Saturday, July 14, 2012

Reinforced Concrete Design

What makes Unique of RC...?

  • It requires APPLICATION of more involved Principles of Mechanics...
  • Structural Design is iterative requiring both ANALYSIS and DESIGN DECISIONS aided by judgment and EXPERIENCE.
  • ACI 318 -the model code in the United States of America for guiding the design of RC members, look at Chapter 8.
  • NSCP Code -the code in the Philippines..conforms to the provisions of ACI 318 Code!!!
Important Material Properties...

Concrete Strength and Steel Strength...
  • 28-day Compressive Strength, f'c: ACI 318 Code 2011 edition, Chapter 5.
  • Modulus of Elasticity of Concrete, Ec: ACI 318 Code 2011 edition, Chapter 8.5
  • Strength property or yield strength, fy..
  • Modulus of Elasticity of Steel, Es: 29,000,000 psi --ACI 318 Code 2011 edition.

1. --Procedures on how to Design Reinforced Concrete Beams!!!

Concrete Beam Sizing..!

Determination of Beam Size (b x h)---USE Spreadsheet or Hand Calculation!!!

Concrete Beam Size (b x h) or (b x d), FORMULA:

Formula for Beam Sizing
Beam Section, Strain and Force Diagram

Equilibrium Equation or Neutral Axis Distance, c -- Quadratic for c

Rebars Determination..

Area of Steel (As) determination!!!

Strength Formula and Area of Steel (As)
Area Steel (As) Formula
rho formula

The ACI Code 10.3.3 to 10.3.5 limits on the Steel Ratio (rho):

rho maximum
rho balance
1.1 Minimum Beam Size for which Deflections are NOT LIKELY to be a Problem.
1.1.1 Set Neutral Axis distance, c =< 0.375cb....


1.2 Arrangement of Rebars, Splicing points and splice length, development length, hooks requirement, and required Stirrups.

Design of Stirrups and Spacing
Stirrups Spacing Requirements per ACI Code

Structural Integrity Requirements for Perimeter Beam

Structural Integrity requirements for Interior Beams

ACI Standard Bar Details
Recommended Bar Details for Beams ACI 318-1999 to 2014
Design of Low-Rise Reinforced Concrete Buildings by David Fanella

2. --Procedures on how to Design Reinforced Concrete Columns!!!

Lateral Tie Design

ACI Standard Bar Detailing for Columns
ACI Columns Rebars splicing details

ACI Standard Bar Bending Diagram

Minimum Column Steel and Ties requirements
2.A.--Structural design for Column using Interaction Diagram.

Column Interaction Diagram
2.B.--Example of ACI Interaction Diagram.
Interaction Diagram-Rectangular Section-Courtesy of ACI
Interaction Diagram-Spiral/Circular Section-Courtesy of ACI
2.C.--Summary of Column detail Requirements.

Column Design Requirement

2.1 Strength Reduction Factor, phi =0.70 -applicable up through ACI 318-1999; they have been changed to phi =0.65, for compression members (columns and beams under compression controls) beginning with ACI 318-2002 Code, and continuing with the ACI 318-05 and 2008 up to present.

3.--Example: Design of Column using MS Spreadsheet.

Design of Column MS Spreadsheet page #1

Design of Column MS Spreadsheet page #2

Rectangular Beam Design Example:

  1. Load and Span
  2. Material Properties -f'c, fy
material strength
Simple Beam with uniform load and point load
Calculation #1
Calculation #2
Calculation #3
Calculation #4

Hence, in more than 20 years of my practice, reinforced concrete design needs an in depth STUDY, and RESEARCH; therefore, for the information of the DRAFTSMAN drawing and/or drafting ("pag GUHIT" in local dialect) a proposed project and then observing a design drawings are not enough to say that you will know every aspects of concrete design. Concrete Design and Analysis are more on CALCULATIONS and application of more PRINCIPLES of MECHANICS.

