The “Building Code Requirements for Structural Concrete” (“Code”) covers the materials, design, and construction of structural concrete used in buildings and where applicable in nonbuilding structures. The Code also covers the strength evaluation of existing concrete structures. Among the subjects covered are: contract documents; inspection; materials; durability requirements; concrete quality, mixing, and placing; formwork; embedded pipes; construction joints; reinforcement details; analysis and design; strength and serviceability; flexural and axial loads; shear and torsion; development and splices of reinforcement; slab systems; walls; footings; precast concrete; composite flexural members; prestressed concrete; shells and folded plate members; strength evaluation of existing structures; provisions for seismic design; structural plain concrete; strut-and-tie modeling in Appendix A; alternative design provisions in Appendix B; alternative load and strength reduction factors in Appendix C; and anchoring to concrete in Appendix D. The quality and testing of materials used in construction are covered by reference to the appropriate ASTM standard specifications. Welding of reinforcement is covered by reference to the appropriate American Welding Society (AWS) standard. Uses of the Code include adoption by reference in general building codes, and earlier editions have been widely used in this manner. The Code is written in a format that allows such reference without change to its language. Therefore, background details or suggestions for carrying out the requirements or intent of the Code portion cannot be included. The Commentary is provided for this purpose. Some of the considerations of the committee in developing the Code portion are discussed within the Commentary, with emphasis given to the explanation of new or revised provisions. Much of the research data referenced in preparing the Code is cited for the user desiring to study individual questions in greater detail. Other documents that provide suggestions for carrying out the requirements of the Code are also cited.

"building code requirements for structural concrete (aci 318-11) and commentary"

A model for evaluating structural damage in reinforced concrete structures under earthquake ground motions is proposed. Damage is expressed as a linear function of the maximum deformation and the effect of repeated cyclic loading. Available static (monotonic) and dynamic (cyclic) test data were analyzed to evaluate the statistics of the appropriate parameters of the proposed damage model. The uncertainty in the ultimate structural capacity was also examined.

Mechanistic Seismic Damage Model for Reinforced Concrete

In this article, the authors propose a simplified MCFT (modified compression field theory) and demonstrate that this simplified MCFT is capable of predicting the shear strength of a wide range of reinforced concrete (RC) elements with almost the same accuracy as the full theory. The authors summarize the results of over 100 pure shear tests on reinforced concrete panels. The ACI approach for predicting shear strength as the sum of a diagonal cracking load and a 45-degree truss model predicts the strength of these panels poorly, with an average experimental-over-predicted shear strength ratio of 1.40 with a coefficient of variation of 46.7%. The modified compression field theory (MCFT), developed in the 1980s, can predict the shear strength of these panels with an average shear strength ratio of 1.01 and a coefficient of variation (COV) of only 12.2%. The authors contend that their new, simplified method gives an average shear strength ratio of 1.11 with a COV of 13.0%. They demonstrate the application of this new simplified method to panels with numerical examples. They conclude that, on many occasions, a full load-deformation analysis is not needed and this quick calculation of shear strength is appropriate and useful.

Simplified Modified Compression Field Theory for Calculating Shear Strength of Reinforced Concrete Elements

This article attempts to review the progress achieved in the understanding of scaling and size ef­ fect in the failure of structures. Particular emphasis is placed on quasi brittle materials for which the size etTect is important and complicated. After reflections on the long history of size effect studies, attention is focused on three main types of size effects, namely the statistical size effect due to randomness of strength, the energy release size effect, and the possible size effect due to fractality of fracture or microcracks. Definitive conclusions on the applicability of these theories are drawn. Subsequently, the article discusses the application of the known size effect law for the measurement of material fracture properties, and the modeling of the size effect by the cohesive crack model, non local finite element models and discrete element models. Extensions to com­ pression failure and to the rate-dependent material behavior are also outlined. The damage con­ stitutive law needed for describing a microcracked material in the fracture process zone is dis­ cussed. Various applications to quasibrittle materials, including concrete, sea ice, fiber compos­ ites, rocks and ceramics are presented. There are 377 references included in this article.

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Scaling of Structural Failure

The article attempts a broad review of the problem of size effect or scaling of failure, which has recently come to the forefront of attention because of its importance for concrete and geotechnical engineering, geomechanics, arctic ice engineering, as well as for designing large load-bearing parts made of advanced ceramics and composites, e.g. for aircraft or ships. First, the main results of Weibull statistical theory of random strength are briefly summarized, and its applicability and limitations described. In this theory as well as plasticity, elasticity with a strength limit, and linear elastic fracture mechanics (LEFM), the size effect is a simple power law, because no characteristic size or length is present. Attention is then focused on the deterministic size effect in quasibrittle materials which, because of the existence of a nonnegligible material length characterizing the size of the fracture process zone, represents the bridging between the simple power-law size effects of plasticity and of LEFM. The energetic theory of quasibrittle size effect in the bridging region is explained, and then a host of recent refinements, extensions and ramifications are discussed. Comments on other types of size effect, including that which might be associated with the fractal geometry of fracture, are also made. The historical development of the size-effect theories is outlined, and the recent trends of research are emphasized.

