January/February 2019

Communities: Construction
Is Immediate Occupancy the Future of Building Standards?

NIST report defines research needs for higher performance buildings.

Building and infrastructure design codes in the United States have traditionally attempted to provide protection for structures against the effects of earthquakes, windstorms, and fires, with the objective of shielding against a substantial loss of life. But what if building standards went beyond limiting loss of life and focused on better performance designed for protection against a range of different hazards?

A new report by the National Institute of Standards and Technology (NIST) attempts to identify ways to reach those higher levels of performance-based design. The aim is to address research needs for updating US building standards to allow for the continued functioning of a building after a disaster or natural hazard—also referred to as “immediate occupancy.” Immediate occupancy standards would aim to reduce damage to the entire building and its interior contents and enable immediate or near-immediate resumption of building occupancy and function—allowing residential and commercial buildings to provide shelter and continue functioning. This would not only protect individuals but also minimize disruption to lives and property, as well as lessen the social, psychological, and health consequences of events. However, before immediate occupancy performance standards can be implemented in building codes, the report emphasizes, design professionals and others involved in the building process must focus on

• identifying relationships and dependencies between building function levels, damage and recovery levels, and effects on populations and communities;
• standardizing data collection across fields for better communication and reporting on the performance of physical, social, and economic systems in the recovery time period; and
• developing predictive models that address how disasters will affect elements such as systems that control and monitor a building’s mechanical and electrical equipment, groupings of residential or commercial buildings, and the community.

The report states that most buildings are designed using prescriptive standards that have been vetted over decades of research and practice, making them reliable. Prescriptive design standards, however, do not explicitly address building performance outcomes—just the building code performance objectives. These have to do with strength and stiffness to provide structural stability, serviceability, and functionality. Siamak Sattar, a research structural engineer at NIST, explains the way design professionals and building inspectors will have to adapt to thinking for higher performance standards in the building process. “Performance-based design standards, although they have been developed mainly for assessing seismic impacts on buildings, some address objectives in terms of the maximum level of damage a building can tolerate while also satisfying a performance objective,” Sattar says. “This is often done by evaluating the damage state of a building at each hazard level,” from routine to extreme.

Areas of further research for design professionals include design criteria for incorporating building functionality goals, which are lacking in most designs today. For instance, one existing tool, FEMA P-58 (developed for seismic assessment of buildings), is an example of an analytical tool that addresses building functionality levels that relate to immediate occupancy performance.

Even more research, analytical tools, and computer-prediction models are needed to quantify damage levels, develop improved capabilities for design criteria, and develop technologies that detect the resiliency of certain building materials. Similarly, the report stresses the need for research related to environmental effects on the degradation of building materials and on ways to develop low-cost, rapid-repair technologies.

According to NIST, while immediate occupancy performance standards are not yet mandated, design professionals will focus on reaching that stage in the years to come.