Design of Reinforced Concrete

Jack C. McCormac is Alumni Distinguished Professor o Civil Engineering, Emeritus at Clemson University. He holds a BS in civil engineering from the Citadel, an MS in civil engineering from Massachusetts Institute of Technology, and a Doctor of Letters from Clemson University. His contributions to engineering education and the engineering profession have been recognized by many, including the American Society for Engineering Education, the American Institute of Steel Construction, and the American Concrete Institute. Professor McCormac was included in the International Who's Who in Engineering, and was named by the Engineering News-Record as one of the top 125 engineers or architects in the world in the last 125 years for his contributions to the construction industry. He was one of only two educators living in the world today to receive this honor. Professor McCormac belongs to the American Society of Civil Engineers and served as the principal civil engineering grader for the National Council of Examiners for Engineering and Surveying for many years.

Preface xv


1 Introduction 1


1.1 Concrete and Reinforced Concrete 1


1.2 Advantages of Reinforced Concrete as a Structural Material 1


1.3 Disadvantages of Reinforced Concrete as a Structural Material 2


1.4 Historical Background 3


1.5 Comparison of Reinforced Concrete and Structural Steel for Buildings and Bridges 5


1.6 Compatibility of Concrete and Steel 6


1.7 Design Codes 6


1.8 SI Units and Shaded Areas 7


1.9 Types of Portland Cement 7


1.10 Admixtures 9


1.11 Properties of Concrete 10


1.12 Aggregate 18


1.13 High–Strength Concretes 19


1.14 Fiber–Reinforced Concretes 20


1.15 Concrete Durability 21


1.16 Reinforcing Steel 22


1.17 Grades of Reinforcing Steel 24


1.18 SI Bar Sizes and Material Strengths 25


1.19 Corrosive Environments 26


1.20 Identifying Marks on Reinforcing Bars 26


1.21 Introduction to Loads 28


1.22 Dead Loads 28


1.23 Live Loads 29


1.24 Environmental Loads 30


1.25 Selection of Design Loads 32


1.26 Calculation Accuracy33


1.27 Impact of Computers on Reinforced Concrete Design 34


Problems 34


2 Flexural Analysis of Beams 35


2.1 Introduction 35


2.2 Cracking Moment 38


2.3 Elastic Stresses—Concrete Cracked 41


2.4 Ultimate or Nominal Flexural Moments 48


2.5 SI Example 51


2.6 Computer Examples 52


Problems 54


3 Strength Analysis of Beams According to ACI Code 65


3.1 Design Methods 65


3.2 Advantages of Strength Design 66


3.3 Structural Safety 66


3.4 Derivation of Beam Expressions 67


3.5 Strains in Flexural Members, 70


3.6 Balanced Sections, Tension–Controlled Sections, and Compression–Controlled or Brittle Sections 71


3.7 Strength Reduction or φ Factors 71


3.8 Minimum Percentage of Steel 74


3.9 Balanced Steel Percentage 75


3.10 Example Problems 76


3.11 Computer Examples 79


Problems 80


4 Design of Rectangular Beams and One–Way Slabs 82


4.1 Load Factors 82


4.2 Design of Rectangular Beams 85


4.3 Beam Design Examples 89


4.4 Miscellaneous Beam Considerations 95


4.5 Determining Steel Area When Beam Dimensions Are Predetermined 96


4.6 Bundled Bars 98


4.7 One–Way Slabs 99


4.8 Cantilever Beams and Continuous Beams 102


4.9 SI Example 103


4.10 Computer Example 105


Problems 106


5 Analysis and Design of T Beams and Doubly Reinforced Beams 112


5.1 T Beams 112


5.2 Analysis of T Beams 114


5.3 Another Method for Analyzing T Beams 118


5.4 Design of T Beams 120


5.5 Design of T Beams for Negative Moments 125


5.6 L–Shaped Beams 127


5.7 Compression Steel 127


5.8 Design of Doubly Reinforced Beams 132


5.9 SI Examples 136


5.10 Computer Examples, 138


Problems 143


6 Serviceability 154


6.1 Introduction 154


6.2 Importance of Deflections 154


6.3 Control of Deflections 155


6.4 Calculation of Deflections 157


6.5 Effective Moments of Inertia 158


6.6 Long–Term Deflections 160


6.7 Simple–Beam Deflections 162


6.8 Continuous–Beam Deflections 164


6.9 Types of Cracks 170


6.10 Control of Flexural Cracks 171


6.11 ACI Code Provisions Concerning Cracks 175


6.12 Miscellaneous Cracks 176


6.13 SI Example 176


6.14 Computer Example 177


