Performance-Based Design | Reax Engineering

Performance-Based Design

 

Q: What is performance-based fire design?

A: Performance-based fire design, sometimes referred to simply as &performance based design&, is the application of science and engineering to design fire protection and life safety systems in buildings, taking into account the specific characteristics of the building under consideration, rather than applying generic "checklist" requirements found in prescriptive building and fire codes that may not be appropriate due to a building's unique characteristics.

 

Q: If US building codes are prescriptive, how is performance-based fire design achieved in the US?

A: Performance-based design in the United States is generally achieved via "equivalencies" or "alternates". In the US, most buildings are still designed under prescriptive building codes based on the International Building Code (IBC). Although the International Codes (IBC, IFC, IMC, etc.) are largely prescriptive in nature, IBC 104.11 "Alternative materials, design and methods of construction and equipment" and California Building Code Section 108.7 "Alternate materials, designs, tests and methods of construction" allow for performance-based fire design as long it is approved by the Authority Having Jurisdiction. Consequently, any performance-based design in the US must first be discussed with the appropriate AHJs.

 

Q: How does performance-based design work?

A: In performance-based fire design, different candidate designs are evaluated by applying engineering calculations (such as computer fire modeling) to assess the impact of various fire scenarios on the space under consideration and its occupants. Each candidate design might include different variations of the means of egress layouts, sprinkler types (quick response vs. standard response), fire detection system type (spot type smoke detectors, projected beam detectors, flame detectors, etc.) and configuration, smoke control system exhaust rate, and so on. A candidate design is deemed acceptable if fire engineering calculations show that the design meets the quantitative performance criteria established at the start of the design process. These performance criteria are usually related to ensuring that space remains tenable so that its occupants are not exposed to untenable amounts of smoke or heat, and ensuring that structural collapse does not occur. In performance-based design, fire safety is achieved by applying calculations, science, and engineering to determine how a building would respond to fire, rather than by showing that it meets a checklist of prescriptive requirements.

 

Q: What are the advantages of performance-based fire design?

A: performance-based design of fire and life safety systems gives the design team much greater freedom than the conventional prescriptive methods by emphasizing science, engineering, calculation, and modeling rather than arbitrary "checklists" of prescriptive requirements that may not consider a building's unique characteristics. performance-based fire design can lead to significant reductions in construction costs, and make designs possible that would not be possible with a straight prescriptive design. Performance-based design allows designers to answer "what if" questions and evaluate the effectiveness of various fire suppression systems, determine safe separation distances between fuel packages, and optimize the placement of fire and smoke detectors to minimize detection times. In performance-based fire design, unnecessarily conservative and expensive building designs, as sometimes result under the prescriptive building codes, are prevented. By evaluating several candidate designs, performance-based design makes it possible to select a cost-effective design without compromising fire safety.