Load Testing Techniques for the Strength Evaluation of Existing Reinforced Concrete Structures

Evaluating the condition of existing reinforced concrete structures is generally undertaken if the integrity of a structure is in question or if there is concern regarding the structure meeting the safety requirements. Strength evaluation may be undertaken, for example, after extreme events (such as earthquakes) or if the structure will be used for a new function. In situ load testing may play a role in the evaluation process. Currently, the American Concrete Institute (ACI) covers in situ load testing in two separate standards: (a) ACI 318 "Building Code Requirements for Structural Concrete", and (b) ACI 437 "Code Requirements for Load Testing of Existing Concrete Structures". The latter is referenced by ACI 562 "Code Requirements for Evaluation, Repair, and Rehabilitation of Concrete Buildings". In situ load testing methods include the application of a pre-determined load in combination with response measurements of the structure. The main response measurement is deflection, but rotation, strain, crack width, acoustic emission, and other measurements may be included. In this paper, the two aforementioned load testing approaches are compared and evaluated in terms of load test procedure, load magnitude, loading criteria, and acceptance criteria.