ACI PRC-364.4-21 DETERMINING THE LOAD CAPACITY OF A STRUCTURE WHEN STRUCTURAL DRAWINGS ARE UNAVAILABLE – TECHNOTE.
Reinforcement layout Once the basic structural confguration is known, the actual layout of reinforcement may be determined using a combination of destructive and nondestructive methods. It should be noted that the development and splice lengths required by previous codes may be less than the current code requirements. Therefore, determination of the development and splice lengths used in the design and construction of the structure is necessary for the determination of the structure’s load capacity. Development and splice length requirements have changed over time; refer to prior versions of ACI 315R for older detailing requirements that may coincide with the vintage of the building being evaluated. Particular attention should also be given to areas of potentially atypical detailing, such as joints, member connections, and boundary elements. In typical structural members where the concrete cover thickness is less than 2 in. (50 mm), the reinforcement spacing and depth can usually be evaluated using a pachometer. In the cover range from 2 to 4 in. (50 to 100 mm), pachometer surveys may be partially effective. Ground-penetrating radar (GPR) can be used to determine the spacing and depth of reinforcement that is located further inside concrete members and beyond the range of a pachometer. Nondestructive surveys using either a pachometer or GPR may be problematic in areas of congested reinforcement, such as columns and beams, and other areas subject to metallic interference (for example, metallic conduits). GPR, however, is typically more effective than a pachometer at identifying individual reinforcing elements in congested areas of reinforcement. Estimation of the reinforcing bar size(s) is not very reliable, either with the pachometer or GPR. By using multiple measure- ment methods, however, bar diameter can generally be estimated to within two adjacent bar sizes (ACI 228.2R). The exploratory openings may be required to more reliably determine the internal reinforcement bar size(s) and layout.
Load testing Load testing (ACI 318; ACI 437R; ACI 437.1R; ACI 437.2) is another tool for determining the load-carrying capacity of a member or structure. Load tests conducted in accordance with Chapter 27 of ACI 318-19 or with ACI 437R, 437.1R, or 437.2 may be used to verify the load capacity and behavior of a given structure. Load testing may reduce, but not eliminate, the need for investigative feld work, material testing, and structural calculations. ACI 437.2 also includes provisions to allow for a service load level assessment of an existing concrete structure. Determining the most effcient combination of investigative feld work, material testing, structural calculations, and load testing depends on professional judgment, as well as an evaluation of the practical diffculties associ- ated with each task. Each structure in need of load capacity evaluation will present a different set of technical and logistical diffculties and will therefore require the performance of a combination of the aforementioned tasks to be selected based on the LDP’s professional judgment and experience.ACI PRC-364.4 pdf download.