TL 548 l DA 03 93SDraft Translation 548

~/ October 1976

THERMAL STRESSES IN A CONCRETE DAMPOURED IN SECTIONS

D.P. Levenikh

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CORPS OF ENGINEERS, U.S. ARMY

COLD REGIONS RESEARCH AND ENGINEERING LABORATORYHANOVER, NEW HAMPSHIRE

ApijwoMed fa0 ptul.ic re1lease. distribu ion unhimotp

UnclassifledS RITY CLASUIPWCAVION Of THIS PAG 04 m DOef e

REPORT DOCUMENTATION PAGE BEFORECOMPLETI ORM

1. RE[PORIT NUMBERN |GOVT ACCESSION NO. 2. RE1[CIPIENT'S CATALOG NUMBER

Draft Translation 54876. TITLr (Tr asluion) . TYPE OF REPORT a PERIOD COVERED

THERMAL STRESSES IN A CONCRETE DAM POURED IN

SECTIONS 6. PERFORMING ORO. REPORT NUMBER

7. AUTHOR4'a 6. CONTRACT OR GRANT UMMleR()

D.P. Lenenikh

9. PERFORMING ORGANIZATION NAME AND ADDRESS 1O. PROGRAM ELEMENT. PROJECT, TASK

U.S. Army Cold Regions Research and L- AREAS& WORK UNIT NUMBERS

Engineering LaboratoryHanover, New Hampshire

I1. CONTROLLING OFFICE NAME AND ADDRESS I. REPORT DATE

October 1976 L-.1S. NUMBER OF PAGES

2014. MONITORING AGENCY NAME A AOORESS(If d*ifea il ba Cama ,.lnd Offie) IL SECURITY CLASS. (of tis. uIaM)

,04a o ASPICATIO"IDOWNGRADING

I. OISTRIOUTION STATEMENT (of Mt fepeou)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (o( Se abeliel mtered t 8 & S 0. It ¢nffa trim Reput)

Is. SUPPLEMENTARY NOTES

19. KEY WORO (Cawmwel. a reeaa dif mito fni 0m |#ldstlf ip by leak mbau)

REINFORCED CONCRETE CONCRETE PLACINGDAMS CONCRETE COOLINGSTRESS ANALYSIS HYDROELECTRIC POWER GENERATIONELECTRIC POWER PLATS USSR--RASNOYARSK

4$AMftACT (Coame.. av 0140a aitI 8000~r OW DI~*~ bV b100k 0006w)

The "mixed-section concrete pouring technique" is described as used in coldregions, and tables are given for selecting optimal thermal conditions forseparate operations.

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DRAFT TRANSLATION 548

ENGLISH TITLE: THERMAL TRESSEINAOCT AKYUDINJ TOS

FOREIGN TITLE: OSTOIANII POTINY PR" SMESHAZREZKE N A BOKI TONIROVANIIA -

AUTHOR: D-/Levenkh

SOURCE: Moscow Vsesoiuznyi proektno-izyskatel'skii i-nauchno-is edovatel' ski, Lpi-tituit-"Gidroproekt'P ftud

79~

CEREL BIBLIOGRAPHY s

ACCESSIONfI NO.: 26-2707

Translated by Office of the Assistant Chief of Staff for Intelligence forU.S. Army Cold Regions Research and Engineering Laboratory, 1976, 20p.

NOTICE

The contents of this publication have been translated as presented in theoriginal text. No attempt has been made to verify the accuracy of anystatement contained herein. This translation is published with a minimumof copy editing and graphics preparation in order to expedite the disseminationof information. Requests for additional copies of this document should beaddressed to the Defense Documentation Center, Cameron Station, Alexandria,Virginia 22314.

UDC 621.810:624.042.5

THERMAL STRESSES IN A CONCRETE DAM POURED IN SECTIONS

TRUDY LENGIDROPROYEKTA in Russian No 11, pp 4-24

[Article by D.P. Levenikh]

(Text] When the concrete is poured in sections, the downstream part of ahigh dam on a rock foundation has a columnar cross section with planneddimensions of the columns of 10-15 m; on the columns are placed longblocks, 0.7-2 m high each, with no lateral vertical joints (Fig. 1). Theheight of the columnar part of the section may vary within quite a widerange, depending on the shape of the base of the dam, the method used forthe concrete work and the construction periods.

It is recommended that the first long block be densely reinforced, makingit a so-called reinforced zone, the task of which is to prevent throughcracks from developing in the long blocks lying above; the cracks mayappear as a continuation of the joints between the columns, resulting fromthe cooling of the latter.

The sectional pouringwas done at the site at several sections of theKrasnoyarsk dam; Planning studies are now being made for the use of longblocks at the Sayanskaya, Ingurskaya, Ust'-Iliskaya and Zeyskaya dams.

During the construction period of a dam poured in sections, a complex stateof thermal stress occurs, and is to a certain extent retained in the periodof constant operation. The state of thermal stress of the dam during theconstruction process is determined by the cooling of the columns, fastenedwith some flexibility in the rock foundation; the cooling of the long blockslying on the columns; the cooling of the entire mass of the dam after thejoints between the columns are cemented. The process of erecting the danpoured in sections may be divided into five stages (Fig. 2).