  1. Reinforced Concrete Design by Chu-Kia Wang and C. G. Salmon, 6th edition-1998;
  2. Building Code Requirements for Structural Concrete, ACI 318-2011, American Concrete Institute;
  3. Building Code Requirements for Structural Concrete, ACI 318-1963, 1971, 1977, 1995, 2002; 2005, 2008, 2011 editions;
  4. NSCP Code, volume 1-Buildings and volume 2-Bridges, 5th edition-2001, 6th edition-2010, Association of Structural Engineers of the Philippines;
  5. ACI Design Handbook -ACI 318-2004;
  6. ACI Detailing Manual 2004;
  7. ACI Manual for Concrete Practice 2005 and 2008;
  8. CRSI DESIGN HANDBOOK, 10th edition, 2008;
  9. Design of Concrete Structures by Arthur H. Nilson, 12th edition -1997, 13th edition, 14th edition-2008;
  10. Design of Reinforced Concrete by Jack C. McCormac, 3rd edition,-1993, 5th edition 2005; 7th edition;
  11. Reinforced Concrete, Mechanics and Design, by Wight and Macgregor, 6th edition-2012,
  12. Reinforced Concrete Fundamentals by Phil M. Ferguson, John E. Breen, James O. Jirsa, 5th edition -1988;
  13. Building Design and Construction Handbook, by Frederick S. Merritt, Jonathan T. Ricketts, 6th edition -2002, McGraw-Hill International Edition.

Reference Books #1
RC Books#2
RC Books #3

Tuesday, July 10, 2012

History of Reinforced Concrete Design

The average person thinks that concrete has been in common use for many centuries, but such is not the case. Although the Romans made cement – called Pozzolana – before Christ by mixing slaked lime with a volcanic ash from Mount Vesuvius and used it to make concrete for building, the art was lost during the Dark Ages 5th century -15th century A.D.) and was not revived until eighteenth and nineteenth centuries. Marcus Vitruvius Pollio, an Architect/Engineer during the golden age of Caesar Augustus (around 25 BC). In his writings about 25 BC in Ten Books on Architecture distinguished types of aggregate appropriate for the preparation of lime mortars. For the use of structural members, he recommended pozzolana, which were volcanic sand from sandlike of Puteoli, brownish-yellow-gray in color near Naples and reddish brown at Rome. He specifies 1 part lime and 3 parts pozzolana for cements use in buildings. In his textbook, quite humbly titled "On the Origin of all Things", Vitruvius held forth on the fundamental behavior of building materials, and then presented his views about the nature of theory versus practice, Vitruvius suggestion that design engineers should have more construction experience, and vice versa.

Vitruvius expressed his feelings and complained that:
"The workmen are in a HURRY, the UNEDUCATED rather than the EDUCATED are in HIGHER FAVOR", "the architecture and engineering are professed by men, who have no knowledge even the carpenter's trade."
He wrote the textbook De Architectura libri decem (The Ten Books on Architecture), the only complete treatise in classical antiquity. It influenced deeply from the Early Renaissance onward, artists, architects, engineers, among them Leonardo Da Vinci (1452-1519), Michelangelo (1475-1564).
Basilica at Fano Rome, design by Vitruvius -19 BC

In the mid-1800s, Joseph Lambot, in France constructed a small boat which he exhibited at the Paris Exposition of 1854 and he received a patent in 1855 which shown a reinforced concrete beam and a column reinforced with four round iron bars. Another Frenchman, Francois Coignet, published a book in 1861, describing applications and many uses of reinforced concrete and acquired patent for reinforced concrete in 1855. In 1854, William B. Wilkinson of England took out a patent for a reinforced concrete FLOOR.

First reinforced concrete building designed by Francois Coignet in 1853
First reinforced concrete building Francois Coignet House built in 1853
Reinforced Concrete-Steel Detailing, Coignet System -1855 -1860

Joseph Monier, the owner of an important nursery in Paris deserves the credit for making the first practical use of reinforced concrete in 1867. He acquired first French patent in 1867 for iron reinforced concrete tubs, then followed by his pipes, tanks in 1868, flat flates in 1869, Bridges in 1873, stairways in 1875. In 1880-1881, he received German patent for railroads ties, water feeding troughs, circular flower pots, flat plates, and irrigation channels. He apparently had NO QUANTITATIVE KNOWLEDGE regarding its behavior or any method of making Design Calculations.

Chazelet Pedestrian (footbridge), France built by Joseph Monier in 1875
Monier Reinforced Concrete System -1867
Reinforced Concrete -Monier System 1867

In the United States pioneering were made by Thaddeus Hyatt, who conducted experiments on reinforced concrete beams in 1850s. However, Hyatt experiments were unknown until 1877, when he published his works privately.

