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A Short History of the ACI 318 Structural Concrete Building Code

7/1/2019

When giving updates to industry groups on the progress of the changes occurring to the ACI 318 Building Code during the 2014 cycle, I would often have an audience member ask if I could provide some history about the Code. Thankfully, I had seen a presentation that Past President Tony Fiorato had done a few years prior, so I at least knew a few facts to relay. Based on a suggestion from Past President David Lange, who pulled together some historical resources, I thought this would be a topic of general interest to the ACI community.

ACI was founded as the National Association of Cement Users (NACU) at an Engineering Congress held at the St. Louis World's Fair in October 1904. At the time, NACU was based in Philadelphia, PA. In 1913, the name was changed to the American Concrete Institute to more appropriately reflect the predominant cement user—the concrete construction industry. The headquarters was moved to Detroit, MI, in 1919.

The first reinforced concrete building code, titled "Standard Building Regulations for the Use of Reinforced Concrete," was issued by NACU in 1910—it was 14 pages! I think everyone in the structural concrete design and construction community today would greatly appreciate a code that is only 14 pages in length. This standard was adopted as the tentative standard of the Institute.

Through the combined efforts of an ACI committee and the Committee on Engineering Practice of the Concrete Reinforcing Steel Institute, "Tentative Building Regulations for the Use of Reinforced Concrete" was adopted as an ACI standard in the late 1920s. Eventually, the differences in the two previously separate codes were reconciled, and they were combined into a single code of practice prepared by a joint committee. Over time, additions to the standard were made as research results became available and knowledge from field practice was gained—much the same way that changes to the building code are made today. In structural design, the major development was the increased interest in rigid frame analysis, which recognized the monolithic character of reinforced concrete and provided a more accurate method of stress computation, and thus a more rational basis for ensuring safety.

In 1940, a Joint ACI-ASCE Task Group made recommendations to discontinue the "Joint Committee Report of Recommended Practice and Standard Specifications for Concrete and Reinforced Concrete." The joint report was allowed to die out because the ACI 318 Building Code and other more recent standards and manuals adequately covered the material. This action left only the ACI 318 Building Code in the field of design practices for reinforced concrete, placing considerable responsibility on ACI's total committee effort. The work by ACI Committee 318 culminated in revisions of the Building Code in 1941—this was the first time that the structural concrete building code had "ACI 318" in the title.

A major change in the ACI 318 Building Code occurred in 1956. Although the main body of the Code was based on working stress, the revision recognized the ultimate strength method for design of concrete cross sections and was included as an appendix. New provisions for shear provided against failure in diagonal tension near points of zero moment where main reinforcement is typically discontinued.

Another major Code revision was completed in 1971. The Code was based on ultimate strength design and included a Commentary for the first time. The Code and Commentary were published as separate documents. In 1983, the Commentary was published with the Code in the now-familiar side-by-side format. Through the years, the Code was typically published on a 6-year cycle. Then, mainly to conform with the International Building Code cycle, the ACI 318 Building Code began to be published on a more recurrent 3-year cycle in 1992.

The next substantial change came during the 2014 cycle, during which I had the privilege of chairing ACI Committee 318. The Code was completely reorganized in a member-based format to make it easier for design. One major advantage of this format is that it greatly reduced the number of cross references and helps the user be assured that all applicable provisions have been satisfied.

I trust this gives readers a sense of the work and history of ACI Committee 318 over the last 100 years. Next month, I will address the numerous technical changes that we will be seeing with publication of the 2019 Code.

Randall W. Poston