Evaluation of Existing Buildings
The available methods are evaluation by structural analysis based on known material properties, dimensions and loading, evaluation by analysis and physical load testing, and evaluation by analysis and structural modeling depending on the nature of the structure and the level of information available about the existing condition of the structure.
Evaluation by analysis is used when sufficient information is available, load testing is impractical or unsafe due to the complexity of the loading and testing arrangements. Load test is not recommended where a sudden and brittle failure is expected. The gathered information is used to analytically determine the safe load-carrying capacity of the structure or portion of the structure.
Evaluation by physical load testing is used when the complexity of the structure makes evaluation solely by analytical methods impractical or uncertain, the loading and material characteristics cannot be readily determined, the structural distress causes uncertainties into the input parameters of an analytical evaluation, the degree of defects cannot be easily determined, and when there is doubt about the adequacy of the structure under future loading more than the original design criteria. Preliminary and approximate analytical evaluation is performed before the load test to determine the location and magnitude of the test loading and to plan the test.
Evaluation by the construction and testing of structural models may be employed in place of a full-scale load test. This method is used when analytical solution does not provide a unique solution, sudden failure is expected, load testing is physically impractical, design is complex, shrinkage, creep, temperature, and differential settlement, etc., are significant in the presence of restraint, or when the part having doubt can not be tested at full scale with other parts of the structure. The results will be reliable when the structure, loading, restraints and material strengths can reasonably be modeled and the principles of modeling are fully employed to interpret the results.