ETL 1110-2-542 Thermal Studies of Mass Concrete Structures

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This document provide extreme useful techniques for thermal stress analysis when mass concrete construction is involved

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Structural Analysis of Dam;

Design consideration of

DEPARTMENT OF THE ARMY U.S. Army Corps of Engineers Washington, DC 20314-1000

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ETL 111

Technical Letter No. 1110-2-542

30 May

Engineering and Design THERMAL STUDIES OF MASS CONCRETE STRUCTURES

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CECW-EG


ETL 1110-2


30 M


1. Purpose This engineer technical letter (ETL) provides guidance for performing thermal studies of mass concret cretee str struc uctu ture ress (MC (MCS) S) as requ requir ired ed by Engi Engine neer er Manual (EM) 1110-2-2000.

2. Applicability This This ETL ETL app appli lies es to HQUS HQUSAC ACE E ele eleme ment ntss and and USAC USACE E comma command ndss havin having g respo responsi nsibil biliti ities es for for the the design of civil works projects.

Master your semester with Scribd References are listed in Annex 4. & The New York Times 3. References

Special offer for students: Only $4.99/month. 4. Discussion

FE temperature and stress/strain analysis, and finally NISA.

b. Types of mass concrete structures. type typess of of MCS MCS are are comm common only ly used used in civi civill w projects: (1 (1) gravity structures such as dam lock walls; (2) thick shell structures such as dams; and (3) thick reinforced structures such U-frame locks, large pumping stations, powerhouses, large foundations, and massive bridg pier piers. s. MCS MCS cons constr truc ucte ted d usi using ng the the roll roller er-c -com om conc concre rete te (RCC) (RCC) con constr struc uctio tion n metho method d are are tre tre this ETL identically to structures constructe traditional construction methods.

c. ETL content . Thermal studies for of incre have been categorized into three levels Read Free Foron 30this Days Sign up to vote title e o complexity to provide a convenient fram Useful Not useful   ence. This ETL specifically Cancel anytime. provides informati and guidance for thermal studies of MCS and p vides methodology for the first two levels of th

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CECW-EG


ETL 1110-2


30 M


1. Purpose This engineer technical letter (ETL) provides guidance for performing thermal studies of mass concret cretee str struc uctu ture ress (MC (MCS) S) as requ requir ired ed by Engi Engine neer er Manual (EM) 1110-2-2000.

2. Applicability This This ETL ETL app appli lies es to HQUS HQUSAC ACE E ele eleme ment ntss and and USAC USACE E comma command ndss havin having g respo responsi nsibil biliti ities es for for the the design of civil works projects.

Master your semester with Scribd References are listed in Annex 4. & The New York Times 3. References

Special offer for students: Only $4.99/month. 4. Discussion

FE temperature and stress/strain analysis, and finally NISA.

b. Types of mass concrete structures. type typess of of MCS MCS are are comm common only ly used used in civi civill w projects: (1 (1) gravity structures such as dam lock walls; (2) thick shell structures such as dams; and (3) thick reinforced structures such U-frame locks, large pumping stations, powerhouses, large foundations, and massive bridg pier piers. s. MCS MCS cons constr truc ucte ted d usi using ng the the roll roller er-c -com om conc concre rete te (RCC) (RCC) con constr struc uctio tion n metho method d are are tre tre this ETL identically to structures constructe traditional construction methods.

c. ETL content . Thermal studies for of incre have been categorized into three levels Read Free Foron 30this Days Sign up to vote title e o complexity to provide a convenient fram Useful Not useful   ence. This ETL specifically Cancel anytime. provides informati and guidance for thermal studies of MCS and p vides methodology for the first two levels of th

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ETL 1110-2-542 30 May 97

(4) (4) Anne Annex x 3 prov provid ides es a proc proced edur uree for for more more inte intens nsiv ivee Lev Level el 2 the therm rmal al anal analys ysis is,, inc inclu ludi ding ng an exam example ple using using simple simple FE, FE, one one-d -dime imens nsion ional al (1-D (1-D)) strip strip model modelss and and an exam example ple using using more more comp complex lex two-dimensional (2 (2-D), FE FE me methodology.

5. Guidance a. Descriptions Description s and applicati ons of thermal analysis methods. methods. Thermal analysis is categorized into into thre threee leve levels ls of comp comple lexi xity ty.. Thes Thesee leve levels ls are are identif identified ied to to provide provide a conve convenie nient nt frame frame of of refer referenc encee for th the an analyti lyticcal pr processes ses av availab lable to the desi design gner er.. The The lev level el of ther therma mall ana analy lysi siss sel selec ecte ted d shou should ld be be app appro ropr pria iate te for for the the siz size, e, typ type, e, fun funct ctio ion n and and ris risk, k, and and sta stage ge of desi design gn of the the str struc uctu ture re,, as as well as the potentia potentiall for for cost savings savings resultin resulting g from from the analysi analysis. s. Appendix Appendix A provi provides des a sugge suggested sted process cess for for sel selec ectin ting g and and condu conduct cting ing therm thermal al ana analys lysis is appro appropr priat iatee for for MCS. MCS. Small Small,, low-he low-head ad MCS may requir requiree no more more than a very very simpl simplifie ified d therma thermall analanalysis. ysis. A larg larger er str struc uctur ture, e, suc such h as a conc concre rete te gra gravit vity y dam, dam, may may nee need d only only a sim simpl plifi ified ed ther therma mall stud study y at at the feas feasib ibili ility ty lev level el of des design ign,, but but a more more thor thoroug ough h study study during during prec precons onstruc truction tion engine engineeri ering ng and and desig design n (PED (PED)) pha phase. se. Certa Certain in MCS such such as compl complex ex lock lock wall walls, s, high high gra gravity vity dams dams,, and and arc arch dam dams, s, may may requ require ire a NIS NISA A dur during ing PED. PED. Cost Cost sav saving ingss may may be real realiz ized ed thro throug ugh h an an ade adequ quat atee the therm rmal al stud study y whe when n unneces unnecessar sary y joints joints can be elimi eliminat nated ed or or constr constructi uction on control controls, s, such such as as conc concret retee placing placing tempera temperature tures, s, can Special offer for students: Only $4.99/month. be relaxed. relaxed. Each higher higher level of of analysis analysis may may provide vide more more det detail ailed ed inf infor orma matio tion n but, but, gen gener eral ally ly,, at a

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spac spacin ing g and and lift lift heig height hts. s. It is appl applic icab able le to and and low low-h -hea ead d stru struct ctur ures es and and tho those se stru struct ctur ures es therm thermal al crac crackin king g pose posess littl littlee risk risk of loss loss of of f These These struc structur tures es may may incl include ude diver diversio sion n str struc uc for ir irrigation ca canals, lo low-head fl flood pr protect structures, low-head MCS that impound water infrequent basis for short durations, and thick r forced structures such as foundations and mass bridge piers. piers. Annex 2 of Appendix A illustrat this level of analysis.

(2) (2) Leve Levell 2 anal analys ysis is.. Leve Levell 2 the therma rmal a is chara characte cteriz rized ed by a more more rigoro rigorous us deter determina mina concrete te temperature ure his histo torry in in th the str stru ucture a use use of of a wide wide rang rangee of of tem tempe pera ratu ture re anal analys ysis is This This lev level el of of ana analy lysi siss shou should ld be be app appli lied ed to to th eval evalua uati tion onss of of mor moree cri criti tica call str struc uctu ture ress whe where re conseq consequen uences ces of thermal thermal crackin cracking g may may pose pose a nifican nificantt risk risk to peopl peoplee or or prope property, rty, may presen presen bility bility conc concer erns ns or or loss loss of of func functio tion, n, or or may may re signif signific icant ant cost cost savin savings. gs. This This level level of analy analy recomm recommend ended ed to to bette betterr identif identify y therm thermal al crac crac pote potenti ntial al and and min minimi imize ze specif specific ic req requi uire reme ment nt sary sary for for ther therma mall cra crack ck contr control ol that that can can add sig cant cant cos costt to cons constru truct ction ion.. Leve Levell 2 ana analys lysis is m appropri appropriate ate for for the the feasibi feasibility lity study study phase phase of si cant cant struc structu ture ress and and may may be used used to dete determ rmine ine high higheer-le r-leve vell ana analy lysi siss is is nec neceessa ssary duri during ng PED Level Level 2 the therma rmall ana analys lysis is is also also appr appropr opriat iatee f able PED PED for for sign signif ific ican anttFor MCS MCS. . Days It is appl applic icab le to Read Free 30this Sign up to vote on title ruc medium medium to to high-h high-head ead flood flood prote protectio ction n struc st Useful  Not useful  and other other signi significa ficant nt MCS. These These struc structure ture Cancel anytime. include include complex complex lock lock walls, walls, medium medium to high g dams, dams, tunne tunnell plug plugss invo involvi lving ng post postco cooli oling ng and and

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ETL 111030 M

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other structure loading. The method is applicable to critical, high-risk projects, complex or unprecedented structures with little or no previous experience, and structures subject to stress interaction from several simultaneous loading conditions. This level of analysis may also be appropriate for normal thermal studies of more ordinary MSC to optimize thermal controls and potentially reduce construction costs. Candidates for NISA include high gravity dams, arch dams, large and complex lock walls.

materials and mixtures have been identified However, the most basic studies may be perf during a feasibility study for a major project o complex structure where thermal cracking is may control subsequent design changes and complex analysis. Testing requirements shoul coordinated to ensure test data are ready at th appropriate time of the study. Appendix A c more detailed information related to thermal sis and stages of project development.

b. Cracking analysis methods. Analysis of c. Testing. The material properties for cracking for Levels 1 and 2 MCS thermal analysis thermal studies should be based on test resul is performed based on the computed concrete temproposed concrete mixtures for the project, if a perature distributions, using simplified procedures priate to the level of study, the phase of projec to relate thermal changes in volume of the MCS to study, and requirements of the particular proje estimate cracking potential. The procedures involve concrete properties testing is not appropriate approximations and require assumptions regarding specific project, data will be obtained from var conditions of restraint. Cracking analysis methodpublished sources and from consultation wi ology for Levels 1 and 2 thermal analysis is crete specialists at various Field Operating A described in Appendix A. For NISA, the cracking ties (FOA) and CEWES, and with outside tec analysis is integral with the incremental FE thermal specialists. stress-strain analysis as described in ETL 1110-2You're Reading a Preview 365. d . Responsible parties. The materials or structural engineer primarily responsible for th Unlock full access with a free trial. thermal study must ensure that adequate input 6. Action obtained from materials, structural, geotechnic Download Withand Free Trial construction engineers. Coordination is a. Thermal analysis needs. As required in required for selection of environmental condi  EM 1110-2-2000, concrete thermal studies are to concrete properties, foundation properties, and Read Free For 30this Days Sign up to vote on title  be performed for any important concrete structure struction parameters. Review of the thermal st Useful  Not useful  where thermal cracking potential exists. The design should be conducted at levels commensurate w Cancel anytime. Special offer forteam students: Only $4.99/month. must evaluate the necessity of a thermal study the scope of the thermal study to ensure tha and select the appropriate level of analysis in accorplan of action being pursued is appropriate.


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ETL 1110-2-542 30 May 97

f . Documentation. Results of the thermal study should be documented in an appropriate design report. FOR THE COMMANDER:

1 Appendix App A - Techniques for Performing Concrete Thermal Studies

Steven L. Stockton, P.E. Chief, Engineering Division Directorate of Civil Works

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APPENDIX A: TECHNIQUES FOR PERFORMING CONCRETE THERMAL STUDIES

LEVEL 1 AND LEVEL 2

behavior properties of plain or reinforced co members, construction conditions, and should vide a basis for comparing thermal generated s in the structure with strain capacity of the conc An analysis may also need to account for the n A-1. Introduction linear behavior of the concrete members, the in a. Content. This appendix presents general action of the structure, foundation, and backf techniques for performing a thermal analysis for the effects of sequential construction, therma mass concrete structures (MCS), with more detailed ents, and other loadings on the structure. Ver procedures and examples provided in the annexes. accurate prediction of temperature distribution The appendix discusses the general process for resulting strain and stress, and the prediction thermal studies, thermal analysis concepts, available cracking in mass concrete is often difficult, analytical methods for temperature calculation, data impossible, due to the complexity of conditio collection, temperature analysis, cracking analysis, the many uncertainties in materials, propertie documentation of thermal analysis, limitations of construction conditions. However, the inform thermal analysis, and references. Annex 1 presents tools, and methods for thermal analysis desc current practice for determination of concrete tensile this document provide a basis for thermal an strain capacity for use in cracking analysis. Annex that is sufficiently accurate for sound engine 2 provides a stepwise procedure for simple, Level 1 purposes. You're Reading a Preview thermal analysis, including an example. Annex 3 provides a procedure for more intensive Unlock Level 2 cracking. While cracking is i full access with a(2) free Thermal trial. thermal analysis, including an example using simple ent and of little consequence in some concret finite element (FE), one-dimensional (1-D) strip Download Withtures, Freeother Trialstructures may require a relativel models and an example using more complex twouncracked monolithic condition to function a dimensional (2-D), FE methodology. designed. Subsequent cracking, in the latter Read Free Foron 30this Days Sign such up toavote title may render structure unstable under  des b. Purpose. MCS are constructed using the conditions or may allow unnecessary or dam useful  Useful  Not Cancel anytime. principles and methods defined for mass concrete seepage of water. Cracking in some MCS may Special offer for students: Only $4.99/month. by American Concrete Institute (ACI) Commitincrease deterioration rates, the results of wh


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ETL 1110-2-542 30 May 97

requirements. A thermal study provides a guide for formulating advantageous design features, optimizing concrete mixture pro portions, and implementing necessary construction requirements. !

To provide cost savings by revising the structural configuration, material requirements, or construction sequence. Construction requirements for concrete placement temperature, mixture proportions, placement rates, insulation requirements, and schedule constraints that are based on arbitrarily selected parameters can create costly operations. Cost savings may be achieved through items such as eliminating unnecessary joints, allowing increased placing tem peratures, increased lift heights, and reduced insulation requirements.

!

Precooling of concrete materials and co trols on concrete placement tempera

!

Postcooling of concrete.

!

Construction of joints (with waterstop where necessary) to control location cracks.

!

Construction of water barrier membran prevent water from entering cracks.

!

Alteration of structure geometry to avo control cracking.

!

Use and careful removal of insulation.

c. Project design process. A thermal an should be performed as early in the design p as possible, but it is preferable that the actual ! To develop structures with improved performance of a thermal analysis not take p performance where existing similar strucuntil test data are available which will typically tures have exhibited unsatisfactory behavior occur during the preconstruction engineering You're Reading a Preview (such as extensive cracking) during condesign (PED) phase. EM 1110-2-2201 prov struction or operation. Cracking which project design process considerations for Ar Unlock full access with a free trial. requires remedial repairs would be considDams. ered unsatisfactory behavior. Cracking which does not affect the overallDownload structural With Free (1)Trial Project feasibility. Early in the feas behavior or some function of the structure phase of project design, the need to perform a  on would not be classified as unsatisfactory mal analysis should be 30 evaluated, based Read Free For Days Sign up to vote on this title behavior. objectives stated above. Any potential  constru Useful  Not useful  savings, historical related to structur Cancel problems anytime. Special offer for students: Only $4.99/month. ! To more accurately predict behavior of behavior, or special unprecedented structural unprecedented structures for which limited tures should be identified. Proposed solutio


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(2) PED. The initial investigations needed to verify the potential cost savings, functional improvements, or predicted behavior should be performed in the early stages of the PED. The thermal analysis should include project specific material properties based on test data if appropriate. Initial analyses should be used to investigate 1-D portions of the structure. These analyses should be used to evaluate the need for more advanced thermal analysis, as well as the potential changes needed in design, material properties, or construction parameters.

