ACI ITG-4.3R

Abstract

This document addresses the material and design considerations when using normalweight concretes having specified compressive strengths of 6000 psi (41 MPa) or greater in structures designed for moderate to high seismic applications. Irrespective of seismic zone, SPC, or SDC, this document is also applicable to normalweight high-strength concrete in intermediate or special moment frames and intermediate or special structural walls as defined in ACI 318-05 (ACI Committee 318 2005). <br>The term "high-strength concrete," as defined by ACI 363R-92 (ACI Committee 363 1992), refers to concrete having a specified compressive strength for design of 6000 psi (41 MPa) or greater. The 6000 psi (41 MPa) threshold that was chosen for this document is similar to that adopted by ACI Committee 363. <br>Even though high-strength concrete is defined based on a threshold compressive strength, the concept of high strength is relative. The limit at which concrete is considered to be high strength depends largely on the location in which it is being used. In some regions, structures are routinely designed with concrete having specified compressive strengths of 12,000 psi (83 MPa) or higher, whereas in other regions, concrete with a much lower specified compressive strength is considered high strength. Essentially, the strength threshold at which concrete is considered high strength depends on regional factors, such as the characteristics and availability of raw materials, production capabilities, testing capabilities, and experience of the ready mixed concrete supplier. <br>ITG-4 produced three documents: ITG-4.1 is a reference specification that can be cited in the project specifications; ITG-4.2R addresses materials and quality considerations that are the basis for the ITG-4.1 specification; and ITG-4.3R, this document, addresses structural design and detailing. Certain modifications of ACI 318 requirements are proposed in Chapter 10 of ITG-4.3R. <br>From a materials perspective, there are few differences between the properties of high-strength concrete used in seismic applications and those of high-strength concrete used in nonseismic applications; therefore, the information presented in ITG-4.1 and ITG-4.2R is generally applicable to all high-strength concrete. When special considerations are warranted due to seismic applications, they are addressed specifically. Unlike ITG-4.1 and ITG-4.2R, most of the material contained in ITG-4.3R is specific to seismic applications of high-strength concrete structural members. <br>The information in Chapters 4 through 9 of this document is presented in a report format. Chapter 10 contains suggested modifications to design and detailing requirements in ACI 318-05. <br>Some topics, such as compressive stress block and confinement of beam-columns, are more developed than others because there is significantly more literature available on these topics. For all topics, an attempt was made to be as thorough as possible in summarizing the most relevant information pertaining to the design of members with high-strength concrete. For topics with limited information in the literature, however, recommendations were made with the intent of preventing potentially unsafe design.