Use of High-Strength Concrete for Seismic Applications


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Title: Use of High-Strength Concrete for Seismic Applications

Author(s): ACI Innovation Task Group 4

Publication: Special Publication

Volume: 228


Appears on pages(s): 81-84

Keywords: constructability properties; durability properties; high-strength concrete; moderate and high seismic design categories structural properties

Date: 6/1/2005

This synopsis is based on a three-part report to be published by ACI in the near future The origin of ACI’s Innovation Task Group (ITG) 4, High-Strength Concrete for Seismic Applications, can be traced back to an International Conference of Building Officials or ICBO (now International Code Council or ICC) Evaluation Report entitled “Seismic Design Utilizing High-Strength Concrete” (ER-5536). Evaluation Reports are issued by Evaluation Service subsidiaries of model code groups. An ER essentially states that although a particular method, process or product is not specifically addressed by a particular edition of a certain model code, it is in compliance with the requirements of that particular edition of that model code. ER-5536, first issued in April 2001, was generated by Englekirk Systems Development Inc. for the seismic design of moment resisting frame elements using high-strength concrete. High-strength concrete was defined as “normal-weight concrete with a design compressive strength greater than 6000 psi and up to a maximum of 12,000 psi.” It was based on research carried out at the University of Southern California and the University of California in San Diego to support building construction in Southern California using concrete with compressive strengths greater than 6000 psi. The evaluation report (ER-5536) is available on the ICC website for review. A thorough review of the above document brought up several concerns focusing on two primary areas: material and structural aspects. Irrespective of those concerns, it was evident that the evaluation report had been created because quality assurance and design provisions are needed in cities like Los Angeles to allow the use of high-strength concrete in a safe manner. Through the formation of ITG 4, ACI has assumed a proactive role in the development of such provisions with the goal of creating a document that can be adopted nationwide. The mission of ITG 4 is to develop an ACI document that addresses the application of high-strength concrete in structures located in areas of moderate and high seismicity. A structure located in an area of moderate seismicity, in modern terminology, is a structure assigned to Seismic Design Category or SDC C of the International Building Code (IBC) or the NFPA 5000 Building Construction and Safety Code. A structure located in an area of high seismicity is a structure assigned to SDC D, E, or F of the IBC or NFPA 5000. The document is to cover structural design, material properties, construction procedures, and quality control measures. It is to be written or contain example language in a format that will allow building officials to approve the use of high-strength concrete on projects that are being constructed under the provisions of ACI 301 Specifications for Structural Concrete and ACI 318 Building Code Requirements for Structural Concrete. The ITG 4 document, now in draft form, addresses the material and structural design considerations when using concretes having specified compressive strengths of 5000 psi (34 MPa) or greater that must be designed considering moderate to high seismic risk. The term “high-strength concrete,” as defined by ACI Committee 363, refers to concrete having a specified compressive strength for design of 8000 psi (55 MPa), or greater. As such, this document is meant primarily for concretes in that high strength range. However, the strength level 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 lastly, experience. Therefore, depending on the region, the specifier may wish to selectively adopt considerations referenced in this document also when using concretes with specified compressive strengths between 5000 and 8000 psi (34 and 55 MPa). Irrespective of the location or purpose for which it is used, concrete having specified compressive strength below 5000 psi (34 M