1、 AASHTO GUIDE SPECIFICATIONS THERMAL EFFECTS IN CONCRETE BRIDGE SUPERSTRUCTURES 1989 Abridged Version of NCHRP Report 276 Thermal Effects in Concrete Bridge Superstructures 6 hbiished by the American Association of State Highway and Transportation Officials 444 North Capitol Street, N.W., Suite 225
2、Washington, D.C. 20001 OCopyright, 1989, by the American Association of State Highway and Transportation Officials, Inc. All Rights Reserved. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without permission of the publisher. , a a a * * _- AA
3、SHTO TITLE GSCBS 89 0639804 0007YL2 098 AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFPICPALS President: Leno Menghini, Wyoming Vice President: James Pitz, Michigan Elected Regional Members: Region I Region II Region III Eugene McCormick, Illinois Region IV Garth Dull, Nevada Susan C. C
4、rampton, Vermont Kermit Justice, Delaware William S. Ritchie, JI., Nest Virginia Ray D. Pethtel, Virginia Wayne Muri, Missouri Charles L. Miller, Arizona Past Presidents: John R. Tabb, Mississippi Henry Gray, Arkansas William S. Ritchie, Jr., West Virginia John Clements, New Hampshire Richard A. War
5、d, Oklahoma Thomas D. Moreland, Georgia Darre11 V. Manning, Idaho Robert H. Hunter, Missouri Secretary of Transportation: James H. Burnley, IV Treasurer: Clyde Pyers, Maryland Chairpersons of the Standing Committees: Duane Berentson, Washington, Standing Cornmittee on Administration Frederick P. Sal
6、vucci, Massachusetts, Standing Committee on Planning Raymond Stotzer, Texas, Standing Committee on Highways Ronald R. Fiedler, Wisconsin, Standing Committee on Highway Traffic Safety Franklin E. White, New York, Standing Committee on Water Transportation Hal Rives, Georgia, Standing Committee on Avi
7、ation Ray D. Pethtel, Virginia, Standing Committee o11 Public Transportation Henry Gray, Arkansas, Standing Committee on Railway Conference Sam W. Waggoner, Mississippi, Special Select Coinrittee Conference of Commiss :oners and Boards Executive Director: Francis B. Francois, Washington, D.C. (Ex. O
8、fficio) AASHTO TITLE GSCBS 89 m Ob39804 0007453 TZ4 m HIGHWAY SUBCOMMITTEE ON BRIDGES AND STRUCTURES 1988 CLELLON LOVEALL, TENNESSEE, Chairman THEODORE H. KARASOPOULOS, MAINE, Vice Chairman STANLEY GORDON, Federal Highway Administration, Serreary ALABAMA, Charles H. Cook, C. H. McPherion ALASKA, Kar
9、l Melke ARIZONA, Ron Brechler ARKANSAS, Vera1 Pinkerton CALIFORNIA, James E. Roberts COLORADO, (vacant) CONNECTICUT, Clement Zawodniak, Daniel Coffey DELAWARE, Chao Hu D.C., James Spelman, Gary Burch FLORIDA, Henry T. Bollman GEORGIA, Charles Lewis HAWAII, Clarence R. Yamamoto IDAHO, Richard Jobes I
10、LLINOIS, James Rayburn INDIANA, Robert Woods IOWA, William Lundquist KANSAS, Kenneth F. Hurst KENTUCKY, Glen Kelly, Tom Layman LOUISIANA, Louis A. Garrido MAINE, James Chandler, Theodore H. Karasopoulos MARYLAND, Earle S. Freedman, James K. Gatley MASSACHUSETTS, Thomas Eddlem MICHIGAN, Ho Lum Wong M
11、INNESOTA, D. J. Flemming MISSISSIPPI, Bennie D. Verell MISSOURI, Al Laffoon MONTANA, Norman Rognlie NEBRASKA, James R. Holmes NEVADA, Rod Johnson NEW HAMPSHIRE, Andrew J. Lane NEW JERSEY, Jack Freidenrich, Robert Pege NEW MEXICO, Martin A. Gavurnick NEW YORK, Robert C. Keating NORTH CAROLINA, James
12、D. Lee, John L. Smith NORTH DAKOTA, Forest Durow OHIO, B. David Hanhilammi OKLAHOMA, Veldo M. Goins OREGON, Waiter J. Hart PENNSYLVANIA, Mahendra G. Pate1 PUERTO RICO, Jorge L. Acevedo RHODE ISLAND, Richard Kalunian SOUTH CAROLINA, Ben Meetze, Jr., SOUTH DAKOTA, K. C. Wilson TENSSEE, Ciellon Loveall
13、, Ed Wasserman TEXAS, Luis Ybanez U.S. DOT, Stanley Gordon (FHWA), Nick E. Mpras (USCG) UTAH, Dave Christensen VERMONT, Warren B. Tripp VIRGINIA, Fred G. Sutherland WASHINGTON, C. S. Gloyd WEST VIRGMIA, William D. Domico WISCONSIN, Stanley W. Woods WYOMING, Charles H. Wilson ALBERTA, R. W. Kornelson