At the first stage the columnar part of the section is built; each columnis cooled from the volume-average maximal temperature of exothermic heat-ing, T1 , to a certain temperature, T2, independently, and acquires thethermal tension inherent in it.

F! ... .. ..

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At the second stage, reinforced frames are placed on the columns and theblock of the reinforced zone is concreted; in this case, the toothing isleft above the expansion joints in the reinforced zone and the reinforce-ment in it is not joined; there is further cooling of the columns fromT2 to T4 , along with the cooling of the reinforced zone from T3 to T5 ;each column with the block of the reinforced zone placed on it operatesas an independent structure.

At the third stage the reinforcement over the joints is joined and thetoothing of the reinforced zone is concreted. The columns cool from T4to T6 , while the reinforced zone cools from T5 to T7; here the reinforcedzone begins to operate in conjunction with the columns as a single struc-ture, resembling a frame with thick supports and zero spans of the hori-zontal beam.

At the fourth stage the cement grouting of the expansion Joints between thecolumns is carried out, and then the columns cool from T6 to the long-termaverage temperature of the concrete masonry, T8 , while the reinforced zonecools from T7 to Tg; the reinforced zone and the columns operate at thisstage as a unified block, fixed in a resilient base.

At the fifth stage the placement of the long blocks continues, and theircooling from TlO to the long-term average temperature T8 [as published]causes further change in the thermal stressed state of the structure.

The fourth stage may take place in a somewhat different way from thatdescribed earlier. Since the cement grouting of the expansion seamsrequires, to avoid their opening later on, a temperature in the columnsquite close to the long-term average temperature of the concrete, the longblocks may be placed above the reinforced structure before the grouting ofthe expansion joints, and we will have a considerable height of the long-block part of the masonry cooling with the uncemented joints; the fifthstage with this system coincides with that described above.

An approximate method of calculating the thermal stress of the mixed sec-tion is presented in [1], but it does not make it possible to ascertainthe distribution of the stresses in the reinforced zone above the jointsand does not take into consideration the presence of the toothing in thereinforced zone, nor is the fifth stage of the sectioning discussed in it.

An experimental determination of the thermal stressed state of the mixedsection was made at the Hydraulic Engineering Laboratory of Lengidroproyektto supplement and elaborate on these studies. The experiments were madeusing the photoelasticity method on two-dimensional composite models,with equivalent loads in the cold state in a UP-8 laboratory press. Thetheoretical premises of studying the thermal stress of construction blocksfixed in an elastic base, and the methods of the laboratory study weredeveloped by the laboratory of the OIN [expansion unknown] VNIIG (All-Union Scientific Research Institute of Hydraulic Engineering imeni V. Ye.Vedeneyev] [3].

__L

We suggested a method of determining the temperature stresses on a seriesof models obtained consecutively from the same work piece. At all thestages the uniform cooling of the elements of the mixed section werestudied with respect to each other. We will discuss determination of thetemperature stresses with the simultaneous uniform cooling of the columnsand the reinforced zone in relation to the foundation.

D D

4

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p p

Figure 3. Diagram of Loading and Making the Model

Key:1. Piece for the model of the column section2. Model of the foundation3. Glueing

The work piece for the model of the columns and reinforced zone, which isa parallelepiped made of ED-6 epoxy resin, is compressed in a press withan arbitrary equivalent load of the order of 40-50 kg/cm2 (Fig. 3,a);after the compressive strain on the block under the load ceases, the modelof the base is glued on (Fig. 3, b); after the epoxy glue hardens, themodel is relieved of the load and the excess parts of the work piece ob-tained are removed, as the result of which we have model I (Fig. 4), corre-sponding in its stress to the fourth stage of the mixed section, i.e.,to uniform cooling of the structure with the cemented expansion Joints for

where Ed is the modulus of elasticity of the concrete;4 is the coefficient of linear expansion for the concrete.

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Figure 4. Diagram of a Consecutive Study of the Models of Mixed Section

Key:

1. Reinforced zone2. Columns3. Base4. Model 1, model 2, etc.

It should be noted that with an equivalent compression load we obtain astate of stress corresponding to the heating of the structure; alternationof the stresses determined in studying the model gives us a picture of thecooling. Model 1 turns into model 2, corresponding to the third stage,by making sections in the columnar part of the masonry along the lines ofthe expansion joints; when the sections are made the stresses in the modelchange and we obtain the thermal stress of the structure with the combinedwork of the reinforced zone and the columns and the uncemented expansionjoints. Model 2 turns into model 3 by continuing the sections right through

to the upper edge of the reinforced zone; model 3 corresponds to the secondstage, when the reinforcement above the joints is not welded and the tooth-ing of the reinforced zone is not concreted. Finally, model 3 turns intomodel 4 after the reinforced zone is removed, which corresponds to thefirst stage, when the standing columns cool individually.

