设计成果外文翻译

1、CHANGCINSTITUTE OF TECHNOLOGY 混凝土施工事项：学赵CHANGCINSTITUTE OF TECHNOLOGY 混凝土施工事项：学赵：讲师ConcreteConstructionT.Pauly,M.J.N.ermsof accepted, ConcreteConstructionT.Pauly,M.J.N.ermsof accepted, concreteconstructionoperationsleavemuchbedesiredwithrespecttothequality,serviceability,andsafetyofcompletedstructur

2、es.The ings of these operations became abundantly clear when a magnitude 7.6 earthquakestrucknorthernPaki-stanonOctober8,2005,destroyingthousandsofdamaging bridges,and killingan esti-mated 79,000 people.The unusually lowquality constructionoperationsprevalentwasamajorcauseoftheimmense Theconcretesti

3、rringandmixingmakesandSince the concrete requirest higher closely knit ,reason why stir and mix system also need to have the fairly good homogeneity , should be ready for burning as almostforthis1)etmixingtime,mixingateverytimearesecondaryoaexpectgeneral ejection ofcompact block ofwoodn2 2)shoulduse

4、theitionagent,thesolutionqueenwhoshouldmanufacturethickness from ition agent adds the mixer inner, the der or concentration solution will add an agent extranot to adds the mixer inner directly,prevent frommixingisunevenbutpartconcentrates,bothlosetheitionagenteffect,andconcrete3) responds to the red

5、 source of life degree having a spot test on admeasurement concrete at the ervals collapsing in the s being construction , construction is middle if Yu rains or other cause, respond admeasurement concrete at the ervals collapsing in the s being construction , construction is middle if Yu rains or ot

6、her cause, respond to the determining whose water ratio, and adjusting theition being under construction timewhenchangehappenedinsandstonemoisture4) project uses the commodity concrete, has boundary have raised a concrete massandofallkindseffectitionagentadulteratingfallswhenamounts,thewaterhavingco

7、ntrolledaconcretestrictly5) concretes concrete adopt a pump to have given handicraft , effective avoiding concrete producing the phenomenon isolating Mi Shui and leaving out thick sofIfconcreteishesurface,thesur-houldbefilledwithwatertoprevent itfromabsorbingtheconcreteofitswater. Iffresh concreteis

8、tobeplaced onnearby to y,preferablys solidified, the surface of the placed concrete should be reairorwaterjetorsteel-wirebrushes.Theshould be wet, but thereshould be no muchwater. Aty of cement grout be brushed over the whole area, and then followed y with the application of 1/2-inLayer of mortar.Th

9、efreshconcreteshouldbeplaced onoragainst theIn order to decrease the egration re-sulting from carriage after it is placed. con-crete should be placed as nearly as probably in its final . It should be placed layerstopermituniformcompaction.Thentheplacingoflayersbe limited toreperfectbondnthefresh and

10、previously placed In placing concrete in atters, a should be used to limit the free fall not over 3 or 4 ft, in order to prevent concrete egra-tion.Theisa pipe made lightweight metal, having adjustable lengths and attached to the bottom of a which the concrete is ited. As the patters are filled, sec

11、tions of the pipe may yaftertheconcreteisplaced,itshouldbecompactedbyhandpuddingorme-chanical vibrator to eliminate voids. The vibrator should be left in ition long enough to reduce the concrete around itme-chanical vibrator to eliminate voids. The vibrator should be left in ition long enough to red

12、uce the concrete around it to a plastic mass; then the vibrator should moved,oregra-tionoftheaggregatewilloccur.Ingeneral,thevibratorshouldnotpermitted topenetrate hepriorThe mainly advantage of vibrating t it permits the use of a drier concrete, has a higher strength because of the reduced water co

13、ntent. Among the advantages vibrating con-crete are the1. The decreased ermits a lesscementpasteishe cement and fine aggregate ThelowerwatercontentdecreasesshrinkageandThedrierconcretedecreasesthecostoffinishingthe4. Mechanical vibration mayreplacethreetond Thelowerwatercontentincreasesthestrengthof

14、theThedriermixturepermitstheremovalofsomepattersmorequickly, whi reduce the cost of patters.If concreteisto gainumndotherdesirableproperties,itshouldcured with adequate moisture and at a favorable tem-perature. Failure to provide these conditions may result in an inferior concrete.Theinitialmoisture

15、inconcreteisadequatetohydrateallthecement,provideditisshould replace the t does evaporate. This may plished by methods, such as leaving the patters in place, ng the surface wet, or covering surface liquidcuring compound, whichcomes being to awater-tight tprevents the of the initial water. Curing com