A-2. General Process, Analysis, and Coordination for Thermal Studies

a. Process. The thermal study process at level consists of several steps which are summ rized in Table A-1. These steps are similar for levels of analysis. The steps can be subdivi amongst three general tasks: data collection perature analysis, and cracking analysis. The cific efforts within each of these tasks can v considerably, depending upon the level of a selected for the thermal study. Data collecti includes those steps that provide input data and d . Thermal analysis concepts. Mass Concrete preparation of input for subsequent analysis is defined by ACI as “any volume of concrete with Data collection may include information retr dimensions large enough to require that measures and testing. Temperature analysis generates be taken to cope with generation of heat from temperatures or temperature histories for the hydration of the cement and attendant volume which are possible scenarios of thermal loadi change to minimize cracking.” When portland during construction and subsequent cooling cement combines with water, the ensuing exotherCracking evaluation uses temperature data f mic (heat-releasing) chemical reaction causes a temperature analysis, other sources of loadin temperature rise in the concrete mass. The actual material properties, concrete/ foundation int temperature rise in an MCS depends upon the heattion, geometry, construction parameters, etc. You're Reading a Preview generating characteristics of the mass concrete compute strains and evaluate the potential for mixture, its thermal properties, environmental coning in the MCS. This process is directly appli Unlock full access with a free trial. ditions, geometry of the MCS, and construction for evaluating mass gradient and surface gra conditions. Usually the peak temperature is reached cracking for thermal studies (Levels 1 and 2 Download Free Trial FE thermal studies such as NISA in a few days to weeks after placement, followed by Withfor advanced a slow reduction in temperature. Over a period of (Level 3). At all levels of thermal analysis, therma several months to several years, the mass eventumetric studies are an important part of Read Free For 30this Days Sign up to vote on title  ma ally cools to some stable temperature, or a stable ysis and are used to assist the engineer in Useful  Not useful  temperature cycle for thinner structures. A change proper decisions foranytime. design and construction Cancel Special offer forinstudents: Only $4.99/month. volume occurs in the MCS proportional to the b. Thermal analysis levels. temperature change and the coefficient of thermal


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ETL 1110-2-542 30 May 97 Table A-1 Thermal Study Process Data Collection

Temperature Analysis

Cracking Analysis

Levels 1-3

Levels 1-3

Levels 1 and 2

!

Determine Ambient Conditions

Climatological Conditions Foundation Temperature Water Temperatures Solar Radiation

!

!

Prepare Temperature Model

Compute Surface Heat Transfer Coefficients and Other Boundary Conditions Establish Calculation Increments Prepare FE Model (mesh) or Prepare Step-By-Step Method (spreadsheet)

Determine Material Properties

Determine Construction Parameters

Geometry/Lift Height Lift Placement Rate Concrete Placement Temperature Concrete Postcooling Construction Start Date(s) Formwork and Insulation Usage

Determine Restraint

Compute Kf and Kr for: Mass Gradient Analysis Surface Gradien Analysis

!

Concrete Foundation

!

!

Determine Thermal Strains

Strain = (C th)()T )( Kr ) for: Mass Gradient Analysis Surface Gradie Analysis !

Compute Temperature Histories

Mass Gradient Analysis: Determine Peak and Ultimate Stable Temperatures Surface Gradient Analysis: Determine Temperature History at Surfaces Determine Depth of Tensile Zone for K R

!

Estimate Cracking

Mass Gradient Cracking: Use Gradient Strain & Slow Load Surface Gradient Cracking: Surface Gradient Strains & Modified TSC Level 3 - NISA


FE Method: ABAQUS w/ ANACA !

Conclusions & Recommendation

Download Withmaterial Free Trial analysis are necessary. Temperature calculations processing and handling measures. are limited to simple determinations of peak contemperature history of the concrete mass is a crete temperature based on summation of placement mated by using step-by-step iterationusing Read Free Foron 30this Days Sign up to vote title  temperature and temperature rise produced by heat Schmidt or Carlson methods or by FE analys Useful  Not useful  from the concrete mixture. Cooling from the peak using simple 1-D Cancelmodels, anytime. termed “strip” mod Special offer fortemperature students: Only $4.99/month. is assumed to progress to the ambient using 2-D models representing cross section average annual temperature or a cyclic temperature structure. Evaluation of thermal cracking with


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cracking prediction results. Significant effort is necessary to collect environmental data, assess and implement applicable construction parameters, acquire foundation materials properties, determine appropriate construction scenarios, and perform testing required for thermal and nonlinear material properties input. Preparation of FE models and conducting temperature and thermal stress analyses which generate significant volumes of data are generally extensive and costly efforts.

should predict an appropriate set of constru conditions (e.g., time between lifts, lift heig of formwork, formwork removal, constructi date, insulation requirements, etc.) which wil approximate actual field conditions and whi be adequately modeled. Concrete properties s be provided for the proposed concrete mixture the materials engineer. The structural and geo nical engineer should develop appropriate fou tion material properties. The engineer should the monthly average ambient air temperatures other climatological information. The engin must ensure that the specified parameters are erly modeled for the numerical analysis. The e neer performing the thermal analysis may be t materials engineer or the structural engineer, depending on the structure and expertise avai in the design organization.

c. Parametric studies. A parametric study is a rationally planned set of analyses used to gain a better understanding of thermal performance through the identification and understanding of the effects that critical parameters have on the structure. The effects of a parameter on the structure can be determined by varying that parameter in a set of analyses while holding the other parameters constant. Likely candidates for a parametric study are, A-3. Data Collection but are not limited to, determination of the critical material properties, critical lift sequence or configuration, construction start time, insulation requirea. General. Data collection for the therm You're Reading a Preview ments, and placement temperatures. Results from analysis includes acquiring information on a single analyses within the parametric study should weather conditions, concrete properties, fou Unlock full access with a free trial. be interpreted separately to gain an understanding properties, and construction parameters. The f of the thermal response in each analysis. Then lowing are descriptions of these data requirem Download WithData Freeneeds Trialand acquisition costs should alw comparisons of results from each analysis in the parametric study can be made and the influence of measured against the level of thermal analysi  each parameter identified. Once identified and requirements of theFor analysis. Read Free 30this Days Sign up to vote on title  documented, results and conclusions from parametUseful  Not useful  ric studies can be used in subsequent thermal analyb. Ambient environmental conditions Cancel anytime. Special offer forsis students: Only $4.99/month. phases. For example, assume a goal of a current ronmental parameters, including air tempera thermal study is to reduce construction costs wind impounded water, and solar radiation


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stations. NOAA data are available on average daily, monthly, and annual temperatures, maximum and minimum daily and monthly average temperatures, humidity, precipitation, and wind velocity. Ambient temperature data will also be used in the computation of concrete placement temperatures. Depending on the project site location, site weather conditions may depart significantly from even local weather stations, necessitating some judgement in weather data usage, and/or some project collection of site-specific data. Adjustments of data from the nearest recording stations to the site can be used to estimate site temperatures. For every 76 m (250 ft) of elevation increase, there is about a 0.5-deg C (1 deg F) decrease in temperature. To account for a positive 1.4-deg lattitude change, temperatures can be reduced 0.5 deg C (1 deg F). Temperature cycles used in thermal analysis may include:

unpredictable occurrences. Yet, they do occu are commonly the cause of cracking during struction. The design team must use the ther analysis results coupled with experience and neering judgement to develop the final requi for insulation during construction.

(2) Water temperatures. The presence of impounded water is generally not necessary i mal studies, because water impoundment gen occurs long after construction. When needed unusual analyses, the temperature of the wate be assumed to have an annual variation and ma have little variation with great depth. Nearby lar projects are the best source of data.

(3) Solar radiation. The effects of solar ra tion during and following construction have been ignored in thermal analyses. Some therm analyses have incorporated an increase in am ! A normal annual temperature cycle is a sinusoidal-like variation of temperatures for temperature of 0.5 to 1.0 deg C (1 to 2 deg F) a locale obtained from multiyear daily averaccount for solar radiation heating of concrete age temperatures. faces during construction. EM 1110-2-2201 You're ReadingACI a Preview 207.1R provide charts allowing approxim ! An extreme ambient temperature cycle can estimates of solar radiation effects. Due to t Unlock full access with a free trial. also be used. The extreme ambient temperapproximate nature of Level 1 analyses, solar ature cycle can be developed as a sine wave tion should be ignored for Level 1 analysis. Download With Free Trial with a 1-year period which captures the coldest and hottest of the extreme monthly c. Concrete properties. Concrete therma  average temperatures. The extreme ambient mechanical, and physical properties needed Read Free Foron 30this Days Sign up to vote title  be temperature is used to account for the possithermal analysis are defined and discussed Useful  Not useful  bility of seasons (months) having much These concrete properties Cancel anytime. are dependent upon Special offer for students: Only $4.99/month. higher or lower temperatures than the avermaterials used and upon the proportions of t age ambient conditions based on multiyear materials in the concrete mixture Many of


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the material between actual and that predicted by the numerical model, and expected differences between the laboratory mixture and the actual mixture used during construction can be accounted for by performing parametric studies using combinations of the upper and lower bound values of critical properties. Drying shrinkage is generally ignored for analysis of thermal cracking, except for possible application to surface gradient cracking. Test methods identified as ASTM are American Society for Testing and Materials, Philadelphia, PA, methods. Test methods identified as CRD-C (Concrete Research Division-Concrete) are Corps of Engineers methods found in the Handbook for Concrete and Cement published by the U.S. Army Engineer Waterways Experiment Station (WES) (1949). Test methods identified as RTH (Rock Testing Handbook) are Corps of Engineers methods found in the Rock Testing Handbook (USAEWES 1990). Concrete materials and properties are discussed in EM 1110-2-2000, EM 1110-2-2200, EM 1110-22201, and ACI Committee 207 documents.

materials that will be used for the project. Th placement temperature for the test should re the temperature at which the bulk of concrete i likely to be placed for the MCS. Typical val adiabatic temperature rise for mass concrete r from 11 to 19 deg C (20 to 35 deg F) at 5 days 17 to 25 deg C (30 to 45 deg F) at 28 days. projects where adiabatic temperature rise tests not be justified, generic adiabatic temperatu curves in ACI 207.1R can be used. These cur can also be used to develop parametric adiabat temperature rise curves for use in thermal an

(b) Specific heat (c). Specific heat is th amount of heat required per unit mass to caus unit rise of temperature. It is affected by tempe ture changes but should be assumed to be con for the range of temperatures in MCS. Specif is determined according to CRD-C 124 (WES 1949). For mass concrete mixtures, specific h not substantially affected by age. Typical va specific heat of mass concrete range from 0. kg-K (0.18 to 0.28 Btu/lb-deg F).

You're Reading a Preview (1) Concrete thermal properties. ACI reports 207.1R, 207.4R, and 207.5R, many WES published (c) Thermal diffusivity (h2). Thermal di Unlock full access with a free trial. thermal studies, and others listed in the related refivity is a measure of the rate at which temper erences provide a wide range of laboratory deterchange can occur in a material and is the the Download Withconductivity Free Trial divided by the product of speci mined concrete thermal properties. and unit weight. It is determined according to (a) Adiabatic temperature rise (Tad). An adiaCRD-CRead 36 (WES 1949) forDays concrete with u Free Foron 30 Sign up to vote this title  batic system is a system in which heat is neither 75-mm (3-in.) nominal maximum aggregate si Useful  Not useful  allowed to enter or leave. The adiabatic temperaand CRD-C 37 (WES 1949) for concrete wit Cancel anytime. Special offer forture students: Only $4.99/month. rise, therefore, is the change in temperature in larger nominal maximum aggregate size and i concrete due to heat of hydration of cement under ally conducted between ages of 7 and 28 da


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temperature between the two faces. For concrete, thermal conductivity is calculated from the product of thermal diffusivity, specific heat, and density according to CRD-C 44 (WES 1949). Thermal conductivity of mass concrete is not significantly affected by age or by changes in temperature over typical ambient temperature ranges but is influenced by aggregate type. Typical values for thermal conductivity of mass concrete range from 1.73 to 3.46 W/m-K (1 to 2 Btu/ft-hr-deg F). (2) Concrete mechanical and physical properties. Tests and descriptions of concrete mechanical and physical properties used in thermal studies are described below. Test programs to develop these data can be relatively expensive. Modulus of elasticity, creep, and, to some degree, tensile strain capacity are difficult to estimate without testing. When laboratory tests cannot be performed, the best approach is to use results of more easily performed laboratory tests in conjunction with published information for similar concrete materials and mixtures from other projects.

dependency of the modulus of elasticity, tes should span the duration of analysis. Test a 1, 3, 7, 28, 90, 180, and possibly 365 days, a as at the design age, may be considered. Mo of elasticity of mass concrete is about 6.9 GP 10 6 psi) at 1 day, and ranges from about 21 GPa (3 to 5.5 × 106 psi) at 28 days, and from 30 to 47 GPa (4.3 to 6.8 × 10 6 psi) at 1 year. sile Ec is assumed to be equal to the compre Sustained modulus of elasticity (Esus) includ results of creep and can be obtained directly fro creep tests by dividing the sustained load on specimen by the total deformation. ACI 207 includes values of instantaneous and Esus. E tests conducted on specimens loaded at early for a period of 1 year will be about one-half the instantaneous Ec. Esus for tests conducte specimens loaded at 90 days or later ages for period of 1 year will be a slightly higher perce of the instantaneous Ec. Early age creep information is more important for thermal stu (b) Creep. Creep is defined as time-dep

You're Readingdeformation a Preview (strain) due to sustained load.

(a) Modulus of elasticity (Ec). The modulus of creep is creep under unit stress or strain per M Unlock full access with a free trial. elasticity is defined as the ratio of normal stress to (psi). Creep results in an increase in strain, b corresponding strain below the proportional limit. continually decreasing rate, under a state of Download Free Trial For practical purposes, only the deformation which Withstress. Creep is closely related to the modulus occurs during loading is considered to contribute to elasticity and compressive strength of the conc conc the strain in calculating the instantaneous modulus and is thus a function age of the Read Free Forof 30the Days Sign up to vote on this title of elasticity. Subsequent strain due to sustained loading. Concrete with a high modulusof el Not useful  Useful  loading is referred to as creep. The modulus of will generally haveanytime. relatively low creep. Cree Cancel Special offer forelasticity students:isOnly $4.99/month. a function of the degree of hydration determined according to CRD-C 54 (WES 19 and is time and strength dependent. The tempera Creep tests for mass concrete should always


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(c) Tensile strain capacity (,tc). Tensile strain capacity is the change in length per unit length that can be sustained in concrete prior to cracking. This property is used with the results of temperture analysis to determine whether an MCS will crack and the extent of cracking. Tensile strain capacity is discussed in detail in Annex 1. Tensile strain capacity is time-and rate-of-loading dependent and is strongly dependent on strength. Tensile strain capacity tests are conducted on large concrete beams instrumented to measure strain to failure for strain-based cracking analysis. Tensile strain capacity is determined according to CRD-C 71 (WES 1949).

shrinkage,” is a decrease in volume of the con due to hydration of the cementitious materia out the concrete gaining or loosing moisture type of volume change occurs in the interior o large mass of concrete and can be a significa tor. Autogenous shrinkage occurs over a mu longer time than drying shrinkage, the shrink to moisture loss that affects only thinner conc members or a relatively thin layer of the ma crete near the surface. Although no specific t method exists, autogenous shrinkage can be de mined on sealed creep cylinder specimens wi load applied in accordance with CRD-C 54 (WES 1949).