The first cast-in-place reinforced concrete structure in the United States is generally credited to the William Ward house in Port Chester, New York, built in 1870. Ernest L. Ransome, worked as head in San Francisco Concrete-Steel Company, seemingly used form of reinforced concrete in the early 1870s. He continued to increase the application of wire rope and hoop iron to many structures and was the first to use reinforced concrete and patent in 1884, the deformed (twisted bar). In 1890, Ernest L. Ransome built the Leland Stanford Junior Museum in San Francisco, a reinforced concrete building two stories high and 312ft (95m)long. Since that time, development of reinforced concrete in the United States has been rapid.

Leland Stanford Museum Design by Ernest L. Ransome, 1890-94
The Historic Rebars

During 1891-1894, various investigators in Europe published theories and test results; among them were Professor Moller (Germany), R. Wunsch, 1884 (Hungary -builder); Josef Melan, 1892 (Austria -professor/engineer); the German G. A. Wayss the first engineer who made theory, and furnish formulas and methods for design; Francois Hannebique, 1892 (France-contracting engineer) received patent in 1892 in Brussels, he first used reinforced concrete in 1879, in this he demonstrates the utility of stirrups to reinforce beams against SHEAR, and F. von Emperger (Hungary-structural engineer) and received patent in 1893, but practical use was less extensive than in United States, like C.A.P. Turner, Arthur Talbot, W.A. Slater, Arthur Lord.

Throughout the entire period 1850 -1900, relatively little was published, as the engineers working in the reinforced concrete field considered construction and computational methods as trade secrets.

Concrete-Steel Detailing methods, F. Hannebique System- 1892
Continuous Beams, F. Hannebique System -1892
Hannebique Sytem -1892

Designed by F. Hannebique 1899-1900, Photo: Jacques Mossot

Footbridge designed by F. Hannebique-1905, Photo: Jacques Mossot
Dragon Bridge design by Prof. Melan -1901
GA Wayss and Prof. Emil Morsch, Test of Reinforcement in Beams
G.A. Wayss and Prof. Emil Morsch Test of Beams- Hannebique System
Prof. Moller System -1894

CAP Turner presentation of RC detailing
CAP Turner System
Test of Beam by Professor Arthur Talbot

One of the first publications that might be classified as a textbook was that of French engineer Armand Considere in 1899. Considere had been chief engineer with the Ponts et Chaussees in France.

In 1903, with the formation in the United States of a joint committee of representatives of all organizations interested in reinforced concrete, uniform applications of knowledge to design were initiated.

Experimental Research by A. Considere -1899

Bridge at Menier, design by Armand Considere built in 1906- Photo by Jacques Mossot

The earliest textbook in English was that of Frederick E. Turneaure and Maurer published in 1907 entitled “Principles of Reinforced Concrete Construction”. In the first decade of the twentieth century, progress in reinforced concrete was rapid. Extensive testing to determine beam behavior, compressive strength of concrete, and modulus of elasticity was conducted by Arthur N. Talbot at the University of Illinois, by Frederick E. Turneaure and Morton O. Withey at the University of Wisconsin, and by Bach in Germany, among others. In 1912 Ernest L. Ransome and Alexis Saurbrey co-authored published a book reinforced concrete.
Reinforcement of test Beams by Morton O. Withey
Test of Beams conducted by Prof. Talbot

First textbook by Frederick Turneaure
In 1906 major earthquake struck San Francisco, California having magnitude of 7.9, hence most engineers conducted research extensively and devised, revised methods of designs.
1906 San Francisco Earthquake, magnitude 7.9
1906 San Francisco Earthquake, magnitude 7.9
From about 1916 to the mid - 1930s, research centered on axially loaded column behavior. In the late 1930s and 1940s, eccentrically loaded columns, footings, and the Ultimate Strength of beams received special attention.

With the interest in and understanding of the elastic methods of analysis in the early 1900s, the elastic Working Stress method (also called Allowable-Stress Design or straight-line design) was adopted almost universally by codes as the best for design.

