Consulting-Specifying Engineer - September 2008 - (Page 21)

Table 1 The performance-based design process Project information The building design and construction details, site, geographic location, number of occupants, and occupant characteristics are identified. Other important considerations include: building’s symbolic importance, consequences, operations and processes, criticality, and expected threats. Goals and objectives The goals and objectives are established by the stakeholders. Goals are global in nature, and can include protecting life, property, continuity of operations, heritage, and the environment. Objectives refine these goals; design and stakeholder objectives are identified. Performance criteria Performance criteria are the metrics against which design objectives are assessed. For fire scenarios, performance criteria may include smoke temperature, upper-layer thermal radiation, smokelayer depth, smoke visibility, and/or distance containment concentration. Design scenarios A range of design scenarios are selected. Consideration may reflect probabilistic and deterministic considerations. For example: How likely it is the event will occur and, if it does occur, how it is expected to impact the building. Design scenarios are quantified into measurable engineering descriptions. Develop design options Design options are selected. This includes and overall strategy of components that will meet the design objectives. In most cases, a number of candidate design options are considered. In some cases, this may include comparisons with applicable prescriptive code requirements. Evaluate and select design Options are evaluated for compliance with the design objectives and performance criteria. The evaluation process is iterative—mitigation measures are evaluated against the design loads and the design objectives. A suitable option is selected from all options as the final design. Document design The final step is to document the design and analysis. The Society of Fire Protection Engineers Guide states that at a minimum, the following should be included: project scope, designer’s capability, goals and objectives, performance criteria, design fire scenarios, final design, evaluation, critical design assumptions, critical design features, and references. occupants (partial evacuation), to defending occupants in place. In some cases, this is accomplished simply by evacuating people to the exterior of the building. In other cases, they may be relocated to a safe portion of the building. Strategies must be based on the specific hazards expected to threaten the facility. For some buildings, a single response for all events is appropriate. For others, a scalable approach that escalates from protect-in-place to simultaneous full building evacuation may be necessary. An overview of the range of possible strategies follows. Protect-in-place Protect-in-place strategies are also known as defend-in-place and shelter-inplace strategies. The concept of protecting in place is to provide sufficient safety features to allow occupants to remain in place during the event. This strategy is used in facilities in which occupants have a limited ability to be moved, either because they are incapacitated or they are immobile due to medical or other reasons. Protect-in-place strategies also are used for a portion of the population when phased strategies are employed. Obvious examples of facilities that use protect-in-place strategies are hospital surgical suites or intensive care units. In these facilities, it may be difficult—if not impossible—to move patients without significantly jeopardizing their safety. Protect-in-place strategies typically rely on a combination of active and passive fire protection features, along with management procedures, to provide an appropriate level of safety for the occupants to stay in the initial compartment. Typical features include automatic sprinklers and fire-rated compartments to reduce smoke and fire spread, along with enhanced smoke detection to provide early warning of fires, emergency lighting, and emergency power for safety and critical care equipment. Relocate to a safe place The concept of relocating occupants from an area of potential hazard to a protected area of refuge or other safe place within a building is a variation on the protect-in-place strategy. As with protect-inplace strategies, relocation requires special attention to management procedures and may require special detection and warning systems or other life safety features and procedures. Examples of facilities that might use this strategy include hospitals; Editor’s note: Concepts have been taken with permission from the text “Egress Design Solutions: A Guide to Evacuation and Crowd Management Planning.” Consulting-Specifying Engineer • SEPTEMBER 2008 21

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Consulting-Specifying Engineer - September 2008 Contents Viewpoint Letters News M/E�Roundtable Selecting Appropriate Egress Strategies Commissioning On-Site Electrical Systems Mentoring Control Engineers and Technicians Casting Call for Cx Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - September 2008

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