on obtaining the
component level F
µ
factors and describe the required adjustments to the component level F
µ
factors for
weak or soft stories, high frequency response (greater than the amplified portion of the DRS) and the
adjustment for ratcheting. The adjustments to the component level F
µ
factors result in the system level F
µ
factors.
Table 5-1 of the Standard now includes component level F
µ
factors for steel-plate composite
walls and buckling restrained braced frames. Consistent with the emphasis on LRFD, axial load limits in
Table 5-1 for special steel moment frames are now expressed in terms of the ultimate axial load rather
than the axial yield strength. Table 5-2 on allowable drift ratio limits for structural systems now includes
limits for steel-plate composite walls.
The commentary to Chapter 5 includes several new sections. The first is a section on developing
project-specific system level F
µ
factors for existing structures with non-compliant detailing.
ASCE/SEI 41-13 (ASCE 2014) is introduced in this context, though it is pointed out that the
ASCE/SEI 41 data are developed for different limit states than used in this Standard. The commentary
includes a new section that states that the F
µ
factors in this Standard are generally conservative even when
used in conjunction with Response Level 3 damping, with or without SSI effects.
Finally, the commentary provides two alternate methods of estimating the system F
µ
factor. The
first is based on an estimate of a permissible inelastic distortion. With this established, response analyses
are run using inputs scaled to a level at which the elastically computed demand is equal to the yield (or
ultimate) capacity. The input is further scaled until the distortion predicted by the nonlinear response
history analysis reaches a maximum permissible value. The F
µ
factor is equal to this additional scaling
factor. This method may be used to justify an F
µ
factor greater than unity for a specific anchorage
configuration although in most cases, anchorage F
µ
factors are not significantly greater than unity. In the
second method, the system ductility is estimated from the ratio of weighted total displacements to a
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weighted elastically computed displacement when the elastic demand is equal to capacity for the critical
story. Once the system ductility has been established, there are several approaches for determining the F
µ
factor, which are provided in the commentary to Chapter 5.
To reduce detail and redundancy regarding the requirements for steel and concrete structures,
Chapter 6 states simply that steel structures shall meet the minimum requirements of
ANSI/AISC N690-12, and that steel moment frames shall be detailed in accordance with
ANSI/AISC 341. FEMA 350 is no longer included as a reference for detailing of steel moment frames.
The commentary on steel structures notes that not only should ANSI/AISC 341 be followed for ductile
detailing requirements, but that prequalified special moment frame joints per ANSI/AISC 358
(AISC 2016) should be used.
Similarly, all reinforced concrete structures must meet the minimum requirements of ACI 349-13.
In keeping with Chapter 5, Chapter 6 now includes both buckling restrained braced frames and steel-plate
concrete composite shear walls, with steel-plate composite shear wall detailing to be in accordance with
Supplement 1 of ANSI/AISC N690. The provisions for steel structures now include guidance on the
design and analysis of collector items and a new provision that relaxes detailing requirements for Nearly
Rigid Platforms and Supports provided that increased loads are considered in the design.
ASCE 43-05 included a provision that weak-axis bending in reinforced concrete walls must be
governed by out-of-plane wall flexure. The new revision includes an alternate approach that allows out-
of-plane wall shear to limit the strength with respect to weak-axis bending provided that the out-of-plane
shear demand is increased by 50% and the F
µ
factors for flexure and shear are set to unity. There is also a
new provision governing the detailing of combined shear wall and frame systems in reinforced concrete.
The provisions for transverse joint reinforcement in slab-wall moment frame systems have been modified
to remove inconsistencies and to reflect the significant difference between beam-column joints (treated in
ACI 349-13) and slab-wall joints that are common in some Department of Energy facilities. Strut-and-tie
procedures must be used to design slab-wall moment-resisting connections. Three new subsections have
been added to the section on reinforced concrete. The first provides requirements for members not
proportioned to resist forces induced by earthquake shaking; the second treats collector elements; and the
third gives guidance regarding planes of weakness in the seismic load path.