Historic WSD Formula ACI, Prof. Taylor -1907 #1

Historic WSD Formula, ACI, Prof. Taylor -1907  #2

Historic Formula by F. Turneaure 1907 - #1
Ultimate Loads formula by Tuneaure 1907

Historic Formula by F. Turneaure and Maurer 1907 -#2
Historic Formula by F. Turneaure and Maurer 1907 - #3
Historic Formula by F. Turneaure and Maurer 1907 -#4
Historical Formula-Charles Whitney, published in 1921

The first modification of the elastic Working Stress method resulted from the study of axially loaded columns in the early 1930s. By 1940s, the design of axially loaded columns was based on Ultimate Strength.

Rectangular Stress block by Charles S. Whitney

In the 1930s, Charles S. Whitney an american civil engineer proposed the use of a rectangular compressive stress distribution to replace that an average stress of 0.85f’c is used with a rectangle of depth a = β1 x, determine so that a/2 = k*x. In 1942 Charles S. Whitney presented a paper emphasizing this fact and showing how a probable stress-strain curve with reasonable accuracy, a parabola be replaced with an artificial rectangular stress block.

Formula of stress block depth "a" and "c" 

With the rectangular stress block simplification, the 1956 ACI-318 code added an appendix permitting Ultimate Strength Design (USD) as an alternate to Working Stress Design (WSD). The 1963 ACI-318 Code gave both methods equal standing.
Strength Design Stress by Charles S. Whitney
Strength Design, Flexure Formula for Beam Design
Rectangular Beam design Fig.1
Rectangular Beam Analysis Fig. 2