(d) Tensile strength (Ft). Tensile strength may (g) Density (D). Density is defined as mas be used with the results of stress-based thermal per-unit volume. It is determined according analysis to determine if cracking is probable in an CRD-C 23 (WES 1949). Typical values of MCS. ACI 207.2R discusses tensile strength in for mass concrete range from 2,240 to 2,56 some detail. Tensile strength can be measured by (140 to 160 lb/ft3). several methods, including the splitting tensile method (CRD-C 77 (WES 1949)), direct tension d. Foundation properties. The thermal, (CRD-C 164 (WES 1949)), and by the flexural test mechanical, and physical properties of the fo You're Reading a Preview or modulus of rupture method (CRD-C 16 tion are dependent on the type of soil or roc (WES 1949)). The splitting tensile test is more moisture content, and any discontinuities in Unlock full access with a free trial. commonly run for mass concrete, due to the simfoundation. In situ properties may vary signi plicity of the test, and because it can be less sensicantly from those obtained from laboratory Trial tive to drying than other tests. All tensileDownload strength WithofFree small samples obtained from borings or tes tests are age dependent, load rate dependent, and Rock may exhibit anisotropic properties. Ex  for t moisture content dependent. Prediction of tensile thermalRead properties are seldom necessary Free Foron 30this Days Sign up to vote title  f strength based on compressive strength is generally foundation materials, and adequate values Useful  Not useful  not particularly reliable. For preliminary thermal a thermal analysis be obtained from Jum Cancelmay anytime. Special offer foranalysis, students:the Only $4.99/month. split tensile strength relationship to (1977) or Kersten (1949). Likewise, exact m compressive strength is discussed in ACI 207.2R. ical properties are not required, and adequate


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soil foundations ranges from 0.80 kJ/kg-K (0.19 Btu/lb-deg F) for sand to 0.92 kJ/kg-K (0.22 Btu/lb-deg F) for clay. Specific heat for foundation rock generally ranges from 0.80 to 1.00 kJ/ kg-K (0.19 to 0.24 Btu/lb-deg F). Specific heat can be determined according to CRD-C 124 (WES 1949). (b) Thermal conductivity (Kfdn). The thermal conductivity of the foundation material is affected by density and moisture content and the degree of jointing and fracture in rock. The thermal conductivity of foundation materials may range from 4.15 W/m-K (2.4 Btu/ft-hr-deg F) for clay, to 4.85 W/mm-K (2.8 Btu/ft-hr-deg F) for sand, to 5.19 W/m-K (3.0 Btu/ft-hr-deg F) for gravel, and can range from 1.73 to 6.23 W/m-K (1 to 3.6 Btu/ ft-hr-deg F) for rock. Thermal conductivity can be determined according to one of several applicable ASTM procedures.

(b) Coefficient of thermal expansion (C The coefficient of thermal expansion for soil dations is not needed for thermal analysis. The coefficient of thermal expansion for rock fou tions can be determined according to ASTM D 4535. The coefficient can vary widely based rock type; typical values can be found in the ences. Measurements have been recorded rang from 0.9 to 16 millionths/deg C (0.5 to 8.9 lionths/deg F). (c) Density and moisture content. The de and moisture content of the foundation mater must be determined by the geotechnical eng (d) Initial temperature. For Levels 1 and thermal analyses, the initial temperatures fo foundation may be assumed to be at the annu average temperature at the site.

e. Construction parameters. Difference (c) Diffusivity (h ). Diffusivity of the foundathe way an MCS is constructed will impact tion is direct input to the Carlson and Schmidt behavior of the structure significantly. The You're Reading a Preview step-by-step temperature analysis methods and is response of the structure to changes of the co sometimes assumed equal to the concrete diffusivity tion parameters in the analysis will often dic Unlock full access with a free trial. for simplicity. Diffusivity is influenced by material whether or not cost reducing measures can be type, rock type, and density. Typical values for in the field. Construction parameters can al Download Withvaried Free Trial thermal diffusivity of rock range from 0.003 to in an attempt to improve the performa 2 2 0.006 m /hr (0.03 to 0.06 ft /hr). Rock diffusivity a structure. The paragraphs below describe can be determined according to CRD-C 36 (WES primaryRead construction that can be Free Forparameters 30this Days Sign up to vote on title  1949), or may be calculated according to CRD-C ered for changes during the thermal analysis Useful  Not useful  158 (WES 1949), using test values of thermal conaccomplishingCancel costanytime. reductions or improved b Special offer forductivity, students:specific Only $4.99/month. heat, and density. ior. Values for the following parameters, de on the level of thermal analysis, must be selecte 2


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the geometry will generally require some type of revision to the temperature analysis model. (2) Lift height. Since the heat escape from a mass is inversely proportional to the square of its least dimension and since the height of a lift will usually be the smallest dimension, the height of a lift can become an important factor in the thermal behavior of an MCS. Lift heights to be used in initial analyses will typically be selected by the engineer based on previous experience and practical limits. If the initial analyses indicate that the behavior of the structure is satisfactory, then analyses may be performed with increased lift heights as a measure for reducing cost. Likewise, if results indicate unacceptable behavior, a decrease in lift height may be considered to alleviate problems in the structure.

function of the annual ambient temperature In thermal analysis, the placement temperatu the starting point for concrete temperature rise. Placement temperatures are affected by conc constituent materials temperatures, heat added lost due to ambient conditions, and heat adde lost from material processing and handling. placing temperature for the initial analysis s be established by the materials engineer. As w lift heights, if behavior is acceptable then con ation may be given to increasing the placing ature. Increasing the allowable placing tem can lead to cost savings due to decreased co requirements. EM 1110-2-2201 and ACI 2 contain information and guidance on precoo mass concrete.

(5) Construction start date. The time of when construction is started can have a signific (3) Lift placement rate. The time between the effect on the MCS temperatures. The selecti placement of lifts has an effect on the thermal perstart dates is structure and site dependent and formance of the structure due to the insulating effect should be evaluated by the design team based o a new lift has on the previous lift(s). The time past experience and engineering judgement. You're Reading a Preview between placement of lifts must be included in the objective in selection of start dates is to cho thermal analysis. Usually, shorter time intervals among the possible start dates that may prod Unlock full access with a free trial. between lifts, i.e., higher placement rates, cause worst conditions in the MCS. Usually a single higher internal temperatures in an MCS. A 5-day date is inadequate for identifying the worst c Download Withtions FreeatTrial interval between lift placements is typically most locations within the structure, e assumed for traditional concrete. For RCC, the cially since the structure is built in lifts over time interval will depend on the placing rate anticisignificant period of time. Different  start dat Read Free For 30this Days Sign up to vote on title pated and the lift surface area, which often varies yield temperature problems at different  loca Useful  Not useful  during construction. The longer the interval the MCS. The startanytime. dates should be chosen Cancel Special offer for students: Only $4.99/month. between placement of lifts, the longer each lift will ate the largest temperature gradients. Often a have to dissipate the heat that has built up within date representing each of the four annual se


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ETL 1110-2-542 30 May 97

of insulation (the R value) to be used will depend on the project location and should be selected by the engineer for the initial analysis. Both of these parameters may be varied during subsequent analyses to achieve cost savings or to improve performance. The effects of insulation are included in the surface heat transfer coefficient calculations.

A-4. Analytical Methods For Temperature Calculation

All thermal studies require computation of tem ture or temperature distribution changes in a s ture. Depending upon the type and function o structure, less rigorous thermal studies may quate for “acceptable” evaluation of thermal pe (8) Postcooling. Embedded cooling coils to mance. Temperature calculation requiremen control heat generation within an MCS have been thermal studies may range from very simple t used in some large gravity and arch dam projects, as sonably complex. ACI 207.1R discusses seve well as some smaller specialized placements such as approximate methods that are appropriate for s tunnel plugs (to shorten time for joint grouting), but ple evaluations. The Carlson (Carlson 1937 have typically not been needed on navigation-type Schmidt (Rawhouser 1945) methods are ste structures. Postcooling of mass concrete is very step integration techniques, adaptable to spr costly in terms of both installation and maintenance sheet solutions on personal computers, that and has seldom been used in recent years. If placing used for computing temperature gradients w temperatures have been reduced to their lower limit, heat flow and reasonably simple boundary co lift heights have been reduced to a practical minitions are assumed. FE programs for compu mum, and temperatures within the structure remain temperatures (Wilson 1968; Polivka and W excessive, then the addition of cooling coils may be 1976; Hibbitt, Karlsson, and Sorensen 1994) a considered. Because postcooling is so seldom used, appropriate for thermal studies when aspects it’s use is not included in the thermal analysis proanalysis exceed the capabilities of simpler me You're Reading a when Preview cedures. Guidance on postcooling is provided in or application of the FE method is as e EM 1110-2-2201 and in ACI 207.1R. implement as the simple methods. The follo Unlock full access with a free trial. are descriptions of the range of analytical meth (9) Reinforcement. Reinforcement is generally that can be used for Levels 1 and 2 thermal Download Withanalyses. Free Trial not used in the MCS being analysed for thermal concerns but may be used in smaller structures such  as powerhouses and large foundations. Since a. Read Simple maximum and final tempera Free Foron 30this Days Sign up to vote title  excluding reinforcing from an analysis provides calculations. This “quick and dirty” method i Useful  Not useful  conservative results, initial analyses can be perused to compute peak temperatures due to he Cancel anytime. Special offer forformed students: Only $4.99/month. without the effects of reinforcement. The hydration and final stable temperature in the effects of reinforcing on resulting structural behavComputation usually results in a conservativ


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b. Heat dissipation methods. The time required for dissipation of heat and the resultant cooling of MCS can be calculated by the use of heat loss charts or by simple computation as described in ACI 207.1R for solid bodies, such as slabs, cylinders, and spheres. These charts provide an approximate method of calculating the time for the concrete to cool from a peak temperature to some stable temperature. Peak concrete temperature must be determined using other means. Strain and resultant cracking analysis must also be performed by other methods. These heat dissipation methods can be of use in Level 1 analyses.

incorporating internally generated heat into process. The Schmidt Method can be used in Level 2 analyses.

d . FE methods. An FE analysis can be described as a numerical technique for the determination of temperature distribution or s analysis in which structures are mathematic represented by a finite number of separate ele interconnected at a finite number of points cal nodes, where behavior is governed by mathe relationships. All the boundary conditions are applied to the model, including material therm properties, ambient conditions, and construc c. Step-by-step integration methods. schedule. The model is run, and a temperature tory for the model is generated. Temperature i (1) Carlson method. The Carlson method is a calculated for specified times for each node. step-by-step integration method for determining FE method is the preferred methodology for temperature distribution in a concrete structure. puting temperatures in mass concrete structure Carlson (1937)(Department of the Interior, Information on building a data file to run an U.S. Bureau of Reclamation (USBR) 1965) proFE analysis must be obtained from manuals p vides detailed discussions for implementing this vided by the developer of the FE code being method. It is readily adapted to modern computer To use the FE method, an FE model must fi You're Reading a Preview spreadsheet computations and provides reasonable prepared. The model is divided into a grid o approximations of temperature distributions in elements in which element boundaries coinci Unlock full access with a free trial. simple structures. Properly applied, this method material interfaces, lift interfaces, and structur permits modeling of incremental construction, heat boundaries. Generally, smaller elements are FreeofTrial flow between dissimilar materials such asDownload founda- Withareas greatest thermal gradient. The method tions and concrete, and adiabatic temperature rise of ogy permits detailed modeling of virtually all a concrete. This method can be used in Level 2 cable parameters. Few FE Days programs have be Read Free Foron 30 Sign up to vote this title mo analysis. written to compute temperature histories Useful  Not useful  incremental construction Cancel anytime.of MCS. Few, if any Special offer for students: Only $4.99/month. (2) Schmidt method. The Schmidt or Schmidtprograms have been written to model solar ga Binder method is one of the earliest computation lift surfaces. ETL 1110-2-332 and ETL 111


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(2) More recently, the U.S. Army Corps of Engineers has developed user-defined subroutines to supplement ABAQUS (Hibbitt, Karlsson, and Sorensen 1994), a modern, general-purpose FE program. ABAQUS is used with associated usersupplied subroutines DFLUX and HETVAL for modeling heat generation in incremental construction thermal analyses, with user subroutine UMAT, or with the ANACAP-U subroutine to implement a time-dependent material/cracking model for thermal stress analysis of MCS. ABAQUS has been used to perform Level 3 NISA and is the basis for ETL 1110-2-365. ABAQUS can also be readily used for performing temperature calculations for Level 2 analyses, especially by experienced ABAQUS users. This program requires a high level of computer experience and expertise, as well as an advanced computer.

temperature in most MCS is higher than the ambient temperature. Thus, the structure cool a long period of time to a stable temperature to the average ambient air temperature. This simple analysis usually estimates temperatures higher than actual peak temperatures. The ex tion may be for very hot climates where the p temperature may be higher than estimated. small or relatively thin structures, internal tem tures can be assumed to stabilize at an avera annual temperature cycle. Computation of ature variation in smaller MCS as a function depth and ambient temperature cycle is discu ACI 207.1R, including a figure for determini temperature variation with depth. A step-by procedure and example of this level of analys included in Annex 2.

(b) Heat dissipation methods. Using the type of peak temperature analysis, simple com A-5. Temperature Analysis tions or heat loss charts may be used to evaluat time required to cool simple mass concrete stru a. General . This section provides general tures from the peak temperature. The use of You're Reading a Preview methodology for MCS temperature analyses conloss charts is described in detail in ACI 207. ducted at Levels 1 and 2, once objectives have been Unlock full access with a free trial. developed, input data has been collected, a paramet(2) Level 2 temperature analysis. Temp ric analysis plan has been prepared for the temperaanalyses for Level 2 thermal studies may be Download Free Trial ture analysis, and a method of temperature analysis Withmented in two types of analytical methods, nam has been selected. Since the FE method is widely step-by-step integration methods or FE metho  used for determination of temperature distribution Read Free Foron 30this Days Sign up to vote title  histories in thermal analyses of MCS, a description (a) Step-by-step temperature integration Useful  Not useful  of required FE thermal model development is also ods. The Carlson Cancel(Carlson anytime. 1937)(USBR 196 Special offer for students: Only $4.99/month. presented. The information is generic in that it is Schmidt (USBR 1965) methods of tempera not directed for use by a specific FE program. analysis are tabular methods of computing app


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assumptions. Using tabular techniques, the tables essentially solve a large number of simultaneous equations, resulting in progressive temperature distribution. The computations require the structure dimensions, ambient temperature, the temperature distribution at some initial time, the material diffusivity, and the adiabatic temperature rise. The methods will accomodate the presence of forms and insulation, if desired. These methods can be used effectively for parametric analysis of thermal conditions. Although these methods are effective temperature analysis techniques for structures with simple geometry and conditions, current FE analysis com puter software often allows development of FE temperature analysis with about the same level of effort to perform a step-by-step analysis.

conditions characteristic of mass co construction. A step-by-step proced example of this level and type of an included in Annex 3.