16、pounds may be d by brushes resprayers. A gallonwill cover200to 300sq Concreteshouldbeplacedemperaturenotn40orn80F.Atem-perature will decrease therateof setting, while a higher temperature willdecrease ultimate Practice has proved , the common crack of concrete , most is the surface crack of differen

17、tdepth,mainreasonitsPractice has proved , the common crack of concrete , most is the surface crack of differentdepth,mainreasonitswhethertemperaturegradientcausecoldtemperatureoflower too easy to form crack suddenly. So say the warm - ng of the concrete lly important to preventing theearly crackof F

18、rom the of temperature stress, should reach and require to keep 1)Prevent ernal and external temperature poor and concrete gradientfrom,preventthesurface2)Prevent concrete from to be ultra and cold , should is it is it make the temperature is not n the steady temperature of concrete service time tim

19、e in concreteto try totryones3)Prevent the old concrete subcooling , in orderto reduce the restra and new concrete.among the The early enance of the concrete, the main es in ng the warm and humid condition , in order to get the result of two respects, on the other maketheconcreteavoidtheandattackoft

20、heunfavorableandwarm,humidityof , the t prevent from harmfully are cold to contract and do to contract. one hand make cement water function go on smoothly , is in the hope of reaching ensitydesignedandresistingtheabilityofThesuitablewarmconditionerrelated.Mixwarm-ngmeasurepaidcongeal often protect w

21、et results yse , water concrete include moisture can demand , cement of water have enough and to spare newly theoretically. But because reasonofevaporatingetc.oftencauseslossesofthemoisture,tponeorhinderof the cement from, the surface concrete receives this kind of adverse effect easiestly directly.

22、 Key period when ained in initial a few days after so the concrete is shouldpayattentiontoconscientiously inPlacingConcreteinColdWhentheconcreteisplacedduringcoldweather,itisusuallysarytopreheatwater, the aggregate, or both in t the ini-tial temperature will re an initial and gain in strength .Prehe

23、ating the water iswater, the aggregate, or both in t the ini-tial temperature will re an initial and gain in strength .Preheating the water is the most ef-fective method of providing sary tem-perature. For this e a water reservoir should be equipped with coilsthroughcanbepassed,maybedischargedothese

24、veraloutletsbeingusedtogivenbetterdistributionoftheWhenthetemperaturesofthemixturesareknown,somespecificchartsmaybeusedto cal-culate the temperatureofconcrete. Astraightline pass all threescales, passing every two known temperatures, will re the determina-tion of the third temperature. the surface o

25、f sand is dry, the fact lines of the scales giving the temperature of should be used. However, if the sand contains about 3 percent moisture, the dotted lines should be used.Specifications usually t freshly placed concrete shall be atemperature of not n 70Ffor 3 days or 50F for 5 days after it is pl

26、aced. propermethodmustbeprovidedtokeepthedemandedtemperaturewhenthecoldisCompared with concrete, steel is a high strength material. The useful strength ordinary reinforcing steels in as well as , i.e., the yield strength, about15timesthecompressivestrengthofcommonstructuralcon-crete,andwellover100 t

27、imes its tensile strength. On the other hand, steel is a high-cost material compared with concrete. It follow t thetwo materialsare the best used in combinationif theconcrete made to resist the compressive stresses and the compressive force, longitudinal reinforcingbarsarelocatedclosetothefacetoresi

28、sttheforce.,andadditional steel bars are so t they re-sist the inclined t caused by the shear he beams. However, rein-forcement is also used for compressiveprimarilywhereitisdesiredtoreducethecross-sectionalsmembers, he lower-floor columns of multi-story buildings. Even if such sity exits , a minimu

29、m amount of reinforce- ment is placed in all members to safeguard them against the effects of small accidental bending might crack and evenfail anunre-inforced tFor most effective reinforcing members to safeguard them against the effects of small accidental bending might crack and evenfail anunre-in

30、forced tFor most effective reinforcing action, it is t steel and concrete n the two materials to together, i. t therebe asufficientlystrong bond be-t norelativemovementsof thesteelbarsandthe surrounding concreteoccur.Thisis provided by the rela-tively large chemical whichdevelopsatthesteel-erface, b

31、y the natural roughness of the mill scale of hot-rolledrein-forcing bars, and the closely spaced rib-shap- ed surface deformations with which reinforcing bars furnished in order toprovidea highde-gree erlockingofthetwoSteel is wo different ways in con-crete structures: as reinforcing steel and prest

32、ressing steel .reinforcing steel is he forms prior to casting of the Stresses in the steel, as in the hardened concrete, are caused only by the loads on structure,exceptsibleparasiticstressesfromshrinkageorsimilarcauses.Ininpriestessesconcretestructureslargeared tothereinforcementto letting it act l

33、y withthe concreteinresisting The most common type of reinforcing steel he form of round bars, called rebars, available in a large range of diameters, from 10 to 35 mm for applications wo heavy bar sizes off 44 and 57 mm these bars are furnished surface deformations for the e of to slip be-n steel c

34、oncrete minimum requirements for these deformations have been developed experimental research. Different bar producers use different patterns, all of which satisfy these requirements.Welding of rebars in making , or for convenience in fabricating cages for placement in the forms, may etal-lurgical t

35、 reduce ndductility,andl restrictions must be placed both nd ductility, restric-tions must be placed both on the type of steel used and the lproceduresthesofASTMA706relatespecifically to In reinforced concrete a long-time trend is evident toward the use of higher materi-als, both steel and concrete.