The Chapter 6 provisions take a more liberal stance on use of adhesive anchors in elevated
temperature and/or radiation environments. In ASCE 43-05, this practice was prohibited; now the
Standard states that adhesive anchors "…shall be qualified in those environments", with the new
commentary on anchorage stating that adhesive anchors that passed tests per ACI 355.4 (ACI 2011) are
acceptable for application to nuclear structures.
The procedures for determining sliding and rocking demands for unanchored bodies that were in
Chapter 7 of ASCE 43-05 have been moved to ASCE 4-16 because they are analytical procedures that
properly belong in ASCE 4. Recognizing that sliding and overturning are not credible failure modes for
deeply embedded structures (as defined in the Standard) demonstration of sliding and overturning
stability is no longer required for such structures. This change was made to preclude complex checks
where no plausible failure mode exists. A related change is that the reduced soil support on the side of a
building foundation shall be considered when calculating the side traction for the purposes of sliding
checks in embedded structures that are not deeply embedded.
Section 7.5 of the Standard has been condensed to state simply that unreinforced masonry is not
an acceptable structural system, but when used as a barrier, shielding, or partition, unreinforced masonry
walls shall be designed in accordance with ACI 530.
There are several significant changes to Chapter 8. Qualification by analysis of active electrical
equipment is now prohibited, bringing the Standard into alignment with the provisions of Chapter 13 of
ASCE 7. More generally, acceptance criteria for qualifying active components by analysis use ratios of
demand to capacity and not limiting values of stress as in ASCE 43-05. The chapter also points out that
when determining demand on a component for qualification by analysis or by testing, if the input to the
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component is displacement based, then it can be unconservative to set the F
µ
factor equal to 1.0 and an
appropriate value of F
µ
shall be justified.
Section 8.3 on Qualification by Testing and Experience Data and the associated commentary have
been revised significantly to emphasize the differences between qualifications by test versus qualification
by test experience data and to also update and clarify the factors to be applied to seismic demand for
qualification by test, test experience data, and earthquake experience data required to meet the
performance goals of the Standard. The restrictions on the use of factors to be applied to seismic demand
are also documented. New sections have been added to the commentary that provide derivations for the
factors to be applied to the seismic demand for qualification by testing, test experience data and
earthquake experience data in specific situations.
Section 8.3.2.1 of ASCE 43-05 included the following equation for the demand for qualification
by test and test experience data:
D = D
NS
+ 1.4D
S
(12)
where D is the total demand, D
NS
is the non-seismic demand, and D
S
is the elastically computed seismic
demand. In ASCE 43-05, the factor of 1.4 is described as the equipment capacity factor for qualification
by test or test experience spectra that provides the margin to obtain the required confidence level of
performance. Sections 8.3.2.1, 8.3.2.2, 8.3.2.3, and the associated commentary sections of the Standard
have been revised to clarify the use and interpretation of the equations governing demand for qualification
by test, test experience data, and earthquake experience data, respectively. The revised equation for
demand for qualification by test is
D = D
NS
+ γ
test
D
S
(13)
The factor γ
test
is the ratio of the Test Response Spectrum (TRS) to the Required Response
Spectrum (RRS) for qualification by testing. If the qualification testing is performed in accordance with
IEEE 344, setting the factor γ
test
to 1.33 will meet the performance goals of this Standard. If testing
performed to other procedures and criteria, the value of γ
test
must be determined by the user so as to meet
the performance goals of ASCE 43.
Demand for qualification by test experience data is also given by equation (12), but with γ
test
replaced by γ
TES
, where γ
TES
is the factor to be applied to the Test Experience Spectrum (TES) required to
meet the performance goals of this Standard. For non-relay Generic Equipment Ruggedness Spectra
(GERS), setting γ
TES
to 1.33 will meet the performance goals of this Standard. For relay GERS, setting
γ
TES
to 1.75 will meet the performance goals of this Standard. For any component using seismic input
other than GERS, γ
TES
must be shown by the user to meet the performance goals of ASCE 43.