2-D full-section models. Thermal with full-section models must be pe with one of the FE programs which or can be adapted for incremental co tion capability. A 2-D, FE model re ing 2-D heat flow in an appropriate tion(s) of a monolith is used. More plex structure geometry, materials p ties, construction parameters, and boun conditions are used in these analyse results of a Level 2 full-section 2-D ature analysis are temperature distribu (b) FE models. Due to the ease in creating and in the entire plane of the monolith th using FE models for temperature analysis, FE methmodeled. These data are used as th odology is preferred for a Level 2 thermal analysis for more refined mass gradient and and is required for a Level 3 analysis. Level 3 temgradient analyses anywhere in the m perature analysis is NISA, described previously, and step-by-step procedure and example is not covered further in this document. Even when level and type of analysis is include You're Reading a Preview 2-D or 3-D FE analysis is used for the final thermal Annex 3. analysis, 1-D FE analysis can be a productive Unlock full access with a free trial. screening tool for parametric analyses. 3-D-full section models. These more ! plex FE models can be used for MCS w Download With Free Trial 1-D strip models. In many larger struccomplex geometry and may develop ! tures, a model consisting of a “strip” or NISA models.  “line” of elements oriented within the transRead Free Foron 30this Days Sign up to vote title  verse section of a monolith can be used to c. FE thermal analysis considerations Useful  Not useful  provide reasonably accurate temperature Information on developing Cancel anytime. FE temperature a Special offer for students: Only $4.99/month. distributions without complete modeling of models follows. the section. The strip is a 1-D heat flow


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strip meshes entirely contained in one lift usually extend from the surface to the middle of the monolith. Lift boundaries and boundaries between different concrete mixtures or other materials must only exist at element boundaries. Various programs are available that may be used to provide preprocessing capabilities in developing a mesh. If a decision is made to use a preprocessor, users should select a preprocessor which is fully compatible with the FE program and with which they are familiar or feel they can learn easily. Element aspect ratios should follow ETL 1110-2-365 recommendations, and element size will generally depend on geometry and temperature gradients. Time increments must be small enough to capture early age temperature changes that occur more rapidly than later cooling, with 0.25 day often used.

d = 1.086 (0.0513) h = surface heat transfer coefficient or f coefficient V = wind velocity in km/h (mph)

The wind velocity may be based on monthly wind velocities at the project site. Data can be obtained for a given location and then generali over a period of several months for input int analysis. (b) If forms and insulation are in place, values for h computed in the equations above should be modified as follows:

1 (2) Surface heat transfer coefficients. Surface h ) ' b b 1 heat transfer coefficients (film coefficients) are ( )formwork % ( )insulation % ( ) k k h applied to all exposed surfaces to represent the convection heat transfer effect between a fluid (air 1 h ) = or water) and a concrete surface, in addition to the 1 Rformwork % Rinsulation % ( ) You're Reading a Preview conduction effects of formwork and insulation. The h following equations are taken from the American Unlock full access with a free trial. Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) (1977). These equawhere Download With Free Trial tions may be used for computing the surface heat transfer coefficients to be included in any of the FE h' = revised surface heat transfer  codes for modeling convection. coefficient Read Free Foron 30this Days Sign up to vote title

Master your semester with Scribd & The New York Times (a) For surfaces without forms, the coefficients Special offer forshould students: Only $4.99/month. be computed based on the following:

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useful  bUseful  Not = Cancel thickness of formwork or insula anytime.

k = conductivity of formwork or

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on the foundation for an arbitrary time period up to 1 year immediately preceding the construction start date(s). The time period selected is usually a function of the depth of foundation in the model. During this analysis, the lower boundary of the foundation is fixed at the stable foundation temperature, usually mean, annual air temperature. The foundation surface is exposed to the normal, annual ambient temperature cycle. Appropriate adjustments should be made for possible surface thermal conditions during the analysis period, such as snow cover or very hot weather. (4) Output interpretation. This section is intended to give insight into the various methods that have proven useful in presentation of analysis results. The engineer must sufficiently process results to comprehend the behavior of the structure and provide the necessary data (plots, diagrams, tables, etc.) to support cracking analysis and conclusions based on this understanding.

where similar structures have experienced p places where previous analyses have presen results, or places which help explain the ove response of the structure.

(c) Section plots. Plots of results (i.e., temperature, net strain) across a specified sec location at a specific time are useful in determi the behavior of the section or location. Dete tion of the maximum value of a specific resu stress, strain) and its time of occurrence is u determining which section or location to plo the corresponding time.

A-6. Cracking Analysis

a. General. The ability of concrete to res thermal cracking is dependent on the magni the thermal shrinkage or volume change, the d of restraint imposed on the concrete, and the strain capacity of the concrete. This section di (a) Temperature contours. Temperature concusses restraint in MCS that leads to strain in You're Reading a Preview tours should be smooth throughout a lift and across concrete mass or near the MCS surface and po lift interfaces. Temperature contours should never cracking if the tensile strain capacity of the c Unlock full access with a free trial. abruptly intersect free surfaces of the model where is exceeded. Strain due to other loading cond surface heat transfer coefficients are applied, except oftens needs to be considered with thermal stra Free Trial for locations where a very low coefficientDownload is used to Withevaluate cracking potential. The consequenc model an enclosed void. This indicates the applicacracking may be structural instability, seepag tion of an incorrect thermal boundary condition. durability, andFree maintenance problemsor may Read Foron 30this Days Sign up to vote title the Contour plots of temperature, stress, net strain, relatively inconsequential, depending on Useful  Not useful  and/or crack potential are useful in selecting zones design and function. Depending on the orien Cancel anytime. Special offer forinstudents: Only $4.99/month. the structure for more detailed investigation. of cracking, sliding or overturning stability structure may be impaired. Typically, transver


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surface, and result in cracking if the tensile capacity of the concrete exterior is exceeded. b. Thermal volume change. Volume change in MCS is primarily due to cement hydration heat generation and subsequent cooling. However, additional volume change may result from autogenous shrinkage or other mechanisms. Volume change for analysis of thermal cracking is normally discussed in terms of 1-D length change and is determined by multiplying the coefficient of thermal expansion by the effective temperature change induced by cooling of the mass concrete from a peak temperature. This is discussed further under mass gradient and surface gradient cracking subjects below. If concrete is unrestrained, it is free to contract as a result of cooling from a peak temperature, no tensile strain is induced, and it will not crack. However, since most MCS are restrained to some degree, tensile strain is generally induced, leading to cracking if tensile strain capacity is exceeded.

the restraining surface, decreasing with increa distance from that surface.

(2) Surface gradient restraint. Surface g or internal restraint, is caused by changes in t ature within the concrete. This condition exi soon after placement when heat loss from th face stabilizes the temperature of near-surface crete, while the temperature of interior conc continues to rise due to heat of hydration. Thi temperature gradient also continues later, whe temperature of the surface concrete cools mo idly than interior concrete. These temperature dients result in relatively larger volume chan (temperature shrinkage) at the surface relati interior. The result is strain-stress at the surfa shown in Figure A-1, decreasing in magnitu increasing distance from the surface to eventua zero strain-stress region at some point in the i rior. Strain is generated nearer the surface b the adjacent more interior concrete is changi ume at a slower rate. This is sometimes describ c. Restraint in mass concrete. Cracking in the interior concrete “restraining” the exteri You're Reading a Preview mass concrete is primarily caused by restraint of crete. As can be seen in Figure A-1, the interio volume change. Restraint that prevents free volume not “restraining” the surface as the foundati Unlock full access with a free trial. change or contraction after mass concrete has strains” an MCS, since the strain-stress build reached a peak temperature and cools to an ultimate to surface gradients is at the surface, not in th Download FreeThe Trial temperature is of primary concern in mass concrete Withrior. restraint formulas used for mass gr structures. Restraint prevents the free volume strain calculation are also applied to surface  di change of concrete, which causes tensile strain and ent restraint strain calculation, with some Read Free Foron 30this Days Sign up to vote title  stress in the concrete. Restraint may be either ences. In this case, no “restraining” surface e Useful  Not useful  external or internal, corresponding to mass gradient at the interior.Cancel Rather, a point of zero strain-st anytime. Special offer forand students: Only $4.99/month. surface gradient strain-stress, respectively. exists in the interior, with increasing strain-stre ACI 207.2R discusses restraint in some detail. the concrete surface is approached. The therm


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Figure A-1. Mass and surface gradient strain-stress “model” comparison

Readinginitiate a Preview the tensile strain capacity of the concrete.You're The oria crack. Surface gradient cracking is entation of the cracking, if fully developed, can observable on concrete surfaces as pattern c Unlock full access with a free trial. separate the structure into discrete sections. In and often extends into the structure from a fe some cases, cracking in a dam that occurs normal to inches to several feet. This problem is less Download Withlent Free the monolith joints could affect the stability of a in Trial temperate climates and more exagger monolith. In dams where monoliths are very wide, locations with greater temperature variations this cracking can be longitudinal or parallel to the ever, under some circumstances, this crackin Read Free Foron 30this Days Sign up to vote title  Th axis of the dam. This procedure for analysis of lead to more serious cracking conditions. Useful  Not useful  external restraint mass gradient cracking is based shock can induce surface temperature g Cancelsteep anytime. Special offer forupon students: Only $4.99/month. ACI 207.2R, which can be adapted for a ents leading to cracking. This occurs when stress-or a strain-based methodology, as seen in the concrete surfaces are suddenly subjected to c


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(3) Mass/surface gradient interaction cracking. Cracking may not occur due to mass or surface gradient cracking alone. However, if the mass has built up significant mass gradient tensile strains and stress near the threshold of cracking, the additional tensile strain or stress from surface gradients may propagate a crack through the mass. Additionally, other loading, such as hydrostatic pressures from a reservoir, temperature effects from unusually cold water in deep reservoirs, or differential settlement of the foundation, may propagate a surface crack through the structure.

C th = coefficient of thermal expansionlionths/deg C (millionths/deg F) dT = temperature change in the mass co causing strain - deg C (deg F) KR = structure restraint factor K f = foundation restraint factor

(1) Mass gradient restraint factors. A co mass is commonly restrained by the foundat other structures, or by previous lifts. Full restr seldom exists in a structure and then, only at specific locations. The induced strain in a str can be calculated using the restraint formula fied by factors based upon the geometry and internal stiffness of the structure, K R, and upon relative stiffness of the structure compared to t foundation, K . f

(4) Longitudinal cracking. Longitudinal cracking has long been a concern for large dams, since the occurrence of significant longitudinal cracking has the potential to affect the stability of the dam. In traditional dam construction, precooling and postcooling techniques were used to eliminate this concern. With the predominance of RCC in the construction of dams, longitudinal cracking is again a concern for large dams. This is due to the high (a) Structure restraint factor ( K R). The cost and difficulty with using postcooling in RCC. ture restraint factor is determined by Equatio You're Reading a Preview Hence, precooling of the materials is the primary and A-6 from ACI 207.2R. The restraint mo method of controlling RCC temperature. In large (Figure A-2) is a representation of the exter Unlock full access with a free trial. dams, those methods may not be sufficient to prerestraint geometry which is applied to mass gr vent longitudinal cracking. cracking due to foundation restraint. It relat


e. Mass gradient cracking analysis. Master your semester with Scribd Although strain is used as a basis for the following cracking analyses and is the recommended & The New York Times approach, stress has been historically and can still Special offer for students: $4.99/month. be used to Only evaluate cracking. The principle of superposition of incremental strains or stress is


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ETL 111030 M

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magnitude of restraint to the shape of a simple structure where L is length, H is height, and h is the distance from the restraining interface (or restraining plane) at the base of the structure to any location of interest where strain is to be determined. L should be selected with care, since some large structures may be susceptible to mass gradient cracking in more than one direction. This model provides for a structure restraint factor, K R, for external restraint at locations, h, away from the restraining plane. K R is determined by one of the following two equations:

K R =

h/ H

&

2 (A-5)

%

K f = 1

%

1 A g E c A f E f

where Ag = gross area of concrete cross secti foundation plane

for L/H greater or equal to 2.5

L H L H

the difference in the elasticity of the foundati compared to the elasticity of the concrete ma This relationship is expressed as:

1

Af = area of foundation or zone restrai contraction of concrete (recommend maximum value is 2.5 Ag). E f = modulus of elasticity of foundatio restraining element

and for L/H less than 2.5

E c = modulus of elasticity of mass con

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f . Surface gradient cracking analysis Cracking due to temperature gradients from the L & 1 relatively stable interior temperatures to the ex H K R = (A-6) Download WithofFree Trialis analyzed based on the restraint m an MCS L % 10 described below and in ACI 207.2R. This mod H similar Read in nature toFor that30 used for massgradient Free Days Sign up to vote on this title  as cracking analysis. Although strain is used Useful  Not useful  These formulas from ACI 207.2R are reasonable basis for the following cracking analyses, an Cancel anytime. Special offer forapproximations students: Only $4.99/month. of figures shown in ACI 207.2R, recommended approach, stress has been his but Equation A-6 is a somewhat inaccurate repreand can still be used to evaluate cracking. The h/ H

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ETL 1110-2-542 30 May 97

You're Reading a Preview Figure A-3. Internal restraint model usedUnlock in surface gradient full access with aanalysis free trial.

Download With Free The following equation may be used to determine (1)Trial Surface gradient restraint factor. Th the strain due to surface thermal gradients in condegree of restraint is not easily determined bu the e crete (based on ACI 207.2R): be estimated based on the thickness of Read Free For 30this Days Sign up to vote on title  surface layer being restrained. The restraint Useful  Not useful  K R, is computed in anytime. a manner similar to mass gr Cancel Special offer for students: Only $4.99/month. , = (Cth )(dT)(K R) (A-8) ent restraint factor, from Equations A-5 or A depending upon the value of L/H , where L is th


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ETL 111030 M

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and for L/H less than 2.5

K R =

L & 1 H L % 10 H

h/ H

(A-6bis)

Values of L/H less than 2.5 will rarely be applied for surface gradient analysis, since the surface gradient tensile region can be visualized as a flat slab lying along the exterior surface, with large L and small H . Values of K R may be determined at various distances, h, from the interior surface of zero strain-stress, to determine restraint at specific locations. A maximum value of K R = 1.0 will always exist at the exterior surface.

compression in the interior concrete. ACI 2 states that for sectional stability, the summatio tensile stresses (and strains) induced by a temp ture gradient in a cross section must be balance equal compressive stresses (and strains). Assu that the modulus of elasticity and coefficient of thermal expansion are constant across the secti and that stresses and strains are balanced, the i cation is that temperature differences contribut to tensile and compressive strain must also b anced.

(b) Figure A-5 shows the temperature d ences from Figure A-4 adjusted to provide e tension and compression in the section, prov graphical representation of the surface gradien restraint model. This figure shows the locat negative temperature differences relative to mal balance line at )T = 0. Areas with negativ (2) Determining temperature gradients, the temperature differences are in tension, corres surface gradient tension block and H. Surface graing to the tension block shown in Figure Adient strain computations are performed using temwith positive temperature differences are in perature differences, dT , which is the temperature compression. The location of )T = 0 determin You're Reading a Preview change at the point of interest in the mass minus the the location of the tension block relative to th temperature change in the interior. These temperarior surface and the distance H for the K R calcu Unlock full access with a free trial. ture differences represent the temperature gradient tion. A variety of methods are used to determ from the surface to the interior of the mass concrete temperature differences, the tension block lo Download Withand H Free, Trial that generates thermal strains and stresses. If the some of which are shown in the exampl exterior and interior concrete underwent the same Annex 3.  temperature change during initial temperature rise Read Free Foron 30this Days Sign up to vote title  and later cooling, no surface gradient strains and (3) Determining dT . To calculate strain, Useful  Not useful  stresses would be generated. The fact that the extemust be determined for that location. dT is sim Cancel anytime. Special offer forrior students: Only $4.99/month. and interior concrete undergo temperature the temperature difference for that location of changes at different rates gives rise to surface gradiest relative to the interior temperature differen


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ETL 1110-2-542 30 May 97

Figure A-4. Example of temperature difference distribution for surface gradient analysis of lock wall





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ETL 111030 M

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strains in the mass above allowable ,tc values, cracking of that mass is probable. This cracking is typically full cross section transverse cracking of the monolith. However, longitudinal cracking may also occur if the monolith is sufficiently large. If the surface gradient values exceed allowable ,tc, surface cracking is probable. The spacing and widths of the cracks depend on restraint conditions and are determined based on judgement and experience.

experience, three to six cracks of 2-to 5-mm ( 0.2-in.) width might be expected, if no joints installed and the fractured rock foundation i what flexible.

