ML20041E163
| ML20041E163 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 12/31/1981 |
| From: | BECHTEL GROUP, INC. |
| To: | |
| Shared Package | |
| ML20041E159 | List: |
| References | |
| NUDOCS 8203100207 | |
| Download: ML20041E163 (11) | |
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UNION ELECTRIC COMPANY CALLAWAY NUCLEAR 1
ULTIMATE HEAT SINK RETENTION POND 25 - YEAR AND PROBABLE MAXIMUM ICE FORCES
SUMMARY
REPORT BECHTEL JOB 10884
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HYDRAULICS / HYDROLOGY GEOTECHNICAL SERVICES - GAITHERSBURG DECEMBER 1981
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I 8203100207 820302
I. PURPOSE This analysis of 25 year and probable maximum ice forces was performed at the request of the U.S.N.R.C. The calculated forces will be applied to the pond structures to assess their effect on the structures.
Additionally, as part of this study the frequency of degree days was reanalyzed using daily average air temperatures and a longer period of record (62 years) than was reported in the F.S.A.R.
II.
SUMMARY
AND CONCLUSIONS The analysis of frequency of degree days using daily average air tem-peratures resulted in identical calculated ice thicknesses as compared to the analysis using monthly average air temperatures which was reported in the F.S.A.R. The calculated 25 year ice thrust force is 4.2 kips per linear foot for an ice thickness of 19.8 inches. The calculated probable maximum ice
. thrust force is 13.8 kips per linear foot for an ice thickness of 17.8 inches and 14.8 kips per linear foot for an ice thickness of 20.6 inches.
III. 25 YEAR ICE FORCES The 25 year ice force was calculated using the U.S. Army Corps Hydraulic Design Criteria Chart 704 (Ref.1, copy attached). This chart gives ice thrust force in kips per foot for varying ice thickness and rates of temperature rise. A rate of temperature rise of 5 F per hour was assumed which is greater than any temperature rise observed in the Columbia, M0.
3-hourly meteorological sunnaries when the temperature is well below freezing. These curves are based on the work of Rose (Ref. 2) which assumes an initial air tenperature of -40 F. The lowest air temperature recorded
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. at Columbia, M0. is -18"F. Ice thickness was calculated based on a frequency analysis of degree days covering 62 years in the period 1911-1981 and using daily average air temperatures. For the 25 year recurrence interval, the corresponding number of degree days is 700.
Assur's formula (Ref. 3) is used to calculate ice thickness:
h = as/T" h = ice thickness (inches) a = coefficient = 0.75 S = number of degree days The calculated ice thickness is 19.8 inches. The ice thruit force for a 19.8 inch thick ice cover and temperature rise of 5'F/ hour, considering solar energy and with no lateral restraint, is 4.2 kips per linear foot.
IV. PROBABLE MAXIMUM ICE FORCE The exact methodology for computing a probable maximum ice force is not available. Therefore, the analysis consisted of a review of existing literature on the subject, an examination of the historical meteorological data at a station near the site and an analysis combining conservative assumptions which are judged to be very unlikely to occur at the site
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at the same time.
Based on the review of the literature, the report by Michel (Ref. 4) gives conservative values of ice thrust force and is chosen for calculation of probable maximum ice forces. The assumptions used in Michel's analysis are:
- 1. Newly formed ice, uncracked, bare of snow.
- 2. Ice thickness of at least 30 cm (12 inches), remaining constant.
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. 3. The temperature at the bottom of the ice layer is initially at 32*F and the temperature at the top is equivalent to the initial air temperature.
- 4. Air temperature rise of 3"F/ hour.
Assumption 1 is judged to be extremely conservative because the entire ice cover (greater than 4 acres in area) is assumed to act like one continuous body. Diurnal fluctuations in temperature,' wind effects and snow drifts will all centribute to the creation of discontinuities in the ice sheet.
From an examination of historical meterological data at Columbia, M0., about 30 miles NW of the site, below freezing temperatures occur in any year. The absolute minimum temperature recorded was -18'F with two occurrences, one in 1977 and the other in 1936. Minimum daily temperatures of less than 0*F occur infrequently. Therefore, ice thickness of 12 inches or thicker are possible but will take at the least a week to ten days to reach a one foot thickness. '
The rate of temperature rise of 3*F per hour has been recorded. The maximum thrust is attained at this temperature rise because for larger temperature rises "there is not enough time for the ice to develope an important overall thrust before the maximum pressure is attained at the surface," (Ref. 4). See Figure 11 of Reference 4.
