CE-307 :DESIGN OF STRUCTURES – I SLOT- 2 - IIT Bombay

CE-307 :DESIGN OF STRUCTURES – ISLOT- 2MONDAY 9.30 amTUESDAY 11.30 amWEDNESDAY 8.30 amConcretewww.civil.iitb.ac.in/ abhijit/ce307.htmCE-315: DESIGN OF STRUCTURES – I LABMONDAY 2.00 pmwww.civil.iitb.ac.in/ abhijit/ce315.htm Prof. A. Mukherjee,Civil Engineering,IITB1

Contents IntroductionConcreteDesign by working stress methodDesign by Limit state method Prof. A. Mukherjee,Civil Engineering,IITB2

Structural Analysis To determine the response of the structure underthe action of loads.Response may be displacement, internal forceslike axial force, bending moment, shear force etc.Structure geometry and material properties areknown. Prof. A. Mukherjee,Civil Engineering,IITB3

Methods of Analysis1.Manual computation methodsSlope – Deflection MethodStrain Energy MethodMoment Distribution MethodKani’s Method2.Computer MethodsMatrix MethodsFinite Element MethodFinite Difference Method Prof. A. Mukherjee,Civil Engineering,IITB4

Design ProcessPreliminary DesignAnalysisModifyDesignResponseNot SatisfactoryCheckMaterial ParameterSatisfactoryDrawing Prof. A. Mukherjee,Civil Engineering,IITB5

Structural Design Structural design is an art and science of creation,with economy and elegance, a safe, servicableand durable structure.Besides knowledge of structural engineering itrequires knowledge of practical aspects, such asrelevant codes and bye laws backed up by ampleexperience, intuition and judgment. Prof. A. Mukherjee,Civil Engineering,IITB6

Optimum DesignOptimum PointEconomySafetyCost Prof. A. Mukherjee,Civil Engineering,IITB7

Concreteconcrete Prof. A. Mukherjee,Civil Engineering,IITBbinder coarse aggregates fine aggregates waterair admixtures8

A closer lookCentimeterMicro meter Prof. A. Mukherjee,Civil Engineering,IITBMilimeterNanometer9

Coliseum of Rome Prof. A. Mukherjee,Civil Engineering,IITB10

History of concrete3000 BCThe Egyptians began to use mud mixed with straw to binddried bricks. They also used gypsum mortars and mortars oflime in the building of the pyramids800 BCThe Greeks used lime mortars that were much harder thanlater Roman mortars. This material was also in evidence inCrete and Cyprus at this time.300 BCThe Babylonians and Assyrians used bitumen to bind stonesand bricks together299 BC –476 ADThe Romans used pozzolana cement from Pozzuoli, Italynear Mt. Vesuvius to build the Roman Baths of Caracalla, theBasilica of Maxentius, the Coliseum and Pantheon in Rome.They used broken brick aggregate embedded in a mixture oflime putty with brick dust or volcanic ash by the Romans. Prof. A. Mukherjee,Civil Engineering,IITB11

History of concrete contd 1200-1500The quality of cementing materials deteriorated and even the useof concrete died out during The Middle Ages as the art of usingburning lime and pozzolan (admixture) was lost, but it was laterreintroduced in the 1300s1414Fra Giocondo used pozzolanic mortar in the pier of the Pont deNotre Dame in Paris. It is the first acknowledged use of concretein modern times1744John Smeaton discovered that combining quicklime with othermaterials created an extremely hard material that could be usedto bind together other materials.1793John Smeaton found that the calcination of limestone containingclay produced a lime that hardened under water (hydraulic lime).He used hydraulic lime to rebuild Eddystone Lighthouse inCornwall, England. Prof. A. Mukherjee,Civil Engineering,IITB12

Eddystone Lighthouse Prof. A. Mukherjee,Civil Engineering,IITB13

History of concrete contd 1813 1813Louis Vicat of France prepared artificial hydraulic lime bycalcining synthetic mixtures of limestone and clay.1816The world's first unreinforced concrete bridge was built atSouillac, France.1824Joseph Aspdin, a British bricklayer, produced and patented thefirst Portland cement, made by burning finely pulverized limeand clay at high temperatures in kilns. The sintered productwas then ground and he called it Portland cement since itlooked like the high quality building stones quarried atPortland, England1828I. K. Brunel is credited with the first engineering application ofPortland cement, which was used to fill a breach in the ThamesTunnel Prof. A. Mukherjee,Civil Engineering,IITB14