Since the mid-1950s, reinforced concrete design practice has made the transition from that based on elastic methods to the one based on strength.
Hence, in my standpoint, reinforced concrete design has been continuously studied for one hundred fifty years (150) and/or one and half century since it was invented by Joseph Monier in 1849. It is therefore ridiculous to say that working and drafting proposed projects in short period of time would suffice them to professed they know methods of design and processes. If the manager however, does not know something about THEORY OF DESIGN, then the OWNER is taking a great chances. They man in-charge should be an engineer.
References - All these Books below are on the shelves in my Personal Library for additional sources of background information:
  1. American Concrete Institute (ACI) Manual of Concrete Practice six (6) volumes, 2004 to 2008;
  2. American Concrete Institute (ACI) Design Handbook, Publication SP-17 (1997), 6th edition, Fifth Printing, re-approved February 2004;
  3. Building Code Requirements for Structural Concrete -2002, 2005, 2008;
  4. Building Code Requirements for Reinforced Concrete -1977;
  5. Building Code Requirements for Reinforced Concrete -1963;
  6. A Treatise on Concrete, Plain and Reinforced by Frederick W. Taylor and Sanford E. Thompson, 1st edition -1905, 2nd edition -1912, 3rd edition -1916;
  7. Cyclopedia of Civil Engineering-American Technical School by Frederick Turneaure, 8 volumes -1908;
  8. Cyclopedia of Construction (Radford); (carpentry, building and architecture. Based on the practical experience of a large staff of experts in actual construction works), volumes 1 to 12 -1909;
  9. Cassell's Reinforced Concrete by Bernard E. Jones -1913;
  10. Concrete Engineers Handbook by George A. Hool -1918;
  11. Concrete Designer's Manual by Charles A. Whitney and George A. Hool -1921;
  12. Concrete and Reinforced Concrete by W. Noble Twelvetrees -1922;
  13. Concrete Steel by W. Noble Twelvetrees-1905;
  14. Concrete Steel Buildings W. Noble Twelvetrees -1905;
  15. Concrete -Steel Construction by Professor Emil Morsch -Authorized Translation from Third (1908) German edition by E. P. Goodrich, 3rd edition -1909 and 1910;
  16. Concrete -Steel Construction by C. A. P. Turner and Henry T. Eddy, 1st edition -1909, 2nd edition -1914 and 3rd edition-1919;
  17. Concrete and Reinforced Concrete Construction by Homer Reid, 1st edition 1907, 2nd edition 1908;
  18. Concrete and Reinforced Concrete by Walter L. Webb and W. Herbert Gibson -1919;
  19. Engineer's Pocketbook of Reinforced Concrete by E. Lee Heidenreich -1908;
  20. Elementary Reinforced Concrete Building Design by Leonard C. Urquhart, 1st edition-1915;
  21. Experimental Research for Reinforced Concrete by Armand Considere -1903;
  22. Handbook on Reinforced Concrete by F. D. Warren -1906;
  23. Handbook of Building Construction, volume 1 and 2, by George A. Hool, 2nd edition 1929;
  24. Handbook of Cost and Data for Contractor's and Engineers by Halbert P. Gillette, member ASCE, 1,888 pages, 2nd edition -1920;
  25. Johnson's Materials of Construction -A Treatise for Engineers on the Strength of Engineering Materials by John B. Johnson, 1st edition -1897, 841 pages, 2nd edition -1898, 3rd edition -1904, 4th edition -1907 and 1912, 884 pages;
  26. Johnson's Materials of Construction by F. E. Turneaure, M.O. Withey, J. Aston, 5th edition -1919;
  27. Plain and Reinforced Concrete Arches by Josef Melan -1st edition-1915, 2nd edition-1917;
  28. Principles of Reinforced Concrete by Frederick E. Turneaure and Edward R. Maurer, 1st edition -1907, 2nd edition -1909, 3rd edition -1919;
  29. Reinforced Concrete by Charles F. Marsh -1904;
  30. Reinforced Concrete by A. W. Buel and C. S. Hill - 1904;
  31. Reinforced Concrete in Europe by Albert L. Colby, July 1909;
  32. Reinforced Concrete A Manual of Practice by E. McCullough -1908;
  33. Reinforced Concrete by Frederick Rings-1910;
  34. Reinforced Concrete by John P. Brooks-1911;
  35. Reinforced Concrete for Buildings by Ernest l. Ransome and Alexis Saurbrey, 1912;
  36. Reinforced Concrete and Construction by Henry Adams and Ernest R. Matthews-1911 and 1920;
  37. Reinforced Concrete Design volume 1-Theory, by O. Faber and P. G. Bowie, 1st edition-1912, 2nd edition-1919;
  38. Reinforced Concrete Design volume 2-Practice, by Oscar Faber and P. G. Bowie-1920;
  39. Reinforced Concrete Construction -Fundamental Principles, volume 1, by George A. Hool- 1912;
  40. Reinforced Concrete Construction -Retaining Walls and Buildings, volume 2, by George A. Hool-1913;
  41. Reinforced Concrete Construction -Bridges and Culverts, volume 3, by George A. Hool -1916;
  42. Steel and Reinforced Concrete in Buildings by Edward Godfrey -1911;
  43. Structural Engineering- Concrete, Book 2, by Edward Godfrey -1908;
  44. Structural Engineering- Steel Designing, Book 3, by Edward Godfrey -1913;
  45. Kahn System of Reinforced Concrete by Trussed Concrete Steel Company, 5th edition -1913;
  46. Test of Reinforced Concrete Beams by Arthur N. Talbot, Bulletin No. 1-1904;
  47. Test of Reinforced Concrete Columns by Arthur N. Talbot and Arthur Lord, Bulletin No. 56-1912;
  48. Test of Reinforced Concrete Buildings under Load by Arthur N. Talbot and W. A. Slater, Bulletin No. 64-1913;
  49. Test of Reinforced Concrete Flat Slab Structures by Arthur N. Talbot and W. A. Slater-1912;
  50. Reinforced Concrete Wall Footings and Column Footings, Bulletin No.67 by Arthur N. Talbot-1913;
  51. Mechanics of Building Construction by Henry Adams- 1912;
  52. Practical Reinforced Concrete Standards by Hiram B. Andrews -1908;
  53. Moments and Stresses in Slabs -Proceedings of the American Concrete Institute, volume 17 by H. M. Westergaard and W. A. Slater -1921;
  54. A History of Architectural Development-volumes 1, 2 and 3 by F. M. Simpson-1913;
  55. Manual of Structural Design by Jack Singleton, 3rd edition -1947;
  56. Design of Reinforced Concrete by Jack C. McCormac, 3rd edition-1993;
  57. Design of Concrete Structures by A. H. Nilson, 10, 11, 12th edition-1997;
  58. Design of Prestressed Concrete by Arthur H. Nilson, 2nd edition -1987;
  59. Reinforced Concrete Fundamentals by P. Ferguson, J. Breen, J. Jirsa, 5th edition-1988;
  60. Reinforced Concrete Design by C. K. Wang and C. G. Salmon, 6th edition-1998;
  61. Building Design and Construction Handbook by Frederick S. Merritt and Jonathan T. Ricketts, 6th edition -2002.
  62. Foundation Analysis and Design, 4th edition by Joseph E. Bowles -1988.
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