Based on the literature review, the primary factors that affect ice thrust are: initial air temperature, rates of temperature rise, solar energy and restraints conditions.
For ericulating the probable maximum ice thrust at Callaway, the following meteomlogical conditions are used:
. 1. Minimum air temperature with coincident tenperature rise.
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- 2. Maximum rate of temperature rise with coincident initial tenperature. '
- 3. Maximum ice thickness with coincident air tenperature and rate of rise.
For these conditions, full lateral restraint is conservatively assumed.
Inspection of air temperature records showed that the winter of 1976-1977 is the extreme year since it has the maximum number of degree days and it had a minimum air tenperature of -18*F.
In calculating the ice thicknesses for those conditions an a of 0.9 is assumed and used in the analysis. This value is very conservative, since it is based on the assumption that there is no snow accumulation on the ice layer.
Using the air temperature for this period and utilizing Figure 12 and Table II of Michel the probable maximum ice forces for the afore-mentioned conditions are calculated as follows:
A. Minimum Temperature: Janua ry 17, 1977, 3 a.m.
Based on the analysis of cumulative degree days, there are 526 degree days at this time. Using a = 0.9 the ice thickness will be 20.6 l inches.
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) From Table II of Michel (Ref. 4) for an ice thickness greater than 12 inches, a tenperature rise of 3*F per hour, an initial temperature of -18'F, and full lateral restraint, the maximum thrust exerted by the expanding ice sheet is 14.8 kips per linear foot. Solar energy
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'is not considered because of the hour of the day, 3 a.m. The corresponding pressure exerted by the ice sheet is 8.6 kips per 1
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. square foot. If no lateral restraint is assumed, from Figure 12 (Ref. 4) the thrust is 11.5 kips per linear foot, with a corresponding j -
pressure of 6.7 kips per square foot, t .
B. Maximum Temperature Rise: January 11,1977, 9 a.m.
Based on the analysis of cumulative degree days, there are 393 degree days at this time. Using a = 0.9 the ice thickness will be 17.8 inches.
Combining Table II and Figure 12 of Michel (Ref. 4) for an ice thick-ness greater than 12 inches, a temperature rise of 4.7'F per hour, an initial temperature of -10*F, full lateral restraint and accounting for solar energy, the maximum thrust exerted by the expanding ice sheet is 13.8 kips per linear foot. The corresponding pressure exerted by the 17.8 inch ice sheet is 9.3 kips per square foot. If no lateral restraint is assumed, from Figure 12 (Ref. 4) the thrust is 9.5 kips i
per linear foot with a corresponding pressure of 6.4 kips per square i
foot.
f C. Maximum Ice Thickness: February 8, 1977, 9 a.m.
b Based on the analysis of cumulative degree days, there are 857 degree T
days at this time. Using an a of 0.9 the ice thickness will be 26.3 inches.
a Combining Table II and Figure 12 of Michel (Ref. 4) for an ice thick-ness of greater than 12 inches, a temperature rise of 4'F per hour, k
-an initial temperature of 14'F, full lateral restraint and accounting i
- for solar energy, the maximum thrust exerted by the expanding ice v
h sheet is 7.9 kips per linear foot. The corresponding pressure exerted f .- .
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g by the 26 3 inch ice sheet is 3.6 kips per square foot. If no 1ateral restraint is assumed, from Figure 12 (Ref. 4), the thrust is 5.0 kips per linear foot with a corresponding pressure of 2.9
[ kips per square foot.
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D. Discussion and Conclusion on probable Maximum Ice Thickness Based on the above analysis a probable maximum ice force of 13.8 kips per linear foot with an ice thickness of 17.8 inches is selected.
This force is considered conservative for these reasons:
- 1. Michel's curves assume solar energy based on relatively clear skys at a high elevation. The Callaway pond is located below
, elevation 840 feet MSL.
- 2. Since the UHS pond is located within a depression it would be highly unlikely that the ice cover would be free of snow.
Average snowfall in this area is about 23 inches per year.
'. The presence of snow will insulate the ice layer, which inhibits L
the thickening of the ice and minimizes the response of the ice i
layer to temperature changes.
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- 3. The formation of ice covers having 20.6 inch and 17.8 inch thick-ness would take 56 and 50 days, respectively, based on the historical data. It would not be expected that the ice would l remain free of cracks and other discontinuities for this long a period. According to Michel, these cracks and discontinuities will severely limit the magnitude of ice thrust forces.
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, 4. The ice forces for these conditions will be about 4 to 6 kips per foot if Rose's method is used (Ref. 2). This method is widely used in design of hydraulic structures. Both methods
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are based on theoretical considerations.