History of concrete contd 1887Henri le Chatelier of France established oxide ratios toprepare the proper amount of lime to produce Portlandcement1894Anatole de Baudot designs and builds the Church of St. Jeande Montmarte with slender concrete columns and vaults andenclosed by thin reinforced concrete walls1900Basic cement tests were standardized.1903The first concrete high rise was built in Cincinnati, Ohio.1916The Portland Cement Association was formed in Chicago. Prof. A. Mukherjee,Civil Engineering,IITB15

Hoover dam (first concrete dam) Prof. A. Mukherjee,Civil Engineering,IITB16

History of concrete contd 1917The National Bureau of Standards (now the National Bureauof standards and Technology) and the American Society forTesting Materials established a standard formula for Portlandcement.1936The first major concrete dams, Hoover Dam and GrandCoulee Dam, were built1948Pre-stressed concrete was introduced and first used in airportpavements.19701973 Prof. A. Mukherjee,Civil Engineering,IITBFiber reinforcement in concrete was introduced.The Opera House in Sydney, Australia was opened. Itsdistinctive concrete peaks quickly became a symbol for thecity.17

Opera house (Sydney) Prof. A. Mukherjee,Civil Engineering,IITB18

History of concrete contd 1980Superplasticizers were introduced as admixtures1985Silica fume was introduced as a pozzolanic additive.1992The tallest reinforced concrete building in the world wasconstructed at 311 South Wacker Drive in Chicago, Illinois.This was later surpassed by the Petronas Tower,Kualalumpur.1993The J. F. K. Museum in Boston, Massachusetts wascompleted. The dramatic concrete and glass structure wasdesigned by renowned architect I. M. Pei. Prof. A. Mukherjee,Civil Engineering,IITB19

Petronas TowerConcrete(various strength upto grade 0)160,000 cu m in thesuperstructure Prof. A. Mukherjee,Civil Engineering,IITB20

Concrete Mix DesignTheprocessofselectingsuitableingredients of concrete and determiningtheir relative quantities with the object ofproducing as economically as possibleconcrete of certain minimum ty. Prof. A. Mukherjee,Civil Engineering,IITB21

Basic factors in the process of Mix DesignMethodOfCompactionLiability to chemicalattack or size of concrete massQualityControlMinimumStrengthMaximumSize ngthSize of sectionand spacingof ReinforcementAge atwhich Strengthis requiredAggregateShape entRatioOverallGrading ofAggregateProportionof each SizeFractionCapacityof the Mixer Prof. A. Mukherjee,Civil Engineering,IITBMix ProportionsWeights of IngredientsPer Batch22

Basic definitions Mean strength: This is the average strength obtained bydividing the sum of strength of all the cubes by the number ofcubes.x x nwhere Prof. A. Mukherjee,Civil Engineering,IITBxxn mean strength sum of strengths of cubes number of cubes23

Gaussian distribution curves for concretes with aminimum strength of 20.6 MpaProbability DensityABC0102030405060Strength -MPa Prof. A. Mukherjee,Civil Engineering,IITB24

Percentage of Specimens having a strength lowerthan (Mean – k x Standard deviation)Degree ofcontrol Prof. A. Mukherjee,Civil Engineering,IITBkPercentage of specimen havinga strength below than ( x– kσ )1.0015.91.506.71.962.52.331.02.500.63.090.125

Water / Cement ratiocom pressive strengthvibrationHand compactionFully compacted concreteInsufficiently compactedconcrete Prof. A. Mukherjee,Civil Engineering,IITBwater/cement ratio26

Relation between Compressive strength andWater/Cement Ratio for OPC of late ays3Days00.30.40.50.60.70.80.911. 11. 2Wat er/ Cement Rat io by Weight Prof. A. Mukherjee,Civil Engineering,IITB27

Relationship between Water/cement ratio andCompressive strength for OPC of late 1970’s701 Year28 DaysCompressive Strength - MPa607 Days1 .80.9Water/cement ratio by Weight Prof. A. Mukherjee,Civil Engineering,IITB28

Road Note No. 4 type grading curvesfor 19.05 mm aggregate100Percentage passing9080Zone CZone BZone 09.52019.050Metric size (mm) Prof. A. Mukherjee,Civil Engineering,IITB29

