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1 Reinforced Concrete Design Lecture 2 Dr. Nader Okasha.

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1 1 Reinforced Concrete Design Lecture 2 Dr. Nader Okasha

2 2 Introduction Topics  Reinforced concrete structures and concrete-producing materials  Concrete mixing  Mechanical properties of concrete  Steel reinforcement sizes and mechanical properties

3 Reinforced Concrete Structures and Concrete-Producing Materials 3

4 Concrete Concrete is a mixture of cement, fine and coarse aggregates, and water. This mixture creates a formable paste that hardens into a rocklike mass. 4

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9 Concrete Producing Materials Portland Cement Course Aggregates Fine Aggregates Water Admixtures 9

10 Types of Cement  Type I: General Purpose  Type II: Lower heat of hydration than Type I  Type III: High Early Strength Higher heat of hydration quicker strength (7 days vs. 28 days for Type I) 10 Portland Cement

11  Type IV: Low Heat of Hydration Gradually heats up, less distortion (massive structures).  Type V: Sulfate Resisting For footings, basements, sewers, etc. exposed to soils with sulfates. Types of Cement 11

12 Aggregates Coarse Aggregates Fine Aggregates

13 13 Water

14 –Applications: Improve workability (superplasticizers) Accelerate or retard setting and hardening Aid in curing Improve durability Admixtures 14

15 Concrete Mixing 15

16 Concrete Mixing Quality Workability Economy In the design of concrete mixes, three principal requirements for concrete are of importance: 16

17 Quality of concrete is measured by its strength and durability. The compressive strength of concrete is mainly affected by the water/cement ratio, degree of compaction, age, and temperature. Durability of concrete is the ability of the concrete to resist disintegration due to freezing and thawing and chemical attack. 17 Concrete Mixing

18 Workability of concrete may be defined as a composite characteristic indicative of the ease with which the mass of plastic material may be deposited in its final place without segregation during placement, and its ability to conform to fine forming detail. 18 Concrete Mixing

19 Workability Workability is measured by the slump test 1.Layer 1: Fill 1/3 full. 25 stokes 2.Layer 2: Fill 2/3 full. 25 stokes 3.Layer 3: Fill full. 25 stokes 4.Lift cone and measure slump (typically 2-6 in.) ” slump 19 Concrete Mixing

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21 21 Concrete Mixing

22 Economical takes into account effective use of materials, effective operation, and ease of handling. The cost of producing good quality concrete is an important consideration in the overall cost of the construction project. 22 Concrete Mixing

23 Mechanical Properties of Concrete 23

24 Mechanical Concrete Properties Compressive Strength, 24 E c Modulus of Elasticity, E c Maximum ‘Ultimate’ Strain Tensile, Splitting and Rupture Strength, f t, f ct, f r

25 Mechanical Concrete Properties Compressive Strength, Normally use 28-day strength for design strength It is determined through testing standard cylinders 15 cm in diameter and 30 cm in length in uniaxial compression at 28 days (ASTM C470-93a) 25

26 26 Mechanical Concrete Properties

27 27 Mechanical Concrete Properties

28 E c Modulus of Elasticity, E c Corresponds to secant modulus at 0.45 ACI (Sec ) for normal concrete: 28 Mechanical Concrete Properties

29 Maximum ‘ultimate’ strain ACI Code: = Used for flexural and axial compression For normal strength concrete, ~ Mechanical Concrete Properties

30 Typical Concrete Stress-Strain Curves in Compression 30 Mechanical Concrete Properties

31 Tensile Strength –Tensile strength ~ 8% to 15% of –Modulus of Rupture, f r For deflection calculations, use : –Test: ACI Eq P frfr unreinforced concrete beam 31 Mechanical Concrete Properties

32 Tensile Strength –Splitting Tensile Strength, f ct –Split Cylinder Test P Concrete Cylinder Poisson’s Effect Mechanical Concrete Properties

33 Creep Creep is defined as the long-term deformation caused by the application of loads for long periods of time, usually years. Creep strain occurs due to sustaining the same load with time. 33

34 Creep The total deformation is divided into two parts; the first is called elastic deformation occurring right after the application of loads, and the second which is time dependent, is called creep 34

35 Shrinkage Shrinkage of concrete is defined as the reduction in volume of concrete due to loss of moisture 35

36 Steel Reinforcement Sizes and Mechanical Properties 36

37 Steel Reinforcement 37 Bars are deformed to increase bonding with concrete

38 Steel Reinforcement 38 Stress-strain diagrams fufu fyfy Yield stress, f y Ultimate stress, f y

39 Steel Reinforcement 39 Steel grades MPaksi

40 Steel Reinforcement 40 Bar sizes

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