Problems 179


7 Bond, Development Lengths, and Splices 184


7.1 Cutting Off or Bending Bars 184


7.2 Bond Stresses 187


7.3 Development Lengths for Tension Reinforcing 189


7.4 Development Lengths for Bundled Bars 197


7.5 Hooks 199


7.6 Development Lengths for Welded Wire Fabric in Tension 203


7.7 Development Lengths for Compression Bars 204


7.8 Critical Sections for Development Length 206


7.9 Effect of Combined Shear and Moment on Development Lengths 206


7.10 Effect of Shape of Moment Diagram on Development Lengths 207


7.11 Cutting Off or Bending Bars (Continued) 208


7.12 Bar Splices in Flexural Members 211


7.13 Tension Splices 213


7.14 Compression Splices 213


7.15 Headed and Mechanically Anchored Bars 214


7.16 SI Example 215


7.17 Computer Example 216


Problems 217


8 Shear and Diagonal Tension 223


8.1 Introduction 223


8.2 Shear Stresses in Concrete Beams 223


8.3 Lightweight Concrete 224


8.4 Shear Strength of Concrete 225


8.5 Shear Cracking of Reinforced Concrete Beams 226


8.6 Web Reinforcement 227


8.7 Behavior of Beams with Web Reinforcement 229


8.8 Design for Shear 231


8.9 ACI Code Requirements 232


8.10 Shear Design Example Problems 237


8.11 Economical Spacing of Stirrups 247


8.12 Shear Friction and Corbels 249


8.13 Shear Strength of Members Subjected to Axial Forces 251


8.14 Shear Design Provisions for Deep Beams 253


8.15 Introductory Comments on Torsion 254


8.16 SI Example 256


8.17 Computer Example 257


Problems 258


9 Introduction to Columns 263


9.1 General 263


9.2 Types of Columns 264


9.3 Axial Load Capacity of Columns 266


9.4 Failure of Tied and Spiral Columns 266


9.5 Code Requirements for Cast–in–Place Columns 269


9.6 Safety Provisions for Columns 271


9.7 Design Formulas 272


9.8 Comments on Economical Column Design 273


9.9 Design of Axially Loaded Columns 274


9.10 SI Example 277


9.11 Computer Example 278


Problems 279


10 Design of Short Columns Subject to Axial Load and Bending 281


10.1 Axial Load and Bending 281


10.2 The Plastic Centroid 282


10.3 Development of Interaction Diagrams 284


10.4 Use of Interaction Diagrams 290


10.5 Code Modifications of Column Interaction Diagrams 292


10.6 Design and Analysis of Eccentrically Loaded Columns Using Interaction Diagrams 294


10.7 Shear in Columns 301


10.8 Biaxial Bending 302


10.9 Design of Biaxially Loaded Columns 306


10.10 Continued Discussion of Capacity Reduction Factors, φ 309


10.11 Computer Example 311


Problems 312


11 Slender Columns 317


11.1 Introduction 317


11.2 Nonsway and Sway Frames 317


11.3 Slenderness Effects 318


11.4 Determining k Factors with Alignment Charts 321


11.5 Determining k Factors with Equations 322


11.6 First–Order Analyses Using Special Member Properties 323


11.7 Slender Columns in Nonsway and Sway Frames 324


11.8 ACI Code Treatments of Slenderness Effects 328


11.9 Magnification of Column Moments in Nonsway Frames 328


11.10 Magnification of Column Moments in Sway Frames 333


11.11 Analysis of Sway Frames 336


11.12 Computer Examples 342


Problems 344


12 Footings 347


12.1 Introduction 347


12.2 Types of Footings 347


12.3 Actual Soil Pressures 350


12.4 Allowable Soil Pressures 351


12.5 Design of Wall Footings 352


12.6 Design of Square Isolated Footings 357


12.7 Footings Supporting Round or Regular Polygon–Shaped Columns 364


12.8 Load Transfer from Columns to Footings 364


12.9 Rectangular Isolated Footings 369


12.10 Combined Footings 372


12.11 Footing Design for Equal Settlements 378


12.12 Footings Subjected to Axial Loads and Moments 380


12.13 Transfer of Horizontal Forces 382


12.14 Plain Concrete Footings 383


12.15 SI Example 386


12.16 Computer Examples 388


Problems 391


13 Retaining Walls 394


13.1 Introduction 394


13.2 Types of Retaining Walls 394


13.3 Drainage 397


13.4 Failures of Retaining Walls 398


13.5 Lateral Pressure on Retaining Walls 399


13.6 Footing Soil Pressures 404


13.7 Design of Semigravity Retaining Walls 405


13.8 Effect of Surcharge 408


13.9 Estimating the Sizes of Cantilever Retaining Walls 409


13.10 Design Procedure for Cantilever Retaining Walls 413