36、 Reinforcing bars with 40ksi yield stress , almost standard 20 years ago , have largely been replaced by bars with 60ksi yield stress , both becausetheyaremoreeconomicalandbecausetheir usetendstoreducecongestion ofheformsmateri-als, both steel and concrete. Reinforcing bars with 40ksi yield stress ,

37、 almost standard 20 years ago , have largely been replaced by bars with 60ksi yield stress , both becausetheyaremoreeconomicalandbecausetheir usetendstoreducecongestion ofheformsThe ACI Code permits reinforcing steels up to Fy=80ksi. Such high strength usuallyyieldgraduallyvenoyieldhissituationtheAC

38、ICodeat the speci-fied minimum yield strength the total strain shall not exceed 0.0035 this is ne sarytomakecur-rentdesignmethods,whichweredevelopedforsharp-yieldingsteels with a yield plateau, appli-cable to such higher strength steels. there is no specification for deformed bars may be used , acco

39、rding to the ACI Code , providing meet therequirementsedunderl hishigherstrengthhasitsplace, e.g.,inlower-storycolumnsofhigh-riseInordertominimizeofrein-forcementandconsequentspelling of under sever ure ch as in bridge bjected to deicing chemicals galvanized or epoxy-coatedrebarsmaybe RepairofConcre

40、teReinforced concrete is generally a very du-rable structural material and very repairworkisusuallyneeded.However,itsdurabilitycanbeaffectedbyavarietyofincluding those of design and construction faults, use of inferior materials and ure aggressive en-vironment. The need for a repair is primarily ed

41、by the severity of deteriorationasde-terminedfromthediagnosis.Goodworkmanshipisessentialifanynjust acosmetictreatmenttothecreationis1.performancerequirementsofrepairHaving established the causes of the defect by carefully diagnosing the distress, next step should be to consider the requirements of t

42、he re-pair method effective solution to the problem (see fig.).t will offer It is important to select repair t provide adequate durability. used for therepair job should be Protectionofeast as durable as the substrate concrete to which it Theused for therepair job should be Protectionofeast as durab

43、le as the substrate concrete to which it Themechanism ofprotectionprovidedtothereinforcing dependsonthetypeofma-terials used. For le, ions materials can protect the steel from epoxy by their inhibitive effect of increasing the alkalinity of the concrete, ortars can give protection against the ingres

44、s of oxygen, moisture and harmful Bond with The bond with the substrate must produce egral repair to prevent entry moisture and atmospheric gases at y enhanced with the use of a erface. With most re-pair materials, the bond onding aid such as an un-filled epoxy systemsandslurryofPortlandcement,plusa

45、nylatexadditivesforaPortlandcement-repair system. Precautions should also be taken to remove all loose and friable ma-fromthetobebonded. al Stabilityof materials during curing should be kept to a minimum. al change should be very hesubstrateinordertopreventSome initial toEnvironmentallyIn-ducedure c

46、onditions may lead to premature damage lo repairs. le, partially cured Portland cement repairs can dete-riorate from hot preventing full hydration of the cement. To prevent this from happening extra duringcuringtimemaybeEaseofMaterialsshould be easily mixedandap-d t they can be worked osmallandvoids

47、.Ideally,thematerialshouldnotsticktotools,andshouldnoteingtrowellednorslump Thedegreetowhichtherepairmaterialshouldmatchtheexistingconcretewilldepend ontheThedegreetowhichtherepairmaterialshouldmatchtheexistingconcretewilldepend ontheuseofthestructureandthec ntsre-quirements.Asurfacecoatingmayberequ

48、ired when appearance is important or when cover to reinforcement is small.2.SelectionofRepairA suitable repair counteracts all the defi-ciencies which are relevant to the use of structure. The selection of tile correct method and material for a particular, requires careful consideration, whether to

49、meet l requirements for placing durabilityorothershort-orlong-termproperties.Thesecon-si0derationsinclude: 1）. Nature of the DistressIf alive crack is filled with a rigid material, then either the repair material eventually fail or some new cracking will occur adjacent to the original crack. Repairs live cracks must either use flexible materials modate move-ments or else