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V. REFERENCES 1
- 1. U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, Miss. , " Hydraulic Design Criteria," Sheet 704 a'nd Chart 704 on Ice Thrust on Hydraulic Structures, March 1974.
- 2. Rose, E. , " Thrust Exerted by Expanding Ice Sheet," A.S.C.E. Volume 12,
- p. 871, 1947.
- 3. Chow, V.T. , Handbook of Applied Hydrology, McGraw Hill, Inc. ,1959.
- 4. Michel, B. , " Ice Pressure on Engineering Structures," Monograph III-Bib, Cold Regions Research and Engineering Laboratory, (CRREL).
Hanover, New Hampshire,1970.
VI. BIBLIOGRAPHY
- 1. U.S. Army Cold Regions Research and Engineering Laboratory, Draft of
" Engineering and Design, Prediction and Calculation of Incremental Ice Thickening," June 1981, prepared for Dept. of the Army.
- 2. Carstens, T. and Kjeldgaard, J. H., " Thermal Ice Forces," Part I of Working Group on Ice Forces on Structures, A State-of-the-Art Report, T. Carstens, ed., CRREL, Special Report 80-26, June 1980.
- 3. Druin, M. and Michel, B. , "Les poussees d'origine structures thermique exercses par les couverts de glace sur les structures hydrauliques,"
Report S-23, Laval University, 1971.
- 4. Brown, E. and Clark, G., " Ice Thrust in Connection with Hydro-electric Plant Design," Engineering Journal, p.19,1932.
- 5. Monfore, G. E. , and Taylor, F. W., "The Problem of an Expanding Ice Sheet," Proc. Western Snow Cong.,16th meeting,1948.
- 6. Monfore, G. E. , " Laboratory Investigation of Ice Pressure," U.S.B.R.,
Structural Research Laboratory Report SP-31,1951.
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, 7. Monfore, G. E., " Ice Pressure Against Dams. Experimental Investigation by the Bureau of Reclamation," Proc. A.S.C.E.,
f Vol. 78, Technical Separate No. 162, 1952.
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- 8. Monfore, G. E., " Ice Pressure Measurements," U.5,.B.R., Structural Research Laboratory, Report No. 162, 1952. .
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- 9. Instructions for Detemining Ice Loads on River Structures, (SN 76-66),
Moscow 1967. Translated by N.R.C. as TT-1663, Ottawa 1973.
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[ BYDRAULIC DESIGN CRITERIA
(. I SHEET 704 ICE THRUST ON HYDRAULIC STRUCTURES hi 1. The expansion of an ice sheet as the result of a rise in air tem-y perature can develop large thrusts against adjacent structures. The magni-f; tude of this thrust is dependent upon the thickness of the ice sheet, the
, rate of air te=perature rise, the a=ount of lateral restraint, and the ex-A tent of direct penetyatgion of solar enerEy. Ice pressures from 3350 to O
per lin fttle have been used for design purposes. EM 1110 -7.
- 30,}3)lb 2200 suggests a unit pressure of not more than 5000 lb per sq ft of een-tact area and indicates that ice thickness in the United States will not norcally exceed 2 ft.
- 2. Although the work of Rose (2) sticulated a nu=ber of studies on ice pressure, the graphs proposed by him are of value for design purposes.
These graphs are reproduced in HDC 704.
3 The ice thrust curves in HDC 704 are for ice thicknesses up to 4 ft and hourly air te=perature rises of 5,10, and 15 F. Separate curves
.( are presented to show the effects of lateral restraint and solar radiation.
The expected ice thicknesses, air te=perature rise, and possible snov blanket thickness are dependent upon geographical location and elevation
(- above sea level. In the region of chinook vinds rapid air te=perature
{ rises can occur. The U. S. Weather Bureau has recorded a 49 F rise in two minutes at Spearfish, S. Dak. When the ice sheet is confined by steep banks close to the structure, spillway piers, or other vertical restric-tions, the criteria for co=plete lateral restraint should be used. The direct effects of solar energy on the thrust are eliminated when the ice sheet is insulated by a blanket of snow only a few inches thick.
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ah 4. References.
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' (1) American Society of Civil Engineers, " Ice pressure against da=s: A sy=posium." Transactions, American Society of Civil Engineers, vol 119 (1954), pp 1-42.
(2) Rose, E., " Thrust exerted by expanding ice sheet." Transactions, American Society of Civil Engineers, vol 112 (1947), pp 671-900.
(3) U. S. Army, Office, Chief of Engineers, Engineering and Design, Gravity Dam Design. Di 1110-2-2200, 23 September 1956.
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