The demand for qualification by earthquake experience data is given by the following equation:
D = γ
EED
D
S
(14)
The factor γ
EED
is the factor to be applied to earthquake experience data to meet the performance
goals of ASCE 43. The seismic demand from earthquake experience data is defined as an Earthquake
Experience Spectrum (EES). If the seismic demand D
s
is defined by a Seismic Qualification Utility Group
(SQUG) reference spectrum (1.5 times the SQUG bounding spectrum), which is an example of an EES,
setting γ
EED
to 1.0 will meet the performance goals of ASCE 43. If the earthquake experience data are
based on other than a SQUG reference spectrum, the factor γ
EED
must be determined by the user so as to
meet the performance goals of ASCE 43. Information on the SQUG reference spectrum is documented in
SQUG (2001) and in SSRAP (1991).
Table C8-1 of ASCE 43-05 provides a list of standards used for construction and procurement of
mechanical and electrical equipment. This table has been removed because unless or until the design
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approaches and performance goals of the referenced standards can be vetted sufficiently to determine
consistency with ASCE 43, it is inappropriate to keep them in the Standard. Also, ASCE 43 addresses
only seismic design criteria, where the other codes are more general.
Aside from organizational and editorial revisions, the most significant change to Chapter 9 on
quality assurance is the inclusion of detailed provisions on the software quality assurance (SQA).
The Standard specifies requirements for all software used in the analysis and design of SSCs in
nuclear facilities, whether acquired or developed. Such software shall be controlled, verified and validated
(V&V) prior to the use on a project in accordance with the documented QA program, which shall include
a software V&V plan. The plan shall identify significant features of the program that need to be verified,
the type of test or benchmark problems, test cases with acceptance criteria and sample problems for
installation validation. Acquired computer programs not developed under an approved QA program shall
be, as a part of the acquisition process, subject to a dedication activity to provide reasonable assurance
that the computer program will perform its intended safety function for SDC-3 to SDC-5. However, such
dedication activity (commonly referred to as commercial grade dedication) will not be necessary where
the results of such acquired computer programs are verified with the design analysis for each application.
All calculations including computer generated ones shall be documented in sufficient detail for a reviewer
to determine that the design requirements have been correctly identified and implemented. A graded
approach shall be considered for the level of detail and rigor in the documentation.
Chapter 10 is an entirely new chapter on seismically isolated structures, with emphasis on design
and on testing of seismic isolation bearings. The text is taken by-and-large from Chapter 12 of
ASCE 4-16, with the intent that the design and testing provisions and commentary that will appear in
ASCE 43-xx, will be removed from the next revision of ASCE 4. Kumar et al. (2017) show that the
analysis and design provisions of ASCE 4-16 and ASCE 43-xx will achieve the target performance goal
for SDC-5.
ACKNOWLEDGMENTS
The authors gratefully acknowledge the members of the ASCE 43 Working Group for their
contributions to the Standard and to the material presented in this paper.
NOMENCLATURE
AFE Annual Frequency of Exceedance
A
R
Slope factor, which is a ratio of spectral accelerations corresponding to a tenfold increase
in hazard annual exceedance frequency
D Total demand in the context of equipment qualification
DF Design Factor from ASCE 43-05
DF
1
Contributing term to the design factor
DF
2
Contributing term to the design factor
D
NS
Non-seismic demand in the context of equipment qualification
DRS Design Response Spectra
D
S
Seismic demand in the context of equipment qualification
γ
test
Factor on the seismic demand for qualification by test that is required to meet the target
performance goals of this Standard
γ
TES
Factor on the seismic demand for qualification by test experience spectra that is required
to meet the target performance goals of this Standard
γ
EED
Factor on the seismic demand for qualification by earthquake experience data that is
required to meet the target performance goals of this Standard
H
D
Mean hazard AFE at ten times the target performance goal
H
PF
Mean hazard AFE at the target performance goal
MCE
R
Risk-targeted Maximum Considered Earthquake from ASCE 7
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P
F
Target performance goal
R
P
Probability ratio, which is defined as H
D
/P
F
RRS Required Response Spectra
SA Spectral Acceleration
SA
HD
Spectral acceleration from the mean hazard curve at ten times the performance goal AFE
SA
HPF
Spectral acceleration from the mean hazard curve at the performance goal AFE
SDC Seismic Design Category
SF Scale Factor for determining the
SF
1
Contributing term to the scale factor
SF
2
Contributing term to the scale factor
SF
3
Contributing term to the scale factor
TRS Test Response Spectra
UHRS
HD
Uniform Hazard Response Spectra corresponding to an AFE at ten times the target
performance goal
REFERENCES
American Concrete Institute (ACI). (2011). "Qualification of post-installed adhesive anchors in concrete
and commentary." ACI 355.4-11, Farmington Hills, Michigan
American Concrete Institute (ACI). (2013a). "Code requirements for nuclear safety-related concrete
structures and commentary." ACI 349-13, Farmington Hills, Michigan.