/pdf/size-effect-on-structural-strength-a-review-1pd8r6gzud.pdf

Size effect on structural strength: a review

FOUR SERIES OF TEST BEAMS WITH DEPTHS OF 6, 12, 24, AND 48 INCHS WERE TESTED AT THE UNIVERSITY OF TORONTO AND THE RESULTS COMPARED CONSIDERABLE INFLUENCE OF THE ABSOLUTE DEPTH BECAME APPARENT TO SUCH AN EXTENT THAT THE SAFETY FACTOR FOR THE LARGEST BEAMS WAS APPROXIMATELY 40 PERCENT LOWER THAN THE OTHERWISE SIMILAR SMALLER BEAMS THIS TREND INDICATES THAT, WITH A FURTHER INCREASE IN DEPTH, A CORRESPONDINGLY FURTHER DECREASE IN THE SAFETY FACTOR CAN BE EXPECTED /AUTHOR/

How safe are our large reinforced concrete beams.

This paper intends to answer two questions: (a) What is the internal mechanism of the so-called shear failure of a reinforced beam, and (b) What is the strength of this mechanism? Under increasing load a reinforced concrete beam transforms into a comb-like structure. In the tensile zone the flexural cracks create more or less vertical concrete teeth, while the compressive zone represents the backbone of the concrete comb. The analysis of this structural system has revealed that two rather different mechanisms are possible: as long as the capacity of the concrete teeth is not exceeded the beam-like behavior governs; after the resistance of the concrete teeth has been destroyed a tied arch, having quite different properties, remains. For both mechanisms simple analytical expressions have been developed. Tests carried out at the University of Tor onto on sever a I series of reinforced concrete beams have confirmed this theory, as did some other available test results.

The Riddle of Shear Failure and its Solution

REPORTS ARE GIVEN ON TESTS OF RECTANGULAR BEAMS PERFORMED TO DETERMINE THE INFLUENCE OF THE THREE BASIC PARAMETERS IN EQ. /12-2/ & /17-2/ OF AMERICAN CONCRETE INSTITUTE 318-63. THE RESULTS SHOWED' /1/ THE INFLUENCE OF COMPRESSIVE STRENGTH ON SO-CALLED SHEAR STRENGTH WAS INSIGNIFICANT AND COULD BE IGNORED IN THE ANALYSIS OF DIAGONAL FAILURE LOAD OR ALLOWABLE SHEAR STRESS, /2/ THE INFLUENCE OF THE PERCENTAGE OF MAIN REINFORCEMENT ON SHEAR STRENGTH WAS CONSIDERABLE, /3/ THE MINIMUM VALUE OF BENDING MOMENT AT FAILURE FOR BEAMS OF IDENTICAL CROSS SECTION WAS OBTAINED IN THE VICINITY OF A SHEAR ARM RATIO OF 2.5, AND THIS WAS NOT INFLUENCED BY THE PERCENTAGE OF MAIN REINFORCEMENT OR THE COMPRESSIVE STRENGTH, HOWEVER, FLEXURAL LOAD CAPACITY VARIED CONSIDERABLY WITH PERCENT OF MAIN REINFORCEMENT, AND /4/ THERE EXISTS A CLEARLY DEFINED REGION BOUNDED BY LIMITING VALUES OF THE PERCENTAGE OF MAIN REINFORCEMENT AND SHEAR ARM RATIO INSIDE WHICH DIAGONAL FAILURE IS IMMINENT AND OUTSIDE WHICH FULL FLEXURAL STRENGTH IS ATTAINED. /AUTHOR/

Basic Facts Concerning Shear Failure

A TEST PROGRAM IS DESCRIBED WHICH WAS UNDERTAKEN TO ANSWER THE TWO BASIC QUESTIONS: (1) WHAT IS THE STRUCTURAL FUNCTION OF WEB REINFORCEMENT? AND (2) WHAT IS THE RELATIONSHIP BETWEEN THE SHEAR FORCE AND THE REQUIREMENT FOR WEB REINFORCEMENT? ELEVEN SERIES OF REINFORCED CONCRETE BEAMS COMPRISING 44 SPECIMENS WERE TESTED FOR THIS PURPOSE. THREE SERIES HAD WEB REINFORCEMENT CONSISTING OF BENT-UP BARS, THREE HAD INCLINED STIRRUPS, AND FIVE HAD VERTICAL STIRRUPS. TO PROVE A RATIONAL BASIS FOR EXPLAINING THE STRUCTURAL FUNCTION OF WEB REINFORCEMENT, A DISCUSSION OF INTERNAL FORCES PRECEDES THE TEST REPORT. BEGINNING WITH A STUDY OF STRESS TRAJECTORIES, THE PRINCIPLE OF INTERNAL ARCHES IS DEVELOPED AND LEADS TO THE REALIZATION THAT THE PURPOSE OF WEB REINFORCEMENT IS TO PRODUCE SUPPORTS FOR THE INTERNAL ARCHES AND THAT NO DIRECT RELATIONSHIP EXISTS BETWEEN THE SHEAR FORCE AND THE REQUIREMENT FOR WEB REINFORCEMENT. THE PRIME OBJECTIVE OF THE TEST PROGRAM WAS TO SUBSTANTIATE THE VALIDITY OF THIS PRINCIPLE OF INTERNAL ARCHES. /AUTHOR/

G. N. J. Kani

Papers

How safe are our large reinforced concrete beams.

The Riddle of Shear Failure and its Solution

Basic Facts Concerning Shear Failure

A rational theory for the function of web reinforcement