Safety of Dams Flood and Earthquake Criteria (1985) / Chapter Skim
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Appendix B: Design Criteria in Use for Dams Relative to Earthquake Hazards
Appendix B: Design Criteria in Use for Dams Relative to Earthquake Hazards
Pages 175-210
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From page 175... ...
U.S. Nuclear Regulatory Commission PART 2 STATE AGENCIES RESPONSIBLE FOR DAM SAFETY Alaska .
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East Bay Municipal Utility District, California New York Power Authority Salt River Project, Arizona Santee Cooper (South Carolina Public Service Authority)
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From page 177... ...
The report outlines factors to be considered and procedures to be followed in investigations and design for earthquake hazards but does not specify design criteria to be followed. The report does indicate that the design seismic event is usually the maximum credible earthquake (MCE)
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From page 178... ...
The designation of hypothetical MCE events and their associated recurrence interval or probability of occurrence is viewed by the Bureau as a separate function from the assignment of seismic loadings for design of the structure even though often they will be one and the same. Maximum Credible Earthquakes are regarded as an actual geologic condition while (MDE)
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From page 179... ...
Surface faulting potential The potential for surface fault rupture is assessed at each site. Reservoir induced earthquake loading The current procedure for evaluation of reservoir induced seismicity in the Bureau is to consider the reservoir induced event equivalent to the local MCE event.
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From page 180... ...
Response Requirementsfor Seismic Loading Under loading from the Maximum Design Earthquake, the structures of a project vital to the retention or release of the reservoir are required to function (1) without permitting a sudden, uncontrolled release of the reservoir and (2)
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From page 181... ...
Seismic design standards used by the Forest Service have been summarized as follows: The Agency requires an evaluation of earth movement potential and the establishing of appropriate design criteria on a case-by-case basis. The determination of the need for detailed analyses, and subsequent design criteria, is based on factors such as the hazard presented, size of the dam and reservoir, potential ground motion at the site, site geology and the type of structure.
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From page 182... ...
182 DOCUMENTATION OF FOCI IIATlnN Appendix B FACTORS TO CONSIDER IN SELECTION OF DESIGN EARTHQUAKES · REGIONAL TECTONIC SETTING · SEISMIC HI STORY · SEISMOTECTONIC STRUCTURES · LOCAL OR SITE GEOLOGY · SEISMIC ATTENUATION · RESERVOIR INDUCED SEISMICITY _ 1 SE LECTION OF DESIG N EARTHQUAKES · MAXIMUM CREDIBLE EARTHQUAKES · MAXIMUM DESIGN EARTHQUAKE · OPERATING BASIS EARTHQUAKE DETERMINATION OF GROUND MOTION FOR THE DESIGN EARTHQUAKES · PEAK ACCELERATION VELOCITY, AND DISPLACEMENT · DURATION · ACCELERATION TIME-HISTORIES · RESPONSE SPECTRA ~ l REQUIREMENT FOR EARTHQUAKE ANALYSI S · SEISMICITY AND GROUND MOTIONS · FOUNDATION CONDITIONS · TYPE Of DAM · CONSTRUCTION METHODS · MATERIAL PROPERTIES · PAST EXPERIENCE /~ YES -- RUINED -- rMETHODS OF ANALYSES | CONCRETE DAMS · PSEUDOSTATIC METHOD · DYNAMIC ANALYSES METHODS RESPONSE SPECTRUM TIME- HI STORY EMBANKMENT DAMS · LIQUEFACTION EVALUATION · PSEUDOSTATIC METHOD · NEWMARK METHOD · FINITE ELEMENT METHOD EVALUATION OF STRUCTURAL ADEQUACY · EVALUATION OF ANALYSES RESULTS · PAST EXPERIENCE Of DAMS · CONSEQUENCES OF FAILURE FIGURE B-1 Flowchart depicting steps for earthquake analyses and design of dams. Source: ICODS draft of proposed guidelines.
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From page 183... ...
4. Operating Basis Earthquake The second level of design earthquake, the OBE, represents the maximum level of ground shaking that can be expected to occur at the site during the economic life of the project, usually 100 years for dams.
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From page 184... ...
6472.) The report should also summarize other possible earthquake hazards such as ground compaction, landslides,
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From page 185... ...
The General Manager of TVA has pointed out that only a few of the older TVA dams were analyzed for earthquake loadings when they were designed but state-of-the-art methods have been used in the design of newer dams and in analysis of the older dams. The information supplied indicates these methods include dynamic analyses, finite element modelling and evaluations of liquefaction potentials.
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From page 186... ...
The evaluation of dams considers two levels of design earthquakes: the maximum credible earthquake (MCE) and the operating basis earthquake (OBE)
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From page 187... ...
Earthen dams. Earthen dams are to be capable of retaining the reservoir under conditions induced by the maximum credible earthquake (MCE)
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From page 188... ...
The guidelines for Phase I investigations call for assessment of potential vulnerability to seismic events based on location of project within the various zones of seismic activity, type of dam, local geology, etc. The guidelines for Phase II investigations call for more elaborate analyses ranging from the conventional equivalent static force or pseudostatic method to "state-of-theart" investigations and analyses for important high hazard projects.