14、 GUAM, Nonato C. Hailera MANITOBA, G. A. DePauw MARIANA ISLANDS, John C. Pangelinan NEW BRUNSWICK, G. A. Rushton NORTHWEST TERRITORIES, Raymond Ho NOVA SCOTIA, R. Shaffelburg ONTARIO, R. A. Dorton SASKATCHEWAN, L. J. Hamblin MASS. METRO. DIST. COMM., David Lenhardt N.J. TURNPIKE AUTHORITY, Paul M. W
15、eckesser PORT AU“. OF NY U t 9 19 Y SI 3 3 i 7 c 0.66 f t AASHTO TITLE GSCBS 89 m Ob39804 00074ZO Sb4 T, Table 3 Temperature differentials witbin a concrete superstructure for a positive temperature gradient (m Fig. 4 for zone map). P NOT TO SCALE (Note: For Superstructure depths Figure 3. greater t
16、han 2 feet) Positive vertical temperature gradient within superstructure concrete. Plain Concrete Surface Zone 54 46 41 38 14 12 11 9 2 in. Blacktop 4 in. Blacktop Zone 31 25 2?l 22 11 2 11 12 When determining the temperature variations within box girder bridges the values T2 and T3 shall be in- cre
17、ased by 5F. Maximum solar radiation zones are shown in Figure 4. 3.2 Negative Temperature Gradlents Temperature differentials within concrete super- structures that result from a rapid cooling of exposed concrete surfaces shall be assumed to vary at different depths, as shown in Figure 5. This gradi
18、ent is only appli- cable to superstructures with a depth greater than 2 ft. Temperatures shall be assumed to vary with the maxi- mum solar radiation zone and the thickness of black top surfacing on the bridge deck, as specified in Table 4. 4. COEFFICIENT OF THERMAL EXPANSION The coefficient of therm
19、al expansion used to deter- mine temperature effects shaii be based on the type of aggregate to be used, as specified in Table 5. 4. AASHTO TITLE GSCBS 89 0639804 0007423 OTO rn Figure 4. Maximum solar radiation zones for the United States. 0.6:ft -$ “r“ y NOT TO SCALE ( Note: For Superstructure dep
20、ths greater than 2 feet) d T4 /iiil Figure 5. Negative temperature gradient within superstructure concrete. L 5 AASHTO TITLE GSCBS 89 H Ob39804 O0074ZZ T3 W AGGREGATE TYPE Quamite Table 4 for a negative temperature gradient (see Fig. A4 for zone map). Temperature differentials within a concrete supe
21、rsmchm OF CONCRETE (0.CCKWl per T) 7.1 Plain Concrete Surface 2 2 2 2 Zone 14 10 8 6 27 23 21 1Y Granite Dolerite TZ (T) 5.3 5.3 Marble Limestone 4 in. Blacktop 2.4-4.1 4.9 Tabk 5 Cddtnt of thermai expansion based on aggregate type (thermai coc-nt of concrete brued on ne and coame aggregates). I THE
22、RMALCOEFFICIENT I Sandstone Gravel Basalt I 5.0 I Based on fine and com aggregates 5. ANALYSIS PROCEDURES An analysis of temperature effects shall be per- formed to determine the stresses and movements expected to result from temperature-induced strains within specified elements of the bridge supers
23、tructure. The effects of structure continuity shall be included when analyzing both the effects of fluctuations in the effective bridge temperature and the effects of tempera- ture differentials in the superstructure. - _ - AASHTO TITLE GSCBS 89 Ob39804 0007423 973 = c COMMENTARY ON DESIGN GUIDELINE
24、S FOR THERMAL EFFECTS IN CONCRETE BRIDGE SUPERSTRUCTURES C1. APPLICABILITY OF THE GUIDELINES All bridges are subjected to stresses andor move- ments resulting from temperature variation. Although time-dependent variations in the effective bridge tem- perature have caused problems in both reinforced
25、and prestressed concrete bridges, detrimental effects caused by temperature differentials within the superstructure have occurred, thus far, only in prestressed bridges. Except in extreme cases, concrete bridges will not suffer a sudden loss of strength as a result of tempera- ture changes. The prim
