(44f) Building Design for Resilience Beyond Design Basis Blast Loads

One of the guiding principles of API RP-752 is that buildings intended for occupancy are to be designed, constructed, installed, modified, and maintained to protect occupants against explosion, fire, and toxic material releases.  Owners/operators may use either a consequence-based approach or a risk-based approach to evaluate the siting of both new and existing buildings for blast loads.  While a consequence-based approach should be based on a maximum credible event (MCE) for each building and type of hazard considered, a risk-based approach may consider numerous scenarios, accounting for both the consequences and the frequencies of the scenarios.  However, when designing either new buildings or upgrades to existing buildings, designers are typically provided only a single set of blast loads and a single response criteria (for example, medium response per ASCE “Design of Blast-Resistant Buildings in Petrochemical Facilities”).  A lower response level implies lower occupant vulnerability, while higher response levels imply higher occupant vulnerability.  A design for higher magnitude loads to low response criteria would result in very conservative design.  On the other hand, a design for lower magnitude loads to higher response limits would result in a building without capacity to protect occupants in the event of a more severe explosion.

A better approach would be to consider multiple levels of blast loads when developing a design.  Lower magnitude loads (usually from higher probability events) should require designs to meet the lower response limits, while higher magnitude loads (usually from lower probability events) should require designs to meet the higher response limits.  This paper demonstrates this approach by evaluating typically designed building systems for a range of blast loads commonly encountered at refining and chemical plants.  Recommendations are provided for the design of new buildings or upgrades to existing buildings.   By including the concept of resilience in the design process, the designer may provide protection from future yet-to-be-determined hazards or scenarios.