Nonstructural Components and Systems
ASCE 41-17 is the latest performance-based seismic evaluation criteria that have been developed for existing buildings and includes provisions for both structural and nonstructural components and also the nonstructural components for various performance levels. While ASCE 41 tries to address both types of components, the provisions for evaluating nonstructural components have not been as comprehensively developed as those for structural components, and many of their aspects are actually judgment based rather than being based on testing. As a result, the acceptance criteria for some nonstructural components may not provide the intended performance. This can be particularly problematic considering that the past performance of buildings in major earthquakes has demonstrated that the behavior of the nonstructural components is critical to the overall resilience of the building.
An example of a nonstructural component that may critically affect the seismic performance of buildings is the exterior cladding. While the severe damage that may result in a falling hazard and affect life safety is already considered in the standard, other levels of damage that might compromise the ability to occupy the building are not considered. For example, the capability of the exterior cladding to maintain a weather-tight barrier may be critical to allow the building to be operational following an earthquake, but it is not addressed in ASCE 41. Other key nonstructural components are interior partitions. Their damage could affect the post-earthquake performance of a building in several ways, including by reducing its fire resistance, but this is not take into account by the standard. These considerations might be even more critical for structures such as hospitals. Considerations of various performance levels for different types of exterior cladding and interior partition walls are discussed.