American Concrete Institute (ACI). (2013b). "Building code requirements and specification for masonry
structures and companion commentaries." ACI 530/530.1-13, Farmington Hills, Michigan.
American Concrete Institute (ACI). (2014). "Building code requirements for structural concrete." ACI 318-
14. Farmington Hills, Michigan.
American Institute of Steel Construction (AISC). (2010). "Seismic provisions for structural steel
buildings". ANSI/AISC 341-10, Chicago, Illinois.
American Institute of Steel Construction (AISC). (2015). "Specification for Safety-Related Steel Structures
for Nuclear Facilities, Including Supplement No. 1." ANSI/AISC N690, Chicago, Illinois.
American Institute of Steel Construction (AISC). (2016). "Prequalified Connections for Special and
Intermediate Steel Moment Frames for Seismic Applications." ANSI/AISC 358-16, Chicago, Illinois.
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formed steel structural members." AISI S100-2007, Washington, DC.
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and Components in Nuclear Facilities." ASCE/SEI-43-05, Reston, Virginia.
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panels," Journal of Constructional Steel Research, Vol. 105, pp. 49-59,
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24
th
Conference on Structural Mechanics in Reactor Technology
BEXCO, Busan, Korea - August 20-25, 2017
Division VI
Epackachi, S., A. S. Whittaker, A. H. Varma, and E. Kurt. (2015c), "Finite element modeling of
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... All production isolators are tested for mean demands calculated for design basis shaking. Standard ASCE 43-05 is being revised at the time of this writing (Abatt et al., 2017) for re-issue in late 2018 or early 2019. Those provisions and commentary in Chapter 12 of ASCE/SEI 4-16 that do not address analysis of seismically isolated nuclear facilities, including, substructure and superstructure design, isolator-to-structure connections, and prototype and production isolator testing, are being moved to Chapter 9 of ASCE/SEI 4. The provisions and commentary moved to Chapter 9 of ASCE/SEI 43 will then be removed from Chapter 12 of the next version of ASCE/SEI 4. ...
Seismic isolation of nuclear power plants is in its infancy, with only a small number of applications worldwide. This outcome is due in part to the construction of only a small number of new build nuclear power plants since base-isolation technology became mainstream in the 1990s, perceived concerns regarding the long-term mechanical properties of isolation bearings, and a lack of guidance, codes and standards related to isolation of safety-related nuclear facilities. This paper charts the history of seismic isolation, identifies the research that led to the first implementation of isolation for buildings and bridges in the modern era, summarizes the first applications of the technology to nuclear facilities, and describes important research and developments, including the writing of nuclear standards, in the past 20 years. Future research and development needs are identified.
... Standard ASCE 43-05 is being revised at the time of this writing ( Abatt et al. 2017). Those provisions and commentary in Chapter 12 of ASCE/SEI 4-16 that do not address analysis of seismically isolated nuclear facilities, including, substructure and superstructure design, isolator-to-structure connections, and prototype and production isolator testing, will be moved to Chapter 10 of ASCE/SEI 43-xx, which is targeted for publication in 2018. ...
