Load Tests of Concrete Structures: Allowing the Project to Determine Test Protocol

The American Concrete Institute (ACI) is generally recognized as the authority on concrete in the United States, including materials, analyses, design, and repair of new and existing structures. ACI recognizes two different load test protocols that may be used to evaluate the strength of existing concrete structures, understanding that one protocol may be better aligned with project parameters than the other protocol. The two test protocols are the cyclic and monotonic (or 24-hour) tests. Each of the protocols, their application, and acceptance criteria are outlined in ACI 437.2-13, a code-level document titled Strength Evaluation of Existing Concrete Structures. This document is directly referenced by ACI 562-16 Code Requirements for Assessment, Repair, and Rehabilitation of Existing Concrete Structures and Commentary. In addition, adoption of 437.2-13 provisions (including cyclic test protocol and test load magnitudes) is being considered by ACI Committee 318, the committee that produces the Building Code for Structural Concrete. As engineers use the relatively new repair code (ACI 562) more often and gain familiarity, they should also be aware of available load testing provisions cited by the code. The monotonic test protocol has been a part of ACI since the first half of the 20th century. The cyclic test, on the other hand, has only been recently introduced to ACI committee documents, beginning with ACI 437.1R-07 and now in ACI 437.2R-13. Although the two load test methodologies are now both available to engineers, the use of the cyclic test within the U. S. has been limited, in large part due to familiarity and code acceptance of the test. Differences in the application of each of these test protocols lend each to being better suited to specific project applications. In addition to presenting the recent history of the load test protocols, two case studies will be discussed in which the selection of the test protocol was based on its suitability to the respective project.