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From page 189... ...
The capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the guideline exposures of this part. The "Operating Basis Earthquake" is that earthquake which, considering the regional and local geology and seismology and specific characteristics of local subsurface material, could reasonably be expected to affect the plant site during the operating life of the plant; it is that earthquake which produces the vibratory ground motion for which those features of the nuclear power plant necessary for continued operation without undue risk to the health and safety of the public are designed to remain functional.
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From page 190... ...
PART 2 STATE AGENCIES RESPONSIBLE FOR DAM SAFETY Alaska (From letter dated May 16, 1984) State uses criteria consistent with Corps of Engineers Seismic Zone map for Alaska with requirements based, also, on size of the structure, impoundment volume, and hazard class.
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From page 191... ...
As a matter of policy we do not publish standards or criteria so the information provided herein has been compiled from several internal documents specifically to answer your letter. Maximum credible earthquakes have been used to assess the seismic stability of essentially all dams evaluated in the last 12 years.
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From page 192... ...
Another problem is the lack of definition of "Maximum Credible Earthquakes," as related to "small" dams, and if there should be any differentiation between small and large dams with reference to seismic design criteria. Georgia (From letter dated June 5, 1984)
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Louisiana (Letter dated May 23, 1984) No seismic design criteria furnished.
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Information supplied by the Chief Engineer, Dam and Reservoir Safety Program, shows the state is making changes to rules and regulations regarding dam safety. In both the existing regulations and the proposed modifications, factors of safety of 1.0 under earthquake loading are required for the following: · Slope stability of Earth and Rock Conventional Dams, steady seepage, full reservoir · Structural integrity of concrete conventional dams, full or maximum reservoir · Slope stability of industrial water retention, steady seepage, full reservoir.
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From page 195... ...
NOTE: The "Environmental Class" listings in the Missouri proposed regulations refer to developments in the area downstream from the dam that would be affected by inundation in the event of dam failure. The classes are defined as: Class I—contains 10 or more permanent dwellings or any public building.
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From page 196... ...
Proposed state dam safety regulations have been drafted, but this draft contains no requirements relating to earthquake hazards. New Mexico (From letter dated June 4, 1984)
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From page 197... ...
197 New York (From letter dated May 30, 1984) The following is quoted from letter of the Chief, Dam Safety Section: With regard to earthquake hazard, we require investigation for seismic events using an appropriate seismic coefficient depending on the seismic zone that the dam is located in.
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No earthquake design criteria furnished. South Carolina (From letter dated May 17, 1984)
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Washington (Letter dated June 6, 1984) No seismic design criteria furnished.
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From page 200... ...
The following is adapted from a list of procedures, criteria and standards relating to earthquake hazards furnished by the Department of Water and Power: 1. Analyze dams using maximum credible earthquakes for local and regional events.
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: The Authority is currently proceeding with a seismic reassessment of all its concrete and earth dams. In order to maintain a unified approach to the seismic stability analysis of NYPA earth embankments in the present changing regulatory climate, the following procedure has been adopted:
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From page 202... ...
This study was initiated to develop seismic design criteria (response spectrum) for the Maximum Credible Earthquake at Roosevelt Dam on the Salt River.
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From page 203... ...
, design earthquake is selected on the basis of comprehensive seismic and geologic studies. In these cases, the Maximum Credible Earthquake (MCE)
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From page 204... ...
Selection of Design Motion. Once the maximum credible earthquake, including its source and mechanism, is defined, the key parameters such as maximum free field acceleration, predominant period and duration are determined using currently accepted correlations.
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From page 205... ...
If the stresses are within the allowable limits, no further analysis may be performed since the response spectrum analysis yields conservative results. However, if the resulting stresses exceed the allowable stresses, then a time history response analysis is performed using finite-element modelling developed by the USER which analyzes linear deformation.
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From page 206... ...
Further, concrete structures are not normally preferred on sites where a known or potentially active fault is discovered in the foundation. Conclusions.
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From page 207... ...
Main organization has used the seismic design criteria of the U.S. Army Corps of Engineers in its work in other countries and has encouraged the use of those criteria in countries that had no or less conserva· .
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From page 208... ...
We design a project to withstand the DBE with minimal or no possibility of damage occurring and then check to ensure that catastrophic failure will not take place when/if a Maximum Credible Earthquake occurs. With regard to reservoir induced seismicity (RIS)
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From page 209... ...
Maximum Credible Earthquake (MCEJ The MCE is defined as the earthquake that would cause the most severe vibratory ground motion capable of being produced at the site under the currently known tectonic framework. It should be a rational and believable event which can be supported by all known geologic and seismologic data.
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From page 210... ...
Yankee Atomic Electric Company, Framingham, Massachusetts A company representative has made available a report, dated December 1982, titled "Supplemental Seismic Probability Study Yankee Atomic Electric Company, Rome, Massachusetts." The report documents extensive studies of the probability of earthquakes affecting the site of a nuclear power station, specifically to develop estimates of earthquake shock effects having annual probabilities of 10-3 and 1O-4. The report does not discuss design criteria for earthquake hazards as such, but shows the problems in attempting to analyze earthquake potentials in the eastern United States.
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