CHAPTER 4. Reinforced Concrete - assakkaf

1 1 Fifth EditionReinforced Concrete design A. J. Clark School of Engineering Department of Civil and Environmental EngineeringCHAPTER4 Reinforced CONCRETEA Fundamental Approach-Fifth EditionREINFORCED CONCRETEENCE 454 design of Concrete StructuresDepartment of Civil and Environmental EngineeringUniversity of Maryland, College ParkSPRING 2004By Dr . Ibrahim. AssakkafCHAPTER 4. Reinforced CONCRETES lide No. 1 ENCE 454 AssakkafIntroduction Concrete is weak in tension but strong in compression. Therefore, reinforcement is needed to resist the tensile stresses resulting from the applied loads.

2 Additional reinforcement sometimes added to the compression zone to reduce long-term 4. Reinforced CONCRETES lide No. 2 ENCE 454 AssakkafTypes and Properties of Steel reinforcement Steel reinforcement consists of Bars Wires Welded wire fabric The most important properties of steel are: Young s Modulus (Modulus of Elasticity), E Yield Strength, fy Ultimate Strength, fu Steel Grade Designation. Size or Diameter of the bar or 4. Reinforced CONCRETES lide No. 3 ENCE 454 assakkaf Steel is a high-cost material compared with Concrete . It follows that the two materials are best used in combination if the Concrete is made to resist the compressive stresses and the steel the tensile stresses.

3 Concrete cannot withstand very much tensile stress without and Properties of Steel Reinforcement3 CHAPTER 4. Reinforced CONCRETES lide No. 4 ENCE 454 assakkaf (a)(b)(c)Figure - xn As C Reinforced Concrete and Properties of Steel ReinforcementCHAPTER 4. Reinforced CONCRETES lide No. 5 ENCE 454 assakkaf It follows that tensile reinforcement must be embedded in the Concrete to overcome the deficiency. Forms of Steel reinforcement Steel Reinforcing Bars Welded wire fabric composed of steel wire. Structural Steel Shapes Steel and Properties of Steel Reinforcement4 CHAPTER 4.

4 Reinforced CONCRETES lide No. 6 ENCE 454 AssakkafTypes and Properties of Steel ReinforcementDeformed BarCHAPTER 4. Reinforced CONCRETES lide No. 7 ENCE 454 assakkaf Bond between Concrete and Steel To increase the bond, projections called deformationsare rolled on the bar surface as shown in Fig. 1. Reinforcing Bars (rebars) The specifications for steel reinforcement published by the American Society for Testing and Materials(ASTM) are generally accepted for steel used in Reinforced Concrete construction in the United States and are identified in the ACI and Properties of Steel Reinforcement5 CHAPTER 4.

5 Reinforced CONCRETES lide No. 8 ENCE 454 assakkaf Yield Stress for Steel Probably the most useful property of Reinforced Concrete design calculations is the yield stress for steel, fy. A typical stress-strain diagram for reinforcing steel is shown in Fig. 2a. An idealized stress-strain diagram for reinforcing steel is shown in Fig. and Properties of Steel ReinforcementCHAPTER 4. Reinforced CONCRETES lide No. 9 ENCE 454 AssakkafTypes and Properties of Steel ReinforcementStrainStressFyElasticregion yFigure 2. Typical Stress-Strain Curve for Steel(b) IdealizedStrainStressFyElasticregion y(a) As Determined by Tensile TestStrainStressSlope==E6 CHAPTER 4.

6 Reinforced CONCRETES lide No. 10 ENCE 454 AssakkafFigure 3. Typical Stress-Strain Diagrams for Various SteelTypes and Properties of Steel ReinforcementCHAPTER 4. Reinforced CONCRETES lide No. 11 ENCE 454 assakkaf Modulus of Elasticity or Young s Modulus for Steel The modulus of elasticity for reinforcing steel varies over small range, and has been adopted by the ACI Code asTypes and Properties of Steel ReinforcementMPa 10200 ksi 29,000 psi 000,000,296 ===E7 CHAPTER 4. Reinforced CONCRETES lide No. 12 ENCE 454 assakkaf Steel Grades and Strengths Table 1 gives reinforcement -grade strengths.

7 Geometrical Properties Table 2 provides various sizes of bars in US Customary units, while Table 3 gives the sizes in Metric and Properties of Steel ReinforcementCHAPTER 4. Reinforced CONCRETES lide No. 13 ENCE 454 AssakkafTable 1. Reinforced Grades and StrengthsTypes and Properties of Steel Reinforcement85,00075,000, 70,00070,00065,000, 56,000 Smooth wireReinforcedFabric85,00080,00075,00070 ,000 Deformed wireReinforcedFabric80,00060,000 Low-carbon steel(A706) Grade 6070,00090,00040,00060,000 Axial steel (A617)Grade 40 Grade 6070,00090,00040,00060,000 Billet steel (A615)Grade 40 Grade 60 Ultimate Strength, fu(psi)Minimum Yield Point or Yield Strength, fy(psi)1982 Standard Type8 CHAPTER 4.

8 Reinforced CONCRETES lide No. 14 ENCE 454 AssakkafTypes and Properties of Steel ReinforcementTable 2. ASTM Standard - English ReinforcingBarsBar Designation Diameter in Area in2 Weight lb/ft #3 [#10] #4 [#13] #5 [#16] #6 [#19] #7 [#22] #8 [#25] #9 [#29] #10 [#32] #11 [#36] #14 [#43] #18 [#57] Note: Metric designations are in bracketsCHAPTER 4. Reinforced CONCRETES lide No. 15 ENCE 454 AssakkafTypes and Properties of Steel ReinforcementTable 3. ASTM Standard - Metric ReinforcingBarsNote: Metric designations are in brackets Bar Designation Diameter mm Area mm2 Mass kg/m #10 [#3] 71 #13 [#4] 129 #16 [#5] 199 #19 [#6] 284 #22 [#7] 387 #25 [#8] 510 #29 [#9] 645 #32 [#10] 819 #36 [#11] 1006 #43 [#14] 1452 #57 [#18] 2581 9 CHAPTER 4.

9 Reinforced CONCRETES lide No. 16 ENCE 454 AssakkafTypes and Properties of Steel reinforcement Reinforcing Bars (rebars) These bars are readily available in straight length of 60 ft. The bars vary in designation from With additional bars:No. 3 through No. 11No. 14 and No. 18 CHAPTER 4. Reinforced CONCRETES lide No. 17 ENCE 454 AssakkafBar Spacing and Concrete Cover for Steel reinforcement It is necessary to guard against honeycombing and ensure that the wet Concrete mix passes through the reinforcing steel without separation. Usually aggregate size in structural Concrete contains -in (19 mm) diameter coarse aggregate.

10 Therefore, minimum allowable bar spacing and minimum required cover are 4. Reinforced CONCRETES lide No. 18 ENCE 454 assakkaf Also, to protect the reinforcement steel from corrosion and loss of strength in cases of fire, the ACI Code 318 required minimum Concrete cover: Clear distance between parallel bars in layers must not be less than bar diameter dbor 1 in. ( mm). Clear distance between longitudinal bars in columns must not be less than in. Minimum clear cover in cast-in-place Concrete beams and columns should not be less than in ( mm) when there is no exposure to weather or contact with Spacing and Concrete Cover for Steel ReinforcementCHAPTER 4.