(3) Crack spacing and width. Theoretic there are an infinite number of combinations o crack spacing and crack widths that will equa calculated thermal length change. However are some general rules of thumb for crack spac and width based on experience. Foundation co (2) Cracking calculation. The thermal strain is tions of restraint often control the spacing o distributed across the length of the analyzed section. and the number of cracks tends to control the Tensile strain capacity data from slow-loading tests widths. Mass gradient crack spacing in larg are used to define the capacity of the concrete to usually ranges from 30 to 91 m (100 to 300 f “absorb” strain. For example, if a fully restrained Crack widths typically range from 2 to 5 mm dT temperature change occurred over 1 year: to 0.2 in.). Surface gradient cracking is high dependent on the restraint conditions and is us dT = 17 deg C (30 deg F) more closely spaced and narrower than mas ent cracking. Surface gradient crack widths C th = 9 millionths/deg C (5 millionths/deg F) range from 0.5 to 2 mm (0.02 to 0.1 in.) (Ta Shrader 1992). Hairline cracks of about K R = K f = 1 0.0005 mm (0.002 in.) may leak initially if You're Readingunder a Preview pressure is available to one side of the cr Using Equation A-4, but will often heal from calcification. Such Unlock full access with a free trial. is expected to stain the exposed concrete face. millionths. ,induced = (Cth)(dT)(Kr)(K f) = 150


If Master your semester with Scribd , = 100 millionths (when loaded from 7 to 365 days), & The New York Times tc

Special offer forthen students: Only $4.99/month. the remaining strain to be distributed as cracks is

A-7. Limitations of Thermal Studies  Read Free Foron 30this Days Sign up to vote title  descr a. General . The analytical methods Useful  Not useful  in this ETL for Levels 1 and 2 thermal studies Cancel anytime. vide reasonable approaches to the analysis of t mal effects in mass concrete. These thermal

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ETL 1110-2-542 30 May 97

or verified in some way to assure the engineer of the appropriateness and accuracy of the methods used. The design team must use every available means to verify the correctness and accuracy of the input data for thermal analysis, including climatological, structural, material, and construction input parameters. The design team should use any means available to help verify the validity of the results. Using the experience and judgement of the materials engineer, an initial check of the results can be made on a qualitative basis. Exploring previously analyzed structures and their results, performing a simple ambient condition analysis (no creep, shrinkage, aging modulus, or adiabatic temperature rise), and performing simplified analyses are all possible methods for providing confidence and a check on the validity of the analysis.

ambient temperature, surface heat transfer c ents, and other information. Plots of results be included to illustrate the behavior of the ture. These plots could include temperature, s and crack potential contours at critical times, p temperature and stress time-histories at critical locations. There should be a narrative interp of the results. This should explain any pote cracking, whether it is acceptable, what spec design or construction procedure changes m required, and what cost adjustment was made because of these changes.

c. PED studies. PED thermal studies res should be presented in a separate design repor should include a statement of objectives of t study, information on the model(s) used in the ysis, information on all input parameters, prese tion of the model and analysis results, verificat of the model and analysis results, and conclusi A-8. Documentation of Thermal Study Results and recommendations for design and construct Presentation of results is critical in providing th a. General. Thermal studies are performed proper understanding of how the structure be You're Reading a Preview during various phases of project design. Generally, and for supporting any conclusions or recomm Level 1 studies are performed during a feasibility tions that will be made as a result of the the Unlock full access with a free trial. study for a major project or for a complex structure analysis. Results may be displayed in table where thermal cracking issues may require subsegraphs, contour plots, or color plots. Discu Free Trial quent design changes and more complexDownload analysis. Withresults should include cracking potential, accep Detailed thermal analysis is often performed during ability of cracking, and possible corrective mea  the feature design phase of the project. The format for thermal problems. The thermal model resu Read Free Foron 30this Days Sign up to vote title  of the documentation will depend on the design must be verified in a manner that illustrates Useful  Not useful  stage and the level of thermal study. validity of theCancel model results, either through anytime. Special offer for students: Only $4.99/month. pendent analysis, correlation with field data, b. Feasibility studies The thermal study and correlation with field experience Conclusio


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ETL 111030 M

ANNEX 1: DETERMINATION OF TENSILE STRAIN CAPACITY

A1-1. Purpose

requires a minimum of three beams for each te and generally a minimum of three tests is recom Tensile strain capacity (TSC) is the change in mended for each test set to allow for variation length per unit length that can be sustained in contest results. Rapid-load (0.28 Mpa/min)(40 p crete prior to cracking. This property is used with min) and slow-load (0.17 MPa)(25 psi/week) the results of temperature analysis to determine are usually conducted in test series consistin whether a mass concrete structure (MCS) will crack three beam tests each. TSC test specimens a and the extent of cracking. This annex describes 300-mm by 300-mm by 1,680-mm-long (12 testing to determine TSC, methods to estimate TSC, 12-in. by 66-in.-long) beams tested in thirdand methodology for its use in thermal analysis. loading. Strain gauges are located at or near and bottom (compression and tension) surfaces measure strain during the tests. At the age of t A1-2. Background rapid-load test is conducted and a slow-load te begun. Loading continues at the prescribed ra The Corps of Engineers introduced TSC testing until failure. During the slow-load beam test, of concrete several decades ago to provide a basis measurements are made on the beam under l for evaluating crack potential for strain-based theraddition, measurements of autogenous strain a mal studies of MCS (Houghton 1976). This propmade on the third beam. The autogenous shr erty is also used to compare different aggregates strains are used to correct the strain measure a Preview and different concrete mix proportions inYou're MCS. Readingon the beam under slow load. Upon failure TSC varies primarily based on age, strength, aggreslowly-loaded beam, a rapid-load test is perf Unlock full access with a free trial. gate type, shape, and texture. TSC tests are conon the third beam. A TSC test series usuall ducted on large concrete beams instrumented to tains a suite of rapid- and slow-load tests ty Download Withinitiated Free Trial measure strain to failure. TSC is determined in a at 3, 7, 28 days, and/or other ages. series of tests, including rapid and slow loading of differences in TSC capacity from the slow of the beams. The slow-load test was designed to simulate rapid-load beams provide an indication Read Free Foron 30this Days Sign up to vote title  the strain conditions occurring in a mass concrete cumulative creep strain during the slow-load t Useful  Not useful  structure during long-term cooling. By conducting The strains measured in the slow-load beam t Cancel anytime. Special offer fortests students: Only $4.99/month. at several loading ages, TSC data can be used containing both elastic and creep strains are to evaluate mass gradient cracking resistance in a expressed in millionths (1 × 10-6 in./in).


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ETL 1110-2-542 30 May 97

rapid-load tensile strain capacity tested at the same age as the slow-load specimens range from 1.0 to 2.0 and averages 1.4. This average is relatively insensitive to age.

A1-5. Use of Tensile Strain Capacity for Mass Gradient Cracking Analyses Mass gradient tensile loading in an MCS occurs over an extended period of time. The standard slow-load tensile strain capacity test was specifically designed for this condition. Standard slowload TSC tests provide a reasonable limiting strain in mass gradient cracking analyses for the condition of restrained slow loading of mass concrete which occurs in a slowly cooling mass. Using an appro priate loading time period, the slow-load tensile strain capacity can be used directly for mass gradient cracking analysis.

capacity slow-load test, the results of that tes not well represent surface gradient condition accurate tensile strain capacity values may no necessary for surface gradient analysis, exce critical situations. For most situations, the sta test values will suffice for surface gradient crac analysis as well as mass gradient cracking anal In some structures, concrete placed near the sur of the MCS may differ significantly from inter concrete mixtures. Tests for TSC used in sur gradient analysis should be conducted on th priate concrete mixture(s).

b. Simulated surface gradient strains critical situations, slow-load TSC tests cond more rapid rates of loading than the standard s load test may be conducted to simulate the de ment of surface gradient thermal strains. In lie such special load rate testing, an estimate ca made of TSC for use in preliminary surface TSC determinations, using the ratio of 1.4 desc above. An estimate of TSC for surface gradien A1-6. Use of Tensile Strain Capacity for Readinganalysis is determined by testing TSC at the ra You're a Preview load rate and at the age of interest. This value Surface Gradient Cracking Analyses Unlock full access with a free trial. then multiplied by 1.4, to determine a TSC und the slow loading reflective of surface gradient a. Surface gradient strains. Surface gradient Withdevelopment. Download Free Trial This estimate is believed to be strains can be initiated at a very early age, particusonably conservative at ages from 1 to 14 d larly after the removal of insulated formwork, and Because creep rates are greatest at early  ages, Read Free For 30 Days Sign up to vote on this title can develop over a few days or weeks of loading possible that slow-load TSC may be conside  due to the initial temperature rise and subsequent higher especially 1 touseful 7 days. Until tes Useful from Not  Cancel anytime. of$4.99/month. the surface temperature gradient. are available, this may be used for developing Special offer fordevelopment students: Only Because loading under surface gradient conditions face gradient tensile strain capacity values.


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ETL 111030 M

ANNEX 2: LEVEL 1 THERMAL STUDY MASS GRADIENT ANALYSIS PROCEDURE AND EXAMPLE

A2-1. Procedure a. General. This Annex summarizes each step in a Level 1 thermal study mass gradient analysis of a mass concrete sheetware (MCS) and provides an example of how this procedure was applied for a modest-size MCS. Although alternative approaches can be used, this method is in common use for this level MCS thermal analysis. Surface gradient thermal analysis is seldom conducted at this level of analysis.

c.

Temperature analysis.

(1) Step 4: Mass gradient temperature sis. For Level 1 mass gradient analysis, no rate “model” is used to develop temperature h The long-term temperature change is simply c lated as the peak concrete temperature minu ultimate stable concrete temperature. (a) Determine peak temperature. This is sum of the concrete placement temperature adiabatic temperature rise.

b. Input properties and parameters.

(b) Determine ultimate stable temperature (1) Step 1: Determine ambient conditions. Large structures cool to a stable temperature Simple analyses conducted for a Level 1 analysis to the average ambient temperature. Howeve are typically based on average monthly temperature smaller concrete structures cool to a stable a data. temperature cycle, since there is insufficient You're Reading provide a Preview complete insulation of the interior. (2) Step 2: Determine material properties. 207.1R provides a figure relating temperature Unlock full access with a free trial. Laboratory test results on material properties are ation with depth to determine this internal seldom available for this level of thermal analysis. temperature cycle. It is assumed that the concr Download With Free Trial cycles about the average annual Material properties are generally estimated from temperature published data in sources such as American Contemperature.  crete Institute (ACI) documents, technical publicaRead Free Foron 30this Days Sign up to vote title  ch tions, and engineering handbooks. Often known (c) Determine long-term temperature Useful  Not useful  Cancel anytime. information such as compressive strength and The sum of the placing temperature plus adi Special offer foraggregate students: type Only is $4.99/month. used to predict other material temperature rise provides a quick peak tempe properties from published data. The minimum of the MCS Then subtracting the ultimate sta


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ETL 1110-2-542 30 May 97

foundation restraint factor (K )(in ACI 207.2R f termed “Multiplier for foundation rigidity”) are determined as described in Appendix A, and in ACI 207.2R. (b) Determine mass gradient thermal strain. The total induced strain is the product of the longterm temperature change, the coefficient of thermal expansion and restraint factors. Use Equation A-4 (Appendix A).

placement temperature limitations, anticipat concrete precooling measures, need for adjus in concrete properties, joint spacing, and sen of the thermal analysis to changes in param

A2-2. Example

a. Introduction. This example, based on thermal study for the Cache Creek Detentio Weir, illustrates one way to estimate concrete Total strain = (Cth) (dT) (K R) (K f) ing temperature based on ambient air tempe (A-4bis) and material processing schemes and schedules where The study evaluates mass gradient cracking The Cache Creek Detention Basin in California Total strain = induced strain (millionths) roller-compacted concrete (RCC) overflow section in a levee system. The structure is 8 m C th = coefficient of thermal expansion (15 ft) high, 3.6 m (12 ft) wide at the top, has 1 slopes upstream and downstream, and is 530 dT = temperature differential (1,740 ft) long. Compacted sands and silts placed against the full height of the upstream f K R = structure restraint factor The purpose of the study was to determine t of contraction joints spaced at 30-m (10 You're Readingquacy a Preview K f = foundation restraint factor intervals and, if necessary, provide recomme Unlock full access with a free tions fortrial. alternate configurations. Also address Cracking strain is computed by subtracting tensile the adequacy of a maximum placing temper strain capacity from the total strain. TheDownload remainder With29 deg Trial C (85 deg F) for the RCC. The followi Free is the strain that must be accomodated in cracks at paragraphs provide explanation on the selecti some spacing and width across the MCS. criteria and determination of the parameters  Read Free For 30this Days Signthermal up to vote on title summarize study.  (c) Estimate mass gradient cracking. FoundaNot useful  Useful  Cancel anytime. conditions (restraint) control the spacing of b. Input properties and parameters. Special offer fortion students: Only $4.99/month. cracks and the crack width. If the foundation is


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ETL 111030 M Table A2-1 NOAA Temperature Data, Woodland, CA Month

Monthly avg. max. - deg C (deg F)

Monthly avg. min. - deg C (deg F)

Monthly avg. -deg C (deg F)

Jan

11.7 (53)

2.8 (37)

7.2 (45)

Feb

15.5 (60)

4.4 (40)

10.0 (50)

Mar

18.9 (66)

5.5 (42)

12.2 (54)

Apr

23.3 (74)

7.2 (45)

15.0 (59)

May

27.8 (82)

10.0 (50)

18.9 (66)

Jun

32.2 (90)

12.8 (55)

22.8 (73)

138 kg/m3 (233 lb/cy) equiv. ceme 28 days = (36.1 deg C)(138)/(223) = 22.2 deg C (40 deg F) )t ad for

(c) Tensile strain capacity. ACI 207.5R s gests that values of tensile strain capacity rang from 50 to 200 millionths are achievable for ea age, slow-load testing. Lean RCC mixes typic range from 60 to 90 millionths. Since the cem content of 119 kg/m3 (200 lb/cy) is higher th most lean RCC mixes and the coarse aggregate crushed, a value of 80 millionths was selected.