Road Note No. 4 type grading curvesfor 38.1 mm aggregate.Percentage Passing120100Zone CZone BZone A8060402000.0750.1500.3000.6001.2002.4004.7609.520 19.050 38.100Metric Size (mm) Prof. A. Mukherjee,Civil Engineering,IITB30

McIntosh and Erntroy’s type grading curvesfor 9.52mm aggregatePercentage Passing1009080Zone C7060Zone B50Zone A4030201000.0750.150.30.61.22.44.769.52Metric Size (mm) Prof. A. Mukherjee,Civil Engineering,IITB31

Aggregate/Cement Ratio (by weight) with differentGradings of 38.1mm Irregular AggregateDegree ofWorkabilityVery lowGrading curve No.on Fig. -Water/cement ratioby weight0.60LowMedium0.750.80-HighIndicates that the mix was outside the range tested.x Indicates that the mix would segregate. Prof. A. Mukherjee,proportions are based on specific gravities of approximately 2.5 for the coarse aggregate and 2.6 forCivil TheseEngineering,32thefine aggregate.IITB

ExampleMix design for road slab Minimum compressive strength (at 28 Days) 28 MPaMethod of compaction – Needle vibrationQuality control – GoodWorkability – Very lowCement used – Ordinary Portland cementAggregate shape – Irregular Prof. A. Mukherjee,Civil Engineering,IITB33

Estimated relation between Minimum and Mean Compressive Strengthsof Site Cubes with Additional Data on Coefficient of Variation Prof. A. Mukherjee,Civil Engineering,IITB34

Steps in Mix design Minimum strength 30 MPaCalculation of Mean strengthmean strength minimum strength / 0.75 (slide # 33)mean strength 30 / 0.75 40 MPa Determination of Water/Cement ratiowater/cement ratio 0.48 (slide # 26)Determination of Aggregate cement ratioworkability is very low and using water/cement ratio as 0.48from slide # 31 we get,aggregate cement ratio 7.2Proportionfine : 19.0 – 4.75 : 38.1 – 19.0 aggregates 1 : 0.94 : 2.59 Prof. A. Mukherjee,Civil Engineering,IITB35

Steps in Mix design contd . Since the aggregate /cement ratio is 7.2, therefore theproportion of cement and aggregates is 1 : 1.59 : 1.50 : 4.11Determination of cement contentMaterialsSp. gravitywater1.0Cement3.15Coarseaggregate2.50Fine aggregate 2.60 Prof. A. Mukherjee,Civil Engineering,IITB36

Steps in Mix design contd .Expression for calculation of cement contentwhere W, C, A1, A2 are the required weights of water, cement, fineaggregate, and coarse aggregate respectivelySolving the equation, per m3 of concrete the quantitiy ofCement 273.75 kg and hence,Water 0.48 x 273.75 131.4 kgFine aggregates 1.59 x 273.75 435.26 kg19.0 – 4.75 aggregates 1.50 x 273.75 410.63 kg38.1 – 19.0 aggregates 4.11 x 273.75 1125.11 kgTotal 2376.15 kg Prof. A. Mukherjee,Civil Engineering,IITB37

Material graphsfckσc all.strainσ call . Prof. A. Mukherjee,Civil Engineering,IITBf ck F .S .38

Structural MembersFlexural MemberSubjected to transverse loading and resists internal moments and .CV Prof. A. Mukherjee,Civil Engineering,IITBshowinginternal momentsand shearsTVjdshowinginternal momentsasC-T couple39

Assumptionsδδ is very small. Length of the member remains sameduring bending; i.e. deformation is verysmall in comparison to the length. Prof. A. Mukherjee,Civil Engineering,IITB40

Assumptions Plane sections remain plane during the process of bending (i.e.shear deformation is neglected)dw/dxdw/dx Prof. A. Mukherjee,Civil Engineering,IITB41

Assumptions All tensile stresses are taken by steel and none byconcrete.εσccxD dNeutral Planeεsb Strain diagramσsStress diagramNo slippage between concrete and steel Prof. A. Mukherjee,Civil Engineering,IITB42

The stress-strain relationship of steel and concrete, underworking loads, is a straight line.fckfyσc all.σs all.strainstrainσ Prof. A. Mukherjee,Civil Engineering,IITBsall .σ call . fyF .S .f ckF .S .43

RCC Flexural MemberSimply Supported BeamReinforcing steelHoggingmomentContinuous BeamSaggingmoment Prof. A. Mukherjee,Civil Engineering,IITBReinforcing steel44