Seismic isolation of nuclear facilities is in its infancy, with only a small number of applications worldwide. This outcome is due in part to the construction of only a small number of new build nuclear power plants since the technology became mainstream in the 1990s, perceived concerns regarding the long-term mechanical properties of isolation bearings, and a lack of guidance, codes and standards related to isolation of safety-related nuclear facilities. This paper charts the history of seismic isolation, identifies the research that led to the first implementation of isolation for buildings and bridges in the modern era, summarizes the first applications of the technology to nuclear facilities, and describes important research and developments, and the writing of regulatory standards, in the past 20 years. A detailed bibliography is provided at the end of the paper, listing nearly all publications on the subject of seismic isolation published at past SMiRT meetings, other articles cited in this paper, and articles on seismic isolation thought to be seminal by the authors.
In the United States, seismic probabilistic risk assessment is performed on nuclear power plant (NPP) designs to calculate mean annual frequencies of unacceptable performance, including core damage and large early release (of radiation). Seismic (base) isolation is a viable strategy to protect NPPs from extreme earthquake shaking but it has not yet been employed in the United States, in part due to a lack of clear regulatory guidance. Guidance and standards for seismic isolation of NPPs are now becoming available, but they do not explicitly address risk calculations.
One graded approach for the design of nuclear facilities would design high hazard facilities to meet the provisions of ASCE 43 while low hazard facilities would be designed as conventional structures based on the seismic loading and design criteria in ASCE 7. In structures with an intermediate hazard it is not immediately obvious which standard provides a more conservative design. This paper presents a case study that compares the performance of an intermediate hazard structure with ASCE 7 seismic loading and criteria to the target performance goals described in ASCE 43 and DOE-STD-1020. The purposes of seismic design associated with ASCE 7 are; 1) to provide minimum design criteria for structures appropriate to their primary function and use considering the need to protect the health, safety, and welfare of the general public by minimizing the earthquake-related risk to life, and 2) to improve the capability of essential facilities and structures containing substantial quantities of hazardous materials to function during and after design earthquakes. Designs developed using the provisions of ASCE 7 are targeted to a collapse prevention limit state probability of 1% in 50 years. The goal of the earthquake provisions in ASCE 43 is to ensure that high hazard nuclear facilities can withstand the effects of earthquakes with desired performance, expressed as probabilistic Target Performance Goals and various limit, or damage, states. These Target Performance Goals range from 1×10⁻⁴ to 1×10⁻⁵ with limit states ranging from essentially linear response to short of collapse. There are requirements invoked by ASCE 7 that are different than the requirements of ASCE 43 which prevents a direct computation of performance based on comparing the seismic demand levels required by each standard. These differences include the use of building R values in ASCE 7 compared to component specific Fu values in ASCE 43, the use of different analyses methods, ASCE 7 upper bound limits on seismic forces for some components, the limitations on framing system types, among others. The effect of these differences on the performance achieved between the two standards is evaluated for the design of a reinforced concrete shear wall structure that is representative of the types of structures used in nuclear facilities. Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
A finite element model is developed in LS-DYNA to simulate the nonlinear cyclic response of flexure-critical steel-plate concrete (SC) composite shear walls. The developed finite element model is validated using data from tests of four large-scale SC wall piers with an aspect ratio (height-to-length) of 1.0. Each SC wall was constructed with steel faceplates, infill concrete, steel studs and tie rods, and a steel baseplate that was post-tensioned to a reinforced concrete foundation. Steel studs tied the face-plates to the infill concrete and the infill concrete to the baseplate. Damage to the SC walls included cracking and crushing of the infill concrete and yielding, outward buckling and tearing of the steel face-plates. The finite element predictions include global force–displacement responses, equivalent viscous damping ratio, damage to the steel faceplates and infill concrete, strain and stress distributions in the steel faceplates, and estimates of the contribution of the steel faceplates and infill concrete to the lateral resistance of the walls. The DYNA-predicted responses are in good agreement with the measured responses. The impacts of interface friction between the steel faceplates and the infill concrete, and of the distribution of shear studs on the baseplate, to the global response of the SC walls are investigated using the validated DYNA model.