13.11 Cracks and Wall Joints 424


Problems 426


14 Continuous Reinforced Concrete Structures 431


14.1 Introduction 431


14.2 General Discussion of Analysis Methods 431


14.3 Qualitative Influence Lines 431


14.4 Limit Design 434


14.5 Limit Design under the ACI Code 442


14.6 Preliminary Design of Members 445


14.7 Approximate Analysis of Continuous Frames for Vertical Loads 445


14.8 Approximate Analysis of Continuous Frames for Lateral Loads 454


14.9 Computer Analysis of Building Frames 458


14.10 Lateral Bracing for Buildings 459


14.11 Development Length Requirements for Continuous Members 459


Problems 465


15 Torsion 470


15.1 Introduction 470


15.2 Torsional Reinforcing 471


15.3 Torsional Moments that Have to Be Considered in Design 474


15.4 Torsional Stresses 475


15.5 When Torsional Reinforcing Is Required by the ACI 476


15.6 Torsional Moment Strength 477


15.7 Design of Torsional Reinforcing 478


15.8 Additional ACI Requirements 479


15.9 Example Problems Using U.S. Customary Units 480


15.10 SI Equations and Example Problem 483


15.11 Computer Example 487


Problems 488


16 Two–Way Slabs, Direct Design Method 492


16.1 Introduction 492


16.2 Analysis of Two–Way Slabs 495


16.3 Design of Two–Way Slabs by the ACI Code 495


16.4 Column and Middle Strips 496


16.5 Shear Resistance of Slabs 497


16.6 Depth Limitations and Stiffness Requirements 500


16.7 Limitations of Direct Design Method 505


16.8 Distribution of Moments in Slabs 506


16.9 Design of an Interior Flat Plate 511


16.10 Placing of Live Loads 514


16.11 Analysis of Two–Way Slabs with Beams 517


16.12 Transfer of Moments and Shears between Slabs and Columns 522


16.13 Openings in Slab Systems 528


16.14 Computer Example 528


Problems 530


17 Two–Way Slabs, Equivalent Frame Method 532


17.1 Moment Distribution for Nonprismatic Members 532


17.2 Introduction to the Equivalent Frame Method 533


17.3 Properties of Slab Beams 535


17.4 Properties of Columns 538


17.5 Example Problem 540


17.6 Computer Analysis 544


17.7 Computer Example 545


Problems 546


18 Walls 547


18.1 Introduction 547


18.2 Non–Load–Bearing Walls 547


18.3 Load–Bearing Concrete Walls—Empirical Design Method 549


18.4 Load–Bearing Concrete Walls—Rational Design 552


18.5 Shear Walls 554


18.6 ACI Provisions for Shear Walls 558


18.7 Economy in Wall Construction 563


18.8 Computer Example 564


Problems 565


19 Prestressed Concrete 567


19.1 Introduction 567


19.2 Advantages and Disadvantages of Prestressed Concrete 569


19.3 Pretensioning and Posttensioning 569


19.4 Materials Used for Prestressed Concrete 570


19.5 Stress Calculations 572


19.6 Shapes of Prestressed Sections 576


19.7 Prestress Losses 579


19.8 Ultimate Strength of Prestressed Sections 582


19.9 Deflections 586


19.10 Shear in Prestressed Sections 590


19.11 Design of Shear Reinforcement 591


19.12 Additional Topics 595


19.13 Computer Example 597


Problems 598


20 Reinforced Concrete Masonry 602


20.1 Introduction 602


20.2 Masonry Materials 602


20.3 Specified Compressive Strength of Masonry 606


20.4 Maximum Flexural Tensile Reinforcement 607


20.5 Walls with Out–of–Plane Loads—Non–Load–Bearing Walls 607


20.6 Masonry Lintels 611


20.7 Walls with Out–of–Plane Loads—Load–Bearing 616


20.8 Walls with In–Plane Loading—Shear Walls 623


20.9 Computer Example 628


Problems 630


A Tables and Graphs: U.S. Customary Units 631


B Tables in SI Units 669


C The Strut–and–Tie Method of Design 675


C.1 Introduction 675


C.2 Deep Beams 675


C.3 Shear Span and Behavior Regions 675


C.4 Truss Analogy 677


C.5 Definitions 678


C.6 ACI Code Requirements for Strut–and–Tie Design 678


C.7 Selecting a Truss Model 679


C.8 Angles of Struts in Truss Models 681


C.9 Design Procedure 682


D Seismic Design of Reinforced Concrete Structures 683


D.1 Introduction 683


D.2 Maximum Considered Earthquake 684


D.3 Soil Site Class 684


D.4 Risk and Importance Factors 686


D.5 Seismic Design Categories 687


D.6 Seismic Design Loads 687


D.7 Detailing Requirements for Different Classes of Reinforced Concrete Moment Frames 691


Problems 698


Glossary 699


Index 703