26、ary detrimental effect from temperature variation is the formation of unacceptable cracks in the concrete that reduce the serviceability of the bridge. Strength loss may eventually result if these cracks contribute to accelerated deterioration. Safety could be affected if the deterioration were to e
27、scape detection, as might be the case if prestress strands concealed from inspection were to corrode. Because the total elimination of cracks in concrete bridges is not possible, these guidelines are designed to limit temperature-induced cracking tc acceptable levels. Although these guidelines do no
28、t specifically address false-work loads and temperature differentials resulting from the heat of hydration in thick members, they.wil1 be useful in determining those effects. Heat of hydra- tion cooling can be an important cause of cracking, such as in the case of curing and/or cooling of the top de
29、ck slab which is cast on top of the previously constructed bottom slab and/or stems which provide restraint against movement. C2. EFFECTIVE BRIDGE TEMPERATURES Fluctuations in effective bridge temperatures result in expansion and contraction of the superstructure. These movements, in turn, induce st
30、resses in supporting elements such as columns or piers, and result in hori- zontal movement of the expansion joints. The magni- tude of these stresses and movements on a given bridge depends on the range of temperature variation and the temperature of the bridge at the time of construction. These gu
31、idelines establish the criteria for determining the minimum and maximum bridge temperatures that can reasonably be expected. For bridge designers to determine the amount of expansion and contraction that can be expected to occur on a given bridge to be built in a given location, they will need to as
32、sume an effective temperature at the time of construction. C2.1 Bridge Temperature Response Emerson established a method for estimating mini- mum and maximum effective bridge temperatures based on the geographical distribution of minimum and maximum shade temperatures throughout the United Kingdom (
33、19). The procedures established by Emerson were subsequently incorporated into British Standard BS 5400. Because the range of minimum and maximum temperatures for the United States is larger than that reported for the United Kingdom, it was necessary to extrapolate some of the curves relating effect
34、ive bridge temperatures to minimum and maximum shade temper- atures. Minimum temperatures for the United States range from -30F to 40”F, as compared to a minimum temperature range of -11F (-24C) to 23F (-5C) for the United Kingdom. The extrapolated portions of the minimum temperature range presented
35、 by Emerson are shown in Figure C-l. Maximum temperatures for the Uriited States range from approximately 55F to llO”F, as compared to a maximum temperature range of 75F (24C) to 100F (38C) for the United Kingdom. The extrapolated portions of the maximum tempera- ture range are also shown in Figure
36、C-l. The values given in Tables C-1 and C-2 are based on these curves. Note that adjustments in the effective bridge tem- perature are not required for bridge surfacing. C2.2 Minimum and Maximum Air Temperatures The isotherms used for the minimum and maximum air temperature are taken from charts pub
37、lished in the “Climatic Atlas of the United States” (98). The mini- mum air temperatures were obtained from the normal daily minimum temperatures for the month of January, while the maximum air temperatures were obtained from the normal daily maximum temperatures for the month of July. These isother
