IDENTIFYING AND REGULATING FOR MULTIPLE LEVELS OF PERFORMANCE

Building regulations are legal instruments intended to ensure that buildings perform in such a way so as to provide essentially equivalent, socially acceptable levels of health, safety, welfare and amenity for building occupants and for the community in which the building is located. This is typically accomplished through regulatory controls on the design, construction and operation of buildings, covering such diverse areas as structural stability, fire safety, lighting, ventilation, plumbing and sanitary facilities. In a traditional, prescriptive-based regulatory system, the performance objectives are often embodied in specific requirements that vary by building use or occupancy type. Such requirements may be manifest as resistance to loads, construction types, fire resistance ratings, travel distances, pedestrian circulation aids, ventilation rates, and potable and waste water specifications. Based on the collective knowledge, experience and desires of regulatory developers and interested and affected parties, minimum requirements are established for all buildings within each use or occupancy groups. In many performance-based regulatory systems, however, differences between building uses and occupancy types are not so clearly delineated, at least in terms of regulatory requirements. As a result, many of the decisions regarding the “adequacy” or “appropriateness” of the building and systems performance are left to the design team and to the local code authorities. Thus, similar buildings constructed using the same regulations may perform dissimilarly, and because the acceptability of building performance depends on such factors as the use of the building and the users of the building, the social acceptability of the building performance may be unclear. One way to address the various and varied building performance requirements in a performance-based building regulatory system is to introduce the concept of multiple levels of performance. In brief, the establishment of multiple performance levels will help to provide uniformity in building performance, based on the use of buildings and the characteristics of the building users, without prescribing specific requirements. For performance under various hazard conditions, this can be accomplished by identifying risk and importance factors common to different building uses, and by defining associated performance requirements and design loads against which to test the expected performance. Although such an approach does not prescribe how the performance is to be attained, it provides different benchmarks for such diverse building uses as storage sheds, manufacturing facilities and hospitals. It also provides a mechanism by which to evaluate the performance of existing structures and to guide changes to existing structures that may be needed to attain a desired level of performance. This paper outlines the concepts of risk, hazard and importance factors, performance groups, multiple levels of performance, and magnitudes of design loads, with a focus on identifying and describing levels of tolerable building performance, for different buildings, under various magnitudes of design loads.