(3) Step 3: Determine construction param RCC placing temperature was calculated using Jul 35.5 (96) 13.9 (57) 25.0 (77) average annual temperature modified by rule-o Aug 34.4 (94) 13.3 (56) 23.9 (75) thumb temperature effects during construction, Sep 32.2 (90) 12.2 (54) 22.2 (72) shown in Table A2-2. In Table A2-2, the plac temperature is the composite temperature of th Oct 26.1 (79) 9.4 (49) 17.8 (64) aggregate source, (assumed to be the average a Nov 18.3 (65) 5.5 (42) 11.7 (53) temperature), plus the added heat during aggre production, plus the added heat during RCC pr Dec 12.2 (54) 2.8 (37) 7.8 (46) duction. Stockpile aggregate temperatures are You're Annual 16.1 (61)Reading a Preview base temperature, plus the ambient addition, p Unlock full access with a free trial. crushing and production energy. Similarly, RC production temperatures are the stockpile temp meta-sandstone aggregate concrete planned for the plus ambient additions and mixer energy a Download Withture Free Trial project: tions. The ambient temperature additions are calculated as 0.67, an empirical correction fact  Read Free For 30 Days Sign up to vote on this title C th = 9.9 millionths/deg C (5.5 millionths/ times the differential temperature of theaggreg deg F) and the air.Useful The complete useful study is sum  Not thermal Cancel anytime. rized in Table A2-3. A May placing temperatu Special offer for students: Only $4.99/month. was used for following calculations: (b) Adiabatic temperature rise. The study was


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ETL 1110-2-542 30 May 97

(b) Determine ultimate stable temperature. Since the weir is a relatively thin MCS, it is expected to develop a stable temperature cycle, rather than a single stable temperature as in larger MCS’s. The temperatures below were determined using the methodology in ACI 207.1R (“Temperature variation with depth”). Typical distance from the RCC surface to the interior was determined to be 4.6 m (15 ft). From ACI 207.1R figure:

coefficient of thermal expansion and restraint factors: Total induced strain = (Cth)() T)(K R)(K = (9.9 millionths/deg C )(29.2 deg F)(1. = 189 millionths

Temp change in concrete interior = (0.24) (17.5 deg C) = 4.2 deg C (7.6 deg F)

(c) Estimate mass gradient cracking. Th that results in cracking of the structure is the to induced strain less the tensile strain capacity ( the material. The total crack width in the length the structure is the cracking strain multiplied b length of the structure. The estimated number cracks are based on the assumed crack widths. ical crack widths range from 0.002 to 5 mm(0 0.2 in.). The larger crack widths are typical structures founded on flexible or yielding foun tions. Since such a foundation exists here, a crack width of 4 mm (0.15 in.) was assumed

Temp range in concrete interior = 16.2 ± 4.2 deg C (61.1 ± 7.6 deg F)

Cracking strain = total induced strain - , = 189 - 80 = 109 millionths

emp c ange t roug concrete = 0.24 Tem ran e at surface

Temp range at surface = 24.8 - 7.3 = 17.5 deg C (31.5 deg F)


T min = minimum interior concrete temp. = 16.2 Total crack width = (weir length)(cracki Unlock full access with astrain) free trial. - 4.2 = 12 deg C (53.5 deg F) = (530 m)(1,000 mm/m)(109 mi = 58 mm (2.3 in.) (c) Determine long-term temperatureDownload change. With Free Trial This value is simply the peak RCC placement temAssumed crack widths = 4 mm (0.15 in perature less the stable minimum temperature.  Read Free For=on 30 Days Sign up to vote title mm = 15 c Assuming a May placement: Estimated cracks 58this mm/4  Not useful  Useful  Cancel anytime. Estimated crack spacing = 530 m/15 cra )T = T p + T ad - T min = 41.1-11.9 = 29.2 deg C Special offer for students: Only $4.99/month. (53 deg F) = 35 m (116 ft)


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ETL 111030 M

70 deg F) if aggregates are produced the preceding month. If aggregate processing is performed earlier, lower placement temperatures may result. Crack spacing in an unjointed structure is calculated to be 35 m (116 ft). The 30-m (100-ft) contraction joint interval easily accommodates this volume change with joint widths of approximately 3 mm (0.13 in.). (b) June placement schedule. RCC placement temperatures should be 22.2 to 23.9 deg C (72 to 75 deg F) if aggregates are produced the preceding month. If aggregate processing is performed earlier, lower placement temperatures may result. Crack spacing in an unjointed structure is calculated to be 29 m (97 ft). The 30-m (100-ft) contraction joint interval just accommodates this volume change with joint widths of approximately 4 mm (0.15 in.).

Later placements in July and August will re occasional centerline cracking of monoliths, possibly in as many as three or four monolit Lesser cracking is very probable since mate perties were conservatively estimated. (f) Several material properties were appl conservatively. Small reductions of adiabatic perature rise and coefficient of thermal expa and small increases in tensile strain capacity improve thermal cracking performance. If e these properties were individually changed 10 cent, summer crack spacing would be around (100 ft). If these changes were cumulative, c spacing would be over 40 m (130 ft). (2) Recommendations.

(a) Maintain current 29.4-deg C (85-deg (c) July and August placement schedules. RCC maximum placement temperature limitation. placement temperatures should be 23.9 to sider allowing minor temperature violations so 26.7 deg C (75 to 80 deg F) if aggregates are proas the time weighted average of the RCC place duced the preceding month. If aggregate processing is performed earlier, lower placement temperatures You're Readingtemperature a Preview is maintained below 26.7 deg C (80 deg F). may result. Crack spacing in an unjointed structure Unlock full access with a free trial. is calculated to be 26 m (87 ft). The 30-m (100-ft) (b) Maintain current contraction joint spac contraction joint interval is not quite adequate to 30 mTrial (100 ft). The current contraction joint accommodate this volume change at a fixed joint Download WithofFree figuration of 30-m (100-ft) joint intervals is su width of 4 mm (0.15 in.). Joint widths will increase cient to accommodate the total anticipated axia or additional cracking will occur.  Read Free For 30 Days Sign up to vote on this title contractions due to cement induced temperatur  fluctuations during  May and June placements. Not useful (d) Since the anticipated period for RCC con Useful Cancel anytime. Some transverse cracking will occur during the during the late spring or summer Special offer forstruction students:isOnly $4.99/month. and August placement schedule, however the e months, the 29.4-deg C (85-deg F) placement tem-


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ETL 1110-2-542 30 May 97 Table A2-2 Cache Creek Weir Placing Temperature Computation Temperature (deg C) Factor

May

Jun

Jul

Aug

Comments

Avg. annual temperature(deg C)

16.1

16.1

16.1

16.1

Base temperature, from NOAA data

Previous month temperature

15.0

18.9

22.6

24.8

From NOAA data

Added ambient temperature

-1.1

2.8

6.5

8.7

(0.67)(Annual temp. - prev. month te

Aggregate subtotal temperature

15.4

18.0

20.5

21.9

Avg. annual temp. + added amb. tem

Added processing temperature

+1.1

+1.1

+1.1

+1.1

Processing and crushing energy

Aggregate stockpile temperature

16.5

19.1

21.6

23.0

N/A

Current ambient temperature

18.9

22.6

24.8

23.9

From NOAA data


+1.7

+2.3

+2.1

+0.6

(0.67)(Curr. Temp.-agg. stock. temp

Added mixer energy

+1.1

+1.1

+1.1

+1.1

N/A

Placement temperature

19.3

22.6

24.8

24.8

Agg. stockpile temp. + added effe

Temperature (deg F) Avg. annual temperature (deg F)

61.1

Previous month temperature

59.0


-1.4

Aggregate subtotal temperature

59.7

61.1 61.1 You're Reading a61.1 Preview 66.1

72.7

76.6

From NOAA data

3.3

7.8

10.4

(0.67)(Annual temp. - prev. month tem

Unlock full access with a free trial. 64.5 68.9 71.5 Download With Free Trial

Master your semester with Scribd & The New York Times Added processing temperature

+2.0

+2.0

+2.0

+2.0

Aggregate stockpile temperature

61.7

66.5

70.9

73.5

Current ambient temperature

66.1

72.7

76.6

75.1

+3.0

+4.2

+3.8

+1.1

Special offer for Added students: Only $4.99/month. ambient temperature

Base temperature, from NOAA data

Avg. annual temp. + added amb. tem Processing and crushing energy

Read Free Foron 30this Days Sign up toN/A vote title



data Useful From Not useful NOAA

 

Cancel anytime. (0.67)(Curr. Temp.-Agg. Stock. Tem

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ETL 111030 M Table A2-3 Cache Creek Weir Thermal Analysis Summary Temperature (deg C) Parameter

Spring (May)

Late Spring (Jun)

Summer (Jul-Aug

Temperatures RCC placement temperature (deg C)

19.4

22.8

25.0

Adiabatic temperature rise (deg C)

22.2

22.2

22.2

Peak internal temperature (deg C) (Place temp. + adiabatic temp.)

41.7

45.0

47.2

Minimum temperature (deg C) (Based on annual temp. cycle)

12.2

12.2

12.2

Differential temperature (deg C) (Peak temp. - min. temp.)

29.4

32.8

35.0

Strain development Induced strain (millionths) ( C th=9.9 millionths/deg C,

K f=0.65, K R=1.0)

189

211

225

Strain capacity (millionths)

80

80

80

Excess strain (millionths)

109

131

145

51

76

76

15

18

20


29

26

Crack distribution (length of weir = 530 m) (crack width = 4mm) Axis length contraction (mm) Number of cracks (Contraction/crack width)


Avg. crack spacing (m) (Weir length/number of cracks)

35

Temperature (deg F)


Master your semester with Scribd & The New York Times Temperatures

RCC placement temperature (deg F)

Adiabatic temperature rise (deg F)

Special offer forPeak students: $4.99/month. internalOnly temperature (deg F) (Place temp. + adiabatic temp.)

67 Read Free For73 30this Days Sign up to vote on title



40Not useful Cancel anytime.

40 Useful 107

113

77  40 117

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ETL 111030 M

ANNEX 3: LEVEL 2 THERMAL STUDY MASS GRADIENT AND SURFACE GRADIENT ANALYSIS PROCEDURE AND EXAMPLES

A3-1. Procedure a. General. This Annex summarizes typical steps in a Level 2 mass gradient and surface gradient thermal analysis of a mass concrete structure (MCS) and provides two examples of the procedure. Example 1 covers a simple one-dimensional (1-D) (strip model) finite element (FE) mass gradient and surface gradient thermal analysis. Example 2 presents a more complex two-dimensional (2-D) mass gradient and surface gradient thermal analysis. This procedure and the examples use FE methodology only because of the widespread availablility and use of this technology. Although other methods of conducting a Level 2 thermal analysis are available, these procedures are most commonly used.

foundation restraint factors. Tensile strain cap test results are important for cracking evaluatio When tensile strain capacity data are not ava the methodology presented in Annex 1 may b to estimate probable tensile strain capacity p mance of the concrete. Creep test results are sary to determine the sustained modulus of e (or an estimate of Esus is made) if stress-base ing analysis is used.

(3) Step 3: Determine construction par Construction parameters must be compiled wh include information about concrete placeme perature, structure geometry, lift height, cons tion start dates, concrete placement rates, and surface treatment such as formwork and insu that are possible during construction of the To determine concrete placement temperature, You're Reading a Preview b. Input properties and parameters. The first approximation is to assume that concre level of data detail depends on the complexity of a placement temperatures directly parallel the m Unlock full access with a free trial. Level 2 thermal analysis. Parametric analysis daily ambient temperature curve for the proj should be routinely conducted at this level, using a Actual placement temperature data from othe Download With Free Trial rational number and range of input properties and projects can be used for prediction, modified b parameters to evaluate likely thermal problems. ambient temperature data differences between  different sites. The temperature Read Free For 30this Days Sign up to vote on titleof the aggrega does (1) Step 1: Determine ambient conditions. stockpiles may change more slowly than Useful  Not useful  Cancel anytime. Level 2 analyses may be based upon average ambient temperature in the spring and fall. Special offer formonthly students:temperatures Only $4.99/month. for a less complex analysis, placement temperatures during spring months or on average expected daily temperatures for each lag several degrees below mean daily air tem


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ETL 1110-2-542 30 May 97

erally based on complexity of the structure, complexity of the construction conditions, and on the stage of project design. Often 1-D strip models are used first for parametric analyses to identify concerns for more detailed 2-D analysis. (2) Compute temperature histories. Once com puted, temperature data should be tabulated as temperature-time histories and temperature distributions to obtain good visual representations of temperature distribution in the structure. ETL 1110-2-536 has examples of temperature distribution plots. Appropriate locations can then be selected for temperature distribution histories at which mass gradient and surface gradient analysis will be conducted.

mass gradient cracking potential, using Equation A-4 in Appendix A. Computed mas dient strains are compared against tensile st capacity to evaluate cracking potential. For a stress-based mass gradient cracking analysi sustained modulus of elasticity corresponding time frame of the analysis is used to convert calculated by Equation A-4 to stresses. The us the sustained modulus allows for the relief of temperature-induced stress due to creep. Thes stresses are compared to the tensile strength of concrete at the appropriate age to determine wh and when cracking may occur.

(2) Step 8: Surface gradient cracking anal Surface gradient cracking analysis is based on higher temperature differences in the surface co crete compared to the more slowly cooling inte which creates areas of tension in the surface to depth, H . Tensile strain is calculated based the temperature difference at some depth of int and the degree of restraint based on H .

(a) Step 5: Mass gradient temperature analysis. Temperature-time histories, showing the change in temperature with time at specific locations after placing, are generally used to calculate temperature differences for mass gradient cracking analysis. Temperature differences for mass gradient cracking You're Reading a Preview (a) Temperature differences are calculated analysis are generally computed as the difference a free using as trial. a basis the temperature when the conc between the peak concrete temperatures Unlock and thefull access with first begins hardening, rather than a peak temp final stable temperatures that the cooling concrete asTrial used in mass gradient computations. will eventually reach. Download Withture Free temperature differences, with time and depth, a determination of tensile and compression (b) Step 6: Surface gradient temperature analy zone Read Free For 30 Days Sign up to vote on this title the concrete surfaces. The point at which sis. The objective of surface gradient temperature  tensi and compression zones balance usefulis considered a analysis is to determine at desired critical locations  Useful  Not Cancel anytime. stress-strain free boundary (located at H from variation of $4.99/month. surface temperatures with depth and Special offer forthe students: Only surface) used to compute restraint for surface g with time. This can be performed effectively with


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ETL 111030 M

better approximated by an earlier reference time of 0.25 or 0.33 days (6 or 8 hours). (c) Internal restraint factors, K R, are computed using Equation A-5 or A-6 in Appendix A, depending upon the ratio of L/H , where L is the horizontal distance between joints or ends of the structure, and H is the depth of the tension block. Induced tensile strains are computed at each analysis time from Equation A-8 in Appendix A using the coefficient of thermal expansion, the temperature differences between the surface and interior concrete, and the computed internal restraint factors. These strains are compared with slow load tensile strain capacity (selected or tested to correspond to the time that strains are generated) to determine cracking potential.

A3-2. Example 1: One-Dimensional Gradient and Surface Gradient Therma Analysis

a. General. An example of a 1-D mass g ent and a surface gradient analysis in a Leve mal study of an MCS is presented below. Th example is based on preliminary 1-D analyse formed during feasibility studies on a propo large flood control RCC gravity dam on the A can River in California. This dam was planne 146 m (480 ft) high, 792 m (2,600 ft) long, wi downstream face slope of 0.7H:1.0V.