38、ms are based on average daily records for the 30-year period from 1931 through 1960. Although data are available that list the extreme daily minimum and maximum temperatures in the United States for a given period of time, there is no readily available published information that lists the duration i
39、n days that these extreme temperatures have 7 AASHTO TITLE GSCBS 87 Ob39804 0007424 80T W V” -40 -30 -20 -10 O IQ 20 30 40 50 60 70 80 90 100 110 120 Normal Daily Minimum or Maximum Temperature (Of:) Correlation between minimum or maximum temperature and minimum or maximum effective bridge temperatu
40、re. Figure C-1. occurred. Since bridges require 2 to 3 days to respond to a given minimum or maximum temperature, addi- tional data on the actual duration are required. In the “Climatography of the United States No. 84,” mini- mum and maximum extremes for each day are averaged for the years 1941 thr
41、ough 1WO (101). Maximum ex- treme temperatures occurring at 20 randomly selected stations were compared with the isotherms for the nor- mal daily maximums and found to agree within 6F. Minimum extreme temperatures were also compared with the isotherms for the normal daily minimums and found to agree
42、 within 6F. Initially, it was thought that the extremes on a day-to-day basis (averaged over the 30-year period from 1941 through 1970) would be sub- stantially different from those obtained from the of Suprastnicture- Composite “F - 12 -9 -7 -4 -1 2 4 9 14 17 22 26 31 36 40 Steel Only “F - 43 -36 -
43、30 - 24 - 17 - 10 -5 O 5 11 16 22 27 33 38 mum extremes for the United States. Local meteoro- logical data may be more applicable in mountainous areas, coastal areas, urban areas, and sheltered, low- lying areas where frost pockets may develop. It is rec- ommended that local meteorological data rath
44、er than isotherms be used for unusually large or complex bridges located in regions where extreme temperature conditions are known to occur. C3. DIFFERENTIAL TEMPERATURES Variations in temperature at different depths of the superstructure caused by solar radiation effects may re- sult in significant
45、 temperature-induced fiber stresses. These stresses are induced in two ways. The first way occurs when bending moments are generated in contin- uous spans as a result of the differences between the deformations in the top and bottom fibers. These defor- mations will cause a deflection in the superst
46、ructure; stresses result when this deflection is restrained by structure continuity. The second way in which stresses are induced is when nonlinear temperature variations through the depths of the section cause initially plane sections of the superstructure to become distorted. Be- cause shallow sup
47、erstructures have not been adversely affected in the past by temperature differentials, design thermal gradients were developed for superstructures with depths greater than 2 ft. Most typical structures have not experienced diffi- culties because of temperature differentials. Recently, however, conc
48、rete bridge designs have become more sophisticated. As a result, span lengths have increased and designers have kept superstructure weights at a minimum. This has resulted in a reduction of reserve Table C-2 temwrature and maximum effective bridge temperature. Correlation between normal daily maximu
49、m Maximum Effective Bridge Temperature r Normal Daily 1 T Maximum 55 60 65 70 75 80 85 90 95 100 105 110 66 69 73 77 80 84 88 92 95 98 101 105 : of Suprastructure strength for temperature-induced stresses, a reduction which has caused unacceptable cracking in some bridge superstructures. Much of this unacceptable cracking could have been avoided had the designer accurately considered the effects of differential temperatures. Bridges can be protected from excessive temperature- induced stresses in several w