The in-plane shear behavior of steel-plate composite (SC) walls is different from that of reinforced concrete (RC) walls with orthogonal grids of longitudinal and transverse rebar. In SC walls, the steel plates contribute not only their longitudinal and transverse strength, but also there in-plane shear stiffness and strength to the behavior of the composite section. The in-plane shear loading produces principal tension and compression forces in the composite SC section. The principal tension causes the concrete to crack, and after cracking the concrete sandwich behaves like an orthotropic plate with negligible stiffness in the principal tension direction but significant stiffness and compressive strength in the principal compression direction. This paper presents a simple mechanistic representation of this complex in-plane shear behavior of SC composite walls, and a design equation for calculating their in-plane shear stiffness and strength. These equations are compared and evaluated using existing experimental results. Additionally, these equations are further confirmed by conducting a large-scale in-plane shear test using a unique test setup and approach. The experimental results included the measured cyclic shear force-strain response of the SC panel, the shear strains, and the principal strains measured in the steel plates. The experimental results are shown to verify the behavior theory.
Steel-concrete (SC) composite walls being considered and used as an alternative to conventional reinforced concrete (RC) walls in safety-related nuclear facilities due to their construction economy and structural efficiency. However, there is a lack of standardized codes for SC structures, and design guidelines and approaches are still being developed. This paper presents the development and verification of: (a) mechanics based model, and (b) detailed nonlinear finite element model for predicting the behavior and failure of SC wall panels subjected to combinations of in-plane forces. The models are verified using existing test results, and the verified models are used to explore the behavior of SC walls subjected to combinations of in-plane forces and moments. The results from these investigations are used to develop an interaction surface in principle force (Sp1–Sp2) space that can be used to design or check the adequacy of SC wall panels. The interaction surface is easy to develop since it consists of straight line segments connecting anchor points defined by the SC wall section strengths in axial tension, in-plane shear, and compression. Both models and the interaction surface (for design) developed in this paper are recommended for future work. However, in order to use these approaches, the SC wall section should be detailed with adequate shear connector and tie bar strength and spacing to prevent non-ductile failure modes.
An experimental study investigated the behavior of large-scale steel-plate composite (SC) walls subjected to cyclic lateral loading. The testing program involved four rectangular SC wall specimens with an aspect ratio (height-to-length) of 1.0. The specimens were anchored to a concrete basemat with a pre-tensioned bolted connection that was designed to be stronger than the walls. The design parameters considered in the investigation were wall thickness, reinforcement ratio, stud spacing, and tie bar spacing. The pre-test analyses, global force-displacement responses, contributions of the steel faceplates and infill concrete to the lateral resistance, load transfer between the faceplates and infill concrete, and damage to the face plates and infill are documented. The four SC walls failed in a flexural mode characterized by tensile cracking of the concrete, tensile yielding of the steel plates, crushing of concrete at the toes of the wall, outward local buckling of the steel faceplates, and fracture of the steel faceplates. The walls achieved the peak shearing strengths estimated using simplified procedures and ABAQUS. Pinching of the force-displacement response was observed at displacements greater than those associated with peak load. The distance between the baseplate and the first row of connectors affected the post-peak shear strength behavior and the fracture of the faceplates. The connection of the SC wall to the foundation block had a significant influence on the initial stiffness of the walls.
Qualification of post-installed adhesive anchors in concrete and commentary ACI 355.4-11, Farmington Hills, Michigan American Concrete Institute (ACI). (2013a) Code requirements for nuclear safety-related concrete structures and commentary
- American Concrete Institute
American Concrete Institute (ACI). (2011). " Qualification of post-installed adhesive anchors in concrete and commentary. " ACI 355.4-11, Farmington Hills, Michigan American Concrete Institute (ACI). (2013a). " Code requirements for nuclear safety-related concrete structures and commentary. " ACI 349-13, Farmington Hills, Michigan.
ACI) (2013b) Building code requirements and specification for masonry structures and companion commentaries
- American Concrete Institute
American Concrete Institute (ACI). (2013b). " Building code requirements and specification for masonry structures and companion commentaries. " ACI 530/530.1-13, Farmington Hills, Michigan.
Source: https://www.researchgate.net/publication/317171663_Summary_of_changes_to_the_upcoming_revision_of_ASCE_43_and_impacts_on_the_design_and_analysis_of_nuclear_structures
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