(1) The 1-D analysis was used as a scre tool only, to provide preliminary evaluation eral concerns and to develop information for m detailed analyses. These studies were conducte (d) Stress-based surface gradient cracking analascertain the general extent of thermal crackin ysis is often handled in a slightly different way, (cracking due to mass thermal gradients and s particularly in the way creep is accounted for in the thermal gradients), for guidance in selecting an analysis. Commonly, incremental temperature appropriate joint spacing to accommodate tr differences at different depths and times You're are comthermal cracking, to evaluate the possi Readingverse a Preview puted. These incremental temperature differences longitudinal cracking in the structure, and for e Unlock full access with a free trial. are converted to incremental stresses, including planning and cost-estimating purposes. Figu creep effects, using the Cth, E sus, and K R. The incre1 illustrates the 1-D strip models employed i mental stresses generated during each time period Withanalysis and the overall dam proportions. Download Free Trial are summed to determine the cumulative tensile stress in the surface concrete at various depths. (2) FE analysis in this study was used only Read Free For 30 Days Sign up to vote on this title These stresses are compared to the tensile strength determine temperature history for the variou  of the concrete at the appropriate age to determine ule alternatives, using the NotFortran useful program  Useful  Cancel anytime. “THERM.” Stresses were determined by m Special offer forcracking students:potential. Only $4.99/month. computational methods, based on temperature


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ETL 1110-2-542 30 May 97



Master your semester with Scribd Figure A3-1. FE strip models & The New York Times Special offer for students: Only $4.99/month. b. Input properties and parameters. At this





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(shown in Figure A3-2) were developed, each

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ETL 111030 M

Figure A3-2. Daily ambient temperature cycles

You're Reading a Preview Table A3-1 The RCC Material Properties for Mixtures


Property

Units

Coefficient of thermal expansion ( C th)1

Damsite Alluvium

millionths/deg C Download F)With (millionths/deg

Master your semester with Scribd & The New York Times Thermal conductivity ( K ) 2

W/m-K (Btu/ft-hr-deg F) 2

2

Diffusivity (h )

m /hr (ft /hr)

Specific heat ©

kJ/kg-K (Btu/lb-deg F)

Cement content1

kg/m2 (lb/cy)

Special offer for students: Only $4.99/month.

Free Trial

Damsite Amph

7.2 (4.00) 2.42 (1.4)

2.77 (1.6)

0.038 (0.041)

 (0 0.0039

0.92 (0.22)

0.92 (0.22




6.9 (3.86)


Useful

107 (180)



107 (180)

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ETL 1110-2-542 30 May 97





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ETL 111030 M

of each year for the mass gradient analysis. For the surface gradient analysis, a 1 January start date was assumed. (b) Concrete placing temperature. The temperature of the concrete aggregates has the greatest influence on the initial temperature of the fresh RCC. Because of the low volume of mix water, and the minor temperature differential of the water com pared to the aggregate, the water temperature has a much less significant effect on overall temperature. Figure A3-4 provides the basis for the placing temperatures used in this study. Since aggregate production will be done concurrently by with RCC placement and regional temperatures tend to be moderate, stockpile temperatures should closely parallel the average monthly ambient temperatures. Some heat is added because of screening, crushing, and transportation activities, as shown in the figure, based on experience.

direction was not modeled. It is anticipated actual heat dissipation in the dam over the long will be at a more rapid rate than the model p Since RCC construction is the continuous placement of relatively thin lifts, it is best mod with elements of a height equivalent to the li height or less. Unfortunately, since the Am River Dam is a very massive structure, a mes provides ample detail would be monumental. mesh of this magnitude is not necessary for the extent of evaluations to be done at this stage. sequently, it was determined that a reasonabl mination of internal temperatures could be d using strip models. A strip model is simply a cal or horizontal “strip” of elements, usually on one element wide. Heat flows through the en the strip, but no heat flows from the sides. The model is located where necessary to simulat thermal activity at that location. While the of many factors cannot be easily modeled usin method, generalized behavior can be determine

(c) Placement Assumptions. The RCC structure will be composed of two RCC mixtures, as Reading pre(b) The primary mesh for mass gradien You're a Preview viously described. The RCC placement will be in a sis, shown in Figure A3-1, is composed of 5 a free trial. 610-mm (24-in.) lift operation. The FE Unlock modelfull is access with ments and 1,002 nodes. It simulates a strip t dimensioned having elements 305 mm (12 in.) in a cross section of the dam originating 6 m ( height. This allows future evaluations ofDownload 305-mm Withthe foundation Free Trial rock. Elements 1 to 20 form (12-in.) placing schemes, if desired. The RCC rock foundation with the bottom row of node placement was assumed to occur on a schedule of a fixed temperature of 115.5 deg C (60  deg F), Read Free For 30 Days Sign up to vote on this title 6 days per week, 20 hours per day, for the duration mean annual air temperature for the area.  An a of the placement. trary time of 30 days allowed usefulto elapse pr  Useful isNot Cancel anytime. concrete placement to allow the rock temperatu Special offer for students: Only $4.99/month. c. Temperature analysis. to stabilize.


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ETL 111030 M

(2) C ompute temperature histories. (a) Step 5: Mass gradient temperature analysis. Graphical representations for each of the four cases analyzed (one for each season) are shown in Figures A3-5 through A3-12. The first graph in each set is a time-history of nodal temperatures for selected nodes in the structure. This graph is useful to determine the time when certain zones in the structure reach certain temperatures. The second graph dis plays the maximum and minimum temperature experienced by each node. Note that these maximums and minimums occur at different times. The minimum temperatures of adjacent nodes fluctuate approximately 4 deg C (8 deg F) because of ambient temperature fluctuations. This graph is useful in determining the maximum temperature differentials, as well as determining the critical zones.

(b) Step 6: S urface gradient temperatur sis. Graphical representation of the single star case analyzed is shown in Figure A3-13, and comprised of families of curves representing perature change with time for different depths the exterior surface of the MCS. Figure A3shows these temperatures converted to a fami curves of time versus distance from the surfac the x-axis. This conversion is done to ease sequent cracking analysis computations.

d . Cracking analysis. It is assumed for th purposes of this study that the initial (baselin temperatures of the hardened RCC are those temperatures when the RCC is 24 hours old subsequent change in temperature from this forms the temperature gradient. For surface ent analysis, the shallowest interior nodes w





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ETL 1110-2-542 30 May 97



Figure A3-6. Mass gradient peak temperatures for 1 January start

Master your semester with Scribd temperatures do not change are assumed to be the & The New York Times ofOnly the stress and strain-free surface. The Special offer forlocation students: $4.99/month. distance from the surface to the location under


 

y-axis  to the right to corresponding t Useful Not useful a point Cancel anytime. appropriate foundation elevation. In this man the performance of the entire structure can be

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ETL 111030 M



Master your semester with Scribd approximately days of placement. Initial place& The New York200Times

Figure A3-7. Mass gradient temperature histories for 1 October start

for the large monoliths are performed during Special offer forments students: Only $4.99/month. the cool part of the year (winter and early spring),


 

peak occurs during theNot month of July, after useful  Useful Cancel anytime. mately 300 days of placement. Initial placem for the large monoliths are performed during th

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ETL 1110-2-542 30 May 97



Figure A3-8. Mass gradient peak temperatures for 1 October start

Master your semester with Scribd This peak occursTimes after approximately 100 days of & The New York placement (during the month of July) for the early Special offer for students: Only $4.99/month. placements; and 1 year later for the upper dam


 

(85 to  100Useful deg F) are in the part of th Not useful realized Cancel anytime. structure represented by nodes 100 to 400 and to 1000. This peak occurs during the month o

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ETL 111030 M

You're Reading a Preview Unlock full access with a free trial. Figure A3-9. Mass gradient temperature histories for With 1 JulyFree startTrial Download

Master your semester with Scribd schedule evaluated, the nodes and the node loca& The New York Times whereOnly mass gradient thermal cracking is Special offer fortions students: $4.99/month. expected. The “Height Above Foundation” refers


 

placing temperatures, peak temperatures f Useful with Not useful Cancel anytime. those placements of less than 29.4 deg C (85 deg F). Spring and summer placements

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ETL 1110-2-542 30 May 97

You're Reading a Preview Unlock full access with a free trial. Figure A3-10. Mass gradient peak temperatures for 1With July start Download Free

Master your semester with Scribd cracking may occur. As construction progresses, placement of smaller RCC sections (those place& The New York Times founded rock at higher elevations) during Special offer forments students: Only on $4.99/month. hot periods is unavoidable. Longitudinal cracking

Trial

 Read Free For 30 Days Sign up to vote on this title concrete properties with age, such as E and  cre well as changing and H dimensions of the su Useful h  Not useful Cancel anytime. gradient tension block with time.

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ETL 111030 M



Figure A3-11. Mass gradient temperature histories for 1 April start

Master your semester with Scribd change,York measuredTimes from the baseline temperature, & The New

0. Figure A3-15 shows the temperature Special offer forapproaches students: Only $4.99/month. deviations (dT ) from the baseline temperature, as


 

strain-free surface at each time Notincremental useful  Useful Cancel anytime. and is determined from the Temperature Dif Table in Figure A3-15 (note H for each age inc

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ETL 1110-2-542 30 May 97



Figure A3-12. Mass gradient peak temperatures for 1 April start

Master your semester with Scribd From Figure Times A3-15 and similar computations & The New York 30-andOnly 61-m$4.99/month. (100- and 200-ft) joint spacings, Special offer forfor students: the computations indicate that surface cracking is


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optimum Useful for Notproject useful based on th  spacing this Cancel anytime. occurrence of surface cracking. Evaluation combined effects of surface gradient strains w

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ETL 111030 M

85 80 75 70 e r u t a r e p m e T

65 60 RCC Day 0 = 1 55

January

Approx.

50 45 40 0

50

100

150

200

250

300

350

400

Time (days) ( N 4 ) D e p t h =1 1. 3 m (3 7 f t )

( N 1 8) De p th = 9. 1 m (3 0 f t )

( N 3 8) De pt h= 6m (2 0 f t )

(N58) Depth=3m(10 ft)

(N6 8) Dep th=1 .5 m(5 ft)

(N80) Dep th=.15m (6in)

Figure A3-13. Temperature history for selected nodes from surface gradient model



40 ft) of the structure for sections of the dam h increases. After evaluating several placing schedupstream-downstream dimension greater th ules, it was apparent that the most beneficial condi- Withan Download Free Trial 61 m (200 ft). Since the occurrence of a longit tions occurred when the RCC placement of the nal crack could create serious stability lower third of the dam commenced in the fall of the concern Read Free For 30 Days Sign up to vote on this title more rigorous analyses coupling the effects year and was completed during late spring. This  of simultaneous loadings are necessary to better e useful means that, for the larger dam sections, the upper  Useful  Not Cancel anytime. ate the extent of cracking. would then be placed during a hotter Special offer fortwo-thirds students: Only $4.99/month. time period. The reduction in foundation restraint


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ETL 1110-2-542 30 May 97




Figure A3-14. Surface gradient temperature distribution

Completion of RCC placements up to a miniSpecial offer for students: Only $4.99/month. mum elevation during a fall and winter time period


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Useful  Not useful Cancel anytime. Full-section modeling, incorporating foundat properties, restraint conditions, and early-ag

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ETL 111030 M Table A3-2 Summary of Locations of Mass Gradient Thermal Cracks Schedule

Peak Temp deg C (deg F)

Critical Nodes

Height Above Foundation, m (ft)

Jan

37.8 (100)

200-400

27 - 73 (90-240)

Oct

37.8 (100)

300-900

43 - 134 (140-440)

July

37.8 (100)

50-200 and 500-1000

April

37.8 (100)

100-400 and 800-1000

A3-3. Example 2: Two-Dimensional Mass Gradient and Surface Gradient Thermal Analysis

73 - 146 (240-480) 12 - 49 (40-160) and near top o

b. Input properties and parameters.

(1) Step 1: Determine ambient conditions These data were gathered from local records. Ambient temperature data are shown in Figure A3-17.

a. General. An example of each step in the performance of a relatively complex mass gradient and a surface gradient analysis in a Level 2 thermal study of an MCS is presented. This example is (2) Step 2: Determine material propert based on 2-D analyses performed during design Table A3-3 contains thermal properties used in studies for locks and dam facilities on the Mononexample thermal analysis. Adiabatic tempera gahela River in Pennsylvania. These studies were rise is shown in Figure A3-18. This adiabatic conducted to maximize lift heights and determine rise is characteristic of the heat gen You're Readingperature a Preview optimum placement temperatures, to expedite conof an exterior concrete in a mass concrete str Unlock full access with free trial. struction and minimize costs. Although numerous anda is not characteristic of interior mass conc lock monolith configurations exist in the project, the The foundation material is assumed to be lime most massive section was selected for analysis. moderate Download WithofFree Trial strength. Table A3-4 contains Conclusions and recommendations from this analyical properties used in the example thermal sis could be applied to the other project monoliths. modulus of elasticity of concrete and foundatio Read Free Foron 30this Days Sign up to vote title Figure A3-16 shows a cross section representation materials are required for determinationof fo Not useful tensile stra  Useful Slow-load of the geometry of a river wall monolith with nomition restraint factors. Cancel anytime. Special offer fornal students: Only $4.99/month. 3-m (10-ft) lifts used in this example analysis. pacity values were developed using Annex 1 Two-dimensional FE analysis was used to deterodology for use in mass and surface gradient c


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ETL 1110-2-542 30 May 97





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ETL 111030 M



Master your semester with Scribd Figure A3-16. Lock wall section used in example & The New York Times Special offer for students: Only $4.99/month.

follow mean daily temperatures, except during


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Temperature Analysis.

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ETL 110-2-542 30 May 97

27

(80) 1 July placement start

21

(70)

15

(60)

10

(50)

4

(40)

Maximum placement temperature

Concrete Placement Temperatures Mean Daily Temperatures

(30)

-1

Minimum placement temperature

-7 1/1

1/31

3/1

3/31

4/30

5/30

6/29

7/29

8/28

9/27

10/27

11/26

12/26

Date

Figure A3-17. Mean daily ambient temperatures concrete placement temperatures You're and Reading a Preview


Table A3-3 Concrete and Foundation Thermal Properties Download With Free Trial

Master your semester with Scribd & The New York Times Material

Thermal Conductivity W/m-K (Btu/hr-ft-deg F) (Btu/day-in-deg F)

Limestone 0.86 (0.500)(1.000) foundation Only $4.99/month. Special offer for students: Exterior con-

Coefficient of Th Specific Heat Expansion  millio Read Free Foron 30this Days Sign up toF)vote title kJ/kg-K (Btu/lb-deg deg C (millionths 



0.96 (0.230)

Useful

 Not useful

Cancel anytime.

9.90 (5.50)

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ETL 111030 M

70 60 50 40 30 20 Note: exterior mix concrete used in example; not typical of mass concrete.

10 0 0

10

20

30

40

50

60

70

Age (days)

Figure A3-18. Adiabatic temperature rise for Level 2 thermal analysis 2-D example

Table A3-4 You're Reading a Preview Concrete and Foundation Mechanical Properties Material

DensityUnlock full access with Compressive a free trial. Strength

Modulus of Ela

kg/m3 (lb/ft3)

GPa (x 106 ps

Mpa (psi)

Limestone

Download 2,563 (160)

Exterior concrete @ 1 day

2,243 (140)

3.93 (570)

Exterior concrete @ 3 days

same

7.65 (1,110)


same

 Useful  Not useful23.44 (3.40) 11.24 (1,630)Cancel anytime.


same

22.48 (3,260)


With Free 103.4Trial (15,000)

48.26 (7.00) 12.41 (1.80)



Read Free Foron 30this Days Sign up to vote title20.20 (2.93) 

33.65 (4.88)

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ETL 110-2-542 30 May 97

You're Reading a Preview Unlock full access with a free trial. Figure A3-19. Finite element model of lock wall example


Master your semester with Scribd Table A3-5 Read Free Foron 30this Days Sign up to vote title Summary of Surface Heat Transfer Coefficients For FE Thermal Analyses & The New York Times  Useful  Not useful Surface Heat Transfer Coefficient Cancel anytime. W/m 2-K (Btu/day-in2 -deg F)

Wind Velocity

Special offer for students: Only $4.99/month. Time Span

km/h

Wind Velocity

Wind Velocity &

Wind Velocity &

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h

Air Plywood

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ETL 111030 M

Figure A3-20. Typical temperature histories at locations of mass gradient analysis

(c) De Determine temperature change or differences relative to the reference temperatures. Tabl Tablee A3-7 A3-7 sho shows ws dis distr trib ibut utio ions ns of of temp temper erat atur uree difdifferenc ferencee at all all analys analysis is times times rela relative tive to the the refer referenc encee temperatures at 0.5 days age of lift 6 (25.5 days after lift 1). These are developed by subtracting all of the temperatures in Table A3-6 from the respective 0.5-day temperatures at the same horizontal coordinates. Special offer for students: Only $4.99/month.


temperature, T , T 0, is determined such that the are the normalized temperature distribution above belo below w T 0 are equal. Table A3-9 and Figure show balanc balanced, ed, norm normaliz alized ed tempe temperat rature ure differ differ

epth of (f) The depth of T0 defines defines the the d Read Free For 30 Days Sign up to vote on this title the tension block. A formula for the sums  of Useful Not useful points of  temperature vidual  areas between Cancel anytime. malized temperature difference distribution acr section above and below T 0 was used for the de

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ETL 110-2-542 30 May 97 Table A3-6 Temperature Temperature Distributions in Lift 6 for Surface Gradient Analysis Degrees C

Degrees F



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ETL 111030 M

Figure A3-21. Temperature distributions across lift 6 used in surface surface gradient analysis

stif stifffness of the found undation tion mater terial and the the cononcret crete, e, is comp comput uted ed from from Equa Equati tion on A-7 A-7 in in App Appen en-dix A as shown below.

