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"

Influence of porosity on compressive and tensile strength of cement mortar

A review on ultra high performance concrete: Part II. Hydration, microstructure and properties

Effects of steel fiber content and shape on mechanical properties of ultra high performance concrete

Steel-fiber reinforced concrete is increasingly being used day by day as a structural material. The complete stress–strain curve of the material in compression is needed for the analysis and design of structures. In this experimental investigation, an attempt has been made to generate the complete stress–strain curve experimentally for steel-fiber reinforced concrete for compressive strength ranging from 30 to 50 MPa. Round crimped fibers with three volume fractions of 0.5%, 0.75% and 1.0% (39, 59, and 78 kg/m3) and for two aspect ratios of 55 and 82 are considered. The effect of fiber addition to concrete on some of the major parameters namely peak stress, strain at peak stress, the toughness of concrete and the nature of the stress–strain curve is studied. A simple analytical model is proposed to generate both the ascending and descending portions of the stress–strain curve. There exists a good correlation between the experimental results and those calculated based on the analytical model. Equations are also proposed to quantify the effect of fiber on compressive strength, strain at peak stress and the toughness of concrete in terms of fiber reinforcing parameter.

Stress-strain curves for steel-fiber reinforced concrete under compression

Tests conducted to characterize the stress-strain relationship of high-strength fiber concrete in compression using both cylindrical and prismatic specimens are reported. The concrete strength investigated ranges from 70 to 120 MPa. Other parameters include volume fraction of steel fibers and direction of casting in relation to the loading axis. Test results indicate that inclusion of fibers improves the strength and enhances the strain at peak stress but results in a smaller initial tangent modulus for specimens cast in an upright (vertical) position. Vertically cast prisms provide higher strains at peak stress and better postpeak ductility than cylindrical specimens. Based on the test data, an analytical model is proposed to generate the complete stress-strain σ-e curves of high-strength fiber concrete derived from cylinders and horizontally cast prisms. The proposed model has been found to agree well with the stress-strain curves generated experimentally.

Stress-strain relationship of high-strength fiber concrete in compression

Test data are presented on the shear strength of a series of longitudinally reinforced fibrous concrete beams in which the shear span‐to‐effective depth ratio, volume fraction of fibers, percentage of reinforcement, and strength of the concrete were varied. Test results indicate that the fibers have significant influence on the mode of failure and ultimate shear strength of a longitudinally reinforced concrete beam. Conventional reinforced concrete analyses with some modification, as suggested in this paper, to account for the effect of fibers give good predictions of the ultimate strength and the mode of failure for rectangular beams with no shear reinforcement.

Shear Strength of Fibrous Concrete Beams Without Stirrups

An important design issue is the ductility or the ability of a reinforced concrete (RC) member to deform at or near the ultimate load without significant strength loss. This article reports on a study of reinforced high-strength concrete (HSC) beams in flexure. The study included flexural test results generated on 16 reinforced concrete beams. Test parameters considered include concrete compressive strength, ratios of tensile and compressive reinforcements, and spacing of lateral ties. The authors found that the current code provisions for serviceability requirements of maximum crack width and ultimate strength are adequate up to a concrete strength of approximately 130 MPa. The authors express concerns regarding the adequacy of current code provisions, however, for cracking moment and service load deflection. They show that stresses generated by shrinkage of concrete and the creep associated with it can significantly affect the cracking moment and service load deflection of reinforced HSC beams. The authors recommend that the ACI Code specification for maximum spacing of ties in RC flexural members need to be reduced to d/4, particularly at critical sections. This will prevent premature disintegration of the confined concrete core in the compression zone due to buckling of compression reinforcement.

Reinforced high-strength concrete beams in flexure

This paper discusses some important engineering properties of plain concrete for a wide range of compressive strength. A large volume of selected experimental data has been collected from existing literature and then analyzed. Particular emphasis has been given to studying the effects of concrete strength on the modulus of elasticity, tensile strength (flexural and splitting tensile), and Poisson’s ratio of concrete. Study on the effect of the size of specimens on the compressive strength and modulus of elasticity of concrete has also been included. The adequacy of some of the familiar relationships for predicting the modulus of elasticity and tensile strengths of concrete has been critically examined, and suitable expressions are suggested to cover concrete strength up to 120 MPa.

M. A. Mansur

Papers

Stress-strain relationship of high-strength fiber concrete in compression

Shear Strength of Fibrous Concrete Beams Without Stirrups

Reinforced high-strength concrete beams in flexure

Correlations between Mechanical Properties of High-Strength Concrete

A study of jute fibre reinforced cement composites