Studies were made using an analogous scheme of the thermal stress of the

section with uniform cooling of the reinforced zone with respect to thecolumns. The experiments were made for two relations of the width of thecolumn along the foundation to a height of B/H-l, and V!1-2, and with theblock of the reinforced zone hoO.2B thick; in addition, experiments weremade with the height of the long-block part of the section h-0.6B, withB/H-l for the fourth and fifth stages.

4,

~6

L.I. Maslova and V.A. Golubtsov, seniir technicians, participated in theexperiments.* All the experiments were made for a mixed section with sixcolumns and for the ratio of the moduli of elasticity of the concrete andthe foundation ES/El.

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Figure 5. Stresses a , with uniform cooling of reinforced zone relative to

columns at 47" L for section with B - 1 and h-0.2B (+extension, - com-pression). A H

With a large number of columns it is possible, without a significant degreeof error, to consider the state of stress of the mixed section in the middlezone as analogous to that for the central columns in the model discussed here.Figure 5 shows the stress sheet d, with uniform cooling of the reinforcedzone relative to the columns at the third stage.

The magnitudes of the stresses are given in fractions$ -d4T. To determinethe stresses with a given change in the temperature in the reinforced zone4T, the values of the ordinates of stresses given in the diagram should bemultiplied by the formula EfL4T. Given in tables 1-9 in fractions ofEevq4T are the components of the stresses for all the stages of the mixedsection, obtained after studying the above-described models, at the charac-teristic points designated in Fig. 6. We will illustrate the use of theresults obtained from the example of the calculation of stresses a- at point 9of the reinforced zone when B/H-1 and with the temperature regime given inTable 10 for the stages, as well as with the given values E -2.9 105 kg/cm 2,04=10-5 1/degrees.

At stage 1 there is no reinforced zone. At stages 2, 3 and 4 the columnsand reinforced zone cool with respect to the foundation respectively at5.5 and 2*. In tables 2, 3 and 4 we find the corresponding magnitudes of

Similar experiments were made by the method of "freezing" by the laboratoryof OMIN VNIIG imeni B.Ye. Vedeneyev in 1963-1964 on the instructions ofLengidproproyekt for the dam of the Krasnoyarskaya GES.

stress o at point 9 in proportions of E~aaT, equal to 0.098; 0.335 and0.130. In addition, at stages 2, 3 and 4, the reinforced zone cools withrespect to the columns respectively at 4T-.r -ATt-v =15-5=u0*; ,T. -- 4T, 6-5+1* andAT1I - AT,., -4 - 2 - 2a. In tables 5, 6 and 7 we findthe corresponding values of c in proportions of F 6fAAT, equal to 0.178,0.640 and 0.715. Then the resulting stresses a at point 9 at the end ofstage 4 will be

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Figure 6. Diagram of the Arrangement of the Calculating Points toDetermine the Stress From the Tables

Key:1. Central joint2. Axis of column3. Joint

It must be mentioned that in reality the stresses in the structure will beless due to the phenomenon of creep of the concrete in time. By knowing thecalendar periods of the work, this phenomenon may be calculated by multiply-ing the component stresses for the stages by the corresponding coefficientsof relaxation of stress, the magnitude of which depends on the increase inthe concrete by the beginning of the stage and on the length of the stage[2]. For a more precise calculation, it is recommended that each of thestages of cooling be developed for several theoretical periods d t and thestress at each stage be given in the form of the sum of the products ofo'-7o'r Kpr, where 4 are the stresses arising with a change in the tempera-ture for the period of time At; Kpr is the coefficient of relaxation forthe period of time dt.

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Key:

1. Structural element 3. Columns2. Number of stage 4. Reinforced zone

Presently used in the construction of high dams in Siberia is pipe coolingof the concrete masonry, cooling the components of the concrete mix, acasing heated in winter, and other measures aimed at reducing the exo-thermic heating of the concrete, reducing the nonuniformity of cooling theconcrete in the blocks in time, the possibility of controlling the tempera-ture of the concrete masonry, and as a result, a guarantee of the mono-lithic nature and long life of the structures.

When designing concrete dams poured in sections of blocks, this work may beused to select the optimal temperatures, ensuring the monolithic nature ofthe elements of the section with given criteria for the crack-resistance ofthe concrete, as well as to select the reinforcement in the reinforced zone.

BIBLIOGRAPHY

1. Levenikh, D.P., and Ippa, Yu.A. "Calculating the Thermal Stress of theConcrete Masonry of the Dam of the Krasnoyarskaya GES," TRUDYLENGIDROPROYEKTA, collection 1, 1964.

2. Prokopovich, I. Ye. "Vliyaniye dlitel'nykh protsessov na napryazhennoyei deformirovannoye sostoyaniye sooruzheniy" [The Effect of ProlongedProcesses on the Stress and Deformation of Structures], Gosstroyizdat,UkSSR, 1963.

3. Rozanov, N.S. "Setting Up Model Studies of Temperature Stresses inCooling Blocks," IZVESTIYA VNIIG, Vol 73, 1963.

- _ ~.