1 Master your K = semester = 0.64 0.64 with Scribd A E 1 & The New York A E Times f

%

g c

f f

Special offer for students: Only $4.99/month.

(b) Stru Strucctur ture restr strain aint factor tor ( K R). Structu rest restra rain intt fac facto tors rs are are com compu pute ted d at at dis dista tanc nces es,, the vertical centerline of the structure at h = (11.5 ft) and at h = H = H = 7.0 m (23 ft) at the bas the culvert. The length, L length, L,, of the structure is assumed to be 13.4 m (44 ft) in the axial  direct Read Free For 30 Days Sign up to vote on this title Note that that the mass mass gradient gradient analysis analysis shown  assumes the foundation restraint is applied Useful Not useful that  Cancel anytime. the foundation material adjacent to the concrete Therefore, the foundation temperatures used in

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ETL 110-2-542 30 May 97 Table A3-7 Temperature Differences Referenced to Temperature at 0.5 Days Degrees C

You're Reading a Preview Unlock full access with a free trial. Degrees F




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ETL 111030 M Table A3-8 Temperature Differences Normalized in Reference to Surface Temperature Differences For Surface Gradient Analysis Degrees C

You're Reading a Preview Unlock full access with a free trial. Degrees F Download With Free Trial



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ETL 110-2-542 30 May 97

Figure A3-22. Temperature differences in lift 6 for surface gradient analysis

You're Reading a Preview where

Unlock full access with a(2) free Step trial. 8: Surface gradient cracking a

Table A3-11 presents the surface gradient crac L/H = 13.4 m/7.0 m [44 ft / 23 ft] = Download 1.9 Withcalculations. Free Trial The upper portion of the table the determination of restraint factors based on h/H = 3.5 m/ 7.0 m [11.5 ft / 23 ft] = 0.5 and location. The lower portion shows calcu Read Free For 30 Days Sign up to vote on this title of strains using Equation A-8 from Appendix A  (c) Calculate tensile strains. and comparison of  calculate strains with slo Not useful  Useful Cancel anytime. TSC values for the appropriate time period. Special offer for students: Only $4.99/month. , = (Cth )(dT)(K R) = 41 millionths ure A3-24 compares the development of ten


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ETL 111030 M

Table A3-9 Balanced or Effective Temperature Differences to Determine “ H” and Surface Gradients Strains Degrees C

You're Reading a Preview Unlock full access with a free trial. Degrees F




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ETL 110-2-542 30 May 97

Figure A3-23. Balanced temperature difference distributions in lift 6 for surface gradient analysis


Unlock full access with a free trial. (b) Calculate tensile strains. Surface gradient each time period. These are shown on Table tensile strains shown on Table A3-11, are based on for each lock wall face. For this example, on the use of Equation A-8 (Appendix A), shown at the exterior surface are calculated Download Withstrains Free Trial below: hown on Table A3-11. Exterior surface strain shown in this Table for K R = 1.0, for  comparis Read Free For 30 Days Sign up to vote on this title assuming the surface is completely restrained,  , = (Cth )(dT)(K R) (A-8) for various lengths  ( L =Not 11.0, 12.2, and 13.4 m useful  Useful Cancel anytime. 36, 40, and 44 ft) between vertical joints in the Special offer for students: Only $4.99/month. where wall, where the surface restraint is less than


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ETL 111030 M Table A3-10 Mass Gradient Cracking Aanalysis 1 July start, 15.5 deg C (60 deg F) placement temperature, no insulation, exterior mix Rock/Concrete Interface (Node 1925)

Analysis Location/ Node No. T(max)

T(min)

dT ©

T(max)

T(min)

deg C (deg F)

deg C (deg F)

deg C (deg F)

deg C (deg F)

A / 1910

47.8 (118)

12.8 (55)

35.0 (63)

B / 1498

26.1 (79)

-0.6 (31)

26.7 (48)

dT = dT (c)-

Restraint Factor

dT (r)

K r

deg C deg C (deg F) (deg F)

deg C (deg F)

K f =

36.1 (97)

15.0 (59)

21.1 (38)

13.9 (25)

33.3 (92)

25.5 (78)

7.8 (14)

18.9 (34)

dT (r)

Thermal Strain

Slow Load TSC

millionths

millionths

0.28

41

144

0.08

16

144

0.64

Table A3-11 Surface Gradient Cracking Analysis





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ETL 110-2-542 30 May 97

Figure A3-24. Evaluation of surface gradient cracking potential by comparing induced tensile strain wit load tensile strain capacity



(3) Conduct additional mixture proportioning (6) Open culvert space to cool air slowly studies to further reduce the cement content. Download Withavoid Free thermal Trial shock.

Master your semester withsurfaces Scribd (4) Insulate all exposed concrete placed between 15 October and 1 March. & The New York Times (5) Remove insulation only when ambient temSpecial offer for students: Only $4.99/month. peratures are above mean daily temperatures, to aid


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ETL 1111030 M

ANNEX 4: LIST OF REFERENCES

A4-1. Cited References a. U.S. Army Corps of Engineers. ER 1110-2-1150 ER 1110-2-1150, Engineering and Design for Civil Works Projects. EM 1110-2-2000 EM 1110-2-2000, Standard Practice for Concrete for Civil Works Structures. EM 1110-2-2006 EM 1110-2-2006, Roller Compacted Concrete. EM 1110-2-2200 EM 1110-2-2200, Gravity Dam Design. EM 1110-2-2201 EM 1110-2-2201, Arch Dam Design.

U.S. Army Engineer Waterways Experimen Station 1949 U.S. Army Engineer Waterways Experimen Station. 1949. Handbook for Concrete and Cement (with periodic supplements), Vicksbu MS.

Designation CRD C 16-94 Designation CRD C 16-94, “Standard Test Me for Flexural Strength of Concrete (Using Simp Beam with Third-Point Loading).” (ASTM C 78-94)

Designation CRD C 19-94 Designation CRD C 19-94, “Standard Test Me for Static Modulus of Elasticity and Poisson’s of Concrete in Compression.” (ASTM C 469

Designation CRD C 23-91 You're ReadingDesignation a Preview CRD C 23-91, “Standard Test Me for Specific Gravity, Absorption and Voids in Hardened Concrete.” (ASTM C 642-90) Unlock full access with a free trial.

ETL 1110-2-254 Designation CRD C 36-73 ETL 1110-2-254, Finite Element AnalysisDownload WithDesignation Free Trial CRD C 36-73, “Method of Test fo Interpretation and Documentation Guidelines. Thermal Diffusivity of Concrete.”  Read Free Foron 30this Days Sign up to vote title ETL 1110-2-332  Designation CRD C 37-73 Useful  Not useful ETL 1110-2-332, Modeling of Structures For  Cancel C anytime. Designation CRD 37-73, “Method of Test fo Elastic Element Analysis. Special offer forLinear students: OnlyFinite $4.99/month. Thermal Diffusivity of Mass Concrete.”


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ETL 1110-2-542 30 May 97

Designation CRD C 71-80 Designation CRD C 71-80, “Standard Test Method for Ultimate Tensile Strain Capacity of Concrete.”

ACI 207.4R-93 ACI 207.4R-93, “Cooling and Insulating Syst for Mass Concrete,” Part 1.

Designation CRD C 77-91 Designation CRD C 77-91, “Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens.” (ASTM C 496-90)

ACI 207.5R-89 ACI 207.5R-89, “Roller Compacted Mass Co crete,” Part 1.

Designation CRD C 124-73 Designation CRD C 124-73, “Method of Test for Specific Heat Aggregates, Concrete, and other Materials (Method of Mixtures).”

American Society for Testing and Material 1992 American Society for Testing and Materials 1992 Annual Book of ASTM Standards, Philadelphia, PA.

Designation CRD C 158-93 Designation CRD C 158-93, “Standard Test Method for Determining the Mechanical Properties of Hardened Concrete Under Triaxial Loads.”

Designation D 3148-86 Designation D 3148-86, “Test Method for E Moduli of Intact Rock Core Specimens in Unia Compression.”

Designation CRD C 164-92 Designation D 4535-85 Designation CRD C 164-92, “Standard Test Designation D 4535-85, “Test Method for Method for Direct Tensile Strength of Cylindrical Measurement of the Thermal Expansion of Concrete or Mortar Specimens.” a Dilatometer.” You're ReadingUsing a Preview

Unlock full access with a free trial. U.S. Army Engineer Waterways Experiment Station 1990 Other cited references. U.S. Army Engineer Waterways Experiment Download With Free Trial Station. 1990. Rock Testing Handbook (with American Society of Heating, Refrigerating periodic supplements), Vicksburg, MS. Air-Conditioning Engineers 1977  Read Free For 30this Days Sign up to vote on title American Society of Heating, Refrigerating  an Air-Conditioning Engineers. 1977. ASHRAE American Concrete Institute  Useful  Not useful Cancel anytime. American Concrete Institute. 1993. ACI Manual Handbook and Product Directory - 1977 Special offer for students: Only $4.99/month. of Concrete Practice; Detroit, MI. Fundamentals, New York, NY.


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ETL 1111030 M

Hibbitt, Karlsson, and Sorensen 1994 Hibbitt, Karlsson, and Sorensen. 1994. ABAQUS User's Manual, Version 5.3., Pawtucket, RI. Houghton 1976 Houghton, D. L. 1976. “Determining Tensile Strain Capacity of Mass Concrete.” ACI Journal Proceedings, Vol 73, No. 12, 1976, pp 691-700. Hunt 1986 Hunt, R. E. 1986. Geotechnical Engineering Techniques and Practices, McGraw-Hill, New York. Jumikis 1977 Jumikis, A. R. 1977. Thermal Geotechnics, Rutgers University Press, New Brunswick, NJ.

Wilson 1968 Wilson, E. L. 1968. “The Determination of Temperatures within Mass Concrete Structu SESM Report No. 68-17, University of Califo Berkeley, 33 pp.

A4-2. Supplemental References.

Barrett, Foadian, James, and Rashid Barrett, P. R., Foadian, H., James, R. J., Rashid, Y. R. “Thermal-Structural Analysis Methods for RCC Dams,” Roller Compacted Concrete - III , American Society of Civil Engineers, New York, pp 407-422.

Burks 1947 Burks, S.D. 1947. “Five-Year Temperature Records of a Thin Concrete Dam, “ ACI Journ Proceedings, Vol 44, No. 1, Detroit, MI, pp 65

Kersten 1949 Kersten, M. S. 1949. Laboratory Research for the Determination of the Thermal Propert ies of Soils, Engineering Experiment Station, University Calvo, Sudón, and Pfeiffer 1995 of Minnesota, Minneapolis, MN. J., Sudón, J., and Pfeiffer, G. 1995. You're ReadingCalvo, a Preview “Thermal Analysis of RCC Dams Methodolog Unlock full access with a free trial.to Cenza Dam,” Roller Compacte Application Polivka and Wilson 1976 Polivka, R. M., and Wilson, E. L. 1976. “Finite Concrete Dams, Proceedings of the Internatio Element Analysis of Nonlinear Heat Transfer Download WithSymposium, Free Trial pp 575-589. Problems,” SESM Report No. 76-2, University of California, Berkeley. Carlson, Houghton, and Polivka 1979  Read Free Foron 30this Days Sign up toHoughton, vote Carlson, R. W., D.title L., and Polivka,  1979.  “Causes Control of Cracking in Usefuland Not useful Rawhouser 1945 Cancel anytime. C. $4.99/month. 1945. “Cracking and Temperature forced Mass Concrete,” ACI Journal Proceedi Special offer forRawhouser, students: Only Control of Mass Concrete,” ACI Journal Vol 76, No. 7, pp 821-837.


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ETL 1110-2-542 30 May 97

Dusinberre, 1945 Dusinberre, D.M. 1945. “Numerical Methods for Transient Heat Flow,” Transactions American Society of Mechanical Engineers, Vol 67, pp 703772.

Klein, Pirtz, and Adams, 1963 Klein, A., Pirtz, D., and Adams, R. 1963. “Thermal Properties of Mass Concrete During Adiabatic Curing,” Symposium on Mass Conc ACI Special Publication SP-6, American Co Institute, Detroit, MI, pp 199-218.

Fujisawa and Nagayama 1985 Fujisawa, T., and Nagayama, I. 1985. “Cause and Control of Cracks By Thermal Stress in Concrete Dams,” Transactions 15th International Congress on Large Dams (Lausanne 1985), International Commission on Large Dams, Paris, pp 117-142.

Liu and McDonald 1978 Liu, T. C., and McDonald, J. E. 1978. “Pre of Tensile Strain Capacity of Mass Concrete,” Journal Proceedings, Vol 75, No. 5, Detroit, M pp 192-197.

Garner and Hammons 1991 Garner, S., and Hammons, M. 1991. “Development and Implementation of Time-Dependent Cracking Material Model for Concrete, “ Technical Report SL-91-7 , U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, pp 44.

Mead Mead, A. R. “Temperature-Instrumentation Observations at Pine Flat Dam and Folsom D Symposium on Mass Concrete, ACI Special Publication SP-6, American Concrete Institu Detroit, MI, pp 151-178.

Giménez and Fernández 1995 Neville 1981 Giménez, E. C., and Fernández, J. 1995. Neville, A. M. 1981. Properties of Concrete “Prediction of the Thermal State of Dams UsingReadingWiley, New York. You're a Preview Mathematical Models - Application to the Algar Unlock full access with a free trial. Dam (Valencia, Spain), “ Roller Compacted Norman and Anderson 1985 Concrete Dams, Proceedings of the International Norman, C. D., and Anderson, F. A. 1985. Symposium, pp 591-609. Download With“Reanalysis Free Trial of Cracking in Large Concrete Da the US Army Corps of Engineers,” Transactio 15th International Congress on Large Hinks and Copley 1995  Dams Read Free For 30 Days Sign up to vote on this title Hinks, J. L., and Copley, A. F. 1995. “Thermal (Lausanne 1985), Proceedings, International  Analysis For RCC Dams,” Roller Compacted Commission on Large Dams, Paris, pp 157-17 Not useful  Useful  Cancel anytime. Proceedings of the International Special offer forConcrete students:Dams, Only $4.99/month. Symposium, pp 473-484. Polivka, Pirtz, and Adams 1963


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ETL 1110-2-542 Thermal Studies